Valid versus invalid radiation cancer risk assessment methods illustrated using Swiss population data

Area of Science:

• Radiation Risk Assessment
• Epidemiology
• Nuclear Safety

Background:

• Public interest in radiation cancer risk assessment surged after the Fukushima nuclear accident.
• Interpretations of epidemiological studies and cancer risk assessment methods can be unclear and raise questions about validity.
• Valid versus invalid radiation cancer risk assessment methods require clear illustration and comparison.

Purpose of the Study:

• To illustrate valid versus invalid radiation cancer risk assessment methods using Swiss population data.
• To compare the collective dose and cumulative risk assessment methods.
• To discuss radiation risk assessment in different dose ranges and the impact of dosimetry errors.

Main Methods:

• Comparison of collective dose and cumulative risk assessment methods.
• Discussion of risk assessment in dose ranges below 100 mSv.
• Application of the EU-project CONFIDENCE software for lifetime cancer risk calculations.
• Analysis of dosimetry errors' impact on uncertainties using different standard deviations and dose sampling distributions (normal vs. lognormal).

Main Results:

• The cumulative risk assessment method is recommended over the collective dose method due to reduced uncertainties and risk of misinterpretation.
• Below 100 mSv, evidence for a causal relationship between radiation and cancer is limited by significant uncertainties.
• The linear non-threshold (LNT) model is a suitable, prudent, and parsimonious model for dose-response in this range.
• Increased standard deviations in dosimetry significantly widen the 95% confidence intervals for cancer lifetime risk.
• Different dose sampling distributions (normal vs. lognormal) also impact the resulting confidence intervals.

Conclusions:

• Cumulative risk assessment is preferred for its clarity and reduced potential for misinterpretation.
• Radiation cancer risk assessment below 100 mSv is highly uncertain, necessitating cautious interpretation.
• The LNT model provides a pragmatic approach for dose-response modeling within uncertainties.
• Accurate dosimetry and understanding its uncertainties are critical for reliable cancer risk calculations.