Blood trihalomethane levels and the risk of total cancer mortality in US adults

- Trihalomethanes (THM) are classified as either probable or possible carcinogens.
- Limited evidence on the link between THM and the incidence of cancer in humans.
- We investigated the association between blood THM levels and the risk of total cancer mortality.
- High blood THM levels are associated with a high risk of cancer mortality in adults.
- Our findings suggest a possible link between exposure to brominated THM and cancer in humans.

BackgroundAlthough animal data have suggested the carcinogenic activity of trihalomethanes (THMs), there is inconsistent evidence supporting the link between THM exposure and cancers in humans.ObjectivesWe investigated the association between specific and total blood THM levels with the risk of total cancer mortality in adults.MethodsWe analyzed data from the 1999-2004 Third National Health and Nutrition Examination Survey and the Linked Mortality File of the United States. A total of 933 adults (20-59 years of age) with available blood THM levels and no missing data for other variables were included. Four different THM species (chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM) and bromoform) were included, and the codes associated with cancer (malignant neoplasm) were C00 through C97, based on the underlying causes of death listed in the International Classification of Disease 10the Revision.ResultsCompared with adults in the lowest DBCM, bromoform, and total brominated THM tertiles, those in the highest DBCM, bromoform, and total brominated THM tertiles exhibited adjusted hazard ratios (HR) of total cancer mortality of 4.97 (95% confidence interval (CI) = 1.59-15.50), 4.94 (95% CI = 1.56-15.61), and 3.42 (95% CI = 1.21-15.43) respectively. The risk of total cancer mortality was not associated with increases in blood chloroform and total THM levels.ConclusionsWe found that the baseline blood THM species, particularly brominated THMs, were significantly associated with total cancer mortality in adults. Although this study should be confirm by other studies, our findings suggest a possible link between THM exposures and cancer.