Environmental Hazards - Environmental Sciences - Lecture Slides, Slides of Environmental Science

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Four types of environmental hazards (a) Physical hazard a 4 os ws 7 (c) Biological hazard (d) Cultural hazard ©2011 Peatson Esteli, re docsity.com There are many types of environmental hazards • Environmental health = assesses environmental factors that influence human health and quality of life – natural and human-caused factors considered • Physical hazards = occur naturally in our environment – earthquakes, volcanoes, fires, floods, droughts • can’t prevent them…but can prepare for them – increase our vulnerability by deforesting slopes (landslides), channelizing rivers (flooding), etc. – can reduce risk by better environmental choices docsity.com Disease is a major focus of environmental health • Despite technology, disease kills most of us – has a genetic and environmental basis • cancer, heart disease, respiratory disorders • poverty and poor hygiene can foster illnesses docsity.com Infectious diseases kill millions • 15 million people per year – half of all deaths in developing countries – developed countries have better hygiene, access to medicine, and money • Vector = an organism that transfers pathogens to a host – Ex: Mosquitos transfer Malaria docsity.com Many diseases are increasing • Tuberculosis, acquired immunodeficiency syndrome (AIDS), and the West Nile virus • Our mobility spreads diseases • Bacteria are evolving resistance to antibiotics • Climate change will expand the range of diseases • To predict and prevent diseases, experts deal with complicated interrelationships docsity.com Environmental toxicology • Deals with toxic substances that come from or are discharged into the environment • Studies the health effects on – Humans, other animals, and ecosystems • focus mainly on humans…using other animals as test subjects • can serve as indicators of health threats • Don’t forget, chemicals have given us our high standard of living docsity.com Toxic agents in the environment • The environment contains countless natural chemicals that may pose health risks • But…synthetic chemicals are also in our environment – every human carries traces of industrial chemicals 80% of U.S. streams contain at least trace amounts of 83 wastewater contaminants docsity.com Very few chemicals have been thoroughly tested • >100,000 chemicals are on the market today – 72,000 industrial – 8,700 food additives – 2,000 new chemicals introduced per year • We don’t know the effects (if any) they will have long-term – On-going testing is out-paced by new development • Babies are born “pre-polluted” – 232 chemicals were in umbilical cords of babies tested docsity.com Endocrine disruption may be widespread • Theo Colburn wrote Our Stolen Future in 1996 – synthetic chemicals may be altering the hormones of animals – book integrated scientific work from various fields – shocked many readers and brought criticism from the chemical industry docsity.com Evidence for hormone disruption • Frogs also have gonadal abnormalities – male frogs became feminized from atropine concentrations well below EPA guidelines • PCB-contaminated human babies were born weighing less, with smaller heads Alligators and frogs show reproductive abnormalities due to endocrine disruption from pesticides docsity.com Many products mimic female hormones • Bisphenol A (BPA) binds to estrogen receptors – Look for “BPA-free” plastics • Phthalates in plastics disrupt hormones – Toys, perfumes, makeup – Birth defects, cancer, reproductive effects – In the bodies of everyone in the U.S. docsity.com Toxins may concentrate in water • Runoff carries toxins from large land areas to small volumes of surface water • Chemicals can leach into the soil • Chemicals enter organisms through drinking or absorption – aquatic organisms are effective pollution indicators • mosquito fish, algae, midge larvae – Bioindicators docsity.com Airborne toxicants travel widely • Chemicals can travel by air… their effects can occur far from the site of chemical use • Pesticide drift = airborne transport of pesticides • Synthetic chemical contaminants are found globally – appear in arctic polar bears, Antarctic penguins, and people living in Greenland docsity.com Toxicants can accumulate and biomagnify • Some toxicants can be excreted or metabolized – fat-soluble toxicants are stored in fatty tissues • Bioaccumulation = toxicants build up in animal tissues • Biomagnification = toxicants concentrate in top predators docsity.com Dose-response analysis • Dose-response analysis = – measuring how much effect a toxicant produces at different doses – Dose = • the amount of toxicant the test animal receives – Response = • the type or magnitude of negative effects of the animal – Dose-response curve = • the plot of dose given against response docsity.com Dose response curves • LD50/ED50= the amount of toxicant required to kill (or affect) 50% of the subjects – also have LC50 • Threshold = the dose level where certain responses occur – organs can metabolize or excrete low doses of a toxicant • Scientists extrapolate downward from animal studies to estimate the effect on humans – regulatory agencies set allowable limits well below toxicity levels in lab studies docsity.com Individuals vary in their responses to hazards • Different people respond differently to hazards – affected by genetics, surroundings, etc. – people in poor health are more sensitive – sensitivity also varies with sex, age, and weight – fetuses, infants, and young children are more sensitive • Standards for responses are set by the Environmental Protection Agency (EPA) – Standards not low enough to protect all 28 docsity.com Perceiving risks • Everything we do involves some risk • We try to minimize risk, but we often misperceive it – Jet versus Car • We feel more at risk when we cannot control a situation – Public fears nuclear power and toxic waste, but not smoking or overeating 31 docsity.com Analyzing risk quantitatively • Risk assessment = the quantitative measurement of risk and the comparison of risks involved in different activities or substances – identifying and outlining problems • Several steps: – scientific study of toxicity – assessing an individual or population’s likely extent of exposure to the substance (frequency, concentrations, and length of exposure) • Studies are often performed by industry-associated scientists…which may undermine the study’s objectivity docsity.com Risk management • Combines decisions and strategies to minimize risk • Scientific assessments are considered with economic, social, and political needs and values • Developed nations have federal agencies to manage risk – the U.S. has the Centers for Disease Control (CDC), the EPA, and the Food and Drug Administration (FDA) • Comparing costs and benefits is hard – benefits are economic and easy to calculate – health risks (costs) are hard-to-measure probabilities of a few people being affected 33 docsity.com Philosophy affects policy • Different nations use different policies: – Most use a mix between the “innocent until proven guilty” principle and the precautionary principle • Europe is shifting more towards the precautionary principle – Industries like the “innocent until proven guilty” approach • it allows them to produce more and make more money docsity.com US Policy: Fed Govt regulates many substances • Federal agencies apportion responsibility for tracking and regulating synthetic chemicals – FDA: food, food additives, cosmetics, drugs, and medical devices – EPA: pesticides – Occupational Safety and Health Administration (OSHA): workplace hazards • Many public health and environmental advocates fear it isn’t enough – many synthetic chemicals are not actually tested – only 10% have been tested for toxicity – fewer than 1% are regulated by federal oversight docsity.com