chapter 15 (not reviewed yet)

What are two ways to reduce risk?

1) to reduce the size of the loss 2) to reduce the probability that the loss will occur.

What is risk sometimes defined as when several different kinds or magnitudes of loss may occur?

Risk is sometimes defined as a product of the probability and the size of the loss.

What is risk assessment and risk management?

Risk assessment and risk management is a way of helping to prioritize problems and identify solutions.

What is the primary focus of risk assessment and risk management?

The primary focus has been on assessing and reducing risks to human health.

What are the two categories of health risk that are commonly analyzed?

One is the risk of contracting cancer from exposure to a chemical. The second category covers all other human illnesses and disease induced by chemicals in the environment.

What must be considered if the risk of either carcinogenic or noncarcinogenic effects from exposure to a particular chemical is unacceptable?

Measures to reduce or eliminate the risk must be considered.

What must be considered if exposure to a particular chemical has carcinogenic effects?

Measures to reduce or eliminate the risk must be considered.

What are some measures to reduce or eliminate the risk of exposure to a chemical?

Eliminating exposure to a chemical altogether, such as by shutting down a factory, removing all contaminated soil, or containing a chemical after it is released.

What might be the consequences of exposure to only very low levels of a chemical?

Exposure to only very low levels of a chemical might be free of harmful consequences or might pose risks that are so small.

In some cases, what might exposure to a chemical actually confer?

In a few cases, such as with fluoride in drinking water, such exposure might actually confer health benefits.

What do determinations of acceptable risk levels involve?

Determinations of acceptable risk levels involve a substantial amount of judgment (in contrast to "hard" scientific facts).

What provides the basis for most current risk assessments for toxic or hazardous chemicals?

EPA criteria provide the basis for most current risk assessments for chemicals that are designated as toxic or hazardous.

What are the four steps in the risk assessment process defined by the National Research Council?

The four steps include the assessment of hazards, the development of dose-response relationships, exposure assessment, and risk characterization.

What is the first step in risk assessment methodology?

Hazard Assessment.

What does hazard assessment involve?

Determining whether there is any potential problem from exposure to a given chemical.

What data sources are used in hazard assessment?

Laboratory studies, animal studies, and epidemiological studies.

What is the outcome of hazard assessment?

An evaluation and description of the nature and severity of any effects.

What is the second step in risk assessment methodology?

Dose-Response Assessment.

What does dose-response assessment quantify?

The relationship between the dose of a chemical and the resulting response or adverse effect.

Why is dose-response assessment considered difficult and controversial?

There are usually insufficient data to characterize a dose-response relationship.

What is the ideal goal of dose-response assessment?

To determine dose-response relationships for both carcinogenic and noncarcinogenic effects.

What is the third step in risk assessment methodology?

Exposure assessment.

What does exposure assessment involve?

Measuring the magnitude, frequency, and duration of exposure.

What is exposure assessment?

Exposure assessment is the process of measuring the magnitude, frequency, and duration of human exposure to an agent in the environment.

How can exposure be measured?

Exposure can be measured directly or estimated indirectly through consideration of measured concentrations in the environment, models of chemical transport and fate in the environment, and estimates of human intake over time.

What is risk characterization?

Risk characterization conveys the risk assessor's judgment as to the nature and presence or absence of risks, information about how the risk was assessed, where assumptions and uncertainties still exist, and where policy choices will need to be made.

What does risk characterization provide?

Risk characterization provides the information basis to write an integrative risk characterization analysis.

What is the evaluation of chemical carcinogens?

The evaluation of chemical carcinogens assesses their carcinogenic effects.

What is the basis for evaluating chemical carcinogens?

Animal studies in which laboratory animals are given measured doses of a particular chemical.

What is the purpose of normalizing the dose of a chemical?

To express the dose in milligrams per day of chemical per kilogram of body weight (mg/kg-da).

How is the risk of cancer quantified in a dose-response function?

By quantifying the incremental risk of cancer above the normal or background level.

