Theory 26/Nuclear & Radiation /Radiation epidemiology/3 min
Risk Is Repair Capacity
Two workers with the same badge dose can have very different risks. The difference may be measurable.
Individual radiation cancer risk is set by DNA repair capacity rather than by cumulative dose, so a repair-capacity biomarker should predict risk better than occupational dose records, and dose-based regulation should be supplemented by capacity screening.
01The evidence
- Comparisons of normal and double-strand-break repair deficient cells show that the biological consequence of a given dose depends on repair capacity, which is the individual-level variation a capacity model requires.Mutation Research
- Residual DNA damage markers after irradiation vary between individuals at the same dose, which is the measurement a capacity biomarker would formalise.Europe PMC
02The tension
Radiation protection is dose-based and population-averaged. It assumes that the same dose carries the same risk for everyone, which is administratively convenient and biologically implausible. Individual variation is acknowledged and not measured, because there has been no validated assay.
03The theory
Cancer risk from radiation depends on the probability that a damaging lesion escapes repair and becomes a mutation. That probability is a function of repair capacity, which varies between individuals for genetic and age-related reasons.
If capacity is the determinant, then dose is a proxy that works on average and fails at the individual level. The prediction is that a repair-capacity assay should stratify risk within a dose band, and that the highest-risk individuals should be identifiable before exposure rather than after.
The theory also predicts an interaction: the effect of dose should be larger in low-capacity individuals, so the dose-response slope should differ by capacity group. That is a testable heterogeneity in existing cohort data if stored samples allow the assay.
The regulatory consequence is uncomfortable but tractable. Dose limits could remain as a universal floor while capacity screening adds an individual layer for high-exposure occupations, which is how other individual susceptibility factors are already handled.
04What this is not
The dose model assumes a single risk per unit dose. This assumes a distribution of susceptibilities, which predicts heterogeneity that the aggregate model cannot see.
05Predictions
- P1Repair capacity should predict cancer risk within a dose band.
- P2The dose-response slope should be steeper in low-capacity individuals.
- P3Capacity screening should identify high-risk workers before exposure.
06What would refute it
No risk heterogeneity by capacity within dose bands would leave the averaged model adequate.
07What it would change
It would add an individual layer to radiation protection and change how occupational screening is designed.
08Evidence base
- Dose-rate effectiveness and repair deficiency — Mutation Researchhttps://www.sciencedirect.com/science/article/abs/pii/S0304383597004400
- Residual DNA damage markers and individual variation — Europe PMChttps://europepmc.org/article/MED/25738897