About Chemical Hazard, Lecture notes of Environmental Science

Download About Chemical Hazard and more Lecture notes Environmental Science in PDF only on Docsity! CHEMICAL HAZARD - Some chemicals can cause cancers, mutations, birth defects - A toxic chemical is one that can cause temporary or permanent harm or death to humans and animals. - In 2004, the EPA listed arsenic, lead, mercury, vinyl chloride (used to make PVC plastics), and polychlorinated biphenyls (PCBs) as the top five toxic substances in terms of human and environmental health. There are three major types of potentially toxic agents: Carcinogens - (Chemicals, types of radiation, or certain viruses that can cause or promote cancer) Mutagens - (Chemicals or forms of radiation that cause mutations, or changes, in the DNA molecules found in cells, or that increase the frequency of such changes) Teratogens - (Chemicals that cause harm or birth defects to a fetus or embryo) The damage to health resulting from exposure to a chemical is called response. Acute effect is an immediate or rapid harmful reaction ranging from dizziness and nausea to death. Chronic effect is a permanent or long-lasting consequence (Kidney or liver damage, for example) of exposure to a single dose or to repeated lower doses of a harmful substance. Case reports provide information about people suffering some adverse health effect or death after exposure to a chemical. Epidemiological studies , which compare the health of people exposed to a particular chemical (the experimental group) with the health of a similar group of people not exposed to the agent (the control group), but limited by: Too few people have been exposed to high enough levels of a toxic agent to detect statistically significant differences. CHEMICAL HAZARD - All methods for estimating toxicity levels and risks have serious limitations. - Only 10% of the 80,000+ registered synthetic chemicals in commercial use have been thoroughly screened for toxicity, and only 2% have been