Environmental Science (SCBI 360) Environmental health and toxicology. Dr. Patompong Saengwilai SC2-306;

Transcription

1 Environmental Science (SCBI 360) Environmental health and toxicology Dr. Patompong Saengwilai SC2-306;

2 Environmental Health Assesses environmental factors that influence human health and quality of life Seeks to prevent adverse effects on human health and ecological systems Contains environmental toxicology within its scope

3 Hazards Types include: Physical hazards (floods, blizzards, landslides, radon, UV exposure) Chemical hazards (disinfectants, pesticides) Biological hazards (viruses, bacterial infections) Cultural or lifestyle hazards (drinking, smoking, bad diet, crime in neighborhood)

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6 InfecIous diseases In communicable or transmissable disease, a pathogen attacks a host, either directly or through a vector (e.g., mosquito that transfers a malaria parasite to hosts) and the pathogen can be transmitted from one host to another. Infectious disease causes 25% of deaths in the world and nearly half of deaths in developing nations.

7 Respiratory and digestive diseases Other Maternal and perinatal conditions Injuries 10.0% 5.2% 9.1% 12.5% 7.9% Infectious diseases 14.9 million 26.1% Cardiovascular diseases 29.3% Annual deaths (millions) Cancers 0 Respiratory AIDS infections (influenza, pneumonia, etc.) Diarrheal diseases TB Malaria Childhood diseases (measles, Pertussis, tetanus, etc.) Leading causes of death across the world, 2004 Leading causes of death by infectious disease, 2004

8 Toxicology is the study of poisonous substances and their effects on humans and other organisms. Toxicologists assess and compare toxic agents, or toxicants, for their toxicity, the degree of harm a substance can inflict. Environmental toxicology focuses on effects of chemical poisons released into the environment.

9 Toxicants are studied.come from or are discharged into the environment and their: Health effects on humans Effects on animals Effects on ecosystems Animals are studied: For their own welfare As canaries in a coal mine to warn of effects on humans

10 SyntheIc chemicals are everywhere Many thousands have been produced and released. Some persist for long time periods or travel great distances. Of the 100,000 synthetic chemicals on the market today, very few have been thoroughly tested for harmful effects USGS study: 80% of U.S. streams contain up to 82 wastewater contaminants, including antibiotics, perfumes, detergents, drugs, steroids, disinfectants, and so forth.

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12 There has been widespread synthetic chemical production since WWII. People were largely unaware of the health risks of many toxicants. The potent insecticide DDT was sprayed widely in public areas, even on people.

13 Silent Spring Carson s 1962 book alerted the public that DDT and other pesticides could be toxic to animals and people. Further research led the EPA to ban DDT in These developments were central to the modern environmental movement.

14 Types of toxicants Carcinogens: cause cancer Mutagens: cause mutations in DNA Teratogens: cause birth defects Allergens: cause unnecessary immune response Neurotoxins: damage nervous system Endocrine disruptors: interfere with hormones

15 The 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. Thalidomide baby Butch Lumpkin learned to overcome his deformed arms and fingers to become a professional tennis instructor.

16 Endocrine disrupion Some chemicals, once inside the bloodstream, can mimic hormones. If molecules of the chemical bind to the sites intended for hormone binding, they cause an inappropriate response. Thus these chemicals disrupt the endocrine (hormone) system.

17 Hormone Response Receptor Cell membrane Inside cell Normal hormone binding Hormone mimic Hormone Receptor Cell membrane Response (identical to that caused by hormone) Inside cell Hormone mimicry

18 The hormone system is geared to working with tiny concentrations of hormones so, it can respond to tiny concentrations of environmental contaminants. Have chemicals in the environment acted as endocrine disruptors in humans?

19 Frogs 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. The fierce criticism from atrazine s manufacturer reflects the high stakes in environmental toxicology.

20 A 1992 study summarized results of sperm count studies worldwide since Data showed a significant decrease in men s sperm counts over 50 years. Declining sperm count in humans, based on 61 studies

21 Endocrine disrupion Others hypothesize that endocrine disruptors are behind the rise in testicular cancer in many nations.

22 Denmark Norway Germany Finland Sweden Estonia Increasing incidence of testicular cancer

23 Toxicants move in specific ways Synthetic chemicals take many routes in traveling through the environment.

24 Pesticides and fertilizers LE 10-7 Industry and manufacturing Home Work Medical facilities and public spaces Agriculture: crops, rangeland, feedlots Soil Water: surface and groundwater Air Medicines and materials Drinking water Air for breathing Plant growth Drinking water Genes, womb, breast milk Humans Hunting and harvesting Human fetuses and babies Non-human biota

25 Toxicants concentrate in water Surface water and groundwater can accumulate toxicants. Runoff from large areas of land drains into water bodies, becoming concentrated. Toxicants in groundwater or surface water reservoirs used for drinking water pose potential risks to human health.

