Environmental Health & Toxicology

Focuses on external factors that cause disease, including elements of the natural, social, cultural, and technological worlds in which we live.

Rachel Carson’s Silent Spring in 1962 focused on the discharge, movement, fate, and effects of synthetic chemical toxins.

ENVIRONMENTAL HEALTH

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 Disease Ex: 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

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

HIV/AIDS 2/3 of all cases are in Africa; most cannot afford the $10,000 drugs (like people in U.S.) 2.3

Malaria 500 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

DISEASE ETC.MILLIONS OF DEATHS PER

YEAR

Cardiovascular disease 9.7

Cancers 6.0

Chronic Lung Disease Ex: tuberculosis 5.5

Acute Lung Disease Ex: 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

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

HIV/AIDS 2/3 of all cases are in Africa; most cannot afford the $10,000 drugs (like people in U.S.) 2.3

Malaria 500 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

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.

ECOTOXICOLOGY Study of toxins

(poisons) and their effects, particularly on living systems.

A broad field, drawing from biochemistry, histology, pathology, pharmacology, and many other disciplines.

Toxins are harmful even in extremely dilute concentrations. In some cases billionths, or even trillionths of a gram can cause irreversible damage.

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.

Resistance to drugs, antibiotics, pesticides is increasing.

How microbes acquire antibiotic

resistance. (a) Random

mutations make a few cells resistant.

When challenged by antibiotics, only

those cells survive to give rise to a

resistant colony. (b) Sexual reproduction

(conjugation) or plasmid transfer move genes from

one strain or species to another.

The protozoan parasite that causes malaria is now resistant to most drugs, while the mosquitoes that transmit it have developed resistance to many insecticides.

Antibiotic MisuseReasons for antibiotic resistance to develop: Antibiotics do not

work against certain diseases, e.g. viral infections.

Antibiotics are given when the person could recover fully without them.

Starting and not finishing a full prescription.

Widespread use of antibiotics in animal agriculture.

Allergens are substances that activate the immune system. Widely used in plastics, wood

products, insulation, glue, and fabrics concentrations in indoor air can be much higher than in normal outdoor air.

Sick building syndrome: headaches, allergies, chronic fatigue, and other symptoms caused by poorly vented indoor air contaminated by mold spores, CO, nitrogen oxides, formaldehyde, and other toxins released from carpets, insulation, plastics, building materials, and other sources.

Immune System Depressants suppress the immune system. Dead animals

contained high levels of pesticide residues, polychlorinated biphenyls (PCBs), and other

contaminants that are suspected of disrupting the immune system and making it susceptible to a variety of opportunistic

infections.

Endocrine hormone disruptors interfere with the function of normal chemical messengers in the body.

Hormone mimics have similar shapes to natural hormones and amply their effects.

Hormone blockers prevent natural hormones from attaching to their target organ.

Endocrine disruption, linked to increased

risk of breast cancer, develop-

mental and reproductive

toxicity; allergies and

immuno-toxicity.

BPA is known to be a hormone mimic used for plastic products ranging from water bottles to

tooth-protecting sealants. The chemical can cause abnormal chromosome numbers which is the

leading cause of miscarriages and several forms of mental retardation. It also is an environmental estrogen and may alter sexual development in both males and females. Bills are considered to

ban BPA and certain phthalates in children’s toys and feeding products.

Use 1, 2, 4, 5 with your food! All the others are NOT good for you.

Neurotoxins specifically attack nerve cells and are both extremely toxic and fast-acting. Lead and mercury kill nerve cells and

cause permanent neurological damage. Anesthetics (ether, chloroform, halothane,

etc.) and chlorinated hydrocarbons (DDT, Dieldrin, Aldrin) disrupt nerve cell membranes necessary for nerve action.

Organophosphates (Malathion, Parathion) and carbamates (carbaryl, zeneb, maneb) inhibit the enzyme that regulates signal transmission between nerve cells and the tissues or organs they innervate.

These dozen chemicals may be

responsible for widespread

behavioral and cognitive

problems, but the scope of the

chemical dangers in our environment

is likely even greater!

Mutagens are agents, such as chemicals and radiation,

that damage or alter genetic material (DNA) in

cells. This can lead to birth defects if the damage occurs during embryonic or fetal growth, or trigger neoplastic (tumor) growth in adults.

When damage occurs in reproductive cells, the results can be passed on to future generations.

There is no “safe” threshold for exposure to mutagens. Any exposure has some possibility of causing damage.

Teratogens are chemicals that

cause birth defects in an unborn fetus: ethanol, benzene,

lead, mercury

Mercury can cause sensory impairment, lack of coordination, and disrupt other nervous

system functions. Lead, another neurotoxin, was used as an additive in gasoline until

1976. Following a ban of its use, an 80% drop in

blood lead levels were observed, as well as a 6-point gain in the average IQ of children.

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).

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.

The question is: Should we set pollution levels that will protect everyone, including the most sensitive people, or

only aim to protect the average person?

A convenient way to describe toxicity of a chemical is to determine the dose to which 50 % of the test population is

sensitive. In the case of a lethal dose, this is called the LD50.

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…

Substance LD50 (mg/kg)

Table sugar 29,700

Monosodium Glutamate (MSG) 16,600

Vitamin C 11,900

Alcohol (Ethanol) 7,060

Table salt 3,000

Aspirin 200

Caffeine 192

Nicotine 50

Capsaicin (active component of chili peppers)

47.2

Poison Dart Frog Toxin 0.002

Polonium-210 (Nuclear Waste) 0.000000001

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

Examples of labels that have been required or proposed as a result of public health concerns.

Environmental Impact of IndustriesIndustr

yAir Water Land Human

Petrochemical

noxious and toxic emissions from refining, processing plants

factory emissions to water bodies

landfill disposal of waste solids & sludge; accidental spills during transport & storage

toxicity and disruption of lifestyle

Metal particulate, gas emissions during forging, working, fabrication

discharge of pickling liquors & other waste disposal; heavy metals

slag, waste products from processing

toxicity

Mining particulates from surface mining & transportation; noxious & toxic fumes from smelting

runoff from mines and waste disposal

dumping of tailings & processed wastes; disruption of agriculture, forestry, recreation

heavy metals, particulates

Environmental Impact of IndustriesIndustr

yAir Water Land Human

Food noxious fumes from food processing

sewage with high organic content

uncomposted organics and other wastes to landfill

toxicity and allergens

Agri-culture

drift of agricultural chemicals (pesticides, herbicides, fungicides, fertilizers), pollen, & dust

runoff of agrochemicals to surface waters; percolation to groundwater; silting of water

erosion, depletion of organic material & organisms

toxicity of chemical; loss of soil

Pulp & Paper Industry

noxious fumes

emissions of mercury, chlorines, organics; silt from deforestation; loss of habitat

destruction of habitat by clear-cutting; erosion

mercury contamina-ted seafood

“Do you want to stop reading

those ingredients while we’re

trying to eat?”