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Spanish work claims link between tap water and bladder cancer (16/05/06)

A Spanish research team has published a paper that suggests higher consumption of tap water may slightly increase the risk of bladder cancer.

The study, published in the International Journal of Cancer, looked at six case studies and found the increased risk of bladder cancer consistently across all of the studies, which the authors suggest makes chance an unlikely explanation.

The authors warn that the finding does not easily translate into public health recommendations.

The results are based on 2749 bladder cancer cases and 5150 cancer-free controls, most living in the US, Canada or Finland, with additional data from cases in France and Italy.

The study suggests that the risk of bladder cancer was 50% higher in men that drank over two litres of tap water per day compared to those that drank 0.5 litres per day or less, with a less significant association for women.

Coffee consumption, which on average makes up about a third of tap water consumption, was implicated ? over five cups a day, particularly among men that smoked, increased bladder cancer risk. However, drinking tap water alone was also associated with an increased risk.

The team correlated current and historical average THM levels in water. Respondents in the study, from age 15 to the interview, had an average residential THM level of 32.2mug/l.

The team leader?s previous study looked at other possible routes of THM ingestion including showers, baths and swimming pools, with experimental studies showing substantial differences in THM uptake and internal distribution by route. Dermal absorption and inhalation were found to be significant routes.

Drinking fluids other than tap water was not associated with an increased risk, the current study team found. The team speculated that the increased risk may be associated with ingestion of disinfection byproducts, notably THMs, though they found no concrete evidence to link the risk to THM exposure.

Lis Stedman