In the U.S. one of the issues we have with our tap water is that the health standards for these toxic treatment byproducts are enforced based on a rolling annual average where violations occur only when the average contamination levels in four consecutive quarters exceed the limit. This means that contamination levels can be far above the safe level for one or two quarters (representing three to six months’ exposure), as long as the other quarters bring the average down below the standard. The logic is that these contaminants are potentially cancer-causing, and therefore long-term average exposures are what matters. But is tap water with intermittent high levels of potential carcinogens safe for everyone, including infants and young children?
Source: Richard Wiles, Frederick