In a population of 100 mice, 2 animals developed tumors when exposed to a daily average dose of 1 mg/kg-da of a particular chemical. What is the cancer rate in this case?

2 percent or a risk of 0.02.

What is the typical human exposure dosage to the chemical mentioned?

Approximately 1 × 10-5 mg/kg-da.

Assuming a linear dose-response relationship and the same incidence rate in both mice and people, how many animals would have to be tested to detect the expected cancer rate at the lower dose?

The number of animals would depend on the expected cancer rate at the lower dose, which is not provided in the text.

How many animals would have to be tested to detect the expected cancer rate at the lower dose?

More than 10 million animals would have to be tested to observe the expected effect.

What is the expected rate of tumors in mice at the lower dose?

The expected rate of tumors in mice would be 2 x 10-5 percent.

What is the fraction that corresponds to the expected rate of tumors in mice at the lower dose?

The fraction that corresponds to the expected rate of tumors in mice is 2 X 10-7.

What are some other adverse health effects that might be identified in a hazard assessment?

Other adverse health effects that might be identified include kidney or liver damage, nerve damage, and diseases such as diabetes.

What is a key assumption for noncarcinogens?

A key assumption for noncarcinogens is the existence of a dosage threshold.

Are there risks of injury, disease, or other adverse effects above the dosage threshold for noncarcinogens?

Yes, above the dosage threshold for noncarcinogens, there are risks of injury, disease, or other adverse effects.

What is the existence of a dosage threshold for noncarcinogens?

The existence of a dosage threshold for noncarcinogens means that above a certain level of exposure, there are risks of injury, disease, or other adverse effects.

What is the purpose of exposure assessment?

The purpose of exposure assessment is to quantify the dose actually received in a particular situation and to measure or estimate the frequency, intensity, and duration of human exposure to a chemical agent in the environment.

What is the most significant route of exposure to chemicals in the environment?

The most significant route of exposure to chemicals in the environment is often inhalation.

What is the difference between the threshold for carcinogens and other types of health effects?

A zero threshold is commonly used for carcinogens, whereas a nonzero threshold is employed for other types of health effects.

What does exposure assessment involve?

Exposure assessment involves either measuring or estimating the concentrations of chemicals in the environment where people are likely to be exposed.

What is the average daily dose (in mg/kg-da) received by an average adult, assuming that all the inhaled material is taken up by the body?

1.3 × 10-3 mg formaldehyde/ kg-da

What is the acceptable lifetime risk level for a known or suspected carcinogen according to the EPA?

A lifetime risk level of 10-6 (one chance in a million) or less can generally be regarded as acceptable or inconsequential, whereas a lifetime risk of 10-3 (one in a thousand) or greater is considered serious and is a high priority for attention.

What is one way of judging the acceptability of a risk level?

One way of judging the acceptability of a risk level is to compare it to background cancer rates.

What are some possible routes of exposure to toxic chemicals in contaminated waste disposal sites?

Exposure to toxic chemicals can occur via ingestion of contaminated drinking water or contaminated soil, as well as via inhalation of vapors given off by soil or water.

What is the chronic daily intake (CDI) used for?

To account for the actual exposure via each environmental medium or exposure route.

What is the concentration of benzene in the soil at the site?

At or below 0.9 mg benzene/kg of soil (0.9 ppmw).

What is the proposed use for the site?

A children's playground.

How many hours per day would a child use the playground?

Four hours a day.

How many days per year would a child use the playground?

350 days per year.

How many years would a child use the playground?

10 years.

What is the weight of the child?

15 kg.

How much soil does the child ingest per day?

About 200 mg of soil per day (equal to 2 X 10-4 kg/da).

What is the lifetime in years?

70 years.

What is the potency factor for benzene (oral ingestion)?

5.5 X 10-2 (mg/kg-da)-1.

What is the chronic daily intake formula for benzene in the proposed playground?

CDI \= (Concentration in soil X Soil intake rate / Body weight) X ( Total exposure time/ Total lifetime ) \= 2.7 × 10-7 mg benzene kg-da

What is the formula for calculating the incremental lifetime cancer risk?

