Disinfection byproducts and bladder cancer: a pooled analysis.
BACKGROUND
Exposure to disinfection byproducts in drinking water has been associated with an increased risk of bladder cancer. We pooled the primary data from 6 case-control studies of bladder cancer that used trihalomethanes as a marker of disinfection byproducts.


METHODS
Two studies were included from the United States and one each from Canada, France, Italy, and Finland. Inclusion criteria were availability of detailed data on trihalomethane exposure and individual water consumption. The analysis included 2806 cases and 5254 controls, all of whom had measures of known exposure for at least 70% of the exposure window of 40 years before the interview. Cumulative exposure to trihalomethanes was estimated by combining individual year-by-year average trihalomethane level and daily tap water consumption.


RESULTS
There was an adjusted odds ratio (OR) of 1.24 in men exposed to an average of more than 1 microg/L (ppb) trihalomethanes compared with those who had lower or no exposure (95% confidence interval [CI] = 1.09-1.41). Estimated relative risks increased with increasing exposure, with an OR of 1.44 (1.20-1.73) for exposure higher than 50 microg/L (ppb). Similar results were found with other indices of trihalomethane exposure. Among women, trihalomethane exposure was not associated with bladder cancer risk (0.95; 0.76-1.20).


CONCLUSIONS
These findings strengthen the hypothesis that the risk of bladder cancer is increased with long-term exposure to disinfection byproducts at levels currently observed in many industrialized countries.
Villanueva
Cristina M
CM
Respiratory and Environmental Health Research Unit, Institut Municipal d'Investigació Mèdica (IMIM), Barcelona, Spain.
Cantor
Kenneth P
KP
Cordier
Sylvaine
S
Jaakkola
Jouni J K
JJ
King
Will D
WD
Lynch
Charles F
CF
Porru
Stefano
S
Kogevinas
Manolis
M
D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D016001:Confidence Intervals; D004202:Disinfectants / Q000009:adverse effects* / Q000737:chemistry; D005260:Female; D014943:Global Health; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D018570:Risk Assessment; D017678:Sex Distribution; D016019:Survival Analysis; D022882:Trihalomethanes / Q000009:adverse effects*; D001749:Urinary Bladder Neoplasms / Q000453:epidemiology* / Q000209:etiology*; D018508:Water Purification; D014881:Water Supply
D004202:Disinfectants; D022882:Trihalomethanes