A landfill is a large area of land or an excavated site that is designed and built to receive wastes. There were 3,536 active municipal landfills in the United States in 1995 according to the U.S. Environmental Protection Agency (EPA). Today, about 55 percent of America’s trash (more than 220 million tons annually) is disposed of in landfills.

Municipal solid-waste landfills (MSWLFs) accept only household, commercial, and nonhazardous industrial waste. Hazardous waste generated by industrial sources must be disposed of in special landfills that have even stricter controls than MSWLFs.

In the past, garbage was collected in open dumps. Most of these small and unsanitary dumps have been replaced by large, modern facilities that are designed, operated, and monitored according to strict federal and state regulations. These facilities may be distant from urban centers, requiring the large-scale transport of waste. About 2,300 municipal solid waste landfills were operating in the United States in 2000.

A typical modern landfill is lined with a layer of clay and protective plastic to prevent the waste and leachate (liquid from the wastes) from leaking to the ground or groundwater. The lined landfill is then divided into disposal cells. Only one cell is open at a time to receive waste. After a day’s activity, the waste is compacted and covered with a layer of soil to minimize odor, pests, and wind disturbances.

A network of drains at the bottom of the landfill collects the leachate that flows from the decomposing waste. The leachate is usually sent to a recovery facility to be treated. Methane gas, carbon dioxide, and other gases produced by the decomposing waste are monitored and collected to reduce their effect on air quality. EPA regulations require many larger landfills to collect and burn landfill gas.

EPA’s Landfill Methane Outreach Program was created in 1994 to educate communities and local government about the benefits of recovering and burning methane as an energy source. By 2002 the program had helped develop 220 projects that convert landfill gas to energy. Such projects, when analyzed in 2001, offset the release of carbon dioxide from conventional energy sources by an amount equivalent to removing 11.7 million cars from the road for one year.

Fresh Kills Landfill in Staten Island, the largest landfill in the United States, accepting approximately 27,000 tons of garbage a day in the late 1980s, closed in March 2001. Although landfills occupy only a small percentage of the total land in the United States, public concern over possible ground water contamination as well as odor from landfills makes finding new sites difficult.

Medical Waste

Medical wastes are generated as a result of patient diagnosis and/or treatment or the immunization of human beings or animals. The subset of medical waste that potentially could transmit an infectious disease is termed infectious waste.

The Centers for Disease Control (CDC), the U.S. Environmental Protection Agency (EPA), and the World Health Organization (WHO) concur that the following wastes should be classified as infectious waste: sharps (needles, scalpels, etc.), laboratory cultures and stocks, blood and blood products, pathological wastes, and wastes generated from patients in isolation because they are known to have an infectious disease.

Medical wastes can also include chemicals and other hazardous materials used in patient diagnosis and treatment. In some cases this subset of medical waste is classified as hazardous waste. Hospitals, clinics, research facilities, diagnostic labs, and other facilities produce medical waste.

The bulk of the wastes generated by most health care facilities, however, is municipal solid waste (MSW), or trash. MSW includes large quantities of paper, cardboard and plastics, metals, glass, food waste, and wood. Medical waste, though a smaller portion of the total health care waste stream, is of special concern because of the potential hazards from pathogens that may be present, or from hazardous chemicals.

Risk and Health Care Waste

In the late 1980s there were a series of syringe wash ups on beaches along the East Coast of the United States, which were mistakenly attributed to health care facilities. The federal Medical Waste Tracking Act (MWTA) was passed and the EPA attempted to set standards for managing the infectious waste component of medical waste that they renamed regulated medical waste.

Few states adopted its stringent guidelines. The MWTA expired in the early 1990s, making each state responsible for establishing its own classification and management guidelines for medical waste.

There are very few documented cases of disease transmission from contact with medical waste. The notable exception is needle stick, or “sharps” injuries. Paralleling the concern over beach wash ups of medical waste, was a growing awareness of the increase in HIV-AIDS and other cases of infectious diseases being diagnosed and treated in health care settings.

This, along with a series of events, led to the Occupational Safety and Health Administration (OSHA), which established rules designed to protect health care workers (OSHA blood-borne pathogen standards and universal precautions) by stipulating the need for such personnel to wear protective clothing and equipment, and to take special precautions when handling or disposing of sharps.

The interpretation of rules surrounding worker safety regulations led to some confusion over waste classification, thus causing a greater amount of wastes to be considered as potentially infectious. (For example, under the OSHA universal precautions guidelines, a worker handling a bandage with a single drop of blood on it should wear gloves, but the waste itself would most likely not be classified as infectious).

Noting that there are multiple risks inherent in medical waste including toxic chemicals and radioactive materials, the WHO has chosen to use the term health care risk waste instead of medical waste.

Proper Management, Treatment, and Disposal

There is general consensus among professional health care organizations, the waste management industry, and regulators that proper management starts with the identification of wastes requiring special handling and treatment because of their hazardous nature (biological, chemical, or radioactive). Waste identification is necessary for proper segregation, so that only those wastes needing special treatment and handling are treated. Proper management of all waste streams enhances worker safety, protects the environment, and can reduce costs.

Wastes that are deemed potentially infectious may be treated prior to disposal by a number of different technologies that either disinfect or sterilize them. These technologies include incineration, steam sterilization, dry heat thermal treatment, chemical disinfection, irradiation, and enzymatic (biological) processes among others. In 2002 there were more than one hundred specific technologies in use. In order for treatment systems to work properly, distinctive protocols for the classification and segregation of wastes must be in

Most treatment technologies for infectious wastes cannot process chemical or radioactive waste. Misclassification and inappropriate treatment of infectious wastes can result in significant harm to the environment and human health; for example, residual chemotherapeutic agents are should not be treated in autoclaves, but rather should be set aside and treated by either incineration (hazardous waste incinerators) or chemically neutralized where feasible.

The EPA has cited medical waste incinerators as among the top sources of mercury and dioxin pollution. New regulations governing the operation of, and emissions from, medical waste incinerators in the late 1990s have resulted in the closure of most such incinerators in the United States. Other countries such as the Philippines have completely banned incineration because of its adverse environmental impacts.

The health care industry is rapidly changing in ways that continue to have significant impact on the volume and characteristics of wastes produced.
  • New (e.g., laproscopic and laser) surgical techniques result in procedures that produce very little blood-contaminated waste.
  • Advances in cancer treatment have produced many drugs used in chemotherapy that are highly toxic in small quantities, producing more hazardous chemical wastes.
  • Patient residence time in hospitals has declined. Procedures that previously required an extended stay now commonly occur on an outpatient basis without necessitating an overnight stay.
  • Home care continues to grow, shifting the location of service delivery. Dialysis, chemotherapy, and hospice care are but a few examples of health care that often take place in a home setting, the result being that many wastes regulated as infectious or hazardous waste in a hospital are being disposed of as ordinary trash at curbside. (Household waste is exempt from many regulations.)
  • As hospitals close their incinerators, biohazardous and sometimes (inadvertently) hazardous wastes are being hauled significant distances to centralized facilities for treatment and disposal.

All of these changes represent new challenges in continuing efforts to properly define, classify, regulate and manage medical wastes.


Mercury is a metal with chemical similarities to zinc and cadmium. The metal is liquid at room temperature, with a freezing point at –31°C, and it is one of the most volatile metals. It occurs as the element Hg0 and as the mercuric ion Hg++, which has a great affinity for reduced sulfur (sulfide, S=).

Most mercury ore deposits consist of the very insoluble mineral cinnabar (HgS), with little droplets of elemental Hg. Mercury also occurs as impurities in many other ore minerals, creating mercury contamination when these minerals are mined or processed. Most common rocks have very low Hg contents, about ten to one hundred parts per billion (ppb) Hg .

Elemental mercury is barely soluble in pure water, with only twenty-five ppb Hg dissolving at room temperature, but it is more soluble at higher temperatures. The mercuric ion is very soluble in most ambient waters, but very insoluble in the presence of sulfide. Natural enrichments of mercury occur in and around ore deposits and in geothermal hot spring areas and volcanoes.

Bacteria in coastal waters convert inorganic Hg ions back into the elemental state, which then evaporate from the water back into the atmosphere. The physical transport of mercury from ore regions and the vapor transport from geothermal areas and the oceans provide the natural background contamination of mercury.

Mercury is a toxic element that damages the human nervous system and brain. Elemental mercury is less dangerous when it is ingested than when it is inhaled. The use of mercury in felt-making led to widespread elemental mercury poisoning of hatmakers (“mad as a hatter”), which was expressed by tremor, loss of hair and teeth, depression, and occasional death. The organic forms of mercury—methylmercury compounds, CH3Hg+ and (CH3)2Hg— are very bioavailable or are easily taken up by living organisms and rapidly enter cells, and are therefore the most hazardous.

Minamata disease was an episode of mercury poisoning of a small coastal community in Japan (1954) through the direct industrial release of methylmercury in the bay. Another infamous episode of mercury contamination occurred in Iraq, where people ate wheat that was treated with a mercury-containing fungicide.

The continuous flux of mercury from the atmosphere results in the low level of mercury pollution nationwide. A small fraction of the Hg++ from atmospheric deposition is converted by bacteria into the very dangerous methylmercury form. The methylmercury is then taken up by the lowest life forms and makes its way up the food chain and bioaccumulates in the larger fish.

As a result, large predator fish such as bass, tuna, shark, and swordfish have the highest levels of Hg in the methylmercury form. Most states in the United States have advisories for eating only limited amounts of freshwater fish. Limiting intake of mercury-contaminated fish is especially important for pregnant women and young children. The current U.S. legal limit for Hg in fish for consumption is 1 ppm.

