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ENVIRONMENTAL HEALTH & TOXICOLOGY Ch. 14 Part 2 This lecture will help you understand: • Environmental health and hazards • Toxic substances in the environment and factors that affect their toxicity • Defenses organisms posses against toxic substances • Movement of toxic substances and their affect on ecosystems • Hazards and their effects • Risk assessment and risk management • Philosophical approaches to risk • Regulatory policy in the United States and internationally Disease is a major focus of environmental health • Despite our technology, disease kills most of us • Disease has a genetic and environmental basis • Cancer, heart disease, respiratory disorders have some genetic basis • Air pollution, poverty, and poor hygiene foster illnesses • Noninfectious diseases cause over half of the world’s deaths • Infectious diseases account for 1 in 4 deaths Disease is a major focus of environmental health • Where you live determines your disease • Infectious disease causes half of all deaths in developing countries • Money lets developed countries have access to hygiene and medicine to combat these diseases • Lifestyles in developed nations affect diseases • U.S. smoking dropped 42%, obesity has more than doubled • Public health efforts decrease some infectious diseases • But some (AIDS) are spreading • Some develop resistance to antibiotics Social and environmental factors can influence the spread of infectious disease • Our mobility spreads diseases worldwide • Severe acute respiratory syndrome (SARS) in 2003 • H1N1 swine flu in 2009–2010 • Climate change will expand the range of diseases • New disease threats may arise • Some pathogens evolve rapidly • Humans can alter existing diseases to make them more deadly—bioterrorism is a growing concern We are fighting disease with diverse approaches • One of the best way to reduce disease is to improve the basic living conditions of the poor • Food security, sanitation, clean drinking water • Also, provide expanded access to health care • Health clinics, immunizations, pre- and postnatal care We are fighting disease with diverse approaches • Education campaigns work in rich and poor nations • Agencies, organizations, and governments work together • The United Nations, the World Health Organization, U.S. Agency for International Development, etc. • Private organizations donate millions of dollars PLAY PANDEMIC TO LEARN MORE ABOUT HOW DISEASE SPREADS: http://www.crazymonkeygames.com/Pandemic-2.html Toxicology is the study of chemical hazards • Toxicology = the study of the effects of poisonous substances on humans and other organisms • Toxicity = the degree of harm a toxicant can inflict • Toxicant = any toxic substance (poison) • “The dose makes the poison”: toxicity depends on the combined effect of the chemical and its quantity ~.095g a cup 5-10g could kill you… that’s more than 6 gallons of McDonald's coffee Toxicology is the study of chemical hazards • We have been adding increased amounts and numbers of chemicals into the environment around us • Environmental toxicology = deals with toxic substances that come from or are discharged into the environment • Studies health effects on humans, other animals, and ecosystems Many environmental health hazards exist indoors • Americans spend roughly 90% of their lives indoors • Radon = a highly toxic, radioactive gas that is colorless and undetectable • Can build up in basements • Found in areas with certain types of bedrock (decaying uranium) • Asbestos = a mineral that insulates, muffles sounds, and resists fire • Asbestosis = disorder that occurs when inhaled crystals of asbestos cause scarred lungs that cease to function • Can lead to lung cancer Many environmental health hazards exist indoors • Lead poisoning = caused by lead, a heavy metal • Damages the brain, liver, kidney, and stomach • Causes learning problems, behavior abnormalities, and death http://www.vox.com/a/lead-exposure-risk-map • Exposure is from drinking water that flows through lead pipes or from lead paint • Efforts in the United States have led to declines in poisoning, but China still used lead paint in toys until recently • In 2012, the Centers for Disease Control (CDC) cut the danger threshold for lead in children’s blood from 10 to 5 micrograms/deciliter Many environmental health hazards exist indoors • Polybrominated diphenyl ethers (PBDEs) = a group of chemicals with fire-retardant properties • Used in computers, televisions, plastics, and furniture • Persist and accumulate in living tissue • Mimic hormones and affect thyroid hormones • Also affect brain and nervous system development and may cause cancer • Concentrations are rising in breast milk • Now that they’re banned in Europe, concentrations have decreased • The United States has not addressed the issue Toxic Substances and Their Effects on Organisms • The environment contains natural chemicals that may pose health risks • Toxins = toxic chemicals made in tissues of living organisms • Chemicals plants use to defend themselves Synthetic chemicals are