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Chapter 15: Environmental Health, Pollution and Toxicology Disease • Disease is often due to an imbalance resulting from poor adjustment between the individual and the environment. – Continuum from state of health to disease – Gray zone in-between – As a result of exposure to chemicals in the environment we may be in the midst of an epidemic of chronic disease. Disease • Seldom have a one-cause-oneeffect relationship w/ the environment • Depends on several factors – Physical environment – Biological environment – Lifestyle Disease • Chances of experiencing serious environmental health problems and disease depends on – The – The – The – The water we drink air we breathe soil we grow crops in rocks we build our homes on Disease • Natural processes can release harmful materials into the soil, water or air. • Lake Nyos in Cameroon, Africa – Experienced sudden release of carbon dioxide – Killed 1,800 people in near by town. Terminology • Polluted environment – impure, dirty, or otherwise unclean. • Pollution refers to the occurrence of unwanted change in the environment – introduction of harmful materials or the production of harmful conditions. • Contamination – similar to that of pollution – implies making something unfit for a particular use through the introduction of undesirable materials Terminology • Toxic refers to materials (pollutants) that are poisonous to people and other living things. – Toxicology is the science that studies chemicals that are known to be or could be toxic. • Carcinogen is a particular kind of toxin that increases the risk of cancer. – Most feared and regulated toxins in our society. Terminology • Additivity - A biologic response to exposure to multiple substances that equals the sum of responses of all the individual substances added together • Antagonism – A biologic response to exposure to multiple substances that is less than would be expected if the known effects of the individual substances were added together Terminology • Synergism – The interaction of different substances resulting in a total effect great than the sum of the effects of the separate substances. – E.g. sulfur dioxide and coal dust Terminology • Pollutants introduced into the environment at: • Point sources, such as smokestacks, pipes discharging into waterways, stream entering the ocean, or accidental spills. The Clean Water Act specifically defines a "point source" in section 502(14) of the Act. That definition states: Terminology • The term "point source" means any discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, or vessel or other floating craft, from which pollutants are or may be discharged. This term does not include agricultural storm water discharges and return flows from irrigated agriculture. Terminology • Pollutants introduced into the environment at: – Non point sources (Area sources), which are more diffused over the land and include urban and agricultural runoff and mobile sources such as automobile exhaust. Nonpoint Source Pollution • Nonpoint source (NPS) pollution, unlike pollution from industrial and sewage treatment plants, comes from many diffuse sources. NPS pollution is caused by rainfall or snowmelt moving over and through the ground. As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters, and even our underground sources of drinking water. Nonpoint Source Pollution Nonpoint sources include: • Excess fertilizers, herbicides, and insecticides from agricultural lands and residential areas; • Oil, grease, and toxic chemicals from urban runoff and energy production; • Sediment from improperly managed construction sites, crop and forest lands, and eroding streambanks; • Salt from irrigation practices and acid drainage from abandoned mines; • Bacteria and nutrients from livestock, pet wastes, and faulty septic systems; • Atmospheric deposition and hydromodification are also sources of nonpoint source pollution. Point Source or Nonpoint Source? Why? Measuring the Amount of Pollution • How the amount or concentration of a particular pollutant or toxin present in the environment is reported varies widely. – E.g. waste water reported in millions of gallons – Emissions of nitrogen oxides reported in tons per year – Others given by a volume, mass of weight • ppm, ppb, mg/kg or % Practice Suppose 17 grams of sucrose is dissolved in 183 grams of water. What is the concentration of sucrose in ppm? 17 X 1,000,000 = 170000 ppm (17+183) The solubility of AgCl is 0.008 grams/100 grams of water. What is this concentration in ppm? 0.008 X 1000000 = 80 ppm 100 Infectious Agents • Infectious disease – Spread from the interactions between