Bladder cancer risk increased 33% and colorectal cancer by 15% in using chlorine to disinfect water

Chlorinating drinking water at levels common in the United States and European Union probably increases the risk of several cancers, a new analysis of recent research from across the globe finds.

The process of disinfecting water with chlorine creates trihalomethane (THM), a byproduct found in virtually all public drinking water systems across the US and EU – nearly 300 million people in the US have concerning levels in their water, by one estimate.