environmental health and toxicity lecture 2013

7/30/2019 Environmental Health and Toxicity Lecture 2013

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Environmental Health and Toxicology


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Outline:

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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ENVIRONMENTAL HEALTH HAZARDS

Health - A state of complete physical, mental,and social well-being.

Disease -A deleterious change in the bodyscondition in response to an environmentalfactor.

Diet and nutrition, infectious agents, toxicchemicals, physical factors, and

psychological stress all play roles inmorbidity (illness) and mortality (death).


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Infectious Organisms

For most of human history, the greatesthealth threats have been pathogenicorganisms.

Infectious diseases are still responsible forabout 33% of all disease-related deaths.

- Majority of deaths in poorer countrieswith poor nutrition, sanitation, and

vaccination programs.


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Morbidity and Quality of Life

Death rates do not tell everything aboutburden of disease.

Total economic and social consequencesof diseases are difficult to obtain.

- Disability-Adjusted Life Year (DALY)combines premature deaths and loss ofhealthy life resulting from illness or

disability.


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Disability-Adjusted Life Year

WHO reports communicable diseases areresponsible for nearly half of all 1.2 billionDALYs lost each year.

About 90% of all DALY losses occur indeveloping world where one-tenth of allhealth care dollars are spent.

- Malnutrition exacerbates many diseases.


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DALYs = Disability Adjusted Life YearsThe sum of years of potential life lost due to premature

mortality and the years of productive life lost due to disability.

. http://www.who.int/mental_health/management/depression/daly/en/


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Emergent Diseases

An emergent disease is one never knownbefore, or has been absent for at least 20years.

An important factor in the spread of manydiseases is speed and frequency ofmodern travel.

- Foot and Mouth Disease

- Ebola


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Foot-and-Mouth Disease

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Foot-and-mouth disease or

hoof-and-mouth disease

(Aphthae epizooticae) is an

infectious and sometimes

fatal viraldisease that affects

cloven-hoofedanimals,including domestic and wild

bovids. The virus causes a

high fever for two or three

days, followed by blistersinside the mouth and on the

feet that may rupture and

cause lameness.

http://en.wikipedia.org/wiki/Foot-and-mouth_disease
http://en.wikipedia.org/wiki/Infectious_diseasehttp://en.wikipedia.org/wiki/Virus_(biology)http://en.wikipedia.org/wiki/Diseasehttp://en.wikipedia.org/wiki/Cloven-hoofhttp://en.wikipedia.org/wiki/Animalshttp://en.wikipedia.org/wiki/Bovidaehttp://en.wikipedia.org/wiki/Lamenesshttp://en.wikipedia.org/wiki/Lamenesshttp://en.wikipedia.org/wiki/Lamenesshttp://en.wikipedia.org/wiki/Lamenesshttp://en.wikipedia.org/wiki/Bovidaehttp://en.wikipedia.org/wiki/Animalshttp://en.wikipedia.org/wiki/Cloven-hoofhttp://en.wikipedia.org/wiki/Cloven-hoofhttp://en.wikipedia.org/wiki/Cloven-hoofhttp://en.wikipedia.org/wiki/Diseasehttp://en.wikipedia.org/wiki/Virus_(biology)http://en.wikipedia.org/wiki/Infectious_disease


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Ebola

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Ebola hemorrhagic fever (Ebola

HF) is a severe, often-fatal disease inhumans and nonhuman primates

(monkeys, gorillas, and

chimpanzees) that has appeared

sporadically since its initial

recognition in 1976.


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Emerging Ecological Diseases

Domestic animals and wildlife alsoexperience sudden and widespreadepidemics.

Distemper (Seals)

Chronic Wasting Disease (Deer and Elk)

- Transmissible SpongiformEncephalopathies

Black Band Disease (Coral)


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Chronic Wasting Disease

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Infectious Disease Outbreaks


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Antibiotic and Pesticide Resistance

Protozoan parasite that causes malaria isnow resistant to most antibiotics, while themosquitoes that transmit it have developedresistance to many insecticides.

Short life spans.

- Speeds up natural selection andevolution.

Human tendency to overuse pesticidesand antibiotics.


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Antibiotic Resistance

CONSEQUENCES OF INCREASING


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CONSEQUENCES OF INCREASINGANTIBIOTIC RESISTANCE

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Methicillin-resistant Staphylococcus aureus (MRSA), a strain

of bacteria no longer sensitive to different forms of penicillin.It can cause complicated skin infections and pneumonia and

requires stronger antibiotics such as vancomycin for treatment.

Multidrug-resistant tuberculosis, which is very difficult

to treat because it is caused by microorganisms that are resistant

to 2 of the first-choice drugs used to treat tuberculosis.


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Antibiotic Use

At least half of the 100 million antibioticdoses prescribed in the US every year areunnecessary or are the wrong drug.

Many people do not finish full-course.

More than half of all antibiotics manufacturedin the US are routinely fed to farm animals tostimulate weight gain.

