Air Toxics Risk Assessment: Traditional versus New Approaches

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

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

3. 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.

4. 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.

5. 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?

6. 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

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

8. Uncertainty Factors - USEPA Factor* Extrapolation H 10 or less - Average Human to Sensitive Human A 10 or less - Animal to Human S 10 or less - Short-term to Long-term Exposure L 10 or less - LOAEL to NOAEL D 10 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.

9. Cumulative Response as a Function of Dose for Humans and Rats(Hypothetical Data) 100 80 Human Rat 60 Cumulative Response Human NOAEL or BMD 40 Animal NOAEL 20 or BMD UF UF A H 0 0.01 0.1 1 10 100 1000 Dose RfD

10. Response as a Function of Dose for Humans and Rats(Hypothetical Data) 100 90 80 Human 70 Rat 60 Response 50 Human NOAEL or BMD 40 Animal NOAEL 30 or BMD 20 UF UF H A 10 0 0.01 0.1 1 10 100 1000 RfD Dose

11. 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

12. 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

13. 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 ]