all around us—and in us • A 2002 study found that 80% of U.S. streams contain 82 contaminants • Antibiotics, detergents, drugs, steroids, solvents, etc. • A 2006 study of groundwater found 18% of wells and 92% of all aquifers contain 42 volatile organic compounds (from gasoline, paints, plastics, etc.) • Less than 2% violate federal health standards for drinking water • Pesticides are present in streams and groundwater in levels not high enough to affect human health • But high enough to affect aquatic life Synthetic chemicals are in all of our bodies • Every one of us carries traces of hundreds of industrial chemicals in our bodies • Including toxic persistent organic pollutants restricted by international treaties • Babies are born “pre-polluted”—232 chemicals were in umbilical cords of babies tested • Nine out of 10 umbilical cords contained BPA • Not all synthetic chemicals pose health risks • But very few of the 100,000 chemicals on the market have been thoroughly tested Silent Spring began the public debate over synthetic chemicals • Rachel Carson’s Silent Spring (1962) showed DDT’s risks to people, wildlife, and ecosystems • Gathered and presented scientific studies, medical cases, and other data • Chemical companies challenged the book • Attacked Carson’s science and personal reputation • DDT was banned in the United States in 1973 • But is still made in the United States and exported • Used to control disease vectors in developing countries (reward is greater than risk) • New technologies may stop disease without DDT Not all toxicants are synthetic, and not all synthetic chemicals are toxic • Toxic chemicals also exist naturally and in our food • It would be a mistake to assume natural chemicals are all healthy and synthetic ones are all harmful • Plants produce toxic chemicals to defend themselves • Most crop plants have had the level of toxic chemicals reduced by artificial selection, but not eliminated • Eating animals may expose us to the plant chemicals they ate • Bioaccumulation Toxic substances come in different types • Carcinogens = substances that cause cancer • Cells grow uncontrollably, damaging the body • Prevalence of environmentally induced cancer has been underestimated • Hard to identify because of the long time between exposure and onset of cancer and because not everyone exposed gets cancer • Mutagens = substances that cause DNA mutations • Most mutations have no effect, but some can cause cancer • If they occur in sperm or eggs, can impact offspring Toxic substances come in different types • Teratogens = chemicals that cause birth defects in embryos • Thalidomide caused birth defects in the 1960s • Neurotoxins = toxicants that assault the nervous system • Animal venoms, heavy metals, pesticides, and chemical weapons Toxic substances come in different types • Allergens = toxicants that overactivate the immune system • Cause an immune response when one is not needed • Increase in asthma in recent years may be due to increased prevalence of allergenic chemicals • Not universally considered toxicants since they only affect some people and not others Toxic substances come in different types • Pathway inhibitors = toxicants that interrupt vital biochemical processes by blocking one or more steps in pathway • The herbicide atrazine blocks steps in photosynthesis • Endocrine disruptors = toxicants that affect the endocrine (hormone) system = chemical messenger system Toxic substances come in different types • Hormones stimulate growth, development, sexual maturity • Work with extremely small concentrations • Synthetic chemicals interfere with normal signals • Block hormones, preventing signals from working • Mimic hormones, causing a change • Many mimic female sex hormones Organisms have natural defenses against toxic substances • Organisms were exposed to toxic substances before humans starting producing them • Heavy metals occur naturally; plants and animals produce toxic chemicals • Exposure has driven selection for organisms that can tolerate these toxins • Barriers (skin, scales, feathers) prevent uptake • Biochemical pathways break down toxicants or are changed for easier excretion • Some toxicants can not be broken down and are instead stored in fatty tissue (DDT) • Defenses only work at low levels of toxicants 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 Individuals vary in their responses to hazards • The Environmental Protection Agency (EPA) sets standards for responses based on adult responses • Extrapolate adult responses to smaller size for children, infants • Scientists argue that standards are not low enough to protect babies The type of exposure affects the response • Acute exposure = high exposure to a hazard for short periods of time • Easy to recognize • Stems from discrete events: ingestion, oil spills, nuclear accident, etc. • Chronic exposure = low exposure for long periods of time • More common but harder to detect and diagnose • Affects organs gradually: lung cancer, liver damage • Cause and effect may not be easily apparent due to time between onset of exposure and symptoms