San Francisco Bay Area Study Finds Chemical Levels in Bottled Water, Tap Water, and Home-Treated Tap Water

A team of water technicians from water testing company SimpleLab tested chemical levels in hundreds of water samples collected from bottles, household faucets and treated tap water in the San Francisco Bay Area. Their paper is published in the journal PLOS Water.

For many years, tap water was consumed without hesitation by American households because it was considered absolutely safe. However, these beliefs have been challenged in recent years, with the discovery of lead in the drinking water consumed by children in Flint, Michigan.

In response, many consumers have stopped drinking tap water and turned to filters or even commercially bottled water. As part of this new initiative, the SimpleLab team tested drinking water from the three main sources available to residents of the San Francisco Bay Area to see how they compared.

The study tested 100 samples of bottled water, 603 samples of tap water and 111 samples of tap water filtered using a Brita filter. The researchers found that nearly all of the water samples tested met federal health standards for drinking water.

But they also found that the concentrations of chemicals in filtered and bottled water were nearly equal, while tap water contained many more. The chemicals of most concern, they note, were trihalomethanes, released when chlorine is used to disinfect water. All three sources contained some amount of these chemicals.

Trihalomethanes have been linked to several health problems, including liver damage, developmental delays and an increased risk of certain types of cancer. The researchers also caution that their findings are not meant to alarm consumers: Consuming small amounts of trihalomethanes or the other chemicals they found in water is not likely to cause harm.

They conclude that most consumers would benefit from using a filter to drink tap water. They note that it also improves the taste of the water.

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