U S J&J d i t t


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U.S. approves J&J drug-resistanttuberculosis treatment

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By Toni Clarke | ReutersMon, Dec 31, 2012

The U.S. Food and Drug Administration approved the drug,

chemically known as bedaquiline and to be marketed as Sirturo,

on Monday following a positive review by an advisory pane

last month.

Tuberculosis is an air-spread infection that usually attacks the

lungs but it can also affect the brain, the spine and the kidneys.


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Pesticide Resistance

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Toxic Chemicals

Dangerous chemicals are divided into twobroad categories:

Hazardous - Dangerous

-

Flammable, explosive, irritant, sensitizer,acid, caustic.

Toxic - Poisonous

- Can be general or very specific. Oftenharmful even in dilute concentrations.


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Toxic Chemicals

Allergens - Substances that activate theimmune system.

Antigens - Allergens that are recognized asforeign by white blood cells and stimulatethe production of specific antibodies.

- Other allergens act indirectly by bindingto other materials so they become

antigenic.


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Toxic Chemicals

Sick Building Syndrome

Headaches, allergies, and chronic fatiguecaused by poorly ventilated indoor aircontaminated by molds, carbon monoxide,nitrogen oxides, and other toxic chemicals.

- Worker absenteeism and reducedproductivity.

EPA estimates $60 billion annual loss.

NIOSH Al t P ti O ti l


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NIOSH Alert: Preventing OccupationalRespiratory Disease .

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Research studies have shown that

exposures to building dampness

and mold have been associated with

respiratory symptoms, asthma,

hypersensitivity pneumonitis,

rhinosinusitis, bronchitis, and

respiratory infections. Individualswith asthma or hypersensitivity

pneumonitis may be at risk for

progression to more severe disease

if the relationship between illnessand exposure to the damp building

is not recognized and exposures

continue.

http://www.cdc.gov/niosh/docs/201

3-102/


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Toxic Chemicals

Neurotoxins - Special class of metabolic

poisons that specifically attack nerve cells. Different types act in different ways.

- Heavy Metals kill nerve cells.

- Anestheticsand ChlorinatedHydrocarbons disrupt nerve cellmembranes.

- Organophosphates and Carbamatesinhibit signal transmission between nervecells.


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Alice's Adventures in Wonderland

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The phrasemad as a hatterisused to describe the chronic side

effects of mercury exposure from

the process of making felt hats.

Lewis Carroll, author ofAlice's

Adventures in Wonderland, formedthe 'Mad Hatter' character in the

1800s.The Hatter acts irrationally

in the novel and takes a bite of a

teacup in the trial of the Knave ofHearts.

http://en.wikipedia.org/wiki/Mercur

y_poisoning
http://en.wikipedia.org/wiki/Mercury_poisoninghttp://en.wikipedia.org/wiki/Mercury_poisoninghttp://en.wikipedia.org/wiki/Mercury_poisoninghttp://en.wikipedia.org/wiki/Mercury_poisoning


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Cadmium

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Cadmium and its compounds are

highly toxic and exposure to this

metal is known to cause cancer and

targets the bodys cardiovascular,

renal, gastrointestinal,

neurological, reproductive, andrespiratory systems.

Cadmium became an importantmetal in the production of nickel-

cadmium (Ni-Cd) rechargeable

batteries.

http://www.osha.gov/SLTC/cadmiu


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Lead

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Lead overexposure is one of the mostcommon overexposures found in industry and is

a leading cause of workplace illness. Therefore,

OSHA has established the reduction of lead

exposure to be a high strategic priority

Lead poisoning is the leadingenvironmentally induced illness in

children. At greatest risk are children under theage of six because they are undergoing rapid

neurological and physical development.http://www.osha.gov/SLTC/lead/index.html


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Toxic Chemicals

Mutagens - Agents that damage or altergenetic material.

Radiation

Teratogens - Specifically cause abnormalitiesduring embryonic growth and development.

Alcohol - Fetal Alcohol Syndrome

Carcinogens - Substances that cause cancer. Cigarette smoke


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FAS

31http://en.wikipedia.org/wiki/Fetal_Alcohol_Syndrome
http://en.wikipedia.org/wiki/Fetal_Alcohol_Syndromehttp://en.wikipedia.org/wiki/Fetal_Alcohol_Syndrome


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US Age-Adjusted Cancer Death Rates


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Endocrine Hormone Disruptors

Chemicals that disrupt normal endocrinehormone functions.

Hormones are chemicals released in bloodby glands to regulate development and

function of tissues and organs elsewherein the body.

