Objectives It is well known that the risk of lung cancer decrease in ex-smokers some years after exposure have stopped and some studies indicate that the risk of asbestos related lung cancer decrease some years after the exposure had stopped. We have studied how the time after stop of exposure has influenced the risk of asbestos related lung cancer.

Method The incidence of lung cancer was studied in Swedish construction workers who had participated in health controls. The exposure to asbestos was estimated through the occupational titles. Occupational groups with highest risk of malignant mesothelioma were considered to be highly exposed to asbestos and the group with the lowest risk of malignant mesothelioma was considered to have the lowest exposure to asbestos.

Results There were 600 cases of lung cancer in the highest exposed group and 668 in the lowest exposed group. The relative risk comparing high and low exposed decreased the years after exposure had stopped. It was 1.8 during the decade when the exposure come to an end, decreased to 1.5 (95% CI 1.3–1.9) the next decade, to 1.2 (95% CI 1.0–1.5) the decade later and finally to 1.0 (95% CI 0.8–1.2) three decades after the exposure to asbestos had stopped.

Conclusions The time pattern of asbestos related lung cancer seem to follow a similar pattern as the risk of lung cancer in ex-smokers.