individuals and food, water, air or soil. – Can travel globally via airplanes – New diseases emerging and previous ones reemerging – Diseases that can be controlled by manipulating the environment • classified as environmental health concerns Environmentally Transmitted Infectious Diseases • Legionellosis – Occurs where air-conditioning systems have been contaminated by disease-causing organisms. • Giardiasis – a protozoan infection of the small intestine spread via food, water, or person-to-person contact. • Salmonella – a food-poisoning bacterial infection spread via water or food. Environmentally Transmitted Infectious Diseases • Malaria – a protozoan infection transmitted by mosquitoes. • Lyme disease – Transmitted by ticks. • Cryptosporidosis – a protozoan infection transmitted via water or person-to-person contact. • Anthrax – Bacterial infection spread by terrorist activity. Toxic Heavy Metals • The major heavy metals that pose health hazards to people and ecosystems include: – mercury, lead, cadmium, nickel, gold, platinum, silver, bismuth, arsenic, selenium, vanadium, chromium, and thallium. • Each may be found in soil and water not contaminated by humans. Toxic Heavy Metals • Often have direct physiological effects. – Stored and incorporated in living tissue • Fatty body tissue – Content in our bodies referred to as body burden. Toxic Pathways • Chemical elements can become concentrated • Biomagnification- the increased concentration of a toxic chemical the higher an animal is on the food chain. • Bioaccumulation– the accumulation or increase in concentration of a substance in living tissue of a particular organism. – E.g. Cadmium, mercury Minamata By: Laurie Brier, Benny DeShazer, Miranda Holmes, and Matthew Shelnutt. The Town of Minamata • Located on the coast of the Yatsushiro Sea in southwestern Japan. • The village was very poor. – Mostly fishermen and farmers. • Villagers welcome Chisso Corporation http://www.jnto.go.jp/tourism/img/map/86.gif Chisso Corporation • Chisso = nitrogen – Produced fertilizer • 1907: Chisso Corp. builds a fertilizer plant in the Minamata. • Job openings • 1925: plant begins dumping untreated wastewater into Minamata Bay – Kills fish – Fisherman Payoffs http://www.japanfocus.org/images/592-3.jpg Chisso Corporation • 1932: Chisso plant begins to produce acetaldehyde to be used in the production of plastic, perfume and drugs. • Acetaldehyde is made from acetylene and water with a mercury catalyst. • After WWII plastic production boomed and Chisso Corp. grew. • By 1970: Chisso brought Japan 60% of its income and owned nearly 70% of the land in Minamata. http://www-personal.umich.edu/~tobin/Smith2.jpg Bizarre Behavior in Animals • Early 1950’s: – Dead fish wash ashore – Crows fall out of sky – Suicidal dancing cats • Mercury moves up the food chain. http://flickr.com/photos/tropicalrips/127535537/ Mid 1950’s: Behavior Seen in Humans • Behaviors witnessed: – Loss of motor control in hands – Violent tremors – Swaggered walk – Insanity • “Cat-dancing” disease • Nobody knew the cause of the epidemic. – Many hid for fear of ridicule http://www.hamline.edu/personal/amurphy01/es110/eswebsite/Proj ectsSpring03/ebarker/Minamata%20Web%20Page.htm Putting the Pieces Together • 1956: Researchers at Chisso Corp. Hospital experiment on cats with wastewater from the Chisso plant. • They warn Chisso corp. • Chisso corp. redirects the flow of wastewater to avoid being caught. – A larger geographical area contaminated. – Children born with horrifying deformities. http://www.nimd.go.jp/archives/english/tenji/a_corner/image/hasseimap.gif Putting the Pieces Together • 1968: Government ran Public Health service traces the contamination to the Minamata Chisso plant. • Government halts the production of acetaldehyde • 1972: Government publically announces Chisso Corp’s part in the Minamata epidemic and orders Chisso Corp to pay compensation to the families that were affected. http://www.icett.or.jp/lpca_jp.nsf/505b1fe895fd2a8c492567ca000d587d/e 35dc782654b21d7492567ca000d8c50?OpenDocument Centers for Disease Control and Prevention The Aftermath • 30-70 tons of methyl mercury was dumped into the Bay • 10,000 people affected by Minamata disease. – 3,000 died • Compensation has been given to families as recently as 1990. – Highest compensation for the disaster was just under $3,000. http://www.physorg.com/news110359851.html Methylmercury : In the Body • Methylmercury exposure in humans is from consumption of fish, marine mammals, and crustaceans • 95% of fish-derived methylmercury is absorbed into the gastrointestinal tract and distributed throughout the body – Highest in concentration in hair www.mercury.utah.gov/images/health_effects.jpg Minamata Disease in the Nervous System Areas in red show areas typically affected by the presence of methylmercury in the system . The lesions show characteristic signs and symptoms in Minamata disease. 