2Four categories of human health risks Physical (floods, blizzards, landslides, radon, UV exposure)Biological (viruses, bacterial infections)Chemical (disinfectants, pesticides)Cultural/Lifestyle (drinking, smoking, bad diet, crime in neighborhood)
3Biological RisksInfectious diseases- those caused by infectious agents, known as pathogens.Example: pneumonia and FluAlso referred to as: transmissible, contagious or communicable diseases.Where you live and your level of poverty may increase the probability of contracting some infectious diseases.
9Emergent Diseases HIV/AIDS Ebola Mad Cow Disease Bird Flu West Nile VirusSARSAntibiotic resistant TB
10AgenciesCDC – Center for Disease Control and Prevention (United States)WHO – World Health Organization (global)
11Solutions for Reducing Infectious Disease Improving drinking water conditions in developing countriesDecreasing malnutrition to improve immune systemImplementing global education programs to prevent HIV/AIDSIncreasing availability to vaccines/antibioticsReducing unnecessary use of antibiotics in humans and livestock
12Chemical RisksToxicology – Study of the detrimental effects of chemicals on both humans and wildlifeKey characteristics that cause a chemical to be toxic include:Persistence – not easily degraded/broken downSolubility – fat soluble chemicals will accumulate in body tissues, water soluble chemicals will be dissolved easily in bodies of waterBiomagnification – Increased concentration of chemical through the food chain.
13Bioaccumulationbioaccumulation- an increased concentration of a chemical within an organism over time
14BiomagnificationBiomagnification- the increase in a chemical concentration in animal tissues as the chemical moves up the food chain.
15Dose-Response Studies LD50- lethal dose that kills 50% of the individualsED50- effective dose that causes 50% of the animals to display the harmful but nonlethal effect (referred to as sublethal effects)Because of the short duration of these experiments, referred to as acute studies
16Synergistic interactions- when two risks come together and cause more harm that one would. For example, the health impact of a carcinogen such as asbestos can be much higher if an individual also smokes tobacco.
18Dose-response curve Threshold = dose at which response begins LD50 = dose lethal to 50% of test animalsThreshold = dose at which response begins
19Do The MathBased on a LD50 pesticide study on a rat, what amount of the pesticide would be considered safe for a mammal?LD50 ÷ 10 (mammal)LD 50 = 2mg/kg of mass ÷ 10 = 0.2 mg/kg of massLD50 ÷ 1000 (humans)LD 50 = 2mg/kg of mass ÷1000 = mg/kg of mass
20Problems with Toxicity Testing There are many issues in accurately assessing toxicity of chemicals….Genetic Variability – individuals can exhibit different response to a given level or type of chemicalTest only one response to one chemical at a time, difficult to determine synergistic effectsType of exposure may effect response (acute versus chronic)Regulating agencies may rely on Industry sponsored research
21Chemical Risks Neurotoxins- chemicals that disrupt the nervous system Carcinogens- chemicals that cause cancerTeratogens- chemicals that interfere with the normal development of embryos or fetusesAllergens- chemicals that cause allergic reactionsEndocrine disruptors- chemicals that interfere with the normal functioning of hormones in an animal’s body
23Many health hazards exist indoors Substances in plastics and consumer productsLead in paint and pipesRadonAsbestosPBDE fire retardants
24ChemicalSourcesTypeEffectsArsenicMining, Groundwater, Treated wood productsCarcinogenCancerAsbestosBuilding InsulationLung CancerRadonSoil, Water, BedrockVinyl ChlorideIndustry, water from vinyl chloride pipesCancer, especially liver cancerPCBs (Polychlorinated biphenyls)Industry (electrical insulator, fire retardant, pesticides, adhesives)PhthalatesUsed in production of plastics and as solventsReproductive damage and cancersBisphenol AUsed in production of plastic bottles and food containersReproductive cancersBenzeneEmissions from burning coal , tobacco smokeDioxinsClass of chemical compounds in manufacturing of some herbicidesBioaccumulates, causes cancer
25ChemicalSourceTypeEffectsThalidomideMorning Sickness Medication prescribed in the early 1960sTeratogenBirth DefectsAlcoholAlcoholic beveragesFetuses with reduced fetal growth, brain damageBenzeneEmissions from burning coal and oil, tobacco smokeLong term exposure can cause birth defectsVinyl ChloridePrecursor to making PVCThe drug thalidomide, used to relieve nausea during pregnancy, turned out to be a potent teratogen, and caused thousands of birth defects before being banned in the 1960s.
