Elevated mortality from lung cancer associated with arsenic exposure for a limited duration.

In 1959, arsenic poisoning was detected in the town of Nakajo in Japan. The cause was exposure to inorganic arsenic in well water during 1954 to 1959. To examine the long-term effects of limited-duration arsenic exposure, we conducted mortality and survival studies for patients with chronic arsenic exposure and for control subjects from 1959 to 1992. The ratio of observed deaths to expected deaths from lung cancer was significantly high (7:0.64) for male patients. The lung cancer mortality rate was elevated markedly in subgroups with higher clinical severities of symptoms. Small cell carcinoma was specific to the exposed patients. The cumulative change of survival declined significantly in the exposed patients compared with the controls. The decline disappeared when lung cancer deaths were treated as lost to follow-up. The results showed that a 5-year period of arsenic exposure was associated with risk of lung cancer.