1. Gait disturbance, loss of balance (ataxia), speech disturbance (Dysarthria) 2. Sight disturbance of peripheral areas in the visual fields (constriction of visual fields) 3. Stereo anesthesia (Disturbance of sensation) 4. Muscle weakness, muscle cramp (disturbance of movement) 5. Hardness of hearing (hearing disturbance) 6. Disturbance of sense of pain, touch or temperature (Disturbance of sensation) National institute of Minamata Disease Archives Symptoms of the Disease • Mild – – – – Ataxia Muscle weakness Narrowed field of vision Hearing and speech damage • Severe cases cause – – – – Insanity Paralysis Coma Death W. Eugene Smith Tomoko Uemura in Her Bath Minamata, 1972 More Symptoms • A significant effect of Minamata is the onset of symptoms similar to those of cerebral palsy • Fetal Minamata Disease – A pregnant mother ingests toxic fish and the methylmercury concetrates inside the placenta. – Harms the fetus while the mother is relatively unaffected http://picasaweb.google.com/jazzyv0504/SA KURA#5065603192708172658 These are all children with congenital (fetal) Minamata Disease due to intrauterine methyl mercury poisoning (Harda 1986). Mercury: The Basics • Mercury (Hg) is the only metal that is liquid at room temperature. It melts at 38.9oC and boils at 356.6oC. • Mercury conducts electricity, expands uniformly with temperature and easily forms alloys with other metals (called amalgams). – For these reasons, it is used in many products found in homes and schools. Mercury Chemistry • Mercury exists in three oxidation states: – Hg0 (elemental mercury). – Hg22+ (mercurous). – Hg2+ (mercuric). • Mercurous and mercuric form numerous inorganic and organic chemical compounds. – Organic forms of mercury, especially methyl mercury, CH3Hg(II)X, where “X” is a ligand (typically Cl- or OH-) are the most toxic forms. Uses of Mercury • We use its unique properties to conduct electricity, measure temperature and pressure, act as a biocide, preservative and disinfectant and catalyze reactions. – It is the use of mercury in catalysis that contributed to the events in Minamata. • Other uses include batteries, pesticides, fungicides, dyes and pigments, and the scientific apparati. Mercury in the Environment • Upwards of 70% of the mercury in the environment comes from anthropogenic sources, including: – Metal processing, waste incineration, and coal-powered plants. • Natural sources include volcanoes, natural mercury deposits, and volatilization from the ocean. • Estimates are that human sources have nearly doubled or tripled the amount of mercury in the atmosphere. The Aquatic Mercury Cycle Cleaning up • The Minamata Spill – Dredging • Other ways of cleaning mercury spill Mercury-resistant bacteria, developed by researchers from Inter American University of Puerto Rico, Bayamon Campus, contained either the mouse gene for metallothionein or the bacterial gene for polyphosphate kinase. Both strains of bacteria were able to grow in very high concentrations (120µM) of mercury, and when the bacteria containing metallothionein were grown in a solution containing 24 times the dose of mercury which would kill non-resistant bacteria, they were able to remove more than 80% of it from the solution in five days. Minamata Cleanup • What’s is Dredging? – Underwater excavation Minamata Cleanup • Dredging – Types • Mechanical • Hydraulic • Airlift Hydraulic Mechanical Airlift Minamata Cleanup • Disposal of Sediment – – – – Landfills Disposal facility Ocean placement Confined Disposal Facilities (CDFs) Recycling Separation U.S. Mercury Cleanups • • • • Precipitation/ Co precipitation Absorption treatment Membrane Filtration Biological treatment Other ways of Clean Up • Capping of Mercury – contaminated Sediments w/ sand • Inhibition of Mercury Methylation by Iron Sulfides • Immobilization of Aqueous Hg (II) by Iron Sulfides Experimental Research • • • • Nanotechnology Phytoremediation Air Stripping In Situ Thermal Desorption (ISTD) Minamata Bay Today • Eco Park of Minamata Bay has 2 purposes – A stone memorial – Landfill for Mercury Questions??? Organic Compounds • Organic compounds – compounds of carbon produced naturally by living organisms or synthetically by human industrial practices. • Synthetic organic compounds – Used in industrial processes, pest control, pharmaceuticals, and food additives. – Over 20 million Persistent Organic Pollutants • POPs may produce a hazard for decades