Air Toxics Risk Assessment: Traditional versus New Approaches Mark Saperstein BP Product Stewardship Group

Recent Challenges to Air Toxics Risk Assessment 1.Alternatives Assessment 2.Precautionary Approach 3.Questions of Protection of Sensitive Individuals 4.Incorporation of Human Relevance Analysis and Mode of Action Data

1.Alternatives Assessment Traditional Risk Assessment Approach: evaluate hazard, exposure, estimate risk Risk Assessors: The public may not want to participate in the discussion you want to have. Alternative - Present a full range of options: consider adverse impacts and benefits of each one.

Alternatives Assessment: Comments Does not fit neatly into the usual APCD permitting framework. Risk assessment can still be useful in an alternatives evaluation. At what level of decision does one trigger a full alternatives assessment? Suggesting known, less toxic alternatives versus requiring research program. Predictability is a concern for business.

2.Precautionary Approach “Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost effective measures to prevent environmental degradation.” (Rio Declaration, UN 1992). Is our current air toxics risk assessment framework consistent with this approach?

Precautionary Approach “Strong” versus “Weak” versions Most decisions must be made in situations with competing uncertainties Consider both sides of the “risk ledger” –Risks of proposed action –Risks of inaction or status quo

3. Are Sensitive Populations Protected Under our Current Risk Assessment Framework? Children Stressed populations Vulnerable populations

Uncertainty Factors - USEPA Factor*Extrapolation H10 or less - Average Human to Sensitive Human A10 or less - Animal to Human S10 or less - Short-term to Long-term Exposure L10 or less - LOAEL to NOAEL D10 or less - Minimum to Complete Database * These factors are as used by the U.S. EPA. Other health organizations use similar factors. In EPA, the maximum UF for any given database is 10,000; this is also similar to other health organizations.

Dose Cumulative Response Human Rat UF A H RfD Human NOAEL or BMD Animal NOAEL or BMD Cumulative Response as a Function of Dose for Humans and Rats (Hypothetical Data)

Dose Response Human Rat RfD UF H A Human NOAEL or BMD Animal NOAEL or BMD Response as a Function of Dose for Humans and Rats (Hypothetical Data)

Additional Routine Exposure Considerations Multiple pollutants are summed together Routinely assume 70 year continuous exposure Assume continuous location at point of maximum impact Other upper end exposure assumptions All contribute to margin of safety in risk assessments

4.Framework for Human Relevance Analysis of Information on Modes of Action Default assumption that chemicals that cause an effect in animals will cause that effect in humans. Analysis of the Mode of Action (MOA) and consideration of a Human Relevance Framework (HFR) can improve the risk assessment

The Human Relevance Framework Is the weight of evidence sufficient to establish the MOA in animals Are key events in the animal MOA plausible in humans? [ d-limonene ] Taking into account kinetic and dynamic factors, is the animal MOA plausible in humans? [ phenobarbital ] Statement of confidence; analysis; implications. [ melamine ]