Human Health and

Environmental Toxicology

Chapter 7

Key Topics

1.Developed and developing nations health issues

2.Estrogen - how much is enough?3.Dose-response to chemicals4.Chemical disposal5.Risk assessment6.Precautionary ideas - are they used?

Ecotoxicology

• Dilution paradigm –

“the solution to pollution is dilution”

• Boomerang paradigm –

“what you throw away can come back and hurt you”

Snapshot - SanitationConnections between disease vectors and human waste awakened people to the need for proper disposal.

Cesspools for human wastes were frequently placed under the wooden floors of castles.

In 1183, when the Emperor of the Holy Roman Empire held a Diet in the Palace of Efurt, the floor of the main hall broke; many of the dinner guests fell into the cesspool and drowned; luckily, the Emperor survived.

1858-59: years of the "Big Stink" in London. The Thames River received wastes of thousands of people who lived upstream of Parliament. During low tide the river did not drain. Early sewers were created to convey storm runoff; later on sanitary sewage was added ... the result was a "combined" system

Modern-day flush toilets invented by: Thomas Crapper

Dilution Solution

An average-sized cruise ship, housing three thousand passengers and crew, generates 7 tons of garbage and solid waste everyday. This includes bottles, cans, plastic, cardboard and food wastes. 75-75-80% of the waste is burned at the sea80% of the waste is burned at the sea, and then the ash is dumped into the ocean. There are also 30,000 gallons of human waste, like wastewater from toilets.17,000 gallons of oily bilge waste are being disposed each day.

Emerging v. Reemerging DiseasesEmerging –

Not previously observed within humans:

AIDS, Lyme disease, West Nile virus

Reemerging –

Existed previously, becoming more common again:

Tuberculosis, Yellow fever, Malaria

CholeraBacterial Intestinal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae.

Incubation Period: 1-5 days

Symptoms: diarrhea, vomiting, resulting in blood dehydration & blood pressure drop

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1/09 - The cholera epidemic in Zimbabwe has now killed more than 2,000 people.

England in 1854 Broad Street Cholera outbreak - cause was formulated but germ theory was new and unproven

Polio

At the height of the polio epidemic in 1952, nearly 60,000 cases with more than 3,000 deaths were reported in the United States alone. However, with widespread vaccination, wild-type polio, or polio occurring through natural infection, was eliminated from the United States by 1979 and the Western hemisphere by 1991.

IndiaIndia seemed to be on the verge of eliminating polio last year, when it reported just 66 cases of the disease, down from 1600 in 2002.

Muslim clerics have spread a myth that the polio vaccine is part of an underhanded campaign to sterilize Muslim children and lower the Muslim birth rate.

The Poor“We've never seen anyone coming to take care of us, why are you coming just to give us polio drops?”

COUNTRIES WHERE POLIO IS ENDEMICIndia / Nigeria / Pakistan / Afghanistan / Niger / Somalia / Egypt / Angola /Ethiopia / Sudan

Malaria

What is the emphasis of the opening page? No it’s not malaria ;-)

Kills 1m+ each year

Chemical Persistence

Endocrine Disruptors

Endocrine DisruptorsAn endocrine disruptor is a synthetic chemical that mimics or blocks hormones.

Chemicals that are known human endocrine disruptors include: DDT, Dioxin, Lead, Mercury, PCBs, and many pesticides.

PCB’s - PCBs are relatively fire-resistant, very stable, do not conduct electricity and have low volatility at normal temperatures.

Dioxin - released as byproducts of human activities (the manufacture of chlorine-bleached pulp and paper) and natural processes (fire).

Polychlorinated biphenyls & Dioxin

chlorinated organic chemicals Some have harmful properties, depending on the number and position of chlorine atoms

Endocrine DisruptorsDrugmakers have dismissed the suggestion that their manufacturing contributes significantly to what's being found in water.

Consumers excrete what our bodies don't absorb.

Flush unused drugs down toilets.

Pharmaceuticals and contaminated packaging are thrown away each year by hospitals and long-term care facilities.

DDT & Pesticides

1. Male Genitalia2. Pharmaceuticals(PPB-PPT)3. DES - miscarriages

No Conclusive EvidenceAlthough there is no conclusive proof, it is thought the hormone, which has similar

actions in fish and humans, could be partly to blame for falling sperm counts in men.

British men's sperm counts dropped by almost a third between 1989 and 2002, and one in six couples now have difficulty conceiving.

Overall, a third of the male fish were between sexes. However, in one waterway, near a particularly heavy discharge of treated sewage more than 80 per cent had female characteristics.

Generally, the smaller the fish, the more vulnerable they are to estrogen

Determining Health Effects of Environmental Pollution

Identifying Cancer-Causing Substances

• Carcinogen – agent known to induce cancer.

• Tested with rats is the dose equivalent?

• Can you extrapolate results to humans?

Mixing Chemicals

Chemical Mixtures

• Most studies examine single chemical exposure - what happens when

exposed to multiple chemicals?

• Additive effect? - 1+1=2

• Synergistic effect? - 1+1=3

• Antagonistic effect? - 1+1=1.3

LD-50

Toxicity of a chemical is assessed by determining its LD50

(dose at which 50% of test subjects die)

LD-50

Lethal Dose-50% (LD50)

ED-50

Effective Dose-50% (ED50) –

Dose that induces 50% of test subjects to have some type of effect

Dose response curve –

LD 50

Chemical Category Oral LD50 in Rats (mg/kg)

Aldicarb ("Temik")

Carbamate 1

Carbaryl ("Sevin")

Carbamate 307

DDT Chlorinated hydrocarbon

87

Malathion Organophosphate 885

Rotenone Plant extract 60

Unanticipated Connections

Iron, dung, bacteria, clay, fungi, pesticides

Decision Making

Cost-Benefit Analyses

CostBenefit

Debate over leaded gasoline? What qualifies as clean air?

Precautionary Principle

“An ounce of prevention is worth a pound of cure”

Apply the principle to the following:1. Global Warming2. Ozone3. GMO’s4. Whale Hunting