Communication of Uncertainty in Hazard & Risk Assessment: Panel Discussion Lynn H. Pottenger, PhD, DABT The Dow Chemical Company

Communication of Uncertainty in Hazard & Risk Assessment:

Panel DiscussionLynn H. Pottenger, PhD, DABTThe Dow Chemical Company

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Uncertainty Workshop Focus:

• Focus on identification of sources & communication of uncertainty in a risk assessment– Not how to measure– Not quantitative analysis methods

• Uncertainty is inherent—but sources differ:– Data-related– Derivation of risk estimates

• How best to communicate this inherent uncertainty?– Different types (sources; magnitudes)– Different impact on results of assessment– Different audiences

Different approaches to presenting/communicating uncertainty

LHP 3/24/2015 2015 SOT: Communication of Uncertainty in Hazard & Risk Assessment

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Key Aspects

• Transparent– Identify & characterize key decisions and their impact

• Comprehensible– Simplify complex concepts

• Useful– Geared towards identified audience


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This Workshop examined four approaches:

1. Comparing Values to Other Peer Reviewed Numbers2. Presenting Toxicological Information Visually in the Context of

Alternative Values, Exposure Levels, and Biomonitoring Equivalents3. Unpacking Toxicity Assessments to Understand & Improve Confidence4. Improving Transparency in Dose-Response Decision Making


2015 SOT: Communication of Uncertainty in Hazard & Risk Assessment

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Comparison of Risk Values

•Provides high level cross-assessment comparison of risk estimates•Deeper drill on specifics possible

LHP 3/24/2015

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Oral Noncancer Basic Figure

Dos

e (m

g/kg

/day

)

Point of Departure (POD)

Reference Value

Uncertainty Factor (UF)

Uncertainty Factors can range from 0 to 3000 (maximum). The possible types of UFs are: interspecies uncertainty (UFA); intraspecies variability (UFH); subchronic to chronic extrapolation (UFS); use of a LOAEL in absence of a NOAEL (UFL); database incomplete (UFD)

An estimate of an exposure for a given duration to the human population (including susceptible subgroups that is likely to be without an appreciable risk of adverse health effects over a lifetime. It is derived from a BMDL, NOAEL, LOAEL or suitable point of departure, with uncertainty/variability factors applied to reflect limitations of the data used. Durations include acute, short-term, subchronic, and chronic and are defined individually in this glossary.

The dose-response point that marks the beginning of a low-dose extrapolation. This point can be the lower bound estimate on dose for an estimated incidence or a change in response level from a dose-response model (BMD), or a NOAEL or LOAEL for an observed incidence, or change in level of response.

The range for the values are not on scale but are allowing the visualization of the uncertainty between the POD and the risk value.

The shading in the figure represents a decrease in the value and the potential risk of effects; higher value (darker shade) to a lower value (lighter shade).

Visualization of Tox/Risk/Uncertainty Information

•Focus on visualization of range between POD and risk estimate•Exposure context possible with inclusion of BE•Cross-assessment comparison possible


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Confidence Scoring of 8 ElementsPeer Review +++

Validation -

Toxicity Value Comparison -

•Focus on individual assessment•Potential to score different elements•Includes consideration of confidence

LHP 3/24/20152015 SOT: Communication of Uncertainty in Hazard & Risk Assessment

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Improving Transparency: key decisions & impact

•Detailed focus on individual assessment•Analysis of key decisions—data and other; distinguishes science from policyLHP 3/24/2015


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Four new approaches and EPA/IRIS current one

• ACC ARASP workshop approaches:– From cross-assessment, more general to more &

more detailed, focused on a single assessment– From tabular to figures to combined– Only one addresses exposure issues

• Example of EPA/IRIS current practices for description of uncertainty—B[a]P draft– ‘Consideration-Decision-Justification’ in tabular form


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Starting discussion questions…

• Are these approaches useful and usable?– Improvements/Refinements?

• Additional key aspects to consider?

– Combined approaches?– Intended audiences?

• Different approaches for different audiences?

• How can we begin to define a path towards improved integration of uncertainty communication?– Either these approaches or others, yet undefined…



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Thank-you!

LHP 3/24/2015

Documents

Communication of Uncertainty in Hazard & Risk Assessment: Panel Discussion Lynn H. Pottenger, PhD, DABT The Dow Chemical Company