More than two-thirds of Americans’ drinking water supply has more chromium than the level that California scientists say is safe, according to a new report Photograph: Jessica Lewis/Getty Images

In the 2000 biographical film about a legal clerk who brings a major utility company to its knees for poisoning residents of Hinkley, California, Erin Brockovich ended on a Hollywood high note with a $333m settlement from PG&E. But chromium-6 contamination of America’s drinking water is an ongoing battle the US Environmental Protection Agency (EPA) is losing.

Nearly 200 million Americans across all 50 states are exposed to unsafe levels of chromium-6 or hexavalent chromium, a heavy metal known to cause cancer in animals and humans, according to a new report released Tuesday by the nonprofit research and advocacy organization Environmental Working Group (EWG).

Today, Brockovich says Hinkley wasn’t an isolated event.

“The water system in this country is overwhelmed and we aren’t putting enough resources towards this essential resource,” Brockovich wrote in an email to the Guardian. “We simply can’t continue to survive with toxic drinking water.”

We simply can’t continue to survive with toxic drinking water. Erin Brockovich

In their analysis of the EPA’s own data collected for the first nationwide test of chromium-6 contamination in US drinking water, the report’s co-authors Dr David Andrews and Bill Walker, senior scientist and managing editor of EWG, found that 12,000 Americans are at risk of getting cancer.

Drinking water in Phoenix, Arizona, has the highest concentration of chromium-6 contamination. Of the 80 water samples taken across the city – water that serves 1.5 million people – 79 showed average concentrations of 7.853 ppb. California scientists have recommended a public health goal of 0.02 ppb, but industry pressure led to the adoption in 2014 of a legal safe limit of 10 ppb.

“More than two-thirds of Americans’ drinking water supply has more chromium than the level that California scientists say is safe – a number that’s been confirmed by scientists in both New Jersey and North Carolina,” according to Walker.

“Despite this widespread contamination, the US currently has no national drinking water standard for chromium-6.”

Dr Andrews said: “Part of the reason behind writing this report is really highlighting how our regulatory system is broken – in its ability to incorporate new science, and its ability to publish and update drinking water standards.”

Hexavalent chromium is used in a variety of processes: leather tanning, chrome-plating and small cottage industries that use dyes and pigments. But few unleash as much of it into the environment as the electric power industry.

“In 2009, the electric power industry reported 10.6m pounds of chromium and chromium compounds were released to the environment,” according to a 2011 Earthjustice report. “These 10.6m pounds represent 24% of the total chromium and chromium compounds released by all industries in 2009.”

In 2008, the National Toxicology Program, part of the National Institutes of Health, released a report detailing how cancerous tumors developed in mice and rats that drank heavy doses of chromium-6.

According to EWG, based in part on this study, scientists at the California Office of Health Hazard Assessment concluded in 2010 that ingestion of tiny amounts of chromium-6 can cause cancer in people.

The Agency for Toxic Substances and Disease Registry, an advisory, non-regulatory agency formed to oversee hyper-toxic Superfund sites, reports long term oral exposure to unsafe levels of chromium-6 compounds are associated with gastrointestinal system cancers.

“The California scientists set a so-called public health goal of 0.02 parts per billion in tap water, the level that would pose negligible risk over a lifetime of consumption,” according to the EWG report.

“But in 2014, after aggressive lobbying by industry and water utilities, the state regulators adopted a legal limit 500 times the public health goal.”

EWG says the California Department of Public Health relied on a flawed analysis that “exaggerated the cost of treatment and undervalued the benefits of stricter regulation”.

The report also details how New Jersey and North Carolina scientists recommended a maximum chromium-6 concentration of 0.06 parts per billion following the 2008 report, meeting similar resistance that has impeded passage of drinking water standards.

In their first major chromium-6 report in 2010, EWG found chromium-6 contamination levels 600 times the public health goal in Norman, Oklahoma – the worst found in 31 of 35 US cities tested. Those tests, and a petition from environmental activists, triggered the EPA to add chromium-6 to the list of chemicals for which local utilities must test under the Unregulated Contaminant Monitoring Rule, according to EWG.

This rule requires the EPA to establish a new list every five years of 30 previously unregulated contaminants to be monitored by public water systems.

In the 20 years since the 1996 Safe Drinking Water Act amendments passed to monitor previously unregulated contaminants, the EPA ordered 81 contaminants to be monitored. To date, only perchlorate, a rocket fuel ingredient, has been recommended for regulation. Though two years behind schedule, implementation has yet to occur.

Asked what steps are necessary to fix the country’s broken drinking water program, Dr Andrews said: “One of the first steps has to occur here: EPA has to be able to complete its health risk assessment about the toxicity of chromium-6.”

EWG reports that in 2010, scientists in the EPA’s Integrated Risk and Information System (Iris) “completed but did not officially release a draft risk assessment that classified oral exposure to chromium-6 as ‘likely to be carcinogenic to humans’”.

But the American Chemistry Council, a powerful lobby for the chemical industry, requested that the EPA withhold the release until after studies funded by the Council and the Electric Power Research Institute could trace the biological mechanisms through which chromium-6 triggers cancer.

Dr Vincent Cogliano, director of Iris, initially resisted industry pressure. In an April, 2011 letter to Ann Mason at the American Chemistry Council, he congratulated their willingness to invest $4m in targeted research on hexavalent chromium, but he denied their request for a delay.

“Without prejudging the outcome of mechanistic studies being written up for publication,” he wrote, “it is entirely possible that granting your request could entail a delay of unknown duration with no public discussion or review of the strong new studies that are now available.”

But then an external review panel, found by the Center for Public Integrity to include three members who consulted for PG&E in the Brockovich case, convinced the EPA to grant the American Chemistry Council time to fund their own studies.

In 2012, the EPA quietly announced it had decided to delay the draft risk assessment following the review panel’s recommendation.

Cogliano wrote in an August 24 email to EWG: “We expect to release a draft health assessment document in 2017, though I wouldn’t use the word ‘early’.”

In an email statement to the Guardian, EPA said: “Ensuring safe drinking water for all Americans is a top priority for EPA.”

The EPA says that less than 2% of the latest national monitoring systems reported hexavalent chromium at levels exceeding California’s enforceable maximum contaminant level of 10ppb.

The EWG report, however, found that “even by that far-too-lax benchmark ... more than seven million Americans are served tap water from supplies that had at least one detection of chromium-6 higher than the only legal limit”.

Erin Brockovich urges Americans to disregard the EPA’s reassurances and to take a more active role in their communities to fix the country’s broken water supply.

“Superman’s not coming,” Brockovich said. “Be informed, ask questions, band together with your community and fight at the local level. And make sure you take your local elections as seriously as the national ones. The issues that most impact the average person are made at the local level.”