Incremental cancer risk \= CDI X PF\= (2.7 × 10-7)(5.5 × 10-2) \= 1.5 × 10-8

What is the key parameter used to characterize the safe dose of a noncarcinogenic chemical?

The reference dose for No Observable Adverse Effects Level- NOAEL

How is the reference dose (RfD) calculated?

RfD (mg/kg-da) \= NOAEL/ (UF X ME)

What is the final step in risk assessments for noncarcinogenic chemicals?

Comparing the actual or estimated daily intake of the chemical to the reference dose (RfD value)

What is the metric used in risk assessments to compare an actual dose of a chemical to the reference dose?

Hazard quotient (HQ) \= Average daily dose (ADD) during exposure period (mg/kg-da) / Reference dose (RfD)(mg/kg-da)

What does a hazard quotient less than or equal to 1.0 mean?

There are no known adverse effects from the exposure.

According to EPA guidelines, what is the acceptable risk for a noncarcinogen?

HQ ≤ 1.0

What is the formula for calculating the hazard index (HI)?

Hazard index (HI) \= Sum of hazard quotients \= ∑(HQ)

What are the limitations of risk assessments?

A risk assessment can help identify and prioritize greatest concerns. In turn, this helps direct economic actions to reduce or eliminate the health risk.

What can a risk assessment help identify and prioritize?

Greatest concerns.

What do risk assessment procedures require?

Some degree of professional judgment.

What are the limitations of risk assessments reflected in?

The many uncertainties that characterize each step of the process.

What are some sources of uncertainty in risk assessments?

Types, amounts, and location of contaminants in place.

What are some uncertainties in risk assessments?

Measurement errors, modeling the relationship between contaminant sources and the amounts of chemicals that reach receptors, uncertainty and variability in the way different contaminants affect people and ecological systems.

What is beginning to be included as an explicit component of the analytical framework in environmental risk assessment?

Uncertainty.

What has risk analysis traditionally relied on to account for known or suspected uncertainties?

Various "safety factors" and the use of conservative (worst-case) assumptions.

What are some methods used in risk analysis to account for uncertainties?

Various "safety factors" and the use of conservative (worst-case) assumptions.

What are some examples of parameters used in risk analysis?

Uncertainty factor (UF) and modifying factor (MF) parameters.

What is the purpose of probabilistic risk assessments?

To present risk results as a probability distribution rather than a single value.

What is the first major factor affecting environmental change?

Population.

How is population usually measured in terms of environmental change?

Gross domestic product (GDP) per capita.

What is the second key factor affecting environmental change?

Standard of living or the level of affluence of the population.

What is the third element needed to describe an environmental future?

Expectations for technological change over time.

What is the third critical factor affecting environmental change?

Technology for delivering goods and services.

What is one way to quantify the growth of a population?

Assuming a constant annual growth rate.

How can the annual growth rate be expressed?

Either as a percentage or as a fraction.

What is the general expression for the total population after t years, assuming a constant annual growth rate?

P \= Po (1 + r)t.

What is the current population of the urban area?

1 million people.

What is the annual growth rate of the urban area?

7 percent/year.

How long is the anticipated growth rate expected to continue?

For the next 10 years.

What would be the population of the urban area after 10 years, assuming the anticipated growth rate continues?

(Answer will depend on the calculation of the previous questions)

What is the estimated population growth rate for the next 10 years?

7 percent/year.

What is the formula to calculate the population after a certain number of years?

P \= P . (1 + r)t.

If the current population is 1 million, what would be the population after 10 years?

2 × 106.

What are some other factors to consider when estimating population growth?

Fertility rate, age structure, age-specific birth rates, and death rates per gender.

What is the gross domestic product (GDP)?

The monetary value of all final goods and services produced during a year.

What does GDP per capita measure?

The average affluence of the population.

What is an important indicator of overall economic growth?

The change in GDP per capita.

Are year-to-year changes in GDP larger for developing countries or industrialized countries?

Developing countries.

What do historical trends provide?

Guidelines for assumptions about future economic growth.