Chapter 14: Environmental Health and Toxicology .
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Transcript of Chapter 14: Environmental Health and Toxicology .
Chapter 14: Environmental Health and Toxicology
www.aw-bc.com/Withgott
Environmental Health
assesses environmental factors that influence human health and quality of life
natural human-caused
Physical Hazards
natural disasters earthquakes volcanic eruption fires floods blizzards landslides hurricanes droughts UV radiation difficult to predict areas of high risk can be determined
Chemical Hazards
synthetic chemicals society produces– disinfectants (Lysol products)– pesticides (DDT)
Biological Hazard
ecological interaction between organisms infectious diseases swine flu: virus tuberculosis: bacteria Mycobacterium
tuberculosis malaria: parasite Plasmodium sp. cholera: bacteria Vibrio cholerae
Cultural Hazards
behavioral choices– smoking, sunbathing, drug use
location we live in– near an active volcano
Alaskan volcano 2006apod.nasa.gov/apod/ap060607.html
socioeconomic status– Cadillac Heights
occupation– hazardous work or
lack of safety equipment
Dallas Flood June 2007
www.dallasnews.com
Disease
major factor of environmental health
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Indoor Health Hazards
radon– highly toxic gas– seeps up from the ground in certain areas
lead– water from lead pipes and lead paint in homes and toys – damages brain, liver, kidney and stomach– learning disabilities– behavioral abnormalities– anemia– hearing loss– death
Indoor Health Hazards
asbestos– form long thin microscopic fibers– used in insulation (sound, heat)– resists fire– dangerous when inhaled: asbestosis & cancer
PBDEs– fire-retardant– used in electronics, plastics and furniture– evaporates at very low rates– accumulates in tissues– may affect nervous system and cause cancer– banned in the EU
Toxicology
study of poisonous substances environmental toxicology deals with toxics
discharged in the environment– on humans– other animals– ecosystems
Environmental Toxicology
natural toxins– radon, arsenic, mercury– exuded substances from plants and animals
human-made toxins– wastewater contaminants– pesticides & herbicides– Silent Spring by naturalist Rachel Carson
effect of DDT on humans, animals and ecosystems DDT is still in use in tropical areas to control diseases
Types of Toxicants
carcinogens– causes cancer
mutagens– causes mutations in fetus
teratogens– affects fetus during gestation causing birth
defects– Thalidomide
Types of Toxicants
allergens– weakens immune system – increase in asthma
neurotoxins– inorganic: heavy metals (lead, mercury)
Minamata case
– organic: pesticides (DDT, mothballs, nerve gas) some are very stable and can last decades, others may
only last hours
Types of Toxicants
endocrine disruptors– interfere with hormones– affects growth, reproduction, behavior, brain function– similar to hormones so they "mimic" them
certain pesticides→ feminization of males possible cause of human sperm count drop
worldwide possible cause of increase rates of
– testicular cancer– undescended testicles– genital birth defects in men– female breast cancer
Effects of Endocrine Disruptors
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Other Effects of Endocrine Disruptors
brain functioning PCB contamination of food (fish)
– lower birth weight of babies– smaller heads– weak and jerky reflexes– tested poorly in intelligence tests
Means of Toxins' Disperse
water– many are soluble in water– runoff– concentrates toxins in surface waterways– enters tissue through drinking or contact
air– pesticide drift– toxins appeared in tissues of arctic polar bears and
antarctic penguins– thought to be due to global atmospheric circulation
Distribution of Toxins
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Toxins in the Food Chain
BioaccumulationBioaccumulation– stored in tissues according to its solubility
BiomagnificationBiomagnification– increase in toxin concentration up in the food
chain Bald eagle case related to DDT population decrease of polar bears
Epidemiology Studies
application of experimentation due to conditions in the environment
– effect of a contaminant in the air to a population already established
drawback– takes too long– many other factors may affect the health of the subjects– statistical association between health hazard and effect but
it does not confirm it as the cause of the problem
Dose-responce Toxicity
effect of toxins according to amount in the system/body– LD50→ lethal dose for 50%
low LD50 means high mortality high LD50 means low mortality
– ED50→ effective dose for 50% half of the population gets sick but doesn't die
Threshold– toxin level above which a responce is observed
Exposure vs Responce
acute responce– responce to a high exposure during a short period of time
Union Carbide accident in India chronic responce
– responce to a low concentration of a toxin but during a long period of time
exposure to Teflon synergistic effect
– unpredicted consequences of mixing toxins sum cancel multiply or exacerbate
Risk Assessment & Risk Management
Assessment: collection and interpretation of scientific data identifying outlining problems
– expressed in probability risk of crashing if driving too fast
Management: formulation of policy to minimize risk– influenced by political pressure– considers economics and ethics
EPA, CDC, FDA– banning of Seldain D– banning of DDT– containing cholera
Philosophical Approaches
innocent-until-proven-guilty innovation goes ahead doesn't slow down technology can result in disasters recall
Vioxx (short period of testing) vitamins & herbs (unregulated)
Philosophical Approaches
harmful until proven otherwise– precaution principle– experimentation has to be done thoroughly– long process]
regulated medications
EPA
Federal Insecticide, Fungicide and Rodenticide Act of 1947 assured the effectiveness of the product
EPA was created to protect the public and environment from toxic chemicals using risk assessment and management
EPA examines the data from the manufacture assesses the possible risks to humans and
environment approves, denies or sets limits to use
Toxic Substances Control Act (1976)
regulation of synthetic chemicals by the EPA criticized as too weak
– screening of industry is minimal– EPA needs to show proof of toxicity and not the
other way around only 10% have been tested for toxicity only 2% have been tested for carcinogens fewer than 1% are government regulated none have been tested for endocrine, nervous or
immune system damage
International Regulation
Stockholm Convention on persistent Organic Pollutants of 2004
"dirty dozen" guidelines to phase off these chemicals REACH pushes innovation of new chemicals
to do the same job but be less toxic
Dirty Dozen
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The End