Chapter 14, Risk and Toxicology

1. Chapter 14, Risk and Toxicology Know the different types of hazards Understand the role of disease Know what toxicology is

2. Types of Hazards • Environmental health = assesses environmental factors that influence human health and quality of life • Including natural and human-caused factors • Physical hazards = occur naturally in our environment • Earthquakes, volcanoes, fires, floods, droughts • We can’t prevent them, but we can prepare for them • We increase our vulnerability by deforesting slopes (landslides), channelizing rivers (flooding), etc. • We can reduce risk with better environmental choices

3. Types of Hazards • Chemical hazards =synthetic chemicals such as pharmaceuticals, disinfectants, pesticides • Harmful natural chemicals(e.g., venom) also exist • Biologicalhazards =result from ecological interactions • Viruses, bacteria, and other pathogens • Infectious disease =species parasitize humans, fulfilling their ecological roles • Vector = an organism that transfers a pathogen to a host • We can’t avoid risk, but we can reduce infection

4. Types of Hazards • Cultural = result from where we live, our socioeconomic status, our occupation, our behavioral choices • We can minimize some, but not all, of these hazards • Smoking, drug use, diet and nutrition, crime, mode of transportation • Health factors (e.g., living near toxic waste) are often correlated with poverty

6. Indoor environmental health hazards • Radon = a highly toxic, radioactive gas that is colorless and undetectable • It can build up in basements • Asbestos = a mineral that insulates, muffles sounds, and resists fire

7. Indoor environmental health hazards Lead poisoning = caused by lead Damages the brain, liver, kidney, and stomach Causes learning problems, behavior abnormalities, and death Exposure is from drinking water that flows through lead pipes or from lead paint

9. A recently recognized hazard • Polybrominateddiphenyl ethers (PBDEs) = has 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 banned in Europe, concentrations have decreased • The U.S. has not addressed the issue

10. 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 • Poverty and poor hygiene foster illnesses

11. Infectious diseases kill millions • Infectious diseases kill 15 million people/year • Half of all deaths in developing countries • Money lets developed countries have access to hygiene and medicine

13. Infectious and noninfectious diseases • Lifestyles in developed nations affect diseases • U.S. smoking dropped 38% • But obesity has doubled • Public health decreases some infectious diseases • Some (AIDS) are spreading • Some develop resistance to antibiotics

15. Diseases, the environment, and society • Our mobility spreads diseases • West Nile Virus spread from Africa to all lower 48 U.S. states in 5 years • New diseases are emerging • H5N1 avian flu, H1N1 swine flu • Climate change will expand the range • of diseases • To predict and prevent diseases, experts deal • with complicated interrelationships • In technology, land use, and ecology

16. Disease • The best way to reduce disease? • Improve the basic living conditions of the poor • Food security, sanitation, clean drinking water • Expanded access to health care • Health clinics, immunizations, pre- and postnatal care • Education campaigns work in rich and poor nations • Public service and governments give advice • Packaging and ads advise us on smoking, etc. • Sex and reproductive health education slows population growth and spread of HIV/AIDS

17. Toxicology studies poisonous substances • 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 • Environmental toxicology = deals with toxic substances that come from or are discharged into the environment • Studies health effects on humans, other animals, and ecosystems

18. Balancing risks and rewards • There is a tradeoff between the risk and reward of most hazards • We must judge how these compare • We use Bisphenol A despite its health risks • Are safer and affordable alternatives available? • Don’t forget, chemicals have given us our high standard of living • Food, medicine, conveniences

19. Toxic substances in the environment • The environment contains natural chemicals that may pose health risks • Toxins = toxic chemicals made in tissues of living organisms • But synthetic chemicals are also in our environment • Every human carries traces of industrial chemicals The U.S. makes or imports 250 lb of chemicals for every person in the country

20. Chemicals are in the air, water, and soil • 80% of U.S. streams contain 82 contaminants • Antibiotics, detergents, drugs, steroids, solvents, etc. • 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 high enough to affect aquatic life

22. Synthetic chemicals are in all of us • 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 • Not all synthetic chemicals pose health risks • But very few of the 100,000 chemicals on the market have been tested

23. Silent Spring began the debate over chemicals In the 1960s, untested pesticides were sprayed over public areas, with assumption they would do no harm • Rachel Carson’s Silent Spring (1962) showed DDT’s risks to people, wildlife, and ecosystems • Chemical companies challenged the book • Discrediting Carson’s personal reputation • DDT was banned in the U.S. in 1973 • But is still made in the U.S. and exported

24. Toxicants come in different types Neurotoxins = assault the nervous system Allergens =over stimulate the immune system

25. Toxins may concentrate in water • Runoff carries toxins from land to surface water • Chemicals in the soil can leach into groundwater • Contaminating drinking water • Chemicals enter organisms through drinking or absorption • Aquatic organisms (fish, frogs, etc.) are good pollution indicators • Contaminants in streams and rivers enter drinking water and the air

26. Routes of chemical transport

27. Airborne substances can travel widely • Chemicals can travel by air • Their effects can occur far from the site of use • Pesticide drift = airborne transport of pesticides • Synthetic chemicals are found globally • In arctic polar bears, Antarctic penguins, and people in Greenland

29. Some toxicants persist • Toxins can degrade quickly and become harmless • Or they may remain unaltered and persist for decades • Rates of degradation depend on the substance, temperature, moisture, and sun exposure • Breakdown products = simpler products that toxicants degrade into • May be more or less harmful than the original substance • DDT degrades into DDE, which is also highly persistent and toxic

30. Toxicants can accumulate and biomagnify • Toxicants in the body can be excreted, degraded, or stored • Fat-soluble toxicants are stored in fatty tissues • Bioaccumulation = toxicants build up in animal tissues • Biomagnification = concentrations of toxicants become magnified • Near extinction of peregrine falcons and bald eagles

32. Not all toxicants are synthetic • Toxic chemicals also exist naturally and in our food • Don’t assume natural chemicals are all healthy and synthetic ones are all harmful • Some scientists feel that natural toxicants dwarf our intake of synthetic chemicals • Natural defenses are effective against synthetics • Environmentalists say synthetic toxins: • Are harder to metabolize and excrete • Persist and accumulate • Enter people in ways other than in food