Limits for Hg in soils vary from state to state but generally range from 10 to 20 ppm, whereas the Environmental Protection Agency’s limit for drinking water is 2 ppb Hg. The Occupational Safety and Health Administration limits for Hg in the air in the workplace (for an eight hour average) are 0.01 mg organic Hg/m3 air.

Modern sources of mercury contamination from human activities are subdivided into the following groups:
  1. High-temperature combustion processes such as coal-fired power plants, incineration of solid household waste, medical waste, sewage sludge, and ore smelting.
  2. Industrial waste effluents, such as from chlor-alkali plants that use liquid mercury as electrodes.
  3. Effluents of wastewater treatment plants.
  4. Point sources of specific industries, many of them no longer active today (such as hat making, explosives, mercury lights, herbicides, and plastics).

An overview of modern anthropogenic Hg fluxes into the environment shows that more than 80 percent of mercury is injected into the atmosphere through such combustion processes as coal-fired power plants.

The combustion releases mercury as elemental vapor into the atmosphere, where it has an average residence time of about one year before it is oxidized to the mercuric form. The oxidized mercury attaches itself to small dust particles and is removed by wet and dry atmospheric deposition.

As a result of this massive injection of Hg into the atmosphere—more than 100 tons of Hg per year in the United States in the late 1990s—the contaminant is distributed all over the globe. Even the polar ice caps show evidence of mercury contamination over the last 150 years, from atmospheric dispersal and deposition from anthropogenic sources. There are almost no places on earth that are not contaminated by anthropogenic mercury.

Mercury contamination is a matter of ongoing concern, and an extensive study was done for the U.S. Congress to summarize the sources, pathways, and sinks of mercury in the outdoor environment. There are several initiatives to limit the anthropogenic flux of Hg from coal-fired power plants, such as switching to mercury-poor coals and scrubbing the stack gases.

Limiting or banning the production of mercury-containing materials, including switches, thermometers, thermostats, and manometers, both in the household as well as in the medical profession, would also reduce the mercury recycled back into the atmosphere from garbage incineration.


Modern mining is an industry that involves the exploration for and removal of minerals from the earth, economically and with minimum damage to the environment. Mining is important because minerals are major sources of energy as well as materials such as fertilizers and steel.

Mining is necessary for nations to have adequate and dependable supplies of minerals and materials to meet their economic and defense needs at acceptable environmental, energy, and economic costs. Some of the nonfuel minerals mined, such as stone, which is a nonmetallic or industrial mineral, can be used directly from the earth. Metallic minerals, which are also nonfuel minerals, conversely, are usually combined in nature with other materials as ores.

These ores must be treated, generally with chemicals or heat to produce the metal of interest. Most bauxite ore, for example, is converted to aluminum oxide, which is used to make aluminum metal via heat and additives. Fuel minerals, such as coal and uranium, must also be processed using chemicals and other treatments to produce the quality of fuel desired.

There are significant differences in the mining techniques and environmental effects of mining metallic, industrial, and fuel minerals. The discussion here will mostly concentrate on metallic minerals. Mining is a global industry, and not every country has high-grade, large, exceptionally profitable mineral deposits, and the transportation infrastructure to get the mined products to market economically.

Some of the factors affecting global mining are environmental regulations, fuel costs, labor costs, access to land believed to contain valuable ore, diminishing ore grades requiring the mining of more raw materials to obtain the target mineral, technology, the length of time to obtain a permit to mine, and proximity to markets, among others. The U.S. mining industry is facing increasing challenges to compete with nations that have lower labor costs—for example, less stringent environmental regulations and lower fuel costs.

Mining Life Cycle

Minerals are a nonrenewable resource, and because of this, the life of mines is finite, and mining represents a temporary use of the land. The mining life cycle during this temporary use of the land can be divided into the following stages: exploration, development, extraction and processing, and mine closure.

Exploration is the work involved in determining the location, size, shape, position, and value of an ore body using prospecting methods, geologic mapping and field investigations, remote sensing (aerial and satellite-borne sensor systems that detect ore-bearing rocks), drilling, and other methods. Building access roads to a drilling site is one example of an exploration activity that can cause environmental damage.

The development of a mine consists of several principal activities: conducting a feasibility study, including a financial analysis to decide whether to abandon or develop the property; designing the mine; acquiring mining rights; filing an Environmental Impact Statement (EIS); and preparing the site for production. Preparation could cause environmental damage by excavation of the deposit to remove overburden (surface material above the ore deposit that is devoid of ore minerals) prior to mining.

Extraction is the removal of ore from the ground on a large scale by one or more of three principal methods: surface mining, underground mining, and in situ mining (extraction of ore from a deposit using chemical solutions). After the ore is removed from the ground, it is crushed so that the valuable mineral in the ore can be separated from the waste material and concentrated by flotation (a process that separates finely ground minerals from one another by causing some to float in a froth and others to sink), gravity, magnetism, or other methods, usually at the mine site, to prepare it for further stages of processing.

The production of large amounts of waste material (often very acidic) and particulate emission have led to major environmental and health concerns with ore extraction and concentration. Additional processing separates the desired metal from the mineral concentrate.

The closure of a mine refers to cessation of mining at that site. It involves completing a reclamation plan and ensures the safety of areas affected by the operation, for instance, by sealing the entrance to an abandoned mine.

Planning for closure is often required to be ongoing throughout the life cycle of the mine and not left to be addressed at the end of operations. The Surface Mining and Control Act of 1977 states that reclamation must “restore the land affected to a condition capable of supporting the uses which it was capable of supporting prior to any mining, or higher or better uses.”

Abandoned mines can cause a variety of health-related hazards and threats to the environment, such as the accumulation of hazardous and explosive gases when air no longer circulates in deserted mines and the use of these mines for residential or industrial dumping, posing a danger from unsanitary conditions. Many closed or abandoned mines have been identified by federal and state governments and are being reclaimed by both industry and government.

Environmental Impacts

The environmental responsibility of mining operations is protection of the air, land, and water. Mineral resources were developed in the United States for nearly two centuries with few environmental controls. This is largely attributed to the fact that environmental impact was not understood or appreciated as it is today. In addition, the technology available during this period was not always able to prevent or control environmental damage.

All methods of mining affect air quality. Particulate matter is released in surface mining when overburden is stripped from the site and stored or returned to the pit. When the soil is removed, vegetation is also removed, exposing the soil to the weather, causing particulates to become airborne through wind erosion and road traffic. Particulate matter can be composed of such noxious materials as arsenic, cadmium, and lead. In general, particulates affect human health adversely by contributing to illnesses relating to the respiratory tract, such as emphysema, but they also can be ingested or absorbed into the skin.

Mining can cause physical disturbances to the landscape, creating eyesores such as waste-rock piles and open pits. Such disturbances may contribute to the decline of wildlife and plant species in an area. In addition, it is possible that many of the premining surface features cannot be replaced after mining ceases. Mine subsidence (ground movements of the earth’s surface due to the collapse of overlying strata into voids created by underground mining) can cause damage to buildings and roads.

Between 1980 and 1985, nearly five hundred subsidence collapse features attributed to abandoned underground metal mines were identified in the vicinity of Galena, Kansas, where the mining of lead ores took place from 1850 to 1970. The entire area was reclaimed in 1994 and 1995.

Water-pollution problems caused by mining include acid mine drainage, metal contamination, and increased sediment levels in streams. Sources can include active or abandoned surface and underground mines, processing plants, waste-disposal areas, haulage roads, or tailings ponds. Sediments, typically from increased soil erosion, cause siltation or the smothering of streambeds. This siltation affects fisheries, swimming, domestic water supply, irrigation, and other uses of streams.

Acid mine drainage (AMD) is a potentially severe pollution hazard that can contaminate surrounding soil, groundwater, and surface water. The formation of acid mine drainage is a function of the geology, hydrology, and mining technology employed at a mine site. The primary sources for acid generation are sulfide minerals, such as pyrite (iron sulfide), which decompose in air and water. Many of these sulfide minerals originate from waste rock removed from the mine or from tailings.

If water infiltrates pyrite-laden rock in the presence of air, it can become acidified, often at a pH level of two or three. This increased acidity in the water can destroy living organisms, and corrode culverts, piers, boat hulls, pumps, and other metal equipment in contact with the acid waters and render the water unacceptable for drinking or recreational use. A summary chemical reaction that represents the chemistry of pyrite weathering to form AMD is as follows:
Pyrite + Oxygen + Water → “Yellowboy” + Sulfuric Acid

“Yellowboy” is the name for iron and aluminum compounds that stain streambeds. AMD can enter the environment in a number of ways, such as free-draining piles of waste rock that are exposed to intense rainstorms, transporting large amounts of acid into nearby rivers; groundwaters that enter underground workings which become acidic and exit via surface openings or are pumped to the surface; and acidic tailings containment ponds that may leach into surrounding land.

Mold Pollution

Mold pollution is the growth of molds in a building resulting in damage to or the destruction of the structure itself (or its contents) and adverse health effects on the building’s occupants. It is estimated that about 10 percent of U.S. buildings may suffer from mold pollution.

Molds, also known as fungi, are microorganisms that generally have threadlike bodies called mycelium and reproduce by producing spores. Spores are generally round or ovoid single cells (but in some cases are multicellular). Spores can be colorless or pigmented and vary in size. While a human hair is approximately one hundred microns in diameter, spore size ranges from one to five microns.

