Chromium as a pollutant

Chromium and certain chromium compounds are known carcinogens. Long-term exposure of workers to airborne levels of chromium higher than those in the natural environment has been associated with lung cancer. Compounds containing hexavalent chromium - chromium(VI) - is believed to be the major problem when inhaled. Evidence for other chromium compounds is inconclusive. Inhalation exposure to chromium may result in additional adverse effects on the respiratory system and may affect the immune system.

Most chromium enters the body from dietary intake. Some chromium exposure occurs from breathing air and drinking water, but exposure from these sources is normally small compared to intake from food. However, exposure from breathing chromium may increase for people living near industrial sites where chromate is produced or used, and exposure from drinking water may increase due to passage of corrosive water through steel alloy pipes or plumbing containing chromium.

Much higher exposure to chromium occurs to people working in certain chromium industries (occupational exposure) and to people who smoke cigarettes. The two largest sources of chromium emission in the atmosphere are from the chemical manufacturing industry and combustion of natural gas, oil, and coal. Other sources of chromium exposure are as follows: cement-producing plants, since cement contains chromium; the wearing down of asbestos brake linings from automobiles or similar sources of wind-carried asbestos, since asbestos contains chromium; incineration of municipal refuse and sewage sludge; exhaust emission from catalytic converters in automobiles; emissions from air conditioning cooling towers that use chromium compounds as rust inhibitors; waste waters from electroplating, leather tanning, and textile industries when discharged into lakes and rivers; and solid wastes from the manufacture of chromium compounds, or ashes from municipal incineration, when disposed of improperly in landfill sites. Some consumer products that contain small amounts of chromium are: some inks, paints, and paper; some rubber and composition floor coverings; some leather materials; magnetic tapes; stainless steel and a few other metal alloys; and some toner powders used in copying machines. Occupational sources of chromium exposure mainly occur in industries that produce the following: stainless steel products (from welding); chromates (chemicals made from chromium and used in chemical industries); chrome-plated products; ferrochrome alloys; chrome pigments; and leather (from tanning). Examples of additional occupations that have potential for chromium exposure include: painters; workers involved in the maintenance and servicing of copying machines and in the disposal of some toner powders from copying machines; battery makers; candle makers; dye makers; printers; and rubber makers.

In 1994, chromium chemicals were banned as coolants in cooling towers. Around 800 cooling towers at 400 sources were affected.