Chapter 15.3Risk Assessment

2002 WHO report: “Focusing on risks to health is the key to preventing disease and injury.”

risk assessment—process of evaluating the risks associated with a particular hazard before taking some action in a situation in which the hazard is present risk can be expressed as days of lost life expectancy may also be expressed as probability of dying from a

specific hazard

environmental risk assessment by the EPA

risk assessment began at the EPA in the mid-1970s as a way of addressing the cancer risks associated with pesticides and toxic chemicals

currently has four steps: hazard assessment dose-response assessment exposure assessment risk characterization

hazard assessment

process of examining evidence linking a potential hazard to its harmful effects for automobile accidents, link is clear other cases are not as clear; may be time

delay between first exposure and final outcome

Ex. establishing link between exposure to chemical and cancer

animal testing

test involving several hundred animals (usually mice) takes about 3 years and costs more than $250,000

if a significant number develop tumors after being fed substance, then the substance is either a possible or probable carcinogen

three objections to animal testing rodents and humans may have very different responses to

a chemical doses used on animals are often much higher than those

humans would be exposed to testing on animals is unethical

dose response assessment

when animal tests or human studies show a link between exposure to a chemical and an ill effect, the next step is to analyze the relationship between the concentrations of chemicals in the test (dose) and both the incidence and severity of the response

unless there is reason to assume otherwise, a linear response is used to determine an acceptable level of exposure

exposure assessment

involves identifying human groups already exposed to the chemical, learning how their exposure came about, and calculating the doses and length of time of their exposure

risk characterization

pulls together all the information gathered in the first three steps to determine the risk and any uncertainties

risk is commonly expressed as probability of a fatal outcome due to the hazard

Clean Air Act directs the EPA to regulate chemicals that have a cancer risk of greater than one in a million for the people who are subject to the highest doses

FDA applies same standard to regulate chemicals in food, drugs, and cosmetics

final estimate always recognizes degree of uncertainty

public health risk assessment

DALY risk data must be assessed with a common

measure if risk data is to be compared WHO reports use DALY—disability adjusted life

year one DALY represents the loss of one healthy year of a

person’s life assesses burden of disease in terms of life lost due to

premature mortality and timed lived with disability

risk management

involves: (1) a thorough review of the information available

pertaining to the hazard in question and the risk characterization of the hazard

(2) a decision as to whether the weight of the evidence justifies a regulatory action

a regulatory decision will usually depend on: 1. cost-benefit analysis 2. risk-benefit analysis 3. public preference

risk perception

intuitive judgments about risks Ex. protests against nuclear power plants

people’s perceptions are not always consistent with results coming from scientific analysis of risk

perceptions can be based on lack of familiarity with technology public impression of hazards media coverage

as always…

…the precautionary principle

LD50

the amount or dose of a chemical (toxic substance) that kills half the test population (test organisms/specimens)

threshold level of toxicity

The dose (level) below which no toxic (lethal) effects are observed and/or above which the toxic (lethal) effects are apparent.