1. Toxicology: Chemical Risks
Ch 17 APES

2. CHEMICAL HAZARDS
A toxic chemical can cause temporary or permanent harm or death.
Mutagens
chemicals or forms of radiation that cause or increase the frequency of mutations in DNA.
Type of carcinogen
Carcinogens
chemicals or types of radiation that can cause or promote cancer.
Teratogens
chemicals that cause harm or birth defects to a fetus or embryo.
Allergens
Chemicals that cause allergic reactions. Can cause abnormally high response of the immune system

4. Mutagens Ionizing Radiation PAH – polycyclic aromatic hydrocarbons
Gamma, X and UV
Radioactive decay
PAH – polycyclic aromatic hydrocarbons
PAH – mutagen and carcinogen - largest group of known carcinogens – major components in fossil fuel and released during fossil fuel combustion
If affect sperm/egg can be passed down to children
Cystic Fibrosis, Down Syndrome, Sickle Cell
Benzo[a]pyrene

5. Carcinogen Asbestos (synergistic with smoking tobacco)
Acrylamide (used as a polymer; plastics)
Dioxins (herbicides & paper bleaching)
BPA (bisphenol-A), PCB
BPA found in plastics
PCB used to manufacture electronics (banned in 1979)
Many chemicals in cigarette smoke
Viruses- HPV
Key factors in cancer risk:
#1 Smoking (30%)
#2 Diet (30%)
#3 Industrial Chemicals (30%)
Occupational (15), Environmental (10)
#4 Genetic (10%)

6. Teratogen PCB’s (polychlorinated biphenyl ) Herbicides Thalidimide
Acutane (acne medicine)
Heavy Metals
Arsenic, lead, cadmium, mercury
Alcohol

7. Endocrine Disrupters
Chemicals that interfere with the normal functions of hormones.
Found in drinking water from sewage, farming, & pesticides that mimic animal hormones
Growth hormones in cattle etc., human birth control pills
Many male fish, amphibians, and reptiles becoming feminized:
Low sperm count
Testes that produce both egg and sperm
Examples: DDT, Atrazine (herbicide)

9. Effects of Chemicals on the Immune, Nervous, and Endocrine Systems
Endocrine Disruptors
p235
Reduced penis size, female shellfish with male organs, decreased fertility rates, decreased sperm counts and endometirosis, early puberty
Figure 18-9

10. CHEMICAL HAZARDS
A hazardous chemical can harm humans or other animals because it:
Is flammable
Is explosive
An irritant
Interferes with oxygen uptake
Induce allergic reactions.

11. Effects of Chemicals Immune, Nervous, and Endocrine Systems
Chronic vs. Acute
Long-term exposure to some chemicals at low doses may disrupt the body’s:
Immune system: affect cells and tissues that protect the body against disease and harmful substances. Synthetic Pesticides, PCB
Nervous system: brain, spinal cord, and peripheral nerves. DDT, Heavy Metals – Pb, Hg, Cd
Endocrine system: complex network of glands that release minute amounts of hormones into the bloodstream. DDT, BPA, PCB, Dioxin, Pthalates, diethylstilbestrol (DES)
Epidemiological studies from Canada and the former Soviet Union find that children and adults exposed to pesticides suffer similar immune system alterations and higher rates of infectious disease. The risks of pesticide-induced immunosuppression are known to be greatest to infants and children, the aged, people malnourished or chronically ill.

12. Industrial Disasters Bhopal, India –
The world’s worst industrial accident occurred in 1984 at a pesticide plant in Bhopal, India.
An explosion at Union Carbide pesticide plant in an underground storage tank released a large quantity of highly toxic methyl isocyanate (MIC) gas.
15,000-22,000 people died
Indian officials claim that simple upgrades could have prevented the tragedy.
Minamata, Japan – methylmercury, caused Minimata Disease
Love Canal – Industrial Waste near town and site turned school. NIAGARA FALLS, N.Y
.--Twenty five years after the Hooker Chemical Company stopped using the Love Canal here as an industrial dump, 82 different compounds, 11 of them suspected carcinogens, have been percolating upward through the soil, their drum containers rotting and leaching their contents into the backyards and basements of 100 homes and a public school built on the banks of the canal.

