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San Francisco water some of the cleanest in the U.S.

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Although there’s still reason to look askance at the sink

The Hetch Hetchy reservoir at sunset.
Hetch Hetchy in 2010.
Justin Gaerlan

What’s in the water? The average American consumer is right to be curious—and wary—of what comes out of the tap, but Washington DC-based environmentalist group American Working Group has taken most of the guess work out of it, for better or for worse.

As CityLab and Mother Jones report, EWG’s new Tap Water Database compiles data from utility reports collected between 2010 and 2015 and assesses the level and severity of possible contaminants in every US ZIP code with the push of a button.

Note that EWG is here employing a much stricter standard of water purity than the federal government does. Say CityLab:

These guidelines differ from the EPA’s legal limits for what’s considered safe, which EWG says are often based on outdated studies. According to EWG, the EPA has not added a new contaminant to the list of regulated contaminants at the federal level in more than 20 years.

Hetch Hetchy in 2011.
King of Hearts

What’s on tap for San Francisco? Well, the good news is that our famed Hetch Hetchy supply is good to the last drop after all.

The EWG report on the San Francisco City Water System (which excludes the Presidio and Treasure Island, for the record) records only nine types of contaminants, and only three at potentially alarming levels.

Admittedly, that’s nine more than anyone wants. But for perspective, EWG singles out Merrick, New York as among the best water quality in the country, but Merrick reports 17 types of questionable materials in the aqua (although only one at levels that exceed the group’s guidelines).

And down in, say, Los Angeles, the database turns up 21 contaminants, including five to be worried about. So local numbers are by a certain standard encouraging.

The worrisome elements locally are:

Chromium-6: This is the very same cancer-causing metal that Erin Brokovich sued PG&E over in the 1990s, alleging that the utility’s natural gas pipeline poisoned the town of Hinkley’s water supply. (PG&E settled for a landmark $333 million.)

The EPA appears wishy-washy about the effects of Chromium in drinking water, although it does cause lung cancer when inhaled. The amount in San Francisco’s water is just a little more than 1/9th the national average and less than 1/18th the average in California.

Radium 228: A radioactive mineral that’s apparently fairly common in groundwater in trace amounts. In 2011, SF water monitoring detected 1.39 picocuries per liter of Radium 228.

Which is actually not all that much—the EPA puts a cap on five per liter as maximum exposure. Still, as the Illnois Department of Public Health points out, “it is assumed that any radiation exposure carries some degree of risk.” It’s radioactive, after all.

Trihalomethanes: These are byproducts of chlorine treatment. Twenty years ago the EPA found that the effects of trihalomethanes were “difficult to predict” but that they led to liver and kidney cancer in lab mice.

The level in San Francisco’s water is more than twice the national average and nearly three times the state average, although still below the legal limit (which EWG considers inadequately lax).

Anita Ritenour