Chapter 19.1 Toxicology and Chemical Hazards study of harmful effects of chemicals on human and environmental health acute effects—might occur upon ingestion or contact with skin chronic exposure—occurs over years carcinogenic potential data on toxic chemicals http://ntp.niehs.nih.gov/ (National Toxicology Program) http://ntp.niehs.nih.gov/ntp/roc/toc11.html (Report on Carcinogens) http://cfpub.epa.gov/ncea/iris/index.cfm (EPA Integrated Risk Information System) http://www.scorecard.org/ (Environmental Defense)

dose response and threshold in investigating a suspect chemical, a toxicologist would conduct tests on animals, investigate human involvement with the chemical, and present information linking the dose with the response dose: level of exposure multiplied by the length of time over which exposure occurs response: acute or chronic effect, or the development of tumors LDL0: lowest dose at which death occurred in animal testing

threshold level in dose-response relationship, there is usually a threshold organisms are able to deal with certain levels of many substances without suffering ill effects threshold level: level below which no ill effects are observed above this level, effect of a substance depends on concentration and duration of exposure for carcinogens, EPA generally takes a zero-dose, zero-response approach however, the lower the dose, the more likely it is that the response cannot be distinguished from the background level of cancers in a population

HAZMATs HAZMAT = hazardous material categorized based on the following hazardous properties: ignitability—catch fire readily corrosivity—corrode storage tanks and equipment reactivity—chemically unstable and may explode or create toxic fumes when mixed with water toxicity—injurious to health when they are ingested or inhaled

sources of chemicals entering the environment materials making up almost everything we use, from shampoo to toothpaste to TVs, are products of chemical technology our use constitutes only one step in the total product life cycle life cycle begins with obtaining raw materials and ends in the final disposal of the product chemical wastes and by-products are inevitable in any production process, as is the potential for accidents and spills when these steps are multiplied by the hundreds of thousands of products used by billions of people, the magnitude of hazardous materials becomes clear

toxics release inventory introduction of chemicals into the environment may occur in every sector, from major industrial plants to small shops and individual homes some idea of quantities of chemicals released can be obtained from Toxics Release Inventory (TRI) since TRI has been in effect, total releases have decreased by 68% Emergency Planning and Community Right-to-Know Act (EPCRA) of 1986 requires industries to report releases of toxic chemicals to the environment Pollution Prevention Act of 1990 mandates collection of data on toxic chemicals that are treated on-site, recycled, or combusted for energy TRI does not cover small businesses such as dry cleaners and gas stations (facilities do not need to report yearly releases under 500 lb), or household hazardous waste

threat from toxic chemicals fortunately, a large portion of chemicals introduced into the environment are gradually broken down and assimilated by natural processes once these chemicals are diluted, they pose no long-term human or environmental risk, although they may be toxic in acute doses two major classes of chemicals do not readily degrade in the environment: heavy metals synthetic organics

heavy metals most dangerous include lead, mercury, arsenic, zinc, cadmium, tin, chromium, and copper common in metalworking or metal-plating shops, electronics, pesticides, and some medicines once common in paint pigments, glazes, inks, and dyes due to brilliant colors extremely toxic because, as ions in certain compounds, they are soluble in water and may be readily absorbed by the body (usually inhibit the function of enzymes)

organic compounds chemical basis for all plastics, synthetic fibers, pesticides, wood preservatives, and hundreds of other products because of their chemical structure, many are resistant to biodegradation (which is part of what makes them useful) compounds are toxic because they are often readily absorbed into the body, where they interact with specific enzymes high dose  acute poisoning and death low doses over long periods  effects can be mutagenic, carcinogenic, or teratogenic (birth defect-causing)

dirty dozen particularly troublesome class of synthetic organics is halogenated hydrocarbons organic compounds in which one or more hydrogen atoms have been replaced by Cl, Br, F, or I all are toxic to varying extents and most are known animal carcinogens many are also suspected endocrine disruptors at very low levels chlorinated hydrocarbons are most common used in plastics (polyvinyl chloride), pesticides (DDT), solvents, electrical insulation (PCBs), and many other products

PERC tetrachloroethylene, also called perchloroetheylene (PERC) major substance in dry cleaning fluid; effective solvent found in many industrial cleaners evaporates readily when exposed to air, but can enter groundwater easily because it does not bind to soil particles enters body most readily when breathed in with contaminated air breathing PERC for short periods can bring on dizziness, fatigue, headaches, and unconsciousness over long periods, can cause liver and kidney damage Report on Carcinogens: “reasonably anticipated to be a carcinogen” studies have shown higher risk of cancer along with neurological impairment in dry cleaner employees EPA issued ruling to phase out PERC by 2020

Minamata tragic episode in early 1970s revealed potential for biomagnification of mercury and other heavy metals in the mid-1950s, cats in the small fishing village of Minamata, Japan began to show spastic movements, followed by partial paralysis, coma, and death at first, most thought the syndrome was specific to felines however, same symptoms began to appear in humans chemical company near the village was discharging wastes containing mercury into a river that flowed into a bay where villagers fished mercury settled with detritus, then absorbed and bioaccumulated by bacteria, then biomagnifed up the food chain in the end, 50 died and 150 suffered bone and nerve damage