Waste Management

Hazardous wastes are materials considered harmful or potentially harmful to human health or the environment. Wastes may be deemed hazardous because they are poisonous, flammable, or corrosive, or because they react with other substances in a dangerous way.

Industrial operations have produced large quantities of hazardous waste for hundreds of years. Some hazardous wastes, such as mercury and dioxins, may be released as gases or vapors. Many hazardous industrial wastes are in liquid form. One of the greatest risks is that these wastes will contaminate water supplies.

An estimated 60% of all hazardous industrial waste in the United States is disposed using a method called deep-well injection. With this technique, liquid wastes are injected through a well into an impervious rock formation that keeps the waste isolated from groundwater and surface water. Other methods of underground burial are also used to dispose hazardous industrial waste and other types of dangerous material.

Hazardous wastes are also disposed at specially designed landfills and incinerators. A controversial issue in international relations is the export of hazardous waste, usually from relatively wealthy industrialized countries, to poorer developing nations. Such exports often take place with the stated intent of recycling, but many of the wastes end up being dumped.

Pesticides used in farming may contaminate agricultural waste. Because of the enormous volumes of pesticides used in agriculture, the proper handling of unused pesticides is a daunting challenge for waste managers. Certain mining techniques also utilize toxic chemicals. Piles of mining and metal-processing waste, known as waste rock and tailings, may contain hazardous substances. Because of a reaction with the oxygen in the air, large amounts of toxic acids may form in waste rock and tailings and leach into surface waters.

Hazardous wastes also come from common household products that contain toxic chemicals. Examples include drain cleaner, pesticides, glue, paint, paint thinner, air freshener, detergent, and nail polish. Until about the early 1970s, most people dumped these products in their domestic garbage. However, local waste managers do not want hazardous domestic wastes in with the regular garbage. They also do not want residents to pour leftover household chemicals down the drain, since municipal sewage treatment plants are not properly equipped to treat them.

The trend during the 1980s and 1990s was for local governments to open facilities where residents could take their household hazardous wastes, or to sponsor periodic collection events for those materials. City and county governments in the United States conduct more than 800 of these events each year.