or hundreds of years. – First produced when their harm was not known – Now banned or restricted Persistent Organic Pollutants • POPs have several properties that define them: – They have a carbon-based molecular structure, often containing highly reactive chlorine. – Most are synthetic chemicals. – They do not easily break down in the environment. Persistent Organic Pollutants – They are polluting and toxic. – They are soluble in fat and likely to accumulate in living tissue. – They occur in forms that allow them to be transported by wind, water, and sediments for long distances. Dioxins • Dioxins & incineration: • A) history • B) chemistry • C) biology • D) health threat AIR EMISSIONS CO2 + H2O ACID GASES: HCI, HF, SO2 NOx TOXIC METALS: Pb, Cd, Hg, As, Cr etc COMPOUNDS: PCB’s PCDDs (DIOXINS) PCDFs (FURANS) NANO PARTICLES History • 1960s, 1970s Most people hear of dioxins in relation to use of Agent Orange in Vietnam • 1949 - 1976 dioxins produced in industrial accidents in plants making 2,4,5 Trichlorophenol. Most famous Seveso, Italy in 1976. • 1977 dioxins found in trash incinerator emissions • 1977 -’85 Engineers argue that dioxin problem solved by running incinerator furnaces at high temps. They were wrong • 1985 - find dioxins formed after the furnace. Dioxin 1980s - 1990s • Biggest source of dioxin is from food, particularly animal fat. • Biggest source of dioxin entering food chains = combustion esp. of municipal waste. • Medical, municipal and hazardous waste incineration, backyard burning (PVC), Fires (PVC), copper recycling (PVC), metal smelting • 1990’s better dioxin control from incineration. Many plants retrofitted and older plants closed down. DIOXINS The chemical structures Dioxin like compounds (DLC) • 3 families • PCBs • PCDFs (furans) • PCDDs (dioxins) Polychlorinated biphenyls One of 209 PCBS PCBs = a family of compounds in which chlorine atoms are substituted for hydrogen at 1 to 10 positions of BIPHENYL . Furans (or PCDFs) have an oxygen atom forming a five membered ring (the furan) between the two benzenes of PCBs. There are 135 furans. Furans (or PCDFs) Furans (or PCDFs) have an oxygen atom forming a five membered ring (the furan) between the two benzenes of PCBs. There are 135 furans. 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN Dioxins (or PCDDs) have two oxygen atoms linking the two benzene rings, forming the dioxin ring. There are 75 dioxins. Dioxins (or PCDDs) 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN Dioxins (or PCDDs) have two oxygen atoms linking the two benzene rings, forming the dioxin ring. There are 75 dioxins. There are 17 extremely toxic dioxins and furans. They have chlorine at the 2,3,7 and 8 positions: 7 Dioxins and 10 Furans The biology of Dioxins Dioxin Or Dioxin-like Compound (DLC) CELL Ah receptor Arnt protein Complex With Changed shape DNA NUCLEUS Dioxins do not cause mutations But switch on genes Switching on a gene means producing a specific messenger RNA which codes for a specific protein messenger RNA travels to the ribosome (= protein factory) In the ribosome the messenger RNA directs the production of a specific protein New protein New protein New protein modifies the activity of the cell and may lead to cancers and endocrine disorders esp. in developing Animals. Dioxins - major health concerns • Dioxins accumulate in animal fat. One liter of cows’ milk gives the same dose of dioxin as breathing air next to the cows for EIGHT MONTHS . • In one day a grazing cow puts as much dioxin into its body as a human being would get in 14 years of breathing! • Dioxins steadily accumulate in human body fat. The man cannot get rid of them BUT A woman can… • …by having a baby! • Thus the highest dose of dioxin goes to the fetus and then to the new born infant via breastfeeding… Dioxins interfere with fetal and infant devlopment • Dioxins act like fat soluble hormones • Disrupt at least six different hormonal systems. WE WANT DIOXIN OUT OF OUR BABIES! Institute of Medicine, 2003 • Fetuses and breastfeeding infants may be at particular risk from exposure to dioxin like compounds (DLCs) due to their potential to cause adverse neurodevelopmental, neurobehavioral, and immune system effects in developing systems… Institute of Medicine, 2003 • …The committee recommends that the government place a high public health priority on reducing DLC intakes by girls and young women in the years well before pregnancy is likely to occur. • (by) Substituting low-fat or skim milk, for whole milk, (and)… foods lower in animal fat… WE WANT DIOXIN OUT OF OUR FOOD! Do not build incinerators within 50 km of food production - particularly grazing animals Promoters say that