human health data typically comes from observational studies , in which researchers recruit volunteers and follow their health outcomes over time . But these are expensive , difficult to conduct and come with their own uncertainties because they are not perfectly controlled experiments .
As an alternative , researchers often turn to controlled studies conducted on rodents or other animals to project what the effect might be in humans . In the case of TCP , researchers identified a link between the chemical and cancer in mice and rats in the 1990s , but to date no large-scale studies have investigated its effect in humans .
“ A lot of times people who are not trained formally as scientists or researchers hear those uncertainties up front and say , ‘ Oh well , this isn ’ t good enough , we need to wait ,’” Sydney Evans , senior science analyst at EWG , said of findings on the health effects of TCP . “ One of the issues with the way that contaminants and chemicals are regulated , especially drinking water contaminants , is that it takes entirely too long . And in the meantime , so many people are being exposed , just because we can ’ t be 100 % certain .”
There is also limited information on the contaminants ’ prevalence . The EPA has collected national drinking water data on less than half of its list of contaminants , and it can only monitor for 30 of them every five years . Some advocates for increased drinking water regulation say this limit , which was part of the 1996 amendments , makes it hard for the EPA to stay on top of emerging threats .
Not every small water system is required to participate in each testing round , and even among those that do , the data collected may not be useful to regulators . For example , during the monitoring period for TCP , the lab tests the EPA directed utilities to use couldn ’ t detect the chemical at low levels , similar to the testing