Last week, news broke of research claiming (once again) that chlorinated tap water causes cancer. This latest bit of hysteria emanates from Finnish researchers who exposed rats to high doses of 2-chloro-4(dichloromethyl)-5-hydroxy-2(5H)-furanone, or "MX" for short. MX is a byproduct of chemical reactions that occur in chlorinated drinking water. And, of course, the rats got a variety of cancers.
BUT of what relevance is this research to humans?
First, the rats were given drinking water laden with ultra-high concentrations of MX. Typical drinking water supplies contain MX at concentrations on the order of 10 nanograms per liter. But the rats were given drinking water with up to up to 70 micrograms per milliliter of MX. My math says that this difference means that the rats were getting MX at a concentration on the order of ONE MILLION TIMES GREATER than humans get from typical drinking water supplies.
Second, the rats (which are specially bred to be predisposed to getting cancer) were fed a standard dietary formulation — a formulation known to contain very high levels of the carcinogen manganese. Did the rats get cancer from the MX or from the manganese? Who knows? Certainly not these researchers!
So of what relevance is this study to humans? I'll let the authors speak for themselves:
...these findings cannot be extrapolated to humans.You would think after Peru's tragic and misguided effort to stop chlorinating drinking water (which resulted in a deadly Latin American cholera epidemic), the National Cancer Institute would be more circumspect about publishing such nonsense.
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