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Environmental Health, Toxicology, & Risks. In some parts of Eastern Europe and the former USSR, up to 90% of all children suffer from environmentally linked diseases. 1. Terminology.

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Environmental health toxicology risks l.jpg

Environmental Health, Toxicology, & Risks

In some parts of Eastern Europe and the former USSR, up

to 90% of all children suffer from environmentally linked

diseases.

1


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Terminology

  • Pollution – unwanted change in the environment caused by introducing harmful material, or by producing harmful conditions.

  • Contamination – introduction of undesirable material to one or more of the “spheres” making it unfit.

  • Toxicology – science that studies chemicals that are toxic, or could be toxic .

  • Pollutants – e.g.,

    • infectious agents,

    • toxic heavy metals,

    • organic compounds & persistent organic pollutants (POPs),

    • hormonally active agents (HAA),

    • nuclear radiation,

    • thermal pollution,

    • particulates,

    • electromagnetic fields (EMF),

    • noise pollution,

    • etc.

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FACTBOX

World's 10 Most Polluted Places

February 2, 2009 Below are the world's 10 most polluted places listed, according to Time/CNN

http://www.time.com/time/specials/2007/article/0,28804,1661031_1661028_1661016,00.html

  • Linfen,China (6)- auto/industrial coal/air particulates

  • Tianying, China- mining/processing lead/heavy metals

  • Sukinda, India- chromium mining/processing heavy metals

  • Vapi, India- industrial chemicals & heavy metals

  • La Oroya, Peru (5)- mining/processing Pb, Cu, Zn, SO2

  • Dzerzhinsk, Russia (2) - chemical weapons toxic byproducts

  • Norilsk, Russia (8)- Ni/metal mining/processing air pollution

  • Chernobyl, Ukraine (1)- nuclear meltdown radiation

  • Sumgayit, Azerbaijan- petrochem/indust organic/oil/heavy metals

  • Kabwe, Zambia (4)- Pb mining/processing Pb & Cd

Previous in 2007:

Haina, Dominican Republic (3), Mailuu-Suu, Kyrgyzstan (7), Ranipet, India (9), Rudnaya Pristan, Russia (10)

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What is Health?

  • Health defined by the World Health Organization as: the state of complete physical, mental, & social well-being – not just absence of disease.

  • Disease - a abnormal change in the body’s condition that impairs important physical and psychological functions in response to an environmental factor(nutrition, chemicals, biological agents, etc)

  • Morbidity – illness or disease

  • Mortality – death rate

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smoking?

Deforestation causes insect vectors to move to cities

Infectious diseases used to be the primary cause of death in the past and has been replaced by cardiovascular diseases and cancers

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Morbidity and Quality of Life

  • Death rates do not tell everything about burden of disease.

  • What is the total social burden of diseases?

    • Total economic and social consequences of diseases are difficult to obtain.

      • Disability-Adjusted Life Year (DALY) combines premature deaths and loss of healthy life resulting from illness or disability. It attempts to evaluate the total cost of disease, not just from premature mortality.

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  • Disruption to quality of life & economic productivity caused by premature deaths & loss of healthy life caused by illness/disability.

  • Problems occurring when people live in poverty - eg, 90% DALY losses in the world occur in developing countries.

  • Also when living in crowded conditions – New global mega-cities where managing human-generated wastes is poor.

Morbidity and Quality of Life in Poor Households

(Disability-Adjusted Life Years)

DALY burden

(Millions of yrs lost each yr)*

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Elephantiasis – caused by parasitic worm (& sometimes persistent volcanic ash exposure)

At any given time, about 2 billion people suffer from

worms, protozoans, and other internal parasites.

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Emergent Diseases

  • An emergent disease is one never known before, OR has been absent for at least 20 years.

    • An important factor in the spread of many diseases is speed and frequency of modern travel.

      • Foot and Mouth Disease

      • Ebola

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Recent outbreaks of lethal infectious diseases

At least 30 new infectious diseases have appeared in the past two decades while many well-known have reappeared in more virulent, drug-resistant forms.

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Factors Contributing to the Spread of Contagious Diseases

  • High population densities

  • Contact with water or food that has been contaminated by human waste

  • Settlers pushing into remote areas

  • Human-caused environmental change (elimination of predators increasing rodents, use of fertilizers & pesticides, deforestation, etc)

  • Speed and frequency of modern travel

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Emerging Ecological Diseases

  • Domestic animals and wildlife also experience sudden and widespread epidemics.

