Environmental Health & Toxicology

Chapter 15

APES

2008

Some Vocab…

• WHO- World Health Organization• Health- state of complete physical, mental, and social

well being (not just the absence of disease)• Disease- change in the body’s condition in response to

an environmental factor– Ex: nutritional, chemical, biological or psychological

• Morbidity- illness• Pathogen- disease-causing organism • Vector- organism that spreads disease• Emergent- new, not identified or absent for last 20 years• Zoonotic- transmitted from animal host to humans

PATHOGENIC VS. NON-PATHOGENIC

• 43% of all disease-related deaths are from pathogens

• 57% from cardiovascular disease, cancer, lung disease, injuries, etc.

Pathogenic

Non-Pathogenic

DISEASE ETC.MILLIONS OF DEATHS PER

YEAR

Cardiovascular disease 9.7

Cancers 6.0

Chronic Lung Disease Ex: tuberculosis 5.5

Acute Lung DiseaseEx: pneumonia, flu, pertussis (whooping cough) 4.1

Injuries Mostly in 18-39 age group due to car accidents 4.0

Perinatal conditions Mostly from Infections 3.2

DiarrheaFrom bacteria & pathogens; excessive can cause mental/developmental retardation 3.0

HIV/AIDS2/3 of all cases are in Africa; most cannot afford the $10,000 drugs (like people in U.S.) 2.3

Malaria500 million new cases each year; making a comeback 2.0

Vaccine-preventable infections

Polio, Measles, Hepatitis B, Tetanus; LDC have no access/money for these vaccines 1.7

Other known disease 3.9

Unknown causes 5.9

Total 51.0

Morbidity & Quality of Life

• Not everyone dies from disease, but still can cause severe suffering and debilitation

• When sick…– Crops not planted/harvested– Animals not tended– Work not done– Kids not fed

• Poorest people are most affected because they live in unhealthiest environments & don’t have $ for health care.

• Lack of adequate housing, sanitation, safe drinking water causes most cases of diarrhea which is made worse by malnutrition.

Part I: Infectious Diseases

• Onchocerciasis (river blindness)– Vector: Black fly– Many roundworms get

into eyes & die causing blindness

– Control with insecticide sprays

– Merck & Co. are providing free ivermectin to help eradicate.

Infectious Diseases

• Elephantiasis– Vector: Mosquitoes– Roundworm gets into

lymph system and blocks lymph vessels causing fluid build up in the extremities.

– SmithKline Beecham is supplying free albendazole to eradicate.

Infectious Diseases

• Drancunculiasis- – Guinea worm– Vector: Drinking

Water contaminated with Cyclops

– 3 meter long worm that lives under skin. Forms blister & must be wound out of skin to remove

Infectious Diseases

• Hemorrhagic Fever – Some Types…

• Ebola: Vector- unknown• Lassa: Vector- Mastomys

rat species• Hanta: Vector- Deer mice

– All cause tissue deterioration, bleeding, pulmonary edema.

– Ebola has 90% mortality rate.

Infectious Diseases

• Dengue Fever– Vector: Mosquitoes– 20 million new cases;

2.5 billion current cases

Infectious Diseases

• Malaria– Vector: Mosquitoes– 3 million die each year,

90% of them in Africa– In 1950’s & 60’s, sprayed

DDT & knocked down from millions cases each year to thousands, now back to 2.5 million new cases

– Some Aedes aegypti mosquitoes seen along Gulf Coast of America- due to climate change?

Infectious Diseases

• Cholera– Cause: Bacteria in unclean

drinking water– Severe stomach cramping,

severe diarrhea, vomiting– Thought eradicated but has

made comeback due to ships dumping bilges in harbors of cities with inadequate water treatment

Infectious Diseases

• Tuberculosis– Cause: bacillus bacteria

Mycobacterium tuberculosis

– Eliminated but has returned stronger than ever

– Some strains drug resistant

– Spreads rapidly– EX: Russian prisons

What causes disease to spread so rapidly?

• Population density , so contact • Moving into remote areas for

agriculture exposure.• Deforestation, pollution causing

local & global climate change ( in temp = in mosquito pop.)

• Eliminating predators so in rodent, roach, mosquito pop.

in speed & frequency of travel (airplanes, ships) to other countries

in resistance (Malaria) = “Superbugs”

• Taking medication improperly leads to “superbugs”

• Antibiotics given to farm animals increases their resistance.

Part II:Dangerous Chemicals

Hazardous (dangerous)• Some are harmless

when diluted• Classifications:

– Flammable– Explosive– Irritant– Acids– Caustic

Toxic (poisonous)• Harmful even in small

amounts• Ricin- protein in castor

beans is thought to be the most toxic organic compound on Earth.

• Ricin is 200x more lethal than dioxin.

