Hazardous Chemicals
Chemicals, for which there is statistically evidence based on at least one study conducted in accordance with established scientific principles that acute or chronic health effects may occur in exposed employees, is classifies as a health hazard. Health hazards include chemicals that are carcinogens, toxin or highly toxic agents, reproductive toxins, irritants, corrosives, sensitizers, hepatotoxins, nephrotoxins, neurotoxins, agents which act on the hematopietic systems; and agents that damage the lungs, skin, eye or mucous membranes are hazardous chemicals.

Many chemicals can cause harm by virtue of their toxicity. In this case, the toxicity of a chemical refers to its ability to damage an organ system, such as the liver and the kidney or to disrupt a biochemical process such as the blood clotting mechanism or to disturb an enzyme system at some sites in the body removed from the site of contact.
In actual practice, hazards do not group themselves in neat categories, but usually occur in combination and/or sequence. The following are some characteristics of flammability, a common chemical hazard.

Mercury

Exposure to mercury occurs from breathing contaminated air, ingesting contaminated water and food, and having dental and medical treatments. Mercury, at high levels, may damage the brain, kidneys, and developing fetus.

What happens to mercury when it enters the environment?

  • Inorganic mercury (metallic mercury and inorganic mercury compounds) enters the air from mining ore deposits, burning coal and waste, and from manufacturing plants.
  • It enters the water or soil from natural deposits, disposal of wastes, and volcanic activity.
  • Methylmercury may be formed in water and soil by small organisms called bacteria.
  • Methylmercury builds up in the tissues of fish. Larger and older fish tend to have the highest levels of mercury.

Chromium
Exposure to chromium occurs from ingesting contaminated food or drinking water or breathing contaminated workplace air. Chromium (VI) at high levels can damage the nose and can cause cancer

What happens to chromium when it enters the environment?

  • Chromium enters the air, water, and soil mostly in the chromium (III) and chromium(VI) forms.
  • In air, chromium compounds are present mostly as fine dust particles which eventually settle over land and water.
  • Chromium can strongly attach to soil and only a small amount can dissolve in water and move deeper in the soil to underground water.
  • Fish do not accumulate much chromium in their bodies from water.

Cadmium
Exposure to cadmium happens mostly in the workplace where cadmium products are made. The general population is exposed from breathing cigarette smoke or eating cadmium contaminated foods. Cadmium damages the lungs, can cause kidney disease, and may irritate the digestive tract.

What happens to cadmium when it enters the environment?

  • Cadmium enters air from mining, industry, and burning coal and household wastes.
  • Cadmium particles in air can travel long distances before falling to the ground or water.
  • It enters water and soil from waste disposal and spills or leaks at hazardous waste sites.
  • it binds strongly to soil particles.
  • Some cadmium dissolves in water.
  • It doesn't break down in the environment, but can change forms.
  • Fish, plants, and animals take up cadmium from the environment.
  • Cadmium stays in the body a very long time and can build up from many years of exposure to low levels.

Arsenic
Exposure to higher than average levels of arsenic occur mostly in the workplace, near hazardous waste sites, or in areas with high natural levels. At high levels, inorganic arsenic can cause death. Exposure to lower levels for a long time can cause a discoloration of the skin and the appearance of small corns or warts.

What happens to arsenic when it enters the environment?

  • Arsenic occurs naturally in soil and minerals and it therefore may enter the air, water, and land from wind-blown dust and may get into water from runoff and leaching.
  • Arsenic cannot be destroyed in the environment. It can only change its form.
  • Rain and snow remove arsenic dust particles from the air.
  • Many common arsenic compounds can dissolve in water. Most of the arsenic in water will ultimately end up in soil or sediment.
  • Fish and shellfish can accumulate arsenic; most of this arsenic is in an organic form called arsenobetaine that is much less harmful.

Lead
Lead is a heavy, low melting, bluish-gray metal that occurs naturally in the Earth's crust. However, it is rarely found naturally as a metal. It is usually found combined with two or more other elements to form lead compounds

What happens to lead when it enters the environment?

Lead is a naturally occurring element that people have used almost since the beginning of civilization. Human activities have spread lead widely throughout the environment-the air, water, soil, plants, animals, and man-made constructions. Because lead is spread so widely throughout the environment, it can now be found in everyone's bodies; most people have lead levels that are orders of magnitude greater than that of ancient times (Flegal and Smith 1992, 1995) and within an order of magnitude of levels that have resulted in adverse health effects.