Uncertainty analysis in regulatory programs: Application factors versus probabilistic methods in ecological risk assessments of chemicals

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:211973

Moore, D R.J.; Elliot, B ^[1]

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1. Environment Canada, Hull, Quebec (Canada)

In assessments of toxic chemicals, sources of uncertainty may be dealt with by two basic approaches: application factors and probabilistic methods. In regulatory programs, the most common approach is to calculate a quotient by dividing the predicted environmental concentration (PEC) by the predicted no effects concentration (PNEC). PNECs are usually derived from laboratory bioassays, thus requiring the use of application factors to account for uncertainty introduced by the extrapolation from the laboratory to the field, and from measurement to assessment endpoints. Using this approach, often with worst-case assumptions about exposure and species sensitivities, the hope is that chemicals with a quotient of less than one will have a very low probability of causing adverse ecological effects. This approach has received widespread criticism recently, particularly because it tends to be overly conservative and does not adequately estimate the magnitude and probability of causing adverse effects. On the plus side, application factors are simple to use, accepted worldwide, and may be used with limited effects data in a quotient calculation. The alternative approach is to use probabilistic methods such as Monte Carlo simulation, Baye`s theorem or other techniques to estimate risk. Such methods often have rigorous statistical assumptions and may have large data requirements. Stating an effect in probabilistic terms, however, forces the identification of sources of uncertainty and quantification of their impact on risk estimation. In this presentation the authors discuss the advantages and disadvantages of using application factors and probabilistic methods in dealing with uncertainty in ecological risk assessments of chemicals. Based on this analysis, recommendations are presented to assist in choosing the appropriate approach for different types of regulatory programs dealing with toxic chemicals.

• OSTI ID: 211973
• Report Number(s): CONF-9511137--; ISBN 1-880611-03-1
• Country of Publication: United States
• Language: English

Related Subjects

29 ENERGY PLANNING, POLICY, AND ECONOMY
CALCULATION METHODS
DATA COVARIANCES
FORECASTING
POLLUTION REGULATIONS
PROBABILITY
RISK ASSESSMENT
TOXIC MATERIALS