modern incinerators have solved the dioxin problem, but have they? • When PVC was fed into the high-temperature melter, a significant quantity of PCDD/Fs, cadmium and lead was emitted. • Wet scrubbing with rapid quenching, as well as a low temperature two-step fine filtration, or both of them together cannot effectively control the volatile metal species and gasphase PCDD/Fs. • The removal of PVC from the feed waste stream must also be effective to reduce the emissions of the PCDD/Fs, cadmium and lead species. While modern incinerators have reduced dioxin emissions there is no real accountability in most countries YOU NEED THREE THINGS TO PROTECT THE PUBLIC FROM TOXIC EMISSIONS. YOU NEED THREE THINGS TO PROTECT THE PUBLIC FROM TOXIC EMISSIONS. STRONG REGULATIONS YOU NEED THREE THINGS TO PROTECT THE PUBLIC FROM TOXIC EMISSIONS. STRONG REGULATIONS ADEQUATE MONITORING YOU NEED THREE THINGS TO PROTECT THE PUBLIC FROM TOXIC EMISSIONS. STRONG REGULATIONS ADEQUATE MONITORING TOUGH ENFORCEMENT YOU NEED THREE THINGS TO PROTECT THE PUBLIC FROM TOXIC EMISSIONS. STRONG REGULATIONS ADEQUATE MONITORING TOUGH ENFORCEMENT IF ANY LINK IS WEAK THE PUBLIC IS NOT PROTECTED Hormonally Active Agents • HAA are also POPs. • Have potential to cause developmental and reproductive abnormalities in animals, including humans. – Include a wide variety of chemicals, herbicides, pesticides, phthalates, and PCBs Hormonally Active Agents • Evidence in support of hypothesis – Alligator populations in Florida exposed to DDT have genital abnormalities, low egg production and reduced penis size. – Major disorders studied in wildlife have centered on abnormalities including • thinning of eggshells of birds, decline in populations of various animals and birds, reduced viability of offspring, and changes in sexual behavior. Hormonally Active Agents • In humans – HAAs may be linked to breast cancer – PCBs and neurological behavior – Phthalates (used as plastic softeners and are responsible for that new car smell, which becomes especially pungent after the car has been sitting in the sun for a few hours, is partly the pungent odor of phthalates volatilizing from a hot plastic dashboard. In the evening's cool they then condense out of the inside air of the car to form an oily coating on the inside of the windshield. – Endocrine and hormone disruption Endocrine System • One of two main systems that regulate and control growth , development and reproduction. • Composed of a group of hormone secreting glands – Thyroid, pancreas, pituitary, ovaries and testes. – Hormones transported by blood stream, act as chemical messengers. Hormonally Active Agents • The National Academy of Sciences – recommends that there should be continued monitoring of wildlife and human populations for abnormal development and reproduction. Radiation • Nuclear radiation is linked to serious health problems – Including cancer Thermal Pollution • Occurs when heat released into water or air produces undesirable effects. – Also called heat pollution – Sudden acute event or long term, chronic release – Heated water released into rivers changes temp and dissolved oxygen content • Thereby changing river’s species composition Thermal Pollution • Heating river water changes natural conditions and disturbs the ecosystem – Fish spawning cycles may be disrupted – Fish may have heightened susceptibility to disease. – Physical stress on fish – Easier pray – Change in type and availability of food Thermal Pollution • Solutions to chronic thermal heating – Release of heat into air in cooling towers – Artificial lagoons – Used to heat buildings Particulates • Small particles of dust released into the atmosphere by many natural processes and human activities. – Modern farming – Burning oil and coal – Dust storms – Volcanic eruptions Asbestos • A term for several minerals that take the form of small, elongated particle or fibers. – Use contributed to fire prevention – Insulation • Inhalation leads to asbestosis and cancer • 95% of asbestos now in use in US chrysolite (white asbestos). – Not particularly harmful • Another type crocidolite (blue asbestos) – Exposure can be very hazardous Electromagnetic Fields • EMFs part of everyday urban life – electric motors, transmission lines and appliances – Controversy as to whether they pose a health risk – Children may be at greater risk – Studies have shown that associations between CA and exposure to EMFs is not strong and not statistically significant. Noise Pollution • Unwanted sound • Sound is a form of energy that travels as waves – We hear sounds when waves vibrate our eardrum – Loudness a measure of intensity of energy – Measured in units of decibels