26 Airborne toxicants Volatile chemicals can travel long distances on atmospheric currents. Polychlorinated Biphenyls (PCBs) are carried thousands of miles from developed nations of the temperate zone up to the Arctic, where they are found in tissues of polar bears and seals.

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28 Persistence Some chemicals are more stable than others, persisting in the environment. DDT and PCBs are persistent. Bt toxin in GM crops is not persistent. Temperature, moisture, sun exposure, and so forth, affect the rate of degradation. Most toxicants degrade into simpler breakdown products. Some of these are also toxic. (DDT breaks down to DDE, also toxic.)

29 Poison accumulate in Issues The body may excrete, degrade, or store toxicants. Fat-soluble ones are stored. DDT is persistent and fat soluble, so it builds up in tissues: bioaccumulation. Bioaccumulated chemicals may be passed on to animals that eat the organism up the food chain

30 Poison moves up food chain At each trophic level, chemical concentration increases: biomagnification. DDT concentrations increase from plankton to fish to fish-eating birds.

31 DDT concentration (parts per million) Osprey 25 ppm Large fish 2 ppm Small fish 0.5 ppm Zooplankton 0.04 ppm Water ppm

32 Not all toxic are syntheics Although toxicology tends to focus on man-made chemicals, it s important to keep in mind that there are plenty of natural toxicants. Many are toxins produced by animals or plants for protection against predators and pathogens.

33 Study effects of hazards Toxicologists study effects in several major ways: Wildlife toxicology studies Human epidemiological studies Dose-response studies in the lab

34 Approach in studying Environmental toxicology Human studies rely on: Case history = observation and analysis of individual patients Epidemiological studies = long-term, large-scale comparisons of different groups of people Animal testing

35 Epidemiology Advantages: Realistic All real-life factors included Disadvantages: Statistically correlational only; does not prove causation Takes many years to get results

36 Mixing toxicology with anthropology Mexican children were tested for pesticide effects.

37 4-year-olds 5-year-olds Drawings by children in the foothills 4-year-olds 5-year-olds Drawings by children in the valley

38 Dose response analysis Dose-response analysis is a method of determining the toxicity of a substance by measuring response to different doses. Lab animals are used. Mice and rats breed quickly and give data relevant to humans because they share mammal physiology with us. Responses to doses are plotted on a dose-response curve.

39 Dose response curve Threshold = dose at which response begins LD 50 = dose lethal to 50% of test animals

40 Dose-response curves allow us to predict effects of higher doses. By extrapolating the curve out to higher values, we can predict how toxic a substance may be to humans at various concentrations. In most curves, response increases with dose. But this is not always the case; the increase may not be linear. With endocrine disruption, it may decrease.

41 Factor affecing toxicity Not all people are equal. Sensitivity to a toxicant can vary with sex, age, weight, and so forth. Babies, older people, or those in poor health are more sensitive. Type of exposure: acute = high exposure in short period of time chronic = lower amounts over long period of time

42 Mixtures of toxicants Substances may interact when combined together. Mixes of toxicants may cause effects greater than the sum of their individual effects. These are called synergistic effects. A challenging problem for toxicology: There is no way to test all possible combinations! (And the environment contains complex mixtures of many toxicants.)

43 Which causes birth defects? a. Allergen b. Mutagen c. Carcinogen d. Teratogen e. Endocrine disruptor

44 Which statement is NOT correct regarding the insecticide DDT? a. It was criticized in the book Silent Spring. b. It helps fight malaria. c. It is persistent and bioaccumulates. d. It has no toxic breakdown products. e. Its use was banned by the EPA.

45 Epidemiological studies? a. Can prove a certain toxicant causes a certain effect. b. Search for statistical association between hazard and effect. c. Are rapidly completed. d. Take place with lab animals.

46 Which statement is FALSE? a. Babies are more sensitive to toxicants than 30- year-olds. b. Synergistic effects can occur with mixtures of chemicals. c. Chronic exposure occurs over a short period of time. d. Some doses may elicit no measurable response.

47 Describe some environmental hazards you think you may be living with indoors. How do you think you may have been affected by indoor or outdoor environmental hazards? What steps do you plan to take to deal with these toxicants in your own life?