Toxicology

Toxicologists have ranked the most commonly encountered toxic chemicals in the United States. In descending order of frequency of encounter, they are as follows:

• Arsenic. Toxic exposure occurs mainly in the workplace, near hazardous waste sites, or in areas with high natural levels. A powerful poison, arsenic can, at high levels of exposure, cause death or illness.
• Lead. Toxic exposure usually results from breathing workplace air or dust, or from eating contaminated foods. Children may be exposed to lead from eating lead-based paint chips, or playing in contaminated soil. Lead damages the nervous system, kidneys, and the immune systems.
• Mercury. Toxic exposure results from breathing contaminated air, ingesting contaminated water and food, and possibly having dental and medical treatments. At high levels, mercury damages the brain, kidneys, and developing fetuses.
• Vinyl chloride. Toxic exposure occurs mainly in the workplace. Breathing high levels of vinyl chloride for short periods can produce dizziness, sleepiness, unconsciousness, and, at very high levels, death. Breathing vinyl chloride for long periods of time can give rise to permanent liver damage, immune reactions, nerve damage, and liver cancer.
• Benzene. Benzene is formed in both natural processes and human activities. Breathing benzene can produce drowsiness, dizziness, and unconsciousness. Long-term exposure affects the bone marrow and can produce anemia and leukemia.
• Polychlorinated biphenyls (PCBs). PCBs are mixtures of chemicals. They are no longer produced in the United States, but remain in the environment. They can irritate the nose and throat, and cause acne and rashes. They have been shown to cause cancer in animal studies.
• Cadmium. Toxic exposure to cadmium occurs mainly in workplaces where cadmium products are made. Other sources of exposure include cigarette smoke and cadmium-contaminated foods. Cadmium can damage the lungs, cause kidney disease, and irritate the digestive tract.