Ingested arsenic, characteristics of well water consumption and risk of different histological types of lung cancer in northeastern Taiwan

Our previous study combining two arseniasis-endemic areas in Taiwan confirmed a dose-response association of lung cancer and arsenic exposure. We conducted current analysis to elucidate the dose-response relationship in lower exposure level, and to evaluate whether the association differs in different histological types. In addition, whether specific characteristics of well water consumptions increased lung cancer risk was examined in order to establish a complete risk profile for arsenic exposure.A total of 8086 residents in northeastern Taiwan were followed for 11 years and 6888 participants remained in the final analysis because 1198 residents with unknown arsenic concentration were excluded. The 178 incident lung cancers were ascertained through linkage with the national cancer registry profiles in Taiwan. All analyses were performed by Cox's proportional hazards regression models.We found a significant dose-response trend (P=0.001) of lung cancer risk associated with increasing arsenic concentration. There was no apparent increased risk at concentrations between 10 and 100 μg/L, but concentrations between 100 and 300 μg/L showed evidence of excess risk (RR 1.54, 0.97-2.46). The relative risk was 2.25 (95% CI: 1.43, 3.55) for exposure to 300 μg/L when compared to <10 μg/L. The significant dose-response trends and the synergistic effect of arsenic exposure and cigarette smoking can be found in squamous and small cell carcinomas, but not in adenocarcinoma. Despite lacking statistical precision, when duration is accounted for, all levels of exposure including low concentration were in the direction of increased risk of lung cancer, and these associations tended to increase with longer durations of exposure.This study provides additional evidence linking arsenic to lung cancer, and the indications that arsenic may play a more important role in certain histological type may help with further research in carcinogenic effect of inorganic arsenic on lung cancer.