Beyond Dose Assessment Using Risk with Full Disclosure of Uncertainty in Public and Scientific Communication F. Owen Hoffman, David C. Kocher and A. Iulian Apostoaei SENES Oak Ridge, Inc. Center for Risk Analysis 102 Donner Drive Oak Ridge, TN 37830

Dose Versus Risk as Assessment Endpoint Risk communication paradigms: Peter Sandman Risk = Hazard + Outrage Hoffman et al. (2010) Perceived risk = Estimated risk × Outrage 2 Restricting assessment to dose reduces potential for outrage, but Censorship of risk information leads to distrust

Consequences of Assessments Based on Dose Communication limited to comparisons with –Regulatory standards –Natural background radiation –Doses from medical radiation –Epidemiological limits of risk detection Doses associated with Lowest Observed Adverse Effects Levels (LOAELs) Effects of exposure cannot be compared with those from chemicals or other hazards

Disadvantages of Dose as Assessment Endpoint Two individuals with same dose may have markedly different risks –Risk per unit dose depends on organ exposed, age at time of exposure, gender, attained age, and baseline risk Effective dose is a poor surrogate for risk –Especially for cancers of high incidence but low mortality such as skin and thyroid

Excess Lifetime Risk (All Cancers) from 20 mSv Effective Dose Certainty Acute exposure, high-energy photons, newborn female Mean = 1.1 x Ranges represent 95% uncertainty intervals. Stars represent mean values. Chronic exposure high-energy photons male at age 70 Mean = 7.8 x Single whole-body exposure to high-energy photons

Excess Lifetime Risk (All Cancers) from 20 mSv Effective Dose Ranges represent 95% uncertainty intervals. Stars represent mean values. whole-body exposure Certainty Chronic exposure high-energy photons male at age 70 Mean = 7.8 x Acute x-ray exposure newborn female Mean = 2.7 x 10 -2

Excess Lifetime Risk (Specific Cancer) from 20 mSv Effective Dose Certainty Chronic dose to colon at age 20 from high-energy beta emitter (internal exposure) Risk of Colon Cancer: Mean = 2.2 x Acute dose to thyroid to newborn from x rays Risk of Thyroid Cancer: Mean = 1.4 x Ranges represent 95% uncertainty intervals. Stars represent mean values. Female receiving dose to specified organ at specified age

The public has legitimate questions about risk from radiation exposure; these questions deserve answers

When Addressing Questions about Risk Include information about uncertainty –Uncertainty represents state of knowledge –95% uncertainty ranges more informative than central “best estimate” value Put risk estimates into perspective –Compare with other risks –Communicate benefits, if any

Examples of Risk Evaluations for Major Exposure Situations Indoor Radon CT scans in medicine Fallout from atmospheric testing of nuclear weapons

Indoor Radon- Different Ways to Express Risk Excess lifetime risk of death from lung cancer (never-smoker exposed to 46 Bq m -3 [1.2 pCi L -1 ] ) –20 chances per 10,000 (8 to 50 per 10,000) * –2 × (0.8 × to 5 × )* –0.2% (0.08% to 0.5%)* –2000 deaths per million never-smokers exposed (800 to 5000 cases per million)* –One excess death per 500 exposed (1 per 1250 to 1 per 200 )* * 90% uncertainty range

Indoor Radon Risk to US Population Number of deaths in 1995 from lung cancer –157,400 deaths in total population 146,400 in ever-smokers 11,000 in never-smokers Fraction of lung cancer deaths due to radon –14% (6% to 30%)* in general population –26% (13% to 45%)* in never-smokers Number of deaths in 1995 from radon –21,000 (9,000 to 50,000)* * 90% uncertainty range

CT Scans in Medicine Lifetime risk of cancer incidence from abdominal scan in 50 year-old female –15 (6 to 35)* chances per 10,000 Not including difference in risk between x rays and high-energy gamma rays –36 (7 to 110)* chances per 10,000 Including difference in risk between x rays and high-energy gamma rays * 95% uncertainty range

Risk to US Population from 57 million CT scans in ,000 (15,000 to 45,000)* excess cancers Not including difference in risk between x rays and high-energy gamma rays 60,000 (17,000 to 150,000)* excess cancers Including difference in risk between x rays and high-energy gamma rays –Risk of cancer incidence would increase if non-melanoma skin cancer were included * 95% uncertainty range

Nationwide Exposures to Iodine-131 in NTS Fallout Incidence of thyroid cancer in US (assuming no exposure to fallout) –birth cohorts under age of 20 in 1952 about 400,000 cases Excess thyroid cancer in US from fallout –birth cohorts under age of 20 in ,000 (13,000 to 254,000)* cases 95% uncertainty range

Nationwide Exposures to Iodine-131 in NTS Fallout Probability of causation for a thyroid cancer diagnosed in later life –Female born in 1952 who drank 1 to 3 glasses per day of fresh milk 95% uncertainty range PC (%)City 7% to 79%36%Washington, DC 12% to 88%50%Kansas City, MO 3% to 78%28%San Francisco, CA Probability of Causation (PC)

Placing Risk into Perspective Challenge is to Communicate Risk to a Public Unfamiliar with Concept of Risk Expressed as a Probability

Lifetime Risk of Cancer Incidence from Exposure to Radiation Certainty Indoor radon: smoker (46 Bq m -3 ) Indoor radon: never-smoker ( 46 Bq m -3 ) * Assumes female born in 1952 Childhood exposure to 131 I in NTS fallout * ( thyroid dose of 0.1 Gy) Single abdominal CT scan: 50 year-old female Negligible Individual Dose ** (NCRP-1993) (10 µSv/yr) ** Assumes 70-year chronic exposure

Involuntary Lifetime Risks of Cancer Incidence Certainty Dioxins & furans in foods Current exposure to atmospheric fallout (10 µGy/y) Chromium* Formaldehyde in indoor air PCBs in foods Non-smoker sharing a room with smoker (50 yrs) Benzene* Vinyl Chloride* Air pollution from hazardous chemicals* * outdoor air in California

What Have We Learned from Risk Assessment? Medical exposures now a leading source of future radiation risk to general population –Assessments should account for Risk due to exposure to x rays vs. high-energy gamma rays Risk from incidence of non-fatal skin cancer Indoor radon is second leading cause of lung cancer –May cause from 6% to 30% of lung cancers in general population

What Have We Learned from Risk Assessment? Thyroid cancers from childhood exposures to 131 I in weapons fallout would be compensable nationwide –If risk criteria established for compensation of energy employees were extended to public (i.e., upper 99 th percentile of estimate of probability of causation equals or exceeds 50%)

A Vision for the Future Radiation risk assessment embraced by regulatory and health protection communities Uncertainty in risk used for decision-making –Uncertainty represents limits to our state of knowledge about risk –Uncertainty can include alternative hypotheses about effects at low dose Risk communication overcomes concern that –Risk estimation may alarm, if not harm, an otherwise uninformed public