Noise Pollution • Environmental effects of noise depend on – – – – – Energy Pitch Frequency Time pattern Length of exposure • Very loud noise can cause pain • Any sound above 80dB can cause hearing loss – Rock concert 110dB • Constant high noise causes stress Voluntary Exposure • Sometimes referred to as exposure to personal pollutants. – Tobacco • 30% of cancers tied to smoking – Alcohol and other drugs • ½ of all deaths in automobiles accidents tied to alcohol use by drivers • Violent crimes, overdoses, chronic alcoholism General Effect s of Pollutants • Almost every part of the human body is affected by one pollutant or another. Concept of Dose and Response • Five centuries ago, the physician and alchemist Paracelsus wrote that “everything is poisonous, yet nothing is poisonous.” • For Example – Selenium required in small amounts by living things – May be toxic in high concentrations Concept of Dose and Response • The effect of a chemical on an individual depends on the dose. – Dose response – Dose dependency can be represented by a generalized dose response curve. Concept of Dose and Response • Doses that are beneficial, harmful, or lethal may differ widely for different organisms and are difficult to characterize. • E.g. fluoride and dental health – Fluorine forms fluoride compounds that prevent tooth decay and promote healthy bone structure. – Toxic effects are noticed at concentrations of 6-7 ppm Dose-Response Curve • How individuals will response to a chemical not know. • Instead predictions made about how a percentage of the population will respond to a specific dose. • Dose at which 50% of the population dies – Lethal dose 50, LD-50 Dose-Response Curve • The ED-50 (effective dose 50%) is the dose that causes an effect in 50% of the population of observed subjects. – E.g. ED-50 of aspirin would be the dose that relieves headaches in 50% of the people. Dose-Response Curve • The TD-50 (toxic dose 50%) is defined as the dose that is toxic to 50% of the population. – Often used to indicate responses such as reduced enzyme activity, decreased reproductive success, or onset of specific symptoms. Dose-Response Curve • For a particular chemical, there may be a whole family of dose–response curves. – Which dose is of interest depends on what is being evaluated. – Killing insects vs. pesticide residue – Overlap between the therapeutic dose (ED) and the toxic dose (TD) – Measure of the relative safety of a particular drug is the therapeutic index • Defined as the ratio of the LD-50 to the ED-50. • The greater the therapeutic index, the safer the drug. Threshold effects • Threshold is a level below which no effect occurs and above which effects begin to occur. – If a threshold exists, then a concentration below the threshold is safe. – If there is no threshold dose, then even the smallest amount has some negative toxic effect. • A problem in evaluating thresholds for toxic pollutants is that it is difficult to account for synergistic effects. Ecological Gradients • Changes in vegetation with distance from a toxic source define the ecological gradient. – Weedy species adapted to harsh conditions may be closer – Farther away trees and shrubs Tolerance • The ability to resist or withstand stress resulting from exposure to a pollutant or harmful condition. – Result from behavioral, physiological, or genetic adaptation. • Behavioral tolerance- change in behavior – Learning to avoid traps Tolerance • Physiological tolerance- the body of an individual adjusts to tolerate a higher level of pollutant. – Many mechanisms including detoxification • the toxic chemical is converted to a nontoxic form – Internal transport of the toxin to a part of the body where it is not harmful, such as fat cells. Tolerance • Genetic tolerance- (adaptation) when some individuals in a population are naturally more resistant to a toxin than others. – Strains of mosquitoes resistance to DDT – Antibiotic resistance Acute and Chronic Effects • Acute effect is one that occurs soon after exposure. – Usually to large amounts of a pollutant • Chronic effect takes place over a long period – Often as a result of exposure to low levels of pollutant Risk Assessment • The process of determining potential adverse environmental health effects to people exposed to pollutants and potentially toxic materials. Risk Assessment • Such an assessment generally includes four steps: – – – – Identification of the hazard. Dose–response assessment. Exposure assessment. Risk characterization. • Risk assessment is difficult, costly, and controversial. • Risk management integrates the assessment of risk with technical, legal, political, social, and economic issues.