Unit VI: Our Health and Our Future Chapter 20: The Environment & Human Health 20-1 Pollution and Human Health Pollution causes illness in 2 main ways: 1.directly – poisoning us 2.indirectly – many infectious diseases spread in polluted environments (ex. cholera, malaria) WHO = World Health Organization Toxicology: study of the harmful effects of substances on organisms Toxic: poisonous

Know This Table

Toxicity: How dangerous is it? –Almost any chemical is harmful if ingested (taken in) in large enough amounts –Is the concentration of any particular chemical in the environment high enough to be harmful? Dose: amount of a harmful chemical to which a person is exposed –Response: damage to health that results from exposure to a given dose –Persistent Chemicals: break down slowly in the environment (ex. DDT) More people likely to come into contact More likely to remain in the body –Dose-Response Curve: the relative effect of various doses of a drug or chemical on an organism –Threshold Dose: less than = no bad effect. greater than = worse effects

Epidemiology: study of the spread of diseases Epidemiologists – try to find the origins and preventive measures of outbreaks Risk Assessment: estimate of the risk posed by an action or substance –Used to form government regulations on substances (by the EPA – Environmental Protection Agency)

Pollution from Natural Sources Usually become hazardous when concentrated above normal levels Ex. Radon – gas seeps from granite bedrock into buildings  people unknowingly breathe it in  cause cancer Particulates: particles in the air small enough to breathe into the lungs (ex. dust, soot) –Can cause lung irritation – making conditions like bronchitis and emphysema worse –Some natural sources: dust storm, volcanic eruption, wildfires Heavy Metals – occur naturally in rocks and soil (ex. arsenic, cadmium, lead) –Most cause nerve damage when ingested beyond threshold dose

Most Pollutants come from Human Activities Only about 10% of commercial chemicals have been tested for their toxicity –About 1,000 new chemicals are introduced every year Recent Improvements – U.S. regulations have helped reduce our exposure Burning Fuels – in vehicles, home furnaces, power plants, factories –Creates an enormous amount of air pollutants (ex. carbon monoxide, many particulates) –Gasoline & Coal burning contribute to many premature deaths each yr. from asthma, heart disease & lung disorders –It may be possible to predict an area’s death rate based on the amount of pollution

Pesticides: chemicals designed to kill unwanted organisms (insects, fungi, weeds) – Allow us to grow more food by reducing pest damage –:( Often dangerous to humans in large doses –Most in the U.S. break down quickly in the environment into harmless substances –Organophosphates: pesticides that replaced persistent pesticides like DDT BUT… are very toxic causing nerve damage and perhaps cancer –Persistent Chemicals – still used in many developing countries Pose greatest risk to children – internal organs are still developing, eat & drink more in relation to body weight than adults

Industrial Chemicals –Exposed to low levels every day –Especially in new buildings w/ new furnishings –In building materials, carpets, cleaning fluids, furniture, etc. –Older buildings often have lead-based paint (directly linked to brain damage & learning disabilities) –Often not known to be toxic until used for many years Ex. PCBs (polychlorinated biphenyls) – oily fluids used as insulation in electrical transformers – don’t break down in the environment – children in the womb can develop learning problems and IQ deficits – pregnant women warned not to eat fish from the Great lakes – adults develop memory loss

Waste Disposal – much of our pollution is a byproduct of inadequate waste disposal –Methods have improved –Many old landfills are leaking –Many communities still release raw sewage into a river or the ocean after heavy rains –Laws are not always enforced –Radioactive Waste - US government has not decided how to dispose of waste from nuclear power plants Most is stored in barrels at or near the plants Small quantities of radioactive elements leak into nearby waterways

20-2 Biological Hazards Pathogens: organisms that cause disease (cause most of the diseases that have an environmental component) Host: an organism in which a pathogen lives all or part of its life

The Most Deadly Infections Diseases Worldwide

Waterborne Disease Almost 75% of infectious diseases are transmitted through water Vectors: organisms that transmit diseases to people (i.e. mosquitoes) Widespread construction of irrigation canals and dams has increased the habitat for vectors Cholera & Dysentery – enter the water in human feces, cause dehydration by diarrhea & vomiting –Cause most of the infant mortality around the world Malaria: caused by parasitic protists, transmitted by mosquitoes, no effective vaccine exists

Environmental Change & Disease Soil Erosion spreads pathogens, parasites, and chemicals in polluted soil Antibiotic Resistance –Large quantities fed to livestock –Salmonella, E. coli and other bacteria live in livestock and evolve resistance to antibiotics –Misuse of antibiotics in humans has led to drug-resistant strains of pneumonia and tuberculosis (TB) Malaria: mosquitoes that transmit it live in warm places –Global warming may increase the range of malaria –Historically combated with pesticides – mosquitoes have evolved resistance –Newer methods involve spraying growth regulators

Environmental Change & Disease Emerging Viruses: previously unknown viruses –Ex. AIDS (acquired immune deficiency syndrome) – caused by HIV (human immune deficiency virus), hanta virus, Ebola virus, West Nile virus –Not many effective drugs to fight viral diseases –Main defense is vaccinations But… vaccines are very specific and viruses evolve rapidly

Environmental Change & Disease Cross-Species Transfers: pathogens move from one species to another (on the rise) –HIV & West Nile have lived for centuries in some species w/ little damage –Some ecologists think the way we are altering the environment & destroying habitats ensure that diseases like these will become more common in the future. –Examples Hanta Virus – carried by rodents – cause internal bleeding Influenza (flu) – highly contagious –The Greatest Threat to Human Health (as predicted by epidemiologists): Outbreak of a new, very virulent strain of flu virus – spread rapidly through crowded urban populations