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Report on the Environment

Contaminated Land

Other Land Topics

What are the trends in contaminated land and their effects on human health and the environment?

There are many settings for contaminated lands, ranging from abandoned buildings in inner cities to large areas contaminated with toxic materials from past industrial or mining activities. Contaminated lands include sites contaminated by improper handling or disposal of toxic and hazardous materials and wastes, sites where toxic materials may have been deposited as a result of wind or flood, and sites where improper handling or accidents resulted in release of toxic or hazardous materials that are not wastes.

Land contamination can result from a variety of intended, accidental, or naturally occurring activities and events such as manufacturing, mineral extraction, abandonment of mines, national defense, waste disposal, accidental spills, illegal dumping, leaking underground storage tanks, hurricanes, floods, pesticide use, and fertilizer application. Sites are categorized in a variety of ways, often based on the level and type of contamination and the regulations under which they are monitored and cleaned up. (See the “Categorizing Contaminated Lands” box below for an overview of the common types of contaminated sites.) With the exception of accidental spills and contamination that result from naturally occurring and other unanticipated events, most land contamination is the result of historical activities that are no longer practiced. Hazardous material and waste management and disposal are now highly regulated.

Contaminated soils can leach toxic chemicals into nearby ground or surface waters, where these materials can be taken up by plants and animals, contaminate a human drinking water supply, or volatilize and contaminate the indoor air in overlying buildings. In dry areas, contamination in soil can be further distributed through wind-borne dusts. Once soil contamination migrates to waterways, it may also accumulate in sediments, which can be very difficult to remediate and may affect local ecosystems and human health. Humans can be harmed by contact with toxic and hazardous materials on a contaminated site via exposure to contaminated land, air, surface water, and ground water. When contaminated lands are not properly managed, humans and wildlife can be exposed to contaminants through inhalation, ingestion, or dermal contact. The risks of human exposure are site-specific and difficult to generalize at the national level. Potential effects may be acute or chronic.

Some contaminated sites pose little risk to human health and the environment, because the level of contamination is low and the chance of exposure to toxic or hazardous contaminants is also low. Other contaminated sites are of greater concern because of the chemicals that may be present and their propensity to persist in or move through the environment, exposing humans or the environment to hazards. These sites must be carefully managed through containment or cleanup to prevent hazardous materials from causing harm to humans, wildlife, or ecological systems, both on- and offsite.

Nationally, there are thousands of contaminated sites of varying size and significance. Many sites, particularly the largest and most severely contaminated, are tracked at the national level, but many others are tracked only at state or local levels. The number and status of contaminated sites changes frequently as sites are newly contaminated (e.g., via spills or hurricanes), discovered, documented, and cleaned up.

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