Toxic Chemicals

• Allergens– overactivate immune

system– Ex: formaldehyde

• Immune System Depressants– Suppress immune system– Ex: PCB’s used as flame

retardants & electrical insulators (seals & dolphins died due to infections brought on by suppressed immune system)

Toxic Chemicals

• Mutagens– Chemicals or radiation that

damages or alters DNA– Can cause birth defects or

tumors– Can be passed through

sperm/egg– Ex: aflatoxin (from mold);

caffeine, LSD, benzapyrene (in cigarettes); nitrous oxide; ozone

Toxic Chemicals

• Teratogens– Chemicals that cause

abnormalities during embryonic development

– Ex: Thalidomide• Sold as OTC sleeping pill in

Europe• Caused Phocomelia (had

hands & feet but no arms or legs)

• Can have immediate affect• Positive: can be used to treat

leprosy, AIDS, cancer, tissue rejection

– Alcohol is most prevalent teratogen- Fetal alcohol syndrome results in low birth weight, mental delays

Toxic Chemicals• Carcinogens

– Cause cancer– Increasing in developed countries– 2nd cause of death in US– Maybe result of toxic chemicals in

life• Foods/preservatives• Pesticides• smoking

– Breast, Testicular, & Skin cancers increasing

– Stomach, Uterine, Colon cancers decreasing due to new technology for treatment.

– Ex: • Formaldehyde- particle board• Paradichlorobenzene- toilet

cleaner• Perchloroethylene- dry cleaning• Pesticides- 2,4

dichlorophenoxyacetate

Some foods contain carcinogens (broccoli) but the other benefits

outweigh the risk.

Toxic Chemicals

• Neurotoxins– Kill nerve cells– Disrupt cell membrane of nerve

cell– Inhibit acetylcholinesterase-

enzyme that transmits nerve signals

– suppress nervous system– EX:

• Heavy metals like lead & mercury (Minamata Disease p.300)

• Anesthetics- ether, chloroform, halothane

• Chlorinated Hydrocarbons- DDT, Dieldrin, Aldrin (POPs)

• See page 300 table 15.1• Organophosphates- parathion• Carbamates- carbaryl (Bhopal,

India)

Toxic Chemicals

• Endocrine Disruptors or Hormonally Active Agents (HAAs)- toxicants that interfere with the endocrine system by mimicing the hormone.

• Newly discovered• Includes chemicals such as herbicides, pesticides,

PCBs, phthalates (found in chlorinated plastics)• Problems: breast, prostate, ovarian cancer, abnormal

testicular development, thyroid related abnormalities• Hermaphroditic frogs, alligators w/ genital abnormalities

Bhopal, IndiaWorst Industrial Accident in History

• December 1984• Union Carbide- American company located

in Bhopal manufactured carbaryl & methyl isocyanate (MIC) used to make pesticide Sevin (as in Sevindust)

• Holding tanks at the plant malfunctioned (due to human error & lack of routine maintenance)

• Toxic MIC gas cloud released late at night• People who were exposed began choking,

frothing at the mouth, vomiting blood, many died within minutes. The streets were littered with dead bodies.

• 15,000-33,000 have died from this accident• 100,000 that survived are blind and/or are

having reproductive, neurological, & respiratory problems.

• Soil & water are contaminated• No one has been held responsible- DOW

and Union Carbide have “washed their hands of the problem.”

Minamata Bay and Mercury

• 1950’s in Kyushu, Japan• Japanese live on island so eat fish

and shellfish from Minamata Bay.• 1st signs seen in animals,

especially cats- appeared to dance but were really having seizures.

• People began experiencing neurological problems, paralysis, uncontrollable shaking, vision problems

• Children born with brain atrophy, malformed limbs, etc.

• Plastic factory was dumping mercury into Minamata Bay.

• Mercury was accumulating through the food chain- Biomagnification

OTHER ENVIRONMENTAL HEALTH HAZARDS

• Radiation- power lines, nuclear power plants

• Noise• Trauma- accidents &

violence• Stress- heart attack,

stroke, ulcers increase chance for infectious disease

• Diet- too much bad food causes stress on body, leads to cardiovascular disease

What determines how “dangerous”

a chemical is?• Persistence in

environment• Route/method of

exposure• Characteristics of

target organism

FACTORS RELATED TO TOXIC AGENT

1. Chemical composition & reactivity

2. Physical traits- solubility, state of matter

3. Presence of impurities

4. Stability and storage traits

5. Availability of vehicle to carry agent

6. Movement of agent thru environment & into cells

FACTORS RELATED TO EXPOSURE

1. Dose- concentration & volume of exposure

2. Route, Rate, and site of exposure

3. Duration and frequency of exposure

4. Time of exposure (time of day, season, year)

FACTORS RELATED TO ORGANISM

1. Resistance to uptake, storage, or cell permeability

2. Ability to metabolize or inactivate agent

3. Tendency to change non-toxic to toxic in body

4. Concurrent infections or physical stress

5. Species and genes of organism

6. Nutritional status of subject

7. Age, sex, body weight, immunological status & maturity

Characteristics in determining how, when, and where a toxic material will move thru the environment:

