Chapter 14: Environmental Health and Toxicology

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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

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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