RISK TOXICOLOGY AND HUMAN HEALTH VOCABULARY Risk a

RISK, TOXICOLOGY, AND HUMAN HEALTH

VOCABULARY Risk – a measure of the likelihood that you will suffer harm from a hazard. Hazard –Something that can cause injury, disease, economic loss, or environmental damage. Toxicology – Study of adverse effects of chemicals on health. Toxicity – Measures how harmful a substance is in causing injury, illness, or death to a living organism. Dose - is the amount of a substance a person has ingested, inhaled, or absorbed through the skin. Response – the type and amount of health damage that result from exposure to a chemical or other agent. Poison or toxin – is a chemical that adversely affects the health of a living organisms causing injury, illness, or death.

How Much Exposure to a Particular Toxic Chemical Causes a Harmful Response? Method: Measure chemical’s median lethal dose (LD 50); the amount received in one dose that kills 50% of the organisms (usually rats or mice) in a test population within a 14 day period. 50 % Threshold Level 0. 0001 0. 1 Dose mg/kg (ppm) 1. 0

Measurements for Expressing Levels of Contaminants in Food and Water For Acute Toxicity Tests Dose Metric Equivelent Approximate Amount of Water Parts per million (ppm) Milligrams per kilogram (mg/kg) 1 teaspoon per 1000 gallons Parts per billion (ppb) Micrograms per kilogram ( g/kg) 1 teaspoon per 1, 000 gallons

ACUTE TOXICITY TESTS Ø controlled experiments in which the effects of the chemical on a test group are compared with the responses of a control group of organisms not exposed to the chemical ØControl and experimental groups are as identical as possible in the age, health status, and genetic makeup, and that all are exposed to the same environmental conditions.

Problems With Threshold Acute Toxicity Model Ø 1. validity of extrapolating data from test animals to humans through mathematical models because human physiology and metabolisms is different than that of rats and mice. 2. 2. In daily life, humans are exposed to a variety of chemicals, some of which can interact in ways that decrease or enhance their individual effects over short or long periods of time (synergistic effects). 3. 3. Age of exposure poses problems. Depending on age some chemicals will affect young, old or immunecompromised more rapidly than average healthy adults.

The Good News is… Because all methods of estimating toxicity have serious limitations, allowed exposure levels are usually set well below the estimated harmful levels.