• Solubility– Dissolve in Water

• Move rapidly & widely• Readily access cells in body

– Dissolve in Oil• Need a carrier into & thru body• Penetrate tissue readily, stored in fat cells of body• Take many years to break down

– Bioaccumulation- accumulation of toxins within an individual organism. May be dilute in environment but reach dangerous levels in the body.

• Biomagnification- accumulation of toxins thru a food web.– Chemical intensifies at

each step– DDT, mercury, are

examples

Characteristics in determining how, when, and where a toxic material will move thru the environment:

• Persistence- how long does it last in environment?– Some unstable & degrade

quickly– Some resistant to degradation

(PVC plastic, DDT, CFC’s, asbestos)

• This may be why they are used- asbestos, PVC, DDT

• May be an unfortunate side-effect

– DDT was valued because it broke down slowly & did not have to be reapplied.

– We did not know the affects it would cause in fish, birds of prey, and people (biomagnification).

Characteristics in determining how, when, and where a toxic material will move thru the environment:

• Chemical Interactions– Antagonistic interactions- interfere with effects or

stimulate the breakdown of other chemicals• Ex: Vitamins A and E interfere with some carcinogens

– Synergistic interactions- one substance makes the affects of another worse.

• Occupation asbestos exposure increase lung cancer rate 20 fold

• Smoking increases lung cancer rate 20 fold• A smoker that works with asbestos increases his chance for

lung cancer 400 fold

Mechanisms for minimizing toxic effects

• Every material can be poisonous/toxic at some level.

• Most chemicals have safe levels or thresholds below which their affects are undetectable.

• EX: 100 cups of coffee have enough caffeine to kill if consumed all at once- but most people don’t consume that much.

• Taken in small doses, chemicals can be broken down by the body and released.

Measuring Toxicity

• How a material is delivered plays a vital role in determining toxicity.– At what rate? (a little over time or all at once)– Through which route of entry? (skin, mouth,

nose)– In what medium? (solid, liquid, gas)

• Different species respond differently and different individuals in a species can react differently.

Animal Testing• Most common & widely accepted

measure of toxicity• Cons

– Expensive– Time consuming– Painful/debilitating– Takes thousands of animals & lots

of money• Alternates

– Cell cultures– Computer simulation

• Some animals of a species are more sensitive than others so some die off quicker. Some are hardier than others so they live longer. This produces a bell shaped curve

• Should we set safety limits to protect all including most sensitive or just the average person?

• By protecting all, it might cost more money…

LD50Lethal Dose 50

• LD50- dose at which 50% of the test population dies.

• See Table 15.4 on page 309 of textbook for lethal doses of some toxic organic chemicals.

Acute vs. Chronic Exposure

• Acute effects- caused by single source and are immediately effective causing immediate health problems.

• Chronic- takes place over a long period– Continuous or repeated sub-lethal exposure– For ex. Exposure to low levels of radiation

over lifetime may cause mutations and lead to disease.

FDA Regulations

• 1958 Delaney Clause to US FDA Act forbids the addition of any amount of known carcinogen to food and drugs.

• 1966 No Reasonable Harm addendum says that carcinogens OK if less than one cancer for every million people exposed over a lifetime.

Assessing Risk

• What factors influence how we perceive risk?– People will downplay risk to suit their own agendas– Some don’t understand probability.– Personal experiences can be misleading- (Love

Canal)– We have an exaggerated view of our abilities.– Media is mostly biased– Fear or distrust of certain technologies (Nuclear

Power)

Accepting Risk

• How much risk is acceptable?• Individualized• If you enjoy doing an activity you will accept those risks.• If an activity benefits someone else, you may not take

those risks.• EX:

– Chance of dying from lung cancer if you smoke 1 pack/ day is 1 in 1000.

– EPA limits for trichloroethylene is 2 in 1 billion. People will demand water with 0 levels of trichloroethylene but still smoke cigarettes.

• See Table 9.7 page 206 for list of activities and death risks.

Relative Risks to Human Welfare (from EPA)

• High Risk Problems– Habitat alteration & destruction– Species extinction & loss of diversity– Stratospheric ozone depletion– Global climate change

• Medium Risk Problems– Herbicides/pesticides– Toxics & pollutants in surface water– Acid deposition– Airborne toxics

• Low Risk Problems– Oil spills– Groundwater pollution– Radionuclides (uranium, radon)– Thermal pollution