    • Distemper (Seals)

    • Chronic Wasting Disease (Deer and Elk)

      • Transmissible Spongiform Encephalopathies

    • Black Band Disease (Coral)

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Antibiotic and Pesticide Resistance

  • Indiscriminate use of antibiotics and pesticides – perfect recipe for natural selection

    • Protozoan that causes malaria now resistant to most antibiotics, and mosquitoes have developed resistance to many insecticides

    • Drug resistance: TB, Staph A (eg, flesh-eating bacteria)

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Toxic Chemicals

  • Hazardous chemicals – dangerous (eg, flammables, explosives, irritants, acids, etc)

  • Toxins – poisonous, kills cells

  • Allergens – activate the immune system

  • Neurotoxins – metabolic poisons affecting nerve cells

  • Mutagens – chemicals or radiation that damage/alter genetic material (DNA)

  • Teratogens - chemicals or other factors that causeabnormalities during embryonic growth & development

  • Carcinogens – substances that causecancer (out of control cell growth)

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Toxins: Movement, Distribution, Fate

  • Depends upon:

  • molecular size,

  • solubility,

  • stability, &

  • reactivity,

  • Organisms affected by:

  • amount of dose,

  • route of entry,

  • timing of exposure, &

  • sensitivity of organisms

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Many routes of synthetic chemicals traveling through the environment

(Brennan & Withgott 2005)

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DDT

(dichloro, diphenyl, trichloroethane pesticide

Bioaccumulation and Biomagnification

  • Bioaccumulation – selective absorption & storage of molecules; dilute toxins in the environment can reach dangerous levels inside cells and tissue

  • Biomagnification - large number of organisms at a lower trophic level accumulates toxin and toxin is concentrated in a predator at a higher trophic level(concentrates as it moves up the food chain)

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Rachel Carson - A Voice for Nature

  • In 1962, Silent Spring alerted the public to the dangers of indiscriminate pesticide use.

  • Carson called for selective, ecologically sound use of pesticides.

  • All 12 of the most toxic agents in her book were banned or severely restricted.


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Peregrine falcons disappeared from the eastern U.S. in 1960s due to excess pesticide use

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“DDT (dichlorodiphenyltrichloroethane) Powerful Insecticide, Harmless to Humans”

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Pesticides and Child Development in Mexico’s Yaqui Valley

  • Elizabeth Guillette (anthropologist) – 1994

  • Valley farmers used pesticides but foothill farmers continued traditional farming

  • Valley children were far behind foothill children developmentally in:

    • Coordination

    • Physical endurance

    • Long-term memory

    • Fine-motor skills

(Less exposure to pesticides)

(More exposure to pesticides)

21

(Brennan & Withgott 2005)


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Minimizing Toxic Effects

  • Every material can be poisonous under some conditions

  • Taken in small doses, most toxins can be broken down or excreted before they do much harm – belief in 1800s, arsenic (Napoleon)

  • Liver - primary site of detoxification

  • Tissues and organs - high cellular reproduction rates replace injured cells - down side: tumors, cancers possible

22


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Measuring Toxicity

Animal Testing

  • Most commonly used and widely accepted

  • Expensive - hundreds of thousands of dollars to test one toxin at low doses

  • Time consuming

  • Often very inhumane

  • Difficult to compare toxicity of unlike chemicals or different species of organisms

23


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A Typical Dose/Response Curve

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Median Lethal Dose (LD) and Median Toxic Dose (TD)

LD50 - the dose

of a toxin that is

lethal to half the

test population

TD50 - the dose of a toxin that produces a toxic response in half the test population

25


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Acute Lethal Doses for Some Toxic Organic Chemicals

mouse

rat

It is useful to group materials according to their

relative toxicity. (~ 31 billion ng/oz)

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Acute Versus ChronicDoses and Effects

  • Acute effects - immediate health effect caused by a single exposure to a toxin (effects are reversible if survive)

  • Chronic effects - long lasting (or permanent) health effect caused by:

    • a single exposure to a very toxic substance (experiments generally done this way),

      OR

    • continuous or repeated sub-lethal exposures to a toxin (experiments using this level are expensive and time consuming)

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Risk Assessment and Acceptance

  • Risk = probability of harm X probability of exposure

  • A number of factors influence how we perceive relative risks associated with different situations

    • interests as industrialist vs environmentalist,

    • understanding probability,

    • personal experience,

    • our abilities to control our fate,

    • news media biases,

    • fear of technology

  • Accepting risks - we go to great lengths to avoid some dangers, while gladly accepting others

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Risks of Death

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McKinney & Schoch

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Establishing Public Policy

In setting standards for environmental toxins, we need to consider:

  • Combined effects of exposure to many different sources of damage (synergistic effects of different toxins, eg the smoking & asbestos effects on lung cancer rates)

  • Different sensitivities of members of the population

  • Effects of chronic as well as acuteexposures

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Regulatory Decisions – EPA framework

Other Factors Not Specific to the Problem

The Science Specific to the Problem

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Relative Risks to Human Welfare

How about RISKS to the environment regardless of effects on humans?

Relative Risks to Human Welfare

Cunningham & Cunningham 2002

  • How do we determine what the risk is from different physical/ chemical changes in the environment?

  • How much of the ranking is based on our values –

    • do they reflect the science?

    • do they reflect concern for the environment?

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Summary:

  • Environmental Health Hazards

    • Infectious Organisms

    • Emergent Diseases

    • Antibiotics and Pesticide Resistance

    • Toxic Chemicals

  • Distribution and Fate of Toxins

  • Minimizing Toxic Effects

  • Measuring Toxicity

  • Risk Assessment

  • Public Policy

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