San Francisco Tap Water Tests: Pesticides Not Detected

Much of EWG’s work means warning you about potentially harmful chemicals in your water, food or consumer products. So we’re glad to report some good news: Recent tests of San Francisco tap water detected no harmful pesticides in any of the locations sampled.  

In October, a resident of the Sunset District reported that a home test kit detected pesticides in her tap water. The San Francisco Public Utilities Commission, or PUC, said that could have been a mistake but ordered additional city-wide testing to make sure. EWG decided to commission our own tests, so we distributed sample kits to eight households and one office location. After the sample collection, the kits were sent to SimpleWater, in Berkeley, for analysis.

No pesticides were detected in any of the samples. The results were in accordance with the PUC’s tests, which did not detect any pesticides in the more than 21 drinking water samples collected from around the city.

Table 1. Chemicals tested in tap water from nine locations in San Francisco sampled in November and December 2018.

One of EWG’s samples did contain about three parts per billion of the chemical bis(2-ethylhexyl) phthlate,^[1] a member of the class of chemicals known as phthalates. Phthalates can be used as ingredients in pesticides but are mostly used in the production of plastics like PVC piping. The level detected was at EWG’s drinking water health guideline of three parts per billion, which means a one-in-a-million risk of cancer for someone who drank the water every day for a lifetime.

This does not mean that the city’s residents can take their water quality for granted. As with the water in other major cities, San Francisco’s water contains disinfection byproducts. Water disinfection is essential and saves lives, but disinfection byproducts can also increase the risk of cancer. Families and individuals can easily remove disinfection byproducts from their tap water with a simple counter-top carbon filter.

Most of San Francisco’s tap water comes from the Hetch Hetchy Reservoir, with supplements from surface reservoirs in San Mateo and Alameda counties. As a backup water source, the city has been exploring a groundwater supply project, tapping into the Westside Basin aquifer.

The blending of groundwater from local wells with water flowing from the Hetch Hetchy reservoir started in April 2017, immediately prompting a flood of concerns from city residents about water quality. With state-wide droughts, regulatory changes regarding water use, and growing demands on the water supply, greater use of groundwater may become a necessity for the city.

As reported by the U.S. Geological Survey and the PUC, other contaminants may be present in the aquifer underlying the city, such as nitrate and perchlorate. Groundwater is treated and blended to meet state and federal drinking water standards. However, water customers should remain vigilant about contaminants in their drinking water that may pose health risks below legal limits.

To find out more about your local drinking water quality, you can look up testing results from your water utility using EWG’s Tap Water Database.