- Environmental Estrogens and

Androgens


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Phthalates

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A 2012 study suggested that

high levels of phthalates maybe connected to the current

obesity epidemic in children. It

was found that obese children

show greater exposure to

phthalates than non-obesechildren. It was reported that

the obesity risk increases

according to the level of the

chemical found in the

children's bloodstream.

http://en.wikipedia.org/wiki/Ph

thalate#Endocrine_disruption

Phthalates are found in some soft toys,

flooring, medical equipment, cosmetics

and air fresheners. They are of

potential health concern because theyare known to disrupt the endocrine

system of animals, and some research

has implicated them in the rise of birth

defects of the male reproductive system.

http://en.wikipedia.org/wiki/Endocrine_disruptor#Phthalates


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Diet

Strong correlation between cardiovasculardisease and the amount of salt and animalfat in an individuals diet.

Highly-processed foods, fat, and smoke-

cured, high nitrate meats appear to beassociated with cancer.

Nearly 2/3 of all Americans are considered

overweight.


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DISTRIBUTION AND FATE OF TOXINS

Solubility - Chemicals are divided into twomajor groups:

- Dissolve more readily in water.

- Dissolve more readily in oil.

Water-soluble compounds move rapidlythrough the environment, and have readyaccess to most human cells.

Oil-soluble molecules generally need acarrier to move through the environment.


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Bioaccumulation and Biomagnification

Cells have special mechanisms forBioaccumulation - Selective absorption andstorage.

Dilute toxins in the environment can build

to dangerous levels inside cells andtissues.

Biomagnification - Toxic burden of a large

number of organisms at a lower trophic levelis accumulated and concentrated by apredator at a higher trophic level.


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Sensitivity and Developmental Stage

Many factors help determine reaction of anindividual to a given dose.

Age

Sex

Body Weight

Nutritional / Immunological Status

Repair Mechanisms


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Persistence

Some chemical compounds are veryunstable and degrade rapidly under mostconditions, thus their concentrations declinequickly after release.

Others are more persistent.

Stability can cause problems as toxiceffects may be stored for long period of

time and spread to unintended victims.- (DDT)


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Bioaccumulation


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Chemical Interactions

Antagonistic Reaction - One materialinterferes with the effects, or stimulates thebreakdown, of other chemicals.

Additive Reaction - Effects of each chemical

are added to one another.

Synergistic Reaction - One substancemultiplies the effect of the other.

Synergistic Effects of Mercury with Other Toxic


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Synergistic Effects of Mercury with Other ToxicMetals: Extreme Synergistic Toxicity

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Mercury and lead are extremely

neurotoxic and cytotoxic, but theircombined synergistic effect is much

worse(1,4). A dose of mercury

sufficient to kill 1% of tested rats,

when combined with a dose of leadsufficient to kill less than 1% of

rats, resulted in killing 100 % of

rats tested(1a,4). Thus with

combined exposure the safe dose is

1/100 as much as the dose

individually.

MECHANISMS FOR MINIMIZING


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MECHANISMS FOR MINIMIZINGTOXIC EFFECTS

Every material can be poisonous undercertain conditions.

Most chemicals have a safe thresholdunder which their effects are insignificant.

Metabolic Degradation

In mammals, the liver is the primary site ofdetoxification of both natural andintroduced poisons.

E i


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Excretion

Effects of waste products and environmentaltoxins reduced by eliminating via excretion.

Breathing

Kidneys

- Urine

MEASURING TOXICITY


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MEASURING TOXICITY

Animal Testing

Most commonly used and widely acceptedtoxicity test is to expose a population oflaboratory animals to measured doses of

specific toxins.

- Sensitivity differences pose a problem.

Dose Response Curves

LD50 - Dose at which 50% of the testpopulation is sensitive.

LD50


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LD50

P l ti S iti it V i ti


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Population Sensitivity Variations

A t Ch i Eff t


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Acute vs. Chronic Effects

Acute Effects - Caused by a single exposure

and result in an immediate health problem.

Chronic Effects - Long-lasting. Can be resultof single large dose or repeated smaller

doses.

Very difficult to assess specific healtheffects due to other factors.

RISK ASSESSMENT


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RISK ASSESSMENT

Factors influencing risk perception:

Rating risks based on agendas.

Most people have trouble with statistics.

Personal experiences can be misleading.

We have an exaggerated view of ourabilities to control our fate.

News media sensationalizes rare events.

Irrational fears lead to overestimation ofcertain dangers.

- Fear of the unknown.

A ti Ri k


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Accepting Risks

Most people will tolerate a higher probability

of occurrence of an event if the harm causedby that event is low.

Harm of greater severity is acceptable only

at low levels of frequency.

- EPA generally assumes 1 in 1 million isacceptable risk for environmental

hazards.


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ESTABLISHING PUBLIC POLICY


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Biggest problem in making regulatory

decisions is that we are usually exposed tomany sources of harm, often unwillingly.

May not be reasonable to demand protection

from every potentially harmful contaminant inour environment, no matter how small therisk.



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In setting standards for environmental toxins,

need to consider:

Combined effects of different exposures.

Individual sensitivities within population.

Effects of chronic and acute exposures.


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Summary:


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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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environmental health and toxicity lecture 2013

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