Showering introduces chlorination by-products into bloodstream

Trihalomethanes, which are formed when chlorine used to disinfect water reacts with organic matter, have been found to increase significantly in the human bloodstream after showering, according to a new study by US scientists

The study, carried out by researchers from the School of Public Health at the University of North Carolina, investigated the distribution of trihalomethanes (THMs) in 50 women from Georgia and Texas. They found that showering not only increased the level of THMs in the bloodstream, but that the type of THM in the blood reflected that in the subjects’ home tap water.

“Chlorination of tap water was one of the most important improvements made in public health, and it saves countless lives each year by reducing risk from bacterial contamination,” said Amy Miles, co-author of the research. “Water-borne diseases used to be a major cause of death and illness, and they still are in some parts of the world without chlorination.”

However, if chlorination creates its own risks, it needs to be studied further, said Miles.

The researchers measured THMs in the women’s blood before and after they showered, and compared the levels to concentrations found in tap water at their homes. “Concentrations of THMs were about 1,000 times lower in blood than in tap water, but after the showers, median levels in blood increased by a factor of four,” explained Miles. “This showed THMs were getting into the blood as a result of water use.”

However, the results did not address whether the concentrations were harmful or linked to any particular health problem, she pointed out.

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