Policy Analysis Policies for Chemical Hazard and Risk Priority Setting: Can Persistence, Bioaccumulation, Toxicity, and Quantity Information Be Combined? JON A. ARNOT* AND DON MACKAY The Canadian Environmental Modelling Centre, Trent University, 1600 West Bank Drive, Peterborough, ON, Canada, K9H 7B8
Received January 16, 2008. Revised manuscript received March 30, 2008. Accepted March 31, 2008.
Existing methods used to screen chemical inventories for hazardous substances that may pose risks to humans and the environment are evaluated with a holistic mass balance modeling approach. The model integrates persistence (P), bioaccumulation (B), toxicity (T), and quantity (Q) information for a specific substance to assess chemical exposure, hazard, and risk. P and B are combined in an exposure assessment factor (EAF), P, B, and T in a hazard assessment factor (HAF), and P, B, T, and Q in a risk assessment factor (RAF) providing single values for transparent comparisons of exposure, hazard, and risk for priority setting. This holistic approach is illustrated using 200 Canadian Domestic Substances List (DSL) chemicals and 12 United Nations listed Persistent Organic Pollutants (POPs). Priority setting results are evaluated with those of multiple category-based screening methods employed by Environment Canada and applied elsewhere that use cutoff criteria in multiple categories (P, B, and T) to identify hazardous chemicals for more comprehensive evaluations. Existing methods have categorized the DSL chemicals as either higher priority (requiring further assessment; screened in) or lower priority (requiring no further action at this time; screened out). The priority setting results of the cutoff-based categorization are largely inconsistent with the proposed integrated method, and reasons for these discrepancies are discussed. Many chemicals screened out using existing methods have equivalent or greater risk potential than chemicals screened in. Decisions for screening assessments using binary classification on the basis of cutoff criteria can be flawed, and complementary holistic methods for priority setting evaluations such as the one proposed should be considered.
Introduction International and national chemical management programs seek to protect human health and the environment from the potential risks of hazardous chemicals as identified by the four separate criteria of persistence (P), bioaccumulation (B), and toxic (T) properties, and quantity (Q) information (1–4). Hazard is an intrinsic or intensive property of the * Corresponding author tel: 705-748-1011extn 7645; fax: 705-7481080; e-mail:
[email protected]. 4648
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chemical, whereas risk is an extensive property that requires information on the quantity of chemical released and the resulting exposure (5). Hazard is thus a function of P, B, and T, and risk is a function of P, B, T, and Q. Monitoring data are available for only a small percentage of the estimated 100 000 chemicals that require evaluation, and there is a general lack of measured data on chemical properties (6). For example, of the approximately 11 000 organic chemicals on Canada’s Domestic Substances List (DSL), measured bioaccumulation factors (BAF) in fish exist for