There are about fifty to one hundred different molds typically found growing indoors in water-damaged buildings. Water problems in buildings are generally the result of leaks from roofs or plumbing, condensation, and flooding. When building materials or furnishings such as wood, drywall, ceiling tiles, or carpets become wet, causing molds to grow on them.

The types of substrates and the amount of moisture will often determine the kinds of molds that grow. For example, some molds like Stachybotrys require a highly water-saturated substrate. For other molds such as Aspergillus, only small amounts of excess moisture are necessary for growth. Thus, moisture control is key to controlling mold growth and eliminating their effects on the building or its occupants.

Mold growth can cause structural integrity problems in buildings constructed of wood. This generally goes under the misnomer of dry rot. The dry rot molds, like Merulis lacrymans, are the natural decomposers of leaves, stems, and trees in nature. If structural wood in buildings becomes wet, these molds may grow. The name dry rot comes from the powdery residue that is left after the wood is destroyed. Wood can be protected by the use of chemicals like creosote or by the use of sealants.

Mold pollution in buildings may result in adverse health effects including infections, allergies, and asthma. Bleeding, memory loss, and a condition known as sick building syndrome may also result from mold pollution, but such health effects remain controversial. Epidemiological studies have linked molds to these conditions; however, a direct causal relationship has not been established.

When health effects from molds occur, it is generally as a result of inhaling mold spores. For example, aspergillosis is an infection of the lungs caused by some species of Aspergillus, which can result in difficulty breathing. If left untreated, it can spread through the bloodstream to other organs, resulting in death. It is probably the most common type of building-acquired infection.

Individuals with impaired immune systems are most susceptible to this infection. Mold infections can be acquired in health care facilities (nosocomial infections). Careful attention to removing spores from the air and water may be the best method to protect the public from these kinds of infections.

Occasionally, mold infections result from animals and birds inhabiting buildings. For example, bats or pigeons may deposit guano containing such molds as Histoplasma capsulatum and Cryptococcus neoformans. Disturbing this guano without respiratory protection can result in infection. The best defense against this kind of mold pollution is to keep these creatures out of the building.

In addition to infections, allergic diseases are associated with mold pollution. Asthma is the most common chronic disease of childhood and is the leading causes of school absenteeism, accounting for over ten million missed school days per year.

For most elementary school children with asthma, allergens are the primary trigger for asthma, and their disease is thought to result from early exposure and sensitization to common allergens in their environment (e.g., dust mites, cockroaches, and molds). To prevent allergic disease, excessive mold growth must be controlled or eliminated.

The elimination of molds from structures requires first that water problems be corrected. Then, the mold-infested material must be removed using proper protection. In some cases, heavily mold-infested structures have had to be demolished or burned. In order to make the best decision on how to treat a mold-polluted structure, it is important to understand what molds are present and in what amount.

A mycologist (scientist who studies molds) can often identify and count mold spores collected from indoor air, dust, or surfaces either by culturing them or by observing them under a microscope. However, these are slow and difficult processes.

In order for mycologists to improve their knowledge about molds in the indoor environment, mold DNA (i.e., moldgenomes) are being sequenced. Sequencing of DNA is the process of deciphering the spelling of the DNA alphabet that makes each organism unique.

Like the sequencing of the human genome, this knowledge of mold genomes allows molecular biologists to develop easier and faster methods for the detection and quantification of molds. This is important because all molds in the indoor environment cannot be eliminated. If molds can be monitored, experts can find out when mold concentrations are at dangerous levels. Measures can then be taken to reduce the mold pollution in the environment.

Noise Pollution

Noise pollution is the intrusion of unwanted, uncontrollable, and unpredictable sounds, not necessarily loud, into the lives of individuals of reasonable sensitivities. Using the “reasonable person” standard removes the notion that the judgment of sounds as unwanted is subjective.

Unwanted sounds or noises can be traced back to Old Testament stories of very loud music and barking dogs as well as to ancient Rome where city residents complained about noisy delivery wagons on their cobblestone streets. The Industrial Revolution, the growth of cities, and the demand for transportation made the world even noisier.

With the modern world so dependent on and enchanted with noise-producing and noise-related technology—automobiles, aircraft, helicopters, motorcycles, snowmobiles, jet skis, leaf blowers, amplified music, bass-driven car stereo systems—the ambient noise level is rapidly accelerating. This growth in noise has led to research examining the impact of noise on the lives and activities of reasonable people. The result has been a body of evidence that strongly suggests noise is hazardous to good mental and physical health.

To understand noise, one must know something about sound and how loudness is measured. Sound that travels through the air in waves has two major properties: the frequency or speed at which the waves vibrate and the intensity of each vibration. It is the intensity, or how many molecules are packed together with each vibration, that for the most part produces the sense of loudness, although frequency also contributes to the determination of loudness, with higher-pitched sounds sounding louder.

Loudness is measured by a decibel scale (expressed as dB), but to reflect human hearing more accurately a modified version of this scale, known as the A scale, has been developed. On the A scale, loudness is measured in dBAs.

The scale increases logarithmically so that an increase of 10 dB indicates a doubling of loudness, and an increase of 20 dB represents a sound that is four times louder. Whispers measure 20 dBA, normal conversation 50 to 60 dBA, shouting 85 dBA, and loud music over 120 dBA. Continuous exposure to sounds over 85 dBA may cause permanent hearing loss.

Exposure to very loud sounds that are enjoyable, and not technically noise to the listener, can lead to hearing impairment. Because many people, especially young children and teenagers, are not aware of the dangers of very loud sounds to their hearing, they should be warned that playing computer games with loud audio attachments, setting headsets at consistently high volume, or regularly playing ball in a loud gymnasium may affect their hearing over time. A survey of hearing threshold shifts among youngsters between the ages of six and nineteen found that one out of eight of them suffered a noise-related hearing problem.

Children attending loud movies and sporting events, or visiting video arcades may be unwittingly exposing themselves to dangerously loud sounds. Teenagers are especially vulnerable as they are more likely to equip their cars with high-powered “boom boxes,” attend loud dance clubs, and work in noisy fast-food restaurants.

Sounds need not be very loud to be deemed intrusive—for example, the drip of a faucet, an overhead jet, or a neighbor’s stereo late at night. Noises are especially bothersome at night when one is trying to sleep, and a good night’s sleep is vital to good health. Exposure to bothersome noises over time can be stressful, resulting in adverse health effects, such as hypertension. Although more research is needed to solidify a noise and health link, there is agreement that noise lessens the quality of life.

Noises can be especially harmful to children. Scientific research indicates that noisy homes slow down cognitive and language development in young children. In addition, children living and attending schools near noisy highways, railroads, and airports have lower reading scores, and some children living or attending a school near a major airport have experienced elevated blood pressure.

In 1972 the U.S. government passed legislation recognizing the growing danger of noise pollution. It empowered the Office of Noise Abatement and Control (ONAC) within the Environmental Protection Agency (EPA) to curtail noise levels, but by 1982, during the Reagan administration, the office lost most of its funding.

States and cities were no longer supported in their efforts to abate noise, and ONAC no longer published materials educating people on the dangers of noise. Recently, the federal government has passed legislation to lessen noise in national parks, for example, banning snowmobiles, but states and cities are on their own in controlling noise, with some cities more successful than others.

Traffic noise, especially aircraft noise, is the major source of annoyance calling for better federal regulation within the United States. In contrast, the European Union is finalizing a noise directive that will require member states to produce noise maps and develop action plans to reduce noise levels.

Noise from snowmobiles, jet skis, and supersonic jets has also intruded on the environment, affecting animals’ abilities to communicate, protect their young, and mate. Worldwide, antinoise groups believe their governments are doing too little to lessen the surrounding din, and groups from the United States, Europe, Canada, Australia, Africa, and Asia have joined together to educate both the public and governments about the long-term dangers of noise pollution, urging them to lower the decibel level. A quieter, healthier environment is within our grasp.

Nonpoint Source Pollution

Nonpoint source pollution occurs when rainfall or snowmelt runs over land or through the ground, picks up pollutants, and deposits them into rivers, lakes, wetlands, and coastal waters or introduces them into groundwater. Some of the primary activities that generate nonpoint source pollution include farming and grazing activities, timber harvesting, new development, construction, and recreational boating.

Manure, pesticides, fertilizers, dirt, oil, and gas produced by these activities are examples of nonpoint source pollutants. Even individual households contribute to nonpoint source pollution through improper chemical and pesticide use, landscaping, and other house-hold practices.

After Congress passed the Clean Water Act in 1972, the water-quality community within the United States placed a primary emphasis on addressing and controlling point source pollution (pollution coming from discrete conveyances or locations, such as industrial and municipal waste discharge pipes). Not only were these sources the primary contributors to the degradation of U.S. waters at the time, but the extent and significance of nonpoint source pollution were also poorly understood and overshadowed by efforts to control pollution from point sources.

At the beginning of the twenty-first century, nonpoint source pollution stands as the primary cause of water-quality problems within the United States. According to the National Water Quality Inventory (published by the U.S. Environmental Protection Agency), it is the main reason that approximately 40 percent of surveyed rivers, lakes, and estuaries are not clean enough to meet basic uses such as fishing or swimming.

Leading Contributors to Nonpoint Source Pollution

States and other jurisdictions reported in the National Water Quality Inventory that agriculture and urban runoff are among the leading contributors to deteriorating water quality nationwide. The most common nonpoint source pollutants causing water-quality problems include nutrients (nitrogen and phosphorus), siltation (soil particles), metals, and pathogens (bacteria and viruses).

Agriculture is identified as the leading source of degradation of polluted rivers, streams, and lakes surveyed by states, territories, and tribes in the National Water Quality Inventory. Agricultural activities that result in nonpoint source pollution include concentrated animal feeding operations (CAFOs), grazing, plowing, pesticide spraying, irrigation, fertilizing, planting, and harvesting.

A major nonpoint source pollutant from these activities is an excess of nutrients, which can occur through applications of crop fertilizers and manure from animal production facilities. Excessive nutrients may overstimulate the growth of aquatic weeds and algae, depleting the oxygen available for a healthy aquatic community.

Hydromodification that alters the flow of water is the second leading source of damage to U.S. rivers, streams, and lakes, according to the same National Water Quality Inventory report. Examples of hydromodification projects include channelization, dredging, and construction of dams.

Excess sediment due to erosion caused by projects such as building dams can severely alter aquatic communities by clogging fish gills or suffocating eggs. Sediment may also carry other pollutants into water bodies (e.g., PCBs or mercury) which can accumulate in aquatic species, leading to fish consumption advisories.

Habitat modification is identified as the third-largest source of water pollution in surveyed rivers and streams in the National Water Quality Inventory. Habitat modification occurs when the vegetation along stream banks is removed, diminishing buffers that help filter runoff and provide shade for the adjacent water body. These modifications can result in an increase in the water temperature (because of less shade) and an increase in quantity and velocity of runoff, making the river or stream less suitable for the organisms inhabiting it.

Runoff from urban areas is the fourth-largest source of water pollution in rivers and streams and the third-largest source of water pollution in lakes, according to the National Water Quality Inventory. Increased urban development brings additional roads, bridges, buildings, and parking lots, which can result in large amounts of runoff that quickly and easily drain into rivers and lakes. In contrast, the porous and varied terrain of natural landscapes like forests, wetlands, and grasslands traps rainwater and snowmelt and allows it to filter slowly into the ground.

Urban runoff transports a variety of pollutants, including sediment from new development; oil, grease, and toxic chemicals from vehicles; and nutrients and pesticides from turf management and gardening. It can also carry pathogenic bacteria and viruses released from failing septic systems and inadequately treated sewage, which can result in closed beaches and shellfish beds, contaminated drinking water sources, and even severe human illness.

Programs for Nonpoint Source Control

The United States has made significant progress in addressing nonpoint source pollution since Congress amended the Clean Water Act in 1987 to establish a national program for controlling nonpoint source pollution. Under section 319 of the Clean Water Act, states adopted management programs to control nonpoint source pollution, and since 1990 the EPA has awarded grants to states to assist them in implementing those management programs.

Other federal agencies also provide technical and financial support through grants and loans to states, local communities, and farmers and other landowners, to implement nonpoint source pollution controls. In addition, many state and local entities are dedicating increasing amounts of funding to control nonpoint source pollution.

State nonpoint source programs provide for the control of nonpoint source pollution primarily through best management practices (BMPs), which are on-the-ground technical controls used to prevent or reduce nonpoint source pollution.

Common practices used to control nutrients from agriculture include altering fertilizer and pesticide application methods and storing and properly managing manure from confined animal facilities. Developing a buffer of vegetation between the land and the stream bank can help filter all types of nonpoint source pollutants from entering a receiving water body, including sediment transported by overland flow.

Stream-bank protection and channel stabilization practices are also very effective in preventing sediment deposition in the water by limiting the bank erosion processes and streambed degradation. Urban runoff can be controlled by establishing trenches, basins, and detention ponds at construction sites to hold, settle, and retain suspended solids and associated pollutants.

Basic pollution-prevention measures introduced around the home can also prevent nonpoint source pollutants from entering storm water. Practices include the proper storage, use, and disposal of household hazardous chemicals; proper operation and maintenance of onsite disposal systems; and even proper disposal of pet waste so that it does not wash into storm drains.

Watershed Approach to Managing Nonpoint Source Pollution

Nonpoint source pollution derives from many different sources over large geographic areas so regulating and controlling it are challenging. The watershed approach to managing nonpoint source pollution, however, is proving to be an effective technique. Everyone lives in a watershed, or an area of land in which all water drains.

According to the U.S. Geological Survey, the nation can be divided into approximately 2,149 medium-sized watersheds, averaging about 1,700 square miles in each area. The watershed approach relies on coordinating all relevant federal, state, and local government agencies, and the stakeholders who live in a particular watershed, to help solve priority problems in that watershed.

Historically, many water-quality problems were addressed piecemeal in individual water bodies by individual entities, usually limited by political, social, and economic boundaries. The watershed approach, however, relies on the coordination of all entities and stakeholders to help solve the watershed’s most serious environmental problems, which in many instances are caused by nonpoint source pollution.

International Implications

Managing nonpoint source pollution is an international challenge. Like the United States, many developed countries initially directed resources toward controlling point source pollution. However, significant nonpoint source problems remain, especially resulting from an excess of nutrients and sediment in water bodies. The United Nations Environment Programme has identified increased nitrogen loadings, resulting mainly from agricultural runoff and wastewater, as one of the most serious water-quality issues affecting all countries.

Sedimentation is a significant concern for other countries, frequently resulting from deforestation or clear cutting for fuelwood, or agricultural practices. One of the largest threats in developing countries relates to problems with sewage control, either through poor maintenance of sewage collection systems or a lack of it, leading to severe waterborne diseases.

The increasing world population promises even more challenges for managing nonpoint source pollution. Some international communities are embracing integrated solutions (like the watershed approach) to reduce it. Agenda 21 adopted at the United Nations Conference on Environment and Development in 1992 is but one example.

Ocean Dumping

Ocean disposal of society’s waste got its start indirectly long before the Agricultural Age when nearby streams, lakes, and estuaries were useful as waste repositories. As civilization moved to the coastal zone and navigation began in earnest, the oceans were viewed as even a larger waste repository.

Early civilizations were located adjacent to bodies of water for sources of food, irrigation, drinking water, transportation, and a place to dispose of unnecessary items. Historically, the disposal of wastes into water by humans was universally practiced.

It was a cheap and convenient way to rid society of food wastes (e.g., cleaned carcasses, shells, etc.), trash, mining wastes, and human wastes (or sewage). The advent of the Industrial Age brought with it the new problem of chemical wastes and by-products: These were also commonly disposed of in the water.

Early dumping started in rivers, lakes, and estuaries, whereas ocean dumping was simply not used because of the distance and difficulty in transporting waste materials. The wastes from ships, however, were simply dumped directly into the ocean.

As civilization developed at river deltas and in estuaries adjacent to the ocean, and these areas soon began to display the effects of dumping, disposal in the ocean became a popular alternative. Over the past 150 years, all types of wastes have been ocean dumped.

These include sewage (treated and untreated), industrial waste, military wastes (munitions and chemicals), entire ships, trash, garbage, dredged material, construction debris, and radioactive wastes (both high- and low-level). It is important to note that significant amount of wastes enter the ocean through river, atmospheric, and pipeline discharge; construction; offshore mining; oil and gas exploration; and shipboard waste disposal. Unfortunately, the ocean has become the ultimate dumping ground for civilization.

It has been recognized over the past fifty years that the earth’s oceans are under serious threat from these wastes and their “witches’ brew” of chemicals and nonbiodegradable components. Society has also come to understand that its oceans are under serious threat from overfishing, mineral exploration, and coastal construction activities.

The detrimental effects of ocean dumping are physically visible at trashed beaches, where dead fish and mammals entangled in plastic products may sometimes be observed. They are additionally reflected in the significant toxic chemical concentrations in fish and other sea life. The accumulations of some toxins, especially mercury, in the bodies of sea life have resulted in some harvestable seafood unfit for human consumption.

Seriously affected areas include commercial and recreational fishing, beaches, resorts, human health, and other pleasurable uses of the sea. During the 1960s numerous groups (global, regional, governmental, and environmental) began to report on the detrimental impact of waste disposal on the ocean. Prior to this time, few regulatory (or legal) actions occurred to control or prevent these dumping activities.


Ozone is a gas found in the atmosphere in very trace amounts. Depending on where it is located, ozone can be beneficial (“good ozone”) or detrimental (“bad ozone”). On average, every ten million air molecules contains only about three molecules of ozone.

Indeed, if all the ozone in the atmosphere were collected in a layer at Earth’s surface, that layer would only have the thickness of three dimes. But despite its scarcity, ozone plays very significant roles in the atmosphere. In fact, ozone frequently “makes headlines” in the newspapers because its roles are of importance to humans and other life on Earth.

What Is Ozone?

Chemically, the ozone molecule consists of three atoms of oxygen arranged in the shape of a wide V. Its formula is O3 (the more familiar form of oxygen that one breathes has only two atoms of oxygen and a chemical formula of O2). Gaseous ozone is bluish in color and has a pungent, distinctive smell. In fact, the name ozone is derived from the Greek word ozein, meaning “to smell or reek.”

The smell of ozone can often be noticed near electrical transformers or nearby lightning strikes. It is formed in these instances when an electrical discharge breaks an oxygen molecule (O2) into free oxygen atoms (O), which then combine with O2 in the air to make O3. In addition to its roles in the atmosphere, ozone is a chemically reactive oxidizing agent that is used as an air purifier, a water sterilizer, and a bleaching agent.

Where Is Ozone Found in the Atmosphere?

Ozone is mainly found in the two regions of the atmosphere that are closest to the earth’s surface. About 10 percent of the atmosphere’s ozone is in the lowest-lying atmospheric region, the troposphere. This ozone is formed in a series of chemical reactions that involve the interaction of nitrogen oxides, volatile organic compounds, and sunlight.

Most ozone (about 90%) resides in the next atmospheric layer, the stratosphere. The stratosphere begins between 8 and 18 kilometers (5 and 11 miles) above the earth’s surface and extends up to about 50 kilometers (30 miles).

The ozone in this region is commonly known as the ozone layer. Stratospheric ozone is formed when the sun’s ultraviolet (UV) radiation breaks apart molecular oxygen (O2) to form O atoms, which then combine with O2 to make ozone. Note that this formation mechanism differs from the one mentioned above for ozone in the lower atmosphere.

What Roles Does Ozone Play in the Atmosphere and How Are Humans Affected?

The ozone molecules in the stratosphere and the troposphere are chemically identical. However, they have very different roles in the atmosphere and very different effects on humans and other living beings, depending on their location.

A useful statement summarizing ozone’s different effects is that it is “good up high, bad nearby.” In the upper atmosphere, stratospheric ozone plays a beneficial role by absorbing most of the sun’s biologically damaging ultraviolet sunlight (called UV-B), allowing only a small amount to reach the earth’s surface.

The absorption of ultraviolet radiation by ozone creates a source of heat, which actually defines the stratosphere (a region in which the temperature rises as one goes to higher altitudes). Ozone thus plays a key role in the temperature structure of the earth’s atmosphere. Without the filtering action of the ozone layer, more of the sun’s UV-B radiation would penetrate the atmosphere and reach the earth’s surface.

Many experimental studies of plants and animals and clinical studies of humans have shown that excessive exposure to UV-B radiation has harmful effects. Serious long-term effects can include skin cancers and eye damage. The UV-absorbing role of stratospheric ozone is what lies behind the expression that ozone is “good up high.”

In the troposphere, ozone comes into direct contact with life-forms. Although some amount of ozone is naturally present in the lower atmosphere, excessive amounts of this lower-atmospheric ozone are undesirable (or bad ozone).

This is because ozone reacts strongly with other molecules, including molecules that make up the tissues of plants and animals. Several studies have documented the harmful effects of excessive ozone on crop production, forest growth, and human health. For example, people with asthma are particularly vulnerable to the adverse effects of ozone. Thus, ozone is “bad nearby.”

What Are the Environmental Issues Associated with Ozone?

The dual role of ozone links it to two separate environmental issues often seen in the newspaper headlines. One issue relates to increases in ozone in the troposphere (the bad ozone mentioned above). Human activities that add nitrogen oxides and volatile organic compounds to that atmosphere, such as the fossil fuel burning associated with power-generating plants and vehicular exhaust, are contributing to the formation of larger amounts of ozone near the earth’s surface.

This ozone is a key component of photochemical smog, a familiar problem in the atmosphere of many cities around the world. Higher amounts of surface-level ozone are increasingly being observed in rural areas as well. Thus, the environmental issue is that human activities can lead to more of the bad ozone.

The second environmental issue relates to the loss of ozone in the stratosphere. Ground-based and satellite instruments have measured decreases in the amount of stratospheric ozone in our atmosphere, which is called ozone-layer depletion. The most extreme case occurs over some parts of Antarctica, where up to 60 percent of the total overhead amount of ozone (known as the column ozone) disappears during some periods of the Antarctic spring (September through November). This phenomenon, which has been occurring only since the early 1980s, is known as the Antarctic ozone hole.

In the arctic polar regions, similar processes occur that have also led to significant chemical depletion of the column ozone during late winter and spring in many recent years. Arctic ozone loss from January through late March has been typically 20 to 25 percent, and shorter-period losses have been higher, depending on the meteorological conditions encountered in the Arctic stratosphere.

Smaller, but nevertheless significant, stratospheric ozone decreases have been seen at other, more populated latitudes of the earth, away from the polar regions. Instruments on satellites and on the ground have detected higher amounts of UV-B radiation at the earth’s surface below areas of depleted ozone.

What Human Activities Affect the Stratospheric Ozone Layer?

Initially, theories about the cause of ozone-layer depletion abounded. Many factors were suggested, from the sun to air motions to human activity. In the 1970s and 1980s, the scientific evidence showed conclusively that human-produced chemicals are responsible for the observed depletions of the ozone layer.

The ozone-depleting compounds contain various combinations of carbon with the chemical elements chlorine, fluorine, bromine, and hydrogen (the halogen family in the periodic table of the elements). These are often described by the general term halocarbons. The compounds include chlorofluorocarbons (CFCs which are used as refrigerants, foam-blowing agents, electronics cleaners, and industrial solvents) as well as halons (which are used in fire extinguishers).

The compounds are useful and benign in the troposphere, but when they eventually reach the stratosphere, they are broken apart by the sun’s ultraviolet radiation. The chlorine and bromine atoms released from these compounds are responsible for the breakdown of stratospheric ozone.

The ozone destruction cycles are catalytic, meaning that the chlorine or bromine atom enters the cycle, destroys ozone, and exits the cycle unscathed and therefore able to destroy another ozone molecule. In fact, an individual chlorine atom can destroy as many as 10,000 different ozone molecules before the chlorine atom is removed from the stratosphere by other reactions.

What Actions Have Been Taken to Protect the Ozone Layer?

Research on ozone depletion advanced very rapidly in the 1970s and 1980s, leading to the identification of CFCs and other halocarbons as the cause. Governments and industry acted quickly on the scientific information.

Through a 1987 international agreement known as the Montréal Protocol on Substances That Deplete the Ozone Layer, governments decided to eventually discontinue production of CFCs (known in the United States by the industry trade name “Freons”), halons, and other halocarbons (except for a few special uses). Concurrently, industry developed more ozone-friendly substitutes for the CFCs and other ozone-depleting halocarbons.

If nations adhere to international agreements, the ozone layer is expected to recover by the year 2050. The interaction of science in identifying the problem, technology in developing alternatives, and governments in devising new policies is thus an environmental “success story in the making.” Indeed, the Montréal Protocol serves as a model for other environmental issues now facing the global community.

What Actions Have Been Taken to Reduce the Amount of Ozone at Ground Level?

Ozone pollution at the earth’s surface is formed within the atmosphere by the interaction of sunlight with chemical precursor compounds (or starting ingredients): the nitrogen oxides (NOx) and volatile organic compounds (VOCs). In the United States, the efforts of the Environmental Protection Agency (EPA) to reduce ozone pollution are therefore focused on reducing the emissions of the precursor compounds.

VOCs, a primary focus of many regulations, arise from the combustion of fossil fuel and from natural sources (emissions from forests). Increasingly, attention is turning to reducing the emissions of NOx compounds, which also arise from the combustion of fossil fuels.

The use of cleaner fuels and more efficient vehicles has caused a reduction in the emission of ozone precursors in urban areas. This has led to a steady decline in the number and severity of episodes and violations of the one-hour ozone standard established by the U.S. Environmental Protection Agency (EPA) (which is 120 parts per billion or ppb, meaning that out of a billion air molecules, 120 are ozone).

In 1999 there were thirty-two areas of the country that were in violation of the ozone standard, down from 101 just nine years earlier. Despite these improvements, ground-level ozone continues to be one of the most difficult pollutants to manage.

An additional, more stringent ozone standard proposed by the EPA to protect public health Agency (EPA) to reduce ozone pollution are therefore focused on reducing the emissions of the precursor compounds. VOCs, a primary focus of many regulations, arise from the combustion of fossil fuel and from natural sources (emissions from forests). Increasingly, attention is turning to reducing the emissions of NOx compounds, which also arise from the combustion of fossil fuels.

The use of cleaner fuels and more efficient vehicles has caused a reduction in the emission of ozone precursors in urban areas. This has led to a steady decline in the number and severity of episodes and violations of the one-hour ozone standard established by the U.S. Environmental Protection Agency (EPA) (which is 120 parts per billion or ppb, meaning that out of a billion air molecules, 120 are ozone).

In 1999 there were thirty-two areas of the country that were in violation of the ozone standard, down from 101 just nine years earlier. Despite these improvements, ground-level ozone continues to be one of the most difficult pollutants to manage.

An additional, more stringent ozone standard proposed by the EPA to protect public health, eighty ppb averaged over eight hours, was cleared in early 2001 for implementation in the United States. For comparison, Canada’s standard is sixty-five ppb averaged over eight hours. SEE ALSO Air Pollution; Asthma;eighty ppb averaged over eight hours, was cleared in early 2001 for implementation in the United States. For comparison, Canada’s standard is sixty-five ppb averaged over eight hours.

Persistent Organic Pollutants (POPs)

Persistent organic pollutants (POPs) are a subset of the more comprehensive term persistent bioaccumulative and toxic chemicals (PBTs). POPs commonly stands for organic (carbon-based) chemical compounds and mixtures that share four characteristics.

They are semivolatile, stable under environmental conditions (half-lives of years to decades), fat-soluble, and possess the potential for adverse effects in organisms. Many POPs are organochlorine compounds.

Among the twelve priority POPs defined by the United Nations Environmental Programme (and referred to as the “dirty dozen”) are the pesticides aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, mirex, and toxaphene (chlorobornanes); the industrial chemicals polychlorinated biphenyls (PCBs) and hexachlorobenzene; and the unintentional by-products dioxins and furans.

POPs’ resistance to chemical and biological degradation and their propensity to evaporate led to their global distribution. By a constant process of deposition and reevaporation, POPs are transported by air and water currents to regions far from their sources until they ultimately gather in colder climates.

Because of their lipophilicity, many POPs concentrate in organisms and accumulate to high levels in the top members of the food web such as predatory fish and birds, mammals and humans. Certain chemicals possess the ability to cross the placenta, while others are retained.

Several contaminants present in the mother’s body are thus handed down to the developing embryo in the womb—they are transferred to offspring across the placenta and through mother’s milk. Adverse effects include cancer, endocrine disruption, reproductive dysfunction, behavioral abnormalities, birth defects, and interference with the immune and nervous systems.

Pollution Shifting

Pollution shifting is defined as the transfer of pollution from one medium (air, water, or soil) to another. Early legal efforts to control pollution focused on single media. For example, in the United States, the Clean Air Act covers air and the Clean Water Act covers water. However, pollution is not constrained by statute; it can shift between media by both natural and human action. Pollution management is improved when all media are considered.

Intentional pollution shifting may occur to destroy a pollutant, convert it to a safer form, or reduce its quantity or concentration. Examples of intentional pollution shifting include combustion, air stripping, air scrubbers, and adsorption. Intentional pollution shifting is accomplished by chemical reaction and/or mass transfer.

Chemical reactions can convert reactants in one media into products in a different media. In mass transfer shifting, differences in concentration are used to transfer pollutants from one media to another. For example, volatile compounds will transfer from relatively contaminated water to relatively clean air.

Combustion, Air Stripping, and Adsoprtion

Combustion is the process of burning, a chemical reaction. It involves combining combustible material with oxygen under conditions that produce light and heat in addition to by-products. The combustion of wastes, such as municipal solid waste, sludge, or hazardous waste, results in gaseous emissions and a solid ash residue. It significantly reduces the volume and mass of waste requiring disposal, by shifting some wastes to gaseous form.

Although carbon dioxide has been implicated in global warming, many of the gaseous emissions have no negative health impact, such as nitrogen gas, carbon dioxide, and water vapor. However, pollutants can also be present, including nitrogen oxides, sulfur dioxide, carbon monoxide, particulate matter, metals, acid gases, dioxins, and furans.

Contaminants in exhaust gases are minimized by optimization of the combustion process, for example, maintaining proper temperature and oxygen levels. They can also be captured with pollution-control equipment, such as air scrubbers and filters. In addition, the ash may contain hazardous compounds, such as heavy metals.

In air stripping, contaminates dissolved in water are transferred to gaseous form by contact with relatively clean air, an example of mass transfer. Air stripping works best with volatile organic compounds (VOCs) and dissolved gases. VOCs are compounds with high vapor pressures, that is, compounds that tend to evaporate quickly. A common application of air stripping is the cleanup of groundwater contaminated by leaking fuel storage tanks.

Air stripping is optimized by maximizing the surface area between the contaminated water and clean air, accomplished by creating fine water droplets in air or small air bubbles in water. Systems can be located away from the contamination (e.g., a system cleaning groundwater that is located on the earth’s surface), or located within the contaminated zone (e.g., a system located in wells installed in contaminated groundwater).

In some cases, the contaminated air from air stripping is released to the atmosphere, where the pollutants are destroyed by sunlight or reaction with other chemicals, adsorbed into soil or water, or diluted. Preferably, the organics in the exhaust from air stripping are destroyed by incineration or oxidation, or captured by adsorption.

The air stripping process may also be reversed. In air scrubbing, pollutants are transferred from contaminated air to clean water. However, a chemical reaction is often incorporated into air scrubbing, converting pollutants to a safer form.

For example, sulfur dioxide produced during coal combustion can be removed from exhaust gas by mass transfer to water containing sodium hydroxide or carbonate, which converts the sulfur dioxide to calcium carbonate. Natural air stripping and air scrubbing also occur. Surface waters, such as lakes and oceans, serve as sinks for pollutants released to the atmosphere. Contaminated water left exposed to the atmosphere will release VOCs.

The final pollution shift considered here is adsorption, in which a con taminant in water or air is adsorbed onto a solid material. Adsorption is use for off-gas control, groundwater remediation, landfill leachate treatment, industrial wastewater treatment, and water treatment for drinking or indus trial purposes.

The most commonly used adsorbent is granular activated carbon (GAC). GAC has a tremendous amount of surface area per mass, on the order of one thousand square meters per gram. Its surface attracts many organic compounds; thus, a small amount of GAC can adsorb a significan amount of organic material. GAC may be regenerated, during which con taminants are destroyed.

Multimedia Approach

The multimedia approach to environmental management considers all media. It can be applied to single facilities, entire companies, and regions. According to the U.S. Environmental Protection Agency Multimedia Enforcement Division, it can result in:
  • Improved detection and resolution of environmental compliance problems
  • Achievement of optimal enforcement results
  • More effective enforcement
  • More efficient use of resources
  • Fundamental changes in the regulated community’s perceptions and behavior regarding environmental compliance
Such benefits are realized by considering an entire pollution system, that is, all media.

Radioactive Fallout

The term radioactive fallout, or just fallout, refers to the debris and radioactive materials that settle out of the air after the detonation of a nuclear weapon or after a nuclear accident that produces a cloud of airborne material, or plume.

Detonation of a nuclear weapon results in the immediate propagation of a shock wave and intense heat. As the superheated fireball rises, a vacuum is formed that draws in scorched building material, soil, and other materials from the epicenter of the blast.

In addition, radionuclides produced in the nuclear chain reaction leading to the explosion and any weapon material not consumed in that reaction will also be a part of the subsequent plume. Any similar thermal process, such as the intense fire during the Chernobyl I reactor accident in 1986, will introduce radioactive and other materials into the atmosphere, as well.

The direction and distance the fallout travels depends largely on weather conditions. Wind speed, wind direction, atmospheric stability, and the amount of rain all factor into the extent and timing of the fallout and subsequent contamination.

The amount of radioactive contamination depends on the initial amount of radioactive material contained, for instance, in a nuclear weapon. In the case of a reactor fire or steam explosion, the damage to the reactor, the amount of material at risk, and the length of time until the event is under control are all factors.

Exposure to radioactive materials, either while still in the plume, or after the fact as contamination, is the basis for potential health concerns. While alpha-emitting fallout material is not the external hazard that beta-, gamma- and x-ray-emitting materials can be, all of these materials are a potential internal hazard concern when the contamination spreads to sources of groundwater and surface water, livestock, crops, and other foodstuffs.

Fallout effects can be long lasting, contaminating an area for hundreds or even thousands of years. Fallout also enters the food chain. Cows eating contaminated grass produce contaminated milk, which can pose a widespread health risk.

As with anything to do with radiation, it is the amount of absorbed energy, or the radiation absorbed dose, that matters. Remaining indoors, with doors and windows shut and air conditioning systems turned off until the plume has passed, can reduce exposure to fallout.

Traveling out of the path of an incoming plume, if this can be predicted accurately, may also help avoid or reduce exposure to the fallout. Certain foodstuffs, especially water and milk, may have to be brought in from unaffected areas.

Time will be one of the best countermeasures should such an event occur. The “seven–ten” rule for nuclear detonations states that for every seven-fold increase in time after a weapon detonation, there will be a concomitant tenfold decrease in the amount of dose afforded by the fallout.


Pesticides are substances or a mixture of substances, of chemical or biological origin, used by human society to mitigate or repel pests such as bacteria, nematodes, insects, mites, mollusks, birds, rodents, and other organisms that affect food production or human health.

They usually act by disrupting some component of the pest’s life processes to kill or inactivate it. In a legal context, pesticides also include substances such as insect attractants, herbicides, plant defoliants, desiccants, and plant growth regulators.

History of Pesticides

The concept of pesticides is not new. Around 1000 B.C.E. Homer referred to the use of sulfur to fumigate homes and by 900 C.E. the Chinese were using arsenic to control garden pests. Although major pest outbreaks have occurred, such as potato blight (Phytopthora infestans), which destroyed most potato crops in Ireland during the mid-nineteenth century, not until later that century were pesticides such as arsenic, pyrethrum, lime sulfur, and mercuric chloride used.

Between this period and World War II, inorganic and biological substances, such as Paris green, lead arsenate, calcium arsenate, selenium compounds, lime–sulfur, pyrethrum, thiram, mercury, copper sulfate, derris, and nicotine were used, but the amounts and frequency of use were limited, and most pest control employed cultural methods such as rotations, tillage, and manipulation of sowing dates.

After World War II the use of pesticides mushroomed, and there are currently more than 1,600 pesticides available and about 4.4 million tons used annually, at a cost of more than $20 billion. The United States accounts for more than 25 percent of this market.

Older Insecticides

The first synthetic organochlorine insecticide, DDT (dichlorodiphenyl-trichloroethane), discovered in Switzerland in 1939, was very effective and used extensively to control head and body lice, human disease vectors and agricultural pests, in the decades leading up to the 1970s.

Benzene hexachloride (BHC) and chlordane were discovered during World War II and toxaphene (and heptachlor) slightly later. Shortly thereafter, two cyclodiene organochlorines, aldrin and dieldrin, were introduced, followed by endrin, endosulfan, and isobenzan.

All these insecticides acted by blocking an insect’s nervous system, causing malfunction, tremors, and death. All organochlorines are relatively insoluble, persist in soils and aquatic sediments, can bioconcentrate in the tissues of invertebrates and vertebrates from their food, move up trophic chains, and affect top predators.

These properties of persistence and bioaccumulation led eventually to the withdrawal of registration and use of organochlorine insectides, from 1973 to the late 1990s, in industrialized nations, although they continued to be used in developing countries.

Organophosphate insecticides originated from compounds developed as nerve gases by Germany during World War II. Thus, those developed as insecticides, such as tetraethyl pyrophosphate (TEPP) and parathion, had high mammalian toxicities. Scores of other organophosphates including demeton, methyl schradan, phorate, diazinon, disulfoton, dimethoate trichlorophon, and mevinphos have been registered.

In insects, as in mammals, they act by inhibiting the enzyme cholinesterase (ChE) that breaks down the neurotransmitter acetylcholine (ACh) at the nerve synapse, blocking impulses and causing hyperactivity and tetanic paralysis of the insect, then death. Some are systemic in plants and animals, but most are not persistent and do not bioaccumulate in animals or have significant environmental impacts.

Carbaryl, the first carbamate insecticide, acts on nervous transmissions in insects also through effects on cholinesterase by blocking acetylcholine receptors. Other carbamate insecticides include aldicarb, methiocarb, methomyl, carbofuran, bendiocarb, and oxamyl. In general, although they are broad-spectrum insecticides, of moderate toxicity and persistence, they rarely bioaccumulate or cause major environmental impacts.

Botanical insecticides include nicotine from tobacco, pyrethrum from chrysanthemums, derris from cabbage, rotenone from beans, sabadilla from lilies, ryania from the ryania shrub, limonene from citrus peel, and neem from the tropical neem tree. Most, other than nicotine, have low levels of toxicity in mammals and birds and create few adverse environmental effects.

Newer Insecticides

Synthetic pyrethroid insecticides, with structures based on the natural compound pyrethrum, were introduced in the 1960s and include tetramethrin, resmethrin, fenvalerate, permethrin, lambda-cyalothrin, and deltamethrin, all used extensively in agriculture.

They have very low mammalian toxicities and potent insecticidal action, are photostable with low volatilities and persistence. They are broad-spectrum insecticides and may kill some natural enemies of pests. They do not bioaccumulate and have few effects on mammals, but are very toxic to aquatic invertebrates and fish.

In recent years, new classes of insecticides have been marketed, none of which are persistent or bioaccumulate. They include juvenile hormone mimics, synthetic versions of insect juvenile hormones that act by preventing immature stages of the insects from molting into an adult, and avermectins, natural products produced by soil microorganisms, insecticidal at very low concentrations. Bacillus thuringiensis toxins are proteins produced by a bacterium that is pathogenic to insects.

When activated in the insect gut, they destroy the selective permeability of the gut wall. The first strains were toxic only to Lepidoptera, but strains toxic to flies and beetles have since been developed. B. thuringiensis has been incorporated into plants genetically.


Soil nematocides, such as dichlopropene, methyl isocyanate, chloropicrin, and methyl bromide, are broad-spectrum soil fumigants. Others, aldicarb, dazomet, and metham sodium, act mainly through contact. All have very high mammalian toxicities and can kill a wide range of organisms from both the plant and animal kingdoms. Although transient in soil, they may have drastic ecological effects on soil systems.


Two molluscicides, metaldehyde and methiocarb, are used as baits against slugs and snails. Although of high mammalian toxicity, they cause few problems other than the occasional accidental death of wild mammals. Several molluscicides, used to control aquatic snails, N-trityl morpholine, copper sulfate, niclosamine, and sodium pentachlorophenate, are toxic to fish.


Hormone-type herbicides such as 2,4,5-T; 2,4-D; and MCPA; were discovered during the 1940s. They do not persist in soil, are selective in their toxicity to plants, are of low mammalian toxicity, cause few direct environmental problems, but are relatively soluble and reach waterways and groundwater.

Contact herbicides, which kill weeds through foliage applications, include dintrophenols, cyanophenols, pentachlorophenol, and paraquat. Most are nonpersistent, but triazines can persist in the soil for several years, are slightly toxic to soil organisms and moderately so to aquatic organisms. Herbicides cause few direct environmental problems other than their indirect effects, in leaving bare soil, which is free of plant cover and susceptible to erosion.


Many different types of fungicides are used, of widely differing chemical structures. Most have relatively low mammalian toxicities, and except for carbamates such as benomyl, a relatively narrow spectrum of toxicity to soil- inhabiting and aquatic organisms. Their greatest environmental impact is toxicity to soil microorganisms, but these effects are short term.

Effects on the Terrestrial Environment

Pesticides are biocides designed to be toxic to particular groups of organisms. They can have considerable adverse environmental effects, which may be extremely diverse: sometimes relatively obvious but often extremely subtle and complex. Some pesticides are highly specific and others broad spectrum; both types can affect terrestrial wildlife, soil, water systems, and humans.

Pesticides have had some of their most striking effects on birds, particularly those in the higher trophic levels of food chains, such as bald eagles, hawks, and owls. These birds are often rare, endangered, and susceptible to pesticide residues such as those occurring from the bioconcentration of organochlorine insecticides through terrestrial food chains.

Pesticides may kill grain- and plant-feeding birds, and the elimination of many rare species of ducks and geese has been reported. Populations of insect-eating birds such as partridges, grouse, and pheasants have decreased due to the loss of their insect food in agricultural fields through the use of insecticides.

Bees are extremely important in the pollination of crops and wild plants, and although pesticides are screened for toxicity to bees, and the use of pesticides toxic to bees is permitted only under stringent conditions, many bees are killed by pesticides, resulting in the considerably reduced yield of crops dependent on bee pollination.

The literature on pest control lists many examples of new pest species that have developed when their natural enemies are killed by pesticides. This has created a further dependence on pesticides not dissimilar to drug dependence. Finally, the effects of pesticides on the biodiversity of plants and animals in agricultural landscapes, whether caused directly or indirectly by pesticides, constitute a major adverse environmental impact of pesticides.

Effects on the Aquatic Environment

The movement of pesticides into surface and groundwater is well documented. Wildlife is affected, and human drinking water is sometimes contaminated beyond acceptable safety levels. Sediments dredged from U.S. waterways are often so heavily contaminated with persistent and other pesticide residues that it becomes problematic to safely dispose of them on land.

A major environmental impact has been the widespread mortality of fish and marine invertebrates due to the contamination of aquatic systems by pesticides. This has resulted from the agricultural contamination of waterways through fallout, drainage, or runoff erosion, and from the discharge of industrial effluents containing pesticides into waterways. Historically, most of the fish in Europe’s Rhine River were killed by the discharge of pesticides, and at one time fish populations in the Great Lakes became very low due to pesticide contamination.

Additionally, many of the organisms that provide food for fish are extremely susceptible to pesticides, so the indirect effects of pesticides on the fish food supply may have an even greater effect on fish populations. Some pesticides, such as pyrethroid insecticides, are extremely toxic to most aquatic organisms. It is evident that pesticides cause major losses in global fish production.

Effects on Humans

The most important aspect of pesticides is how they affect humans. There is increasing anxiety about the importance of small residues of pesticides, often suspected of being carcinogens or disrupting endocrine activities, in drinking water and food. In spite of stringent regulations by international and national regulatory agencies, reports of pesticide residues in human foods, both imported and home-produced, are numerous.

Over the last fifty years many human illnesses and deaths have occurred as a result of exposure to pesticides, with up to 20,000 deaths reported annually. Some of these are suicides, but most involve some form of accidental exposure to pesticides, particularly among farmers and spray operators in developing countries, who are careless in handling pesticides or wear insufficient protective clothing and equipment.

Moreover, there have been major accidents involving pesticides that have led to the death or illness of many thousands. One instance occurred in Bhopal, India, where more than 5,000 deaths resulted from exposure to accidental emissions of methyl isocyanate from a pesticide factory.


Plastics are a subspecies of a class of materials known as polymers. These are composed of large molecules, formed by joining many, often thousands, of smaller molecules (monomers) together. Other kinds of polymers are fibers, films, elastomers (rubbers), and biopolymers (i.e., cellulose, proteins, and nucleic acids).

Plastics are made from low-molecular-weight monomer precursors, organic materials, which are mostly derived from petroleum, that are joined together by a process called “polymerization.” Plastics owe their name to their most important property, the ability to be shaped to almost any form to produce articles of practical value.

Plastics can be stiff and hard or flexible and soft. Because of their light weight, low cost, and desirable properties, their use has rapidly increased and they have replaced other materials such as metals and glass. They are used in millions of items, including cars, bullet-proof vests, toys, hospital equipment, and food containers.

More than a hundred billion pounds of plastic were produced in 2000. Their increased use has resulted in concern with:
  1. The consumption of natural resources such as oil, 
  2. The toxicity associated with their manufacture and use, and 
  3. The environmental impact arising from discarded plastics.

Pollution Problems

Industrial practices in plastic manufacture can lead to polluting effluents and the use of toxic intermediates, the exposure to which can be hazardous. Better industrial practices have led to minimizing exposure of plant workers to harmful fumes; for example, there have been problems in the past resulting from workers being exposed to toxic vinyl chloride vapor during the production of polyvinyl chloride.

Much progress has been made in developing “green processes” that avoid the use of detrimental substances. For example, phosgene, a toxic “war gas,” was formerly used in the manufacture of polycarbonates.

New processes, now almost universally employed, eliminate its use. Also, the “just in time” approach to manufacture has been made possible by computer-controlled processes, whereby no significant amounts of intermediates are stored, but just generated as needed. In addition, efforts are ongoing to employ “friendly” processes involving enzyme-catalyzed low-temperature methods akin to biological reactions to replace more polluting high-temperature processes involving operations like distillation.

Spillage of plastic pellets that find their way into sewage systems, and eventually to the sea, has hurt wildlife that may mistake the pellets for food. Better “housekeeping” of plastic molding facilities is being enforced in an attempt to address this problem.

Most plastics are relatively inert biologically, and they have been employed in medical devices such as prosthetics, artery replacements, and “soft” and interocular lenses. Problems with their use largely result from the presence of trace amounts of nonplastic components such as monomers and plasticizers.

This has led to restrictions on the use of some plastics for food applications, but improved technology has led to a reduction in the content of such undesirable components. For example, the use of polyacrylonitrile for beverage bottles was banned at one time because the traces of its monomer, acrylonitrile, were a possible carcinogen.

However, current practices render it acceptable today. There has been concern about endocrine disruption from phthalate-containing plasticizers used for plastics such as polyvinyl chloride (PVC). The subject of this possible side effect is controversial, but caution in use is warranted pending further study.

Plastics may also result in problems resulting from their improper use, and there is need of better education concerning limitations of use, for example, precautions that should be taken with items such as frying pan coatings and microwavable containers. When exposed to high temperatures, some plastics decompose or oxidize and produce low molecular weight products that may be toxic.

Reduced Use and Recycling

There is growing concern about the excess use of plastics, particularly in packaging. This has been done, in part, to avoid the theft of small objects. The use of plastics can be reduced through a better choice of container sizes and through the distribution of liquid products in more concentrated form. A concern is the proper disposal of waste plastics. Litter results from careless disposal, and decomposition rates in landfills can be extremely long.

Consumers should be persuaded or required to divert these for recycling or other environmentally acceptable procedures. Marine pollution arising from disposal of plastics from ships or flow from storm sewers must be avoided. Disposal at sea is prohibited by federal regulation.

Recycling of plastics is desirable because it avoids their accumulation in landfills. While plastics constitute only about 8 percent by weight or 20 percent by volume of municipal solid waste, their low density and slowness to decompose makes them a visible pollutant of public concern. It is evident that the success of recycling is limited by the development of successful strategies for collection and separation.

Recycling of scrap plastics by manufacturers has been highly successful and has proven economical, but recovering discarded plastics from consumers is more difficult. It is well recognized that separated plastics can be recycled to yield more superior products than possible for mixed ones.

Labeling plastic items with symbols has been employed, which enables consumers to identify them easily for placement in separate containers for curbside pickup. However, success depends on how conscientious consumers are in employing such standards and the ability of collectors to keep various types of plastic separate.

Even a small amount of a foreign plastic in recycling feedstock can lead to the appreciable deterioration of properties, and it is difficult to achieve a high degree of purity. Manual sorting at recycling centers helps, but even trained sorters have difficulty identifying recyclables.

Furthermore, manual sorting is an unattractive task and retaining labor willing to be trained for this is problematic. Automatic sorting techniques have been developed that depend on various physical, optical, or electronic properties of plastics for identification. Such methods prove difficult because of the variety of sizes, shapes, and colors of plastic objects that are encountered.

Although in principle it is possible to create devices that can separate plastics
with varying degrees of success, the equipment generally becomes more expensive with increasing efficiency. Technology for this continues to improve, and it is becoming possible to successfully separate mixed plastics derived from curbside pickup using such equipment.

To separate plastics, it is first necessary to identify the different types as indicated in the table. One must also distinguish between thermoplastics and thermosets. The latter, as found in tires and melamine dishes, has molecules that are interconnected by “crosslinks” and cannot be readily melted for recycling unless they are chemically reduced to low-molecular-weight species. For tires, recycling has not proved economical so disposal has involved grinding them up as asphalt additives for roads or burning in cement kilns.

Over 1.5 million pounds of plastic bottles were recycled in 2000, representing a four-fold increase in the amount of plastic recycled the previous decade. Nonetheless, the capacity to recycle bottles appreciably exceeds their supply by about 40 percent, so local governments and environmental groups need to encourage greater participation in this practice among consumers.

Profitable operations are currently in place for recycling polyethylene terephthalate (PET) from bottle sources and converting it into products such as fibers. One persistent problem, though, is obtaining clean enough feed-stock to avoid the clogging of orifices in spinnerets by foreign particles.

This has limited the ability to produce fine denier fibers from such sources. PET recycling is also constrained by regulations limiting its use to produce items in contact with food because there had been concern about contamination in consideration of improved recycling techniques.

A leading candidate for recycle feedstock is carpets because replacement carpets are usually installed by professionals able to identify recyclables and who serve as a ready source for recycling operations. They face the problem, however, of separating the recyclable carpet components from other parts such as jute backing and dirt. Such recycling operations have been only marginally profitable.

Polystyrene (PS) is another potentially recyclable polymer, but identifying a readily collectable source is problematic. One had been the Styrofoam “clamshells” fast-food chains use to package hamburgers. Recyclers were able to profitably collect polystyrene from such sources and produce salable products. However, largely because of public pressure, this use of polystyrene has declined, so related recycling practices have largely disappeared too.

Cafeteria items from school lunchrooms are another potential, but the collection of such objects involves the development of an infrastructure, often not in place. In these cases, it is necessary to separate the polystyrene from paper and food waste, but washing and flotation techniques have been developed for this purpose.

Increasing amounts of plastic components appear in automobiles, and their recovery from junked cars is a possibility. Its success depends on the ability of a prospective “junker” to identify and separate the plastic items. Three efforts may aid in this accomplishment:
  1. The establishment of databases to enable junkers to learn what kinds of plastic are used in what parts of what model cars.
  2. A reduction in the number of different plastics used for car construction.
  3. The design of cars such that plastic parts may be removed easily (this would require special types of fasteners).
This illustrates a general need—the design of plastic-containing products with the ability to recycle in mind. As a consequence of public concern about the environmental problems arising from plastic use, industry is responding to these needs. The effort continues to use fewer different kinds of plastics and to adopt designs that allow for easier recycling but still retain desirable properties.

There are, however, some worthwhile products that can be produced from mixed plastic, such as “plastic lumber” used for picnic benches and marine applications such as docks and bulkheads that successfully replace wooden lumber which often contains toxic preservatives and arsenic. But, the market for such a product is limited, so efforts to obtain separated plastics are preferred.

Degradable Plastics

Discarded plastics are hard to eliminate from the environment because they do not degrade and have been designed to last a long time. It is possible to design polymers containing monomer species that may be attacked by chemical, biological, or photochemical action so that degradation by such means will occur over a predetermined period of time.

Such polymers can be made by chemical synthesis (as with polylactic acid) or through bacterial or agricultural processes (as with the polyalkonates). Although such processes are often more expensive than conventional ones, cost would undoubtedly drop with increased production volume. One success story was the introduction of carbonyl groups into polyethylene by mixing carbon monoxide with ethylene during synthesis.

These carbonyl groups are chomophores that lead to chain breaking upon the absorption of ultraviolet light. The polymer is then broken down into small enough units that are subject to bacterial attack. This approach has been successful, for example, in promoting the disappearance of rings from beverage cans, which are potentially harmful to wildlife.

A problem with the degradation of plastics is that it is probably undesirable in landfills because of the leachants produced that may contaminate water supplies. It is better in these instances to ship the plastics to composting facilities.

This requires the separation of degradable plastics from other materials and the availability of such facilities. In most cases, the infrastructure needed for such an approach is not in place. This has discouraged its use for disposable diapers that are said to constitute 1 to 2 percent of landfill volume.

Degradable polymers may have limited use in the reduction of litter and production of flushable plastics, for example, feminine hygiene products, but it seems unlikely that the use of such materials will be a viable means of disposal for large amounts of plastic products. Degradation leads to the loss of most of the potential energy content of plastics that might be recovered by trash-to-energy procedures.

Trash to Energy

A method of plastic disposal with more positive environmental implications is burning and recovering the energy for power generation or heating. Plastics contain much of the energy potential of the petroleum from which they are made, and they, in a sense, are just borrowing this energy that may be recovered when the plastic is burned. Environmentalists and the public have objected to this procedure, leading to legislative restrictions.

This has arisen, in part, because of the image of “old-fashioned” incinerators polluting the air with toxic fumes and ash. However, it is possible to construct a “high-tech” incinerator designed to operate at appropriate temperatures and with sufficient air supply that these problems are minimized.

Remaining toxic substances in fumes may be removed by scrubbing, and studies have shown that no significant air pollution results. Toxic ash, for the most part, does not arise from the polymer components of the feedstock, but rather from other materials mixed with the polymers as well as from fillers, catalyst content, and pigments associated with the polymers.

Proper design of the polymers and crude separation of the incinerator feedstock can reduce this problem. Furthermore, if the feedstock was not incinerated but placed in landfills, contaminants would ultimately enter the environment in an uncontrolled way.

Incineration reduces the volume, so that the ash, which may contain them, can be disposed of under more controlled conditions. Also, it is possible to insolublize the ash by converting it into a cementlike material that will not readily dissolve.

Facilities for converting trash to energy in an environmentally acceptable way are expensive and at present not cost-effective when considering short-range funding. However, in the long run, they are environmentally desirable and reduce the need for alternative means for plastic waste disposal. It is imperative that legislators and taxpayers soon adopt this long-range perspective.