13. Toxicity Measurement of how harmful a substance is Depends on
Chemical or ionizing radiation
Depends on
Dose
Exposure
Age
Genetic Make-up of Individual
Detoxification System
Solubility
Persistence
Bioaccumulation
Biomagnification
Chemical Interactions

14. Dose-Response Studies
Expose organism to different amounts of a chemical and observe a variety of responses to:
Mortality (most common; i.e. LD-50)
Changes in behavior
Changes in reproduction
Measured as a concentration of a chemical in air, water or food.
Also measured as a dose – the amount of chemical absorbed/consumed by an organism
Because of their short duration (1-4 days) called acute studies.

15. Dose-Response Studies
Count how many die after exposure to each concentration
Data usually exhibits an S-shaped curve
Lowest dose no mortality
Threshold – dose at which effect can be detected
LD50 – measurement useful in comparing harmful effects of different chemicals
Important in assessing the toxicity of new chemicals to determine if the new chemical is more or less lethal
LD50 can be different among species and rats and mice are usually used to test LD50 in humans. Extrapolate to account for mass differences.

16. Testing Standards Chemicals are regulated by EPA as of 1976
Manufacturer of chemical must demonstrate that chemical will not cause adverse effects.
Devised a system of testing a bird, mammal, fish & invert.
Using LD50 values:
Safe concentrations for animals are determined by taking the LD50 value/10
For humans LD50 values determined for rats/mice are divided by 1000 to ensure an extra level of caution (very conservative).

17. Toxicity - Dose LD50 Median lethal dose
The amount of chemical in 1 dose that kills 50% of animals within a 14 day period
Poison - LD50 of 50mg/kg of body weight

19. Toxicity - Dose “The dose makes the poison” Paracelsus, 1540
Supertoxic (dioxin, nerve gas and botulism toxin)
Extremely toxic (nicotine)
Very toxic (mercury salts, codeine)
Toxic (lead salts, caffeine, DDT)
Moderately Toxic (methyl alcohol, aspirin)
Slightly Toxic (ethyl alcohol, soap)
Essentially nontoxic (water)

20. Toxicity - Exposure Methods of Exposure How often and for how long?
Ingestion
Inhalation
Through Skin
How often and for how long?
Acute vs. Chronic
For example DDT was shown to be safe by spraying on children because it does not easily penetrate the skin, however it is eaten in food and inhaled as well.

21. TOXICOLOGY: Exposure
Estimating human exposure to chemicals and their effects is very difficult because of the many and often poorly understood variables involved.
Figure 18-11

22. Persistence Bioacculumlation and Biomagnification Lipid soluble
POP – persistent organic pollutants
PCB, Dioxin, DDT
Heavy Metals – methyl mercury, tetraethyl lead
Algal Blooms – “red tide” makes mussels toxic.

23. DDT and Bioaccumulation(absorbed or stored in organs) and Biomagnification (through a food chain)
Fig. 11-4
p. 231

24. TOXICOLOGY: genetic make-up
Typical variations in sensitivity to a toxic chemical within a population, mostly because of genetic variation.
Figure 18-10

25. Other Studies Chronic Studies: Retrospective vs. Prospective Studies:
Toxicology studies conducted over a long period of time.
Goal is to examine the long-term effects of chemicals on survival and impacts on reproduction
Retrospective vs. Prospective Studies:
Epidemiology – understanding the causes of disease in humans & wildlife
Retrospective Studies – monitor people who have been exposed to a chemical in the past. Ex: Bhopal, India – still monitoring people who were exposed.
Prospective Studies – monitor people who might be exposed to chemicals.