If your kitchen tap delivers water from a public system, chances are good that it meets federal standards. But that doesn’t necessarily mean it’s fit to drink.

This is the central message of a data-mining analysis published this morning by the Environmental Working Group, which aggregated and analyzed self-reported contamination statistics from nearly 50,000 systems across the U.S.

Prompted by the crisis in Flint, Michigan, the two-year project includes an interactive feature that could bring an entirely new dimension to American awareness of drinking water quality: Each system’s contaminant levels are accessible by ZIP code with a few mouse clicks.

You can see, for example, that Minneapolis water met federal health standards even though it contained 14 contaminants of concern — six of them carcinogens, and at levels exceeding an official guideline that defines the threshold for a slight increase in cancer risk.

Five of the six are chemicals considered byproducts of disinfectant treatment, typically with chlorine; the sixth, hexavalent chromium, gets into the water from both natural and industrial sources. (It’s the substance at the heart of the film “Erin Brockovich.”)

Levels of bromodichloromethane, chloroform and chromium were above statewide averages, though below national averages, and also exceeded a guideline set by the California Office of Environmental Health Hazard Assessment as point where cancer risk begins to rise.

Levels of dichloroacetic acid and trichloroacetic acid also were above the Minnesota average, but not the nation’s, and exceeded an EPA threshold for higher cancer risk. Trihalomethanes exceeded both the state and national averages, as well as the EPA guideline.

As for lead, the water systems reported that 90 percent of samples taken between January 2013 and December 2015 tested under 2 parts per billion. That’s well below the EPA’s legal maximum of 15 ppb and also looks good compared to “recent EPA modeling [which] suggests that lead concentrations in the 3.8 to 15 ppb range put a formula-fed baby at risk of elevated blood lead levels.”  

The other eight contaminants, which did not exceed any health guideline applied by EWG, included chromium (in all form), monochloroacetic and haloacetic acids, molybdenum, nitrates, strontium, vanadium and fluoride (which, of course, many consider a beneficial additive).

Safe or unsafe?

Based on these results, is Minneapolis water safe to drink?

Well, I’ll keep drinking it — but I’m more relaxed than many about low-level exposure to toxins. And when I say low-level, we’re talking really low here for some contaminants — the California and EPA thresholds cited above are concentrations that theoretically carry a lifetime risk of one new cancer in a million people.

Still, if I were a younger person, especially a woman of childbearing age — or her husband, or the father of her children — that tapwater profile might look very different to me. And this, in a way, illustrates EWG’s three main points:

• Every household has to make its own decision about trusting or not trusting the safety of the public water supply, and ought to be able to make it on the basis of data like these — which until now have not been so readily available from either EPA or state health departments.
• It’s simply not enough to rely on EPA standards to ensure safety, even if they were rigorously enforced — which, as the post-Flint fallout has demonstrated, they are not.
• In many cases, with lead the leading example, the current standard looks way too forgiving based on the prevailing scientific consensus; moreover, as EWG points out,

Because the Environmental Protection Agency has not added a new chemical to the list of regulated contaminants in 20 years, more than half of the contaminants detected in U.S. tap water had no regulatory limit at all, meaning they could legally be present at any concentration and that utilities don’t have to test for them or tell their customers about them.

Problems around the state

Not all Minnesota water systems were within legal limits, either. Some 30 communities are listed as exceeding EPA standards for one or more chemicals in test data provided to the state health department. Most of these were very small systems; Otsego and Pipestone led the list sizewise at 8,000 and 4,300, respectively.

Nationally, the analysis found some notably widespread patterns of contamination. Excerpts:

Between 2010 and 2015 almost 19,000 public water systems had at least one detection of lead above 3.8 parts per billion, the level at which a formula-fed baby is at risk for elevated blood lead levels.

In 2015, more than 1,800 water systems serving 7 million Americans in 48 states detected nitrates — chemicals from animal waste or agricultural fertilizers — at an average above the level the National Cancer Institute research shows increases the risk of cancer, which is a concentration just half of the government’s legal limit for nitrate in drinking water.

In Iowa, the Des Moines Water Works battles daily to keep nitrate levels from uncontrolled farm pollution just below the EPA legal limit of 10 parts per million, or ppm, in local drinking water. Based on the findings of the National Cancer Institute, EWG’s health guideline for nitrates is 5 ppm, but the average level found in 2015 by the Des Moines utility was more than 7 ppm.

Among the largest utilities, the East Los Angeles Water District detected the most contaminants of concern overall, with 14 different pollutants in its 2015 water tests above established health guidelines. The district serves 115,000 people in an area whose median household income in 2010, the most recent year for which data is available, was more than 20 percent below the national average.

In all, the EWG research found that public water systems are delivering — at levels that may be legal but are nonetheless considered risky by public health authorities — 93 contaminants that can cause cancer, 78 associated with brain and nervous system damage, 63 connected to developmental harm to children or fetuses, 45 linked to hormone disruption and 38 that may cause fertility problems.

And this calls for policy change, according to EWG’s president, Ken Cook:

It’s time to stop basing environmental regulations on political or economic compromises, and instead listen to what scientists say about the long-term effects of toxic chemicals and empower Americans to protect themselves from pollutants even as they demand the protective action they deserve from government.

In the meantime, EWG advises people who don’t want a dose of chromium or chloroform in their tap water to consider empowering themselves by buying filtration equipment; the report offers a comparative assessment of the options available.