Hazardous Waste


Hazardous waste is legally defined by the Resource Conservation and Recovery Act (RCRA) of 1976. The RCRA defines hazardous waste as any waste or combination of wastes, which because of its quantity, concentration, or physical, chemical, or infectious characteristics may: (a) cause, or significantly contribute to, an increase in mortality or an increase in serious irreversible or incapacitating illness; or, (b) pose a substantial present or potential hazard to human health or the environment when improperly treated, stored, transported, disposed of, or otherwise managed.


Of the thousands of millions of tons of waste generated in the United States annually, approximately 60 million tons (54.4 million metric tons) are classified as hazardous.


Classification types of hazardous waste

In the Code of Federal Regulations, the Environmental Protection Agency (EPA) specifies that a solid waste is hazardous if it meets any of these four conditions: (1) It exhibits ignitability, corrosivity, reactivity, or EP toxicity; (2) has been listed as a hazardous waste; (3) is a mixture containing a listed hazardous waste and a nonhazardous waste, unless the mixture is specifically excluded or no longer exhibits any of the four characteristics of hazardous waste; (4) is not specifically excluded from regulation as a hazardous waste.

The EPA established two criteria for selecting the characteristics given above. The first criterion is that the characteristic is capable of being defined in terms of physical, chemical, or other properties. The second criterion is that the properties defining the characteristic must be measurable by standardized and available test procedures. For example, under the term ignitability (Hazard code label I), any one of four criteria can be met: (1) A liquid with a flash point less than 140°F (60°C); (2) if not a liquid, then it is capable under standard temperature and pressure of causing fire through friction, absorption of moisture, or spontaneous chemical changes, and when ignited, burns so vigorously and persistently that it creates a hazard; (3) it may be an ignitable compressed gas; (4) it is an oxidizer.

Similarly under the characteristics of corrosivity, reactivity, and toxicity, there are specifically defined requirements that are spelled out in the Code of Federal Register (CFR). Further examples are given below:

Corrosivity (hazard code C) has either of the following properties: an aqueous waste with a pH equal to or less than 2.0 or greater than 12.5, or a liquid that will corrode carbon steel at a rate greater than 0.25 inches (0.64 cm) per year.

Reactivity (hazard code R) has at least one of the following properties: a substance which is normally unstable and undergoes violent physical or chemical change without being detonated; a substance that reacts violently with water (for example, sodium metal); a substance that forms a potentially explosive mixture when mixed with water; a substance that can generate harmful gases, vapors, or fumes when mixed with water; a cyanide- or sulfide-bearing waste that can generate harmful gases, vapors, or fumes when exposed to pH conditions between 2.0 and 12.5; a waste that, when subjected to a strong initiating source or when heated in confinement, will detonate or generate an explosive reaction; a substance that is readily capable of detonation at standard temperature and pressure.

Toxicity (hazard code E) has the properties such that an aqueous extract contains contamination in excess of that allowed (e.g., arsenic greater than 5 milligrams per liter, barium greater than 0.1 milligrams per liter, cadmium greater than 1 milligrams per liter, chromium greater than 5 milligrams per liter, lead greater than 5 milligrams per liter). Additional codes under toxicity include an acute hazardous waste with code H, a substance that has been found to be fatal to humans in low doses or has been found to be fatal in corresponding human concentrations in laboratory animals. Toxic waste (hazard code T) designates wastes that have been found through laboratory studies to be carcinogenic, mutagenic, or teratogenic to humans or other life forms.

Non-classifiable waste


A notable feature of the legislation that addresses hazardous waste is its attempt to define terms so that professionals in the field and government officials will share the same vocabulary. For example, the difference between toxic and hazardous has been established: Toxic denotes the capacity of a substance to produce injury, and hazardous denotes the probability that injury will result from the use of (or contact with) a substance. Having a shared language makes it is easier for officials from all professions to communicate more clearly and quickly, which is especially useful during accidents and spills.

The RCRA legislation on hazardous waste also targets larger generators of hazardous waste rather than small operations. The small generator is defined as one who generates less than 2,205 pounds (1,000 kg) per month; accumulates less than 2,205 pounds (1,000 kg); produces wastes that contain no more than 2.2 pounds (1 kg) of acutely hazardous waste; has containers no larger than 5.3 gallons (20 L) or contained in liners less than 22 pounds (10 kg) of weight of acutely hazardous waste; has no greater than 220 pounds (100 kg) of residue or soil contaminated from a spill. The purpose of this exclusion is to enable the system of regulations to concentrate on the most egregious and sizable of the entities that contribute to hazardous waste and thus provide the public with the maximum protection within the resources of the regulatory and legal systems.

See also Bhopal, India ; Cadmium ; Environmental Protection Agency (EPA) ; Lead ; Love Canal ; Resource Conservation and Recovery Act ; Seveso, Italy .



Clapp, Jennifer. Toxic Exports: The Transfer of Hazardous Wastes from Rich to Poor Countries. Ithaca, NY: Cornell University Press, 2010.

Deverell, William, and Greg Hise. Land of Sunshine: An Environmental History of Metropolitan Los Angeles. Pittsburgh, PA: University of Pittsburgh Press, 2006.

Meuser, Helmut. Contaminated Urban Soils. New York: Springer, 2010.


Environmental Protection Agency. “Wastes: Hazardous Waste.” http://www.epa.gov/epawaste/hazard/index.htm (accessed December 1, 2012).


Environmental Protection Agency, 1200 Pennsylvania Ave. NW, Washington, DC, 20460, (202) 272-0167, http://water.epa.gov .

Malcolm T. Hepworth
Alison C. Heimer, MA

  This information is not a tool for self-diagnosis or a substitute for professional care.