RISK Targets: 1. Explain risk, toxicology, toxins and factors that affect chemical risks. 2. Explain how toxicity is measured and methods of determining the toxicity of a chemical.

What is risk, risk assessment, and risk management?  Risk is the possibility of suffering harm from a hazard.  Hazard: situation that poses a level of threat to life, health, property or the environment. Ex. cultural, biological, physical, and chemical.  Risk assessment determines insurance rates.  Expressed in terms of probability  Risk management determines safety plans and regulations.

What is toxicology and toxicity? What factor impact toxicity?  Toxicology is the study of adverse effects of chemicals on living organisms.  Toxicity is the measure of how harmful a substance is in causing injury illness or death to a living organism.

© 2004 Brooks/Cole – Thomson Learning Very sensitive Majority of population Very insensitive Dose (hypothetical units) Number of individuals affected Individual responses to chemical hazards Toxicity depends on -dose -frequency -time -size/age -immune system -genetics

What are the guiding principles for determining toxicity? 1. Any synthetic or natural chemical can be harmful if ingested in a large enough quantity. Ex. lethal dosage of caffeine = 100 cups of coffee 2. How much exposure to a particular toxic chemical causes a harmful response? - The dose makes the poison. - The dose makes the poison, but differently for different individuals. - The dose of a usually unknown mixture of chemicals makes the poison, but differently for different individuals.

Describe five factors that affect harm caused by substances. 1. Solubility 2. Persistence 3. Bioaccumulation 4. Biomagnification 5. Chemical interactions

DDT in fish-eating birds (ospreys) 25 ppm DDT in large fish (needle fish) 2 ppm DDT in small fish (minnows) 0.5 ppm DDT in zooplankton 0.04 ppm DDT in water ppm, Or 3 ppt

Table 9-1 Toxicity Ratings and Average Lethal Doses for Humans Toxicity Rating Supertoxic Extremely toxic Very toxic Toxic Moderately toxic Slightly toxic Essentially nontoxic LD50 (milligrams per kg of body weight)* Less than 0.01 Less than 5 5–50 50– –5,000 5,000–15,000 15,000 or greater Examples Nerve gases, botulism toxin, mushroom toxins, dioxin (TCDD) Potassium cyanide, heroin, atropine, parathion, nicotine Mercury salts, morphine, codeine Lead salts, DDT, sodium hydroxide, sodium fluoride, sulfuric acid, caffeine, carbon tetrachloride Methyl (wood) alcohol, ether, phenobarbital, amphetamines (speed), kerosene, aspirin Ethyl alcohol, Lysol, soaps Water, glycerin, table sugar Average Lethal Dose† Less than 1 drop Less than 7 drops 7 drops to 1 teaspoon 1 teaspoon to 1 ounce 1 ounce to 1 pint 1 pint to 1 quart More than 1 quart *Dosage that kills 50% of individuals exposed †Amounts of substances in liquid form at room temperature that are lethal when given to a 70.4-kg (155-pound) human

What is the difference between an acute effect response and a chronic effect response?  Response: type and amount of health damage resulting from exposure to a chemical or other agent.  Acute: immediate or rapid. ex. dizziness to death  Chronic: permanent or long-lasting or single or multiple dose. ex. kidney damage

LD Dose (hypothetical units) Percentage of population killed by a given dose What dose would be right for a pesticide? Top 5 toxics arsenic lead mercury vinyl chloride PCBs (polychlorinated biphenyls)

How do dose-response curves relate to estimating toxicity?  Dose-response curves are  one way to compare the toxicity of different chemicals  developed from acute toxicity tests  use mathematical models to extrapolate low-dose and high-dose levels

© 2004 Brooks/Cole – Thomson Learning Effect Dose Nonlinear dose-response Linear dose-response No threshold Effect Threshold level Dose Dose-response curves

What are some problems with estimating toxicity? 1. We are constantly exposed to a variety of different chemicals. 2. It is difficult to estimate the toxicity of one chemical and determine all possible interactions. 3. The effect of a particular chemical can be dependent on when the exposure occurred.

Should we avoid using all chemicals until they have been tested? "When an activity raises threats of harm to human health or the environment, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically. In this context the proponent of an activity, rather than the public, should bear the burden of proof. The process of applying the precautionary principle must be open, informed and democratic and must include potentially affected parties. It must also involve an examination of the full range of alternatives, including no action." - Wingspread Statement on the Precautionary Principle, Jan. 1998Wingspread Statement

Fig p. 229 Select a Risk……