26Link – Minamata Disease ChemicalSourceTypeEffectLeadPaint, gasolineNeurotoxinNS disorders, DeathMercuryCoal burning, fish consumption, batteries, fluorescent lights, smelting, incineration of municipal wasteBrain damageHeavy Metals (lead, mercury, Arsenic, Cadmium)Neurotoxin/TeratogenBiomagnify through food chain and cause neuological damage especially in fetusesPCB’sIndustry, electrical insulators, fire retardants, adhesives, pesticidesBrain damage, especially in fetusesVinyl ChloridePrecursor to PVCBisphenol APlastic bottles and containersNeurological damageLink – Minamata Disease
27ChemicalSourceTypeEffectAtrazineHerbicidesEndocrine DisruptorFeminization of males, low sperm count, damage to sexual development , reduced penis size, having both male and female sex organsDDTPesticideBiomagnifies, reproductive damage, thin egg shells, cancers in birdsPhthalatesProduction of plastics, solvent in some cosmetic productsFrogs show reproductive abnormalities in response to small doses of the herbicide atrazine, researcher Tyrone Hayes has found.Others suggest that atrazine may have effects on humans as well, lowered sperm count, may also be linked to increasing incidence of breast and testicular cancers.
29Well Known Case Studies Love Canal Housing Development in Niagara Falls, New York – Hazardous waste chemicals buried in old canal leaked into homes, school yard, soil, and ground water. Led to the passage of Comprehensive Environment Response Compensation and Liability Act (CERCLA) aka “Superfund Act”
30Well Known Case Studies Minamata, Japan – mental impairments, birth defects, and deaths caused by mercury dumped in Minamata Bay by a factory. The mercury was converted to methylmercury, bioaccumulated in fish, and biomagnified through food chains. Mercury entered humans who ate a traditional fish based diet.
31Know Well Known Case Studies Bhopal, India – On December 2, 1984, poisonous methyl isocyanate gas was released accidentally by a Union Carbide pesticide plant killing about 5,000 people and causing serious health effects for 50, ,000.
32RiskRisk = the mathematical probability that some harmful outcome will result from a given action, event, or substanceProbability = a quantitative description of the likelihood of a certain outcomeHarmful outcome could be defined as injury, death, environmental damage, economic loss, etc.
33Perception different from reality Our perception of risks tends not to match statistical reality.smokingplane crash
34Risk assessment Analyzes risks quantitatively Measures and compares risks involved in different activities or substancesHelps identify and prioritize serious risksHelps determine threats posed to humans, wildlife, ecosystems
35Risk assessment Involves: Dose-response analysis or other tests of toxicityAssessing likely exposure to the hazard (concentration, time, frequency)
36Risk managementConsider risk assessments in light of social, economic, and political needs and values.Weigh costs and benefits, given both scientific and nonscientific concerns.Decide whether or not to reduce or eliminate risk.
37Risk assessment and risk management inform policy Following risk management, policy decisions are made.
38Philosophical approaches “Innocent until proven guilty”:Assume harmless until shown to be harmfulPrecautionary principle:Assume harmful until shown to be harmless
39Implications for product testing “Innocent until proven guilty”:Industry can introduce any products it wants.Government bears the burden of proof to show if products are dangerous.Precautionary principle:Industry cannot introduce a product until it is very thoroughly tested and shown convincingly to be harmless.
40Implications for product testing Industry has pressured government to take an “innocent-until-proven-guilty” approach.Environmental advocates have pressured government to follow the precautionary principle.
41Stockholm ConventionIn 2001, a group of 127 nations gathered in Stockholm, Sweden, to reach an agreement on restricting the global use of some chemicals12 chemicals were to be banned, phased out, or reduced (aka “dirty dozen”)These include DDT, PCBs, and certain chemicals that are by-products of manufacturing processes.International Treaty – Persistent Organic Pollutants Treaty (POPs)Signed but not ratified by United States