Contaminated tap water causes 100,000 cancer cases in the US over a lifetime, according to a new study from scientists with the Environmental Working Group.
Most of the cancer risk is from naturally occurring arsenic, the byproducts of chemicals used to disinfect water and radioactive contaminants, according to the analysis, which was published in the peer-reviewed journal Heylion.
“We want people to realize that water that meets legal specifications may still cause health risks based on the latest science,” said Sydney Evans, lead author of the study. “This is a concern nationwide, whether urban or rural, with a small or large [water system].”
The number of cancer cases from water contamination is small compared with the total number of cancer cases in the US.
In 2018 alone, the American Cancer Society reported an estimated 1.7m new cancer cases. Assuming a lifetime of 70 years, that adds up to many millions of instances of cancer.
But Olga Naidenko, vice-president of science investigations at the Environmental Working Group, stressed that water contamination is responsible for a high percentage of the cancer cases that have environmental causes.
The US is ranked well for water quality because it has largely eliminated biological contaminants, such as the bacterium E coli, which are more common in developing nations.
Other dangerous contaminants remain problematic, however.
Issues in small, rural communities have been well documented, but the study notes contaminants in the water in large communities also “contribute a significant share of overall cancer risk associated with drinking water”.
The researchers studied water quality profiles from more than 48,000 systems. Evans recommends people check their own local water reports and select a suitable filter, if necessary. The Environmental Working Group maintains a drinking water database for that purpose.
In Washington DC, for example, regulators detected 10 contaminants at levels that exceeded health guidelines, which are recommendations rather than requirements. Most are associated with cancer.