Late Breaking Abstract - Workers’ compensation of lung cancer due to occupational exposure to asbestos in the Netherlands

Background: A lifetime cumulative exposure to asbestos of 25 fiber-years is generally considered the point at which lung cancer risk doubles relative to background risk. This is based on the Helsinki criteria, assuming a 4% risk increase per fiber-year. However, studies suggest the exposure-response curve may be steeper at lower exposure.

Objective: We aimed to calculate the exposure threshold at which lung cancer is more likely than not due to asbestos, for a new one-time compensation scheme in the Netherlands.

Methods: Lung cancer risk due to asbestos fiber-years was estimated via two approaches. First, data from the recent SYNERGY pooled case-control study (14 studies, n = 37,866) were analyzed using mixed-effects logistic regression adjusted for age, sex, smoking status, and time since quitting smoking, accounting for study effects. Second, data from systematic reviews (SR) were updated (22 studies, n ≈ 130,341), and exposure-response estimated by spline meta-regression. Probability of causation (PoC) was calculated as excess relative risk (ERR) divided by 1 + ERR for the point estimate (PE) and upper 95% prediction interval (PI). Exposure thresholds for PoC = 0.5 are reported.

Results: A steeper exposure-response was observed in SYNERGY compared to SR meta-regression. PoC of 0.5 corresponded to 10.59 and 4.31 fiber-years in SYNERGY (PE and upper PI), and to 81.7 and 26.57 fiber-years in SR meta-regression, respectively.

Conclusions: A 4.31 fiber-years threshold has been adopted in the Netherlands for compensation of lung cancer presumably due to asbestos to weigh uncertainties in favor of claimants. Differences between SYNERGY and meta-regression of 22 early studies will be discussed.