According to the EPA, hazardous waste is any substance that is dangerous or potentially harmful to our health or the environment. A hazardous waste can be a solid, a semi-solid, a liquid or a gas. Hazardous waste is harmful because of its quantity, concentration or physical, chemical or infectious characteristics. Chemical companies, paper mills, plastic manufacturers, steel mills, oil refineries and textile manufacturers are among the facilities that generate enormous amount of hazardous waste.
These form one of the most common categories of hazardous waste. Solvents are utilized by a variety of industries to clean and degrease machinery and mechanical parts. Electronic-equipment manufacturers use industrial solvents to clean circuit boards and machinery in their units. The U.S. Air Force uses solvents to clean and degrease aircraft engines and parts. An example of a widely used industrial solvent is trichloroethylene, or TCE. The industries often dump spent TCE onto the ground, where it seeps through the earth and contaminates water supplies.
Dry-cleaning stores use a solvent called perchloroethylene, or perc. Usually, clothes are soaked in a bath of this solvent. Many dry-cleaning operations dispose of perc by simply draining it onto the ground. This eventually contaminates the drinking water and may lead to serious health problems if this water is consumed for long periods.
This category of hazardous waste can pose serious health hazards for the public. Lead, mercury, cadmium, chromium, arsenic, copper and nickel are some examples of heavy metals that are used in diverse industries for manufacturing various products. These industries often dispose of the heavy metals in an improper manner, contaminating the soil and water. Lead and cadmium are used in paint manufacturing. Mining companies often leave sandy deposits of heavy metals piled on the ground, which later drift and spread into the environment. Exposure to lead through contaminated water or the routine inhalation of small amounts of metal dust may lead to kidney damage, high blood pressure, problems with memory and other serious health problems.
PCBs, or polychlorinated biphenyls, are a class of oily, human-made chemicals that are hazardous for the environment and human health. They were used in many industrial and commercial applications. Though the manufacture of PCBs was banned in 1979, they are still found in industrial waste. This is because disposal of older machinery or equipment--manufactured when PCBs were prevalent--results in the disposal of the PCBs inside them.
Dioxins are formed as useless byproducts during certain chemical processes that involve chlorine. Dioxins are long-lasting, toxic compounds that can be carcinogenic and pose other health hazards. Paper mills are a major source of dioxins, because they use chlorine to bleach paper and release dioxins in the process.