Water Pollution

The EPA, in partnership with state and local governments, is responsible for improving and maintaining water quality. These efforts are organized around three themes. The first is maintaining the quality of drinking water. This is addressed by monitoring and treating drinking water prior to consumption and by minimizing the contamination of the surface water and protecting against contamination of groundwater needed for human consumption. The second is preventing the degradation and destruction of critical aquatic habitats, including wetlands, nearshore coastal waters, oceans, and lakes. The third is reducing the pollution of free-flowing surface waters and protecting their uses. The following is a discussion of various pollutants categorized by these themes.

Drinking Water Pollutants

The most severe and acute public health effects from contaminated drinking water, such as cholera and typhoid, have been eliminated in America. However, some less acute and immediate hazards remain in the nation’s tap water. These hazards are associated with a number of specific contaminants in drinking water. Contaminants of special concern to the EPA are lead, radionuclides, microbiological contaminants, and disinfection by-products.

The primary source of lead in drinking water is corrosion of plumbing material, such as lead service lines and lead solders, in water distribution systems and in houses and larger buildings. Virtually all public water systems serve households with lead solders of varying ages, and most faucets are made of materials that can contribute some lead to drinking water.

Radionuclides are radioactive isotopes that emit radiation as they decay. The most significant radionuclides in drinking water are radium, uranium, and radon, all of which occur naturally in nature. While radium and uranium enter the body by ingestion, radon is usually inhaled after being released into the air during showers, baths, and other activities, such as washing clothes or dishes. Radionuclides in drinking water occur primarily in those systems that use groundwater. Naturally occurring radionuclides seldom are found in surface waters (such as rivers, lakes, and streams).

Water contains many microbes—bacteria, viruses, and protozoa. Although some organisms are harmless, others can cause disease. The Centers for Disease Control reported 112 waterborne disease outbreaks from 1981 to 1983. Microbiological contamination continues to be a national concern because contaminated drinking water systems can rapidly spread disease.

Disinfection by-products are produced during water treatment by the chemical reactions of disinfectants with naturally occurring or synthetic organic materials present in untreated water. Since these disinfectants are essential to safe drinking water, the EPA is presently looking at ways to minimize the risks from by-products

Surface Water Pollutants

Pollutants in waterways come from industries or treatment plants discharging wastewater into streams or from waters running across urban and agricultural areas, carrying the surface pollution with them (nonpoint sources). The following is a discussion of surface water pollutants categorized by their main sources.

Raw or insufficiently treated wastewater from municipal and industrial treatment plants still threatens water resources in many parts of the country. In addition to harmful nutrients, poorly treated wastewater may contain bacteria and chemicals.

Sludge, the residue left from wastewater treatment plants, is a growing problem. Although some sludges are relatively “clean,” or free from toxic substances, other sludges may contain organic, inorganic, or toxic pollutants and pathogens.

An important source of toxic pollution is industrial wastewater discharged directly into waterways or indirectly through municipal wastewater treatment plants. Industrial wastes discharged indirectly are treated to remove toxic pollutants. It is important that those wastes be treated because toxics may end up in sludge, making them harder to dispose of safely.

Nonpoint sources present continuing problems for achieving national water quality in many parts of the country. Sediment and nutrients are the two largest contributors to nonpoint source problems. Nonpoint sources are also a major source of toxics, among them are pesticide runoff from agricultural areas, metals from active or abandoned mines, gasoline, and asbestos from urban areas. In addition, the atmosphere is a source of toxics since many toxics can attach themselves to dust, later to be deposited in surface waters hundreds of miles away through precipitation

LAND POLLUTANTS

Historically, land has been used as the dumping ground for wastes, including those removed from the air and water. Early environmental protection efforts focused on cleaning up air and water pollution. It was not until the 1970s that there was much public concern about pollution of the land. It is now recognized that contamination of the land threatens not only future use of the land itself but also the quality of the surrounding air, surface water, and groundwater. There are five different forms of land pollutants. These include

Industrial hazardous wastes

Municipal wastes

Mining wastes

Radioactive wastes

Underground storage tanks

A short description of each is provided below. More detailed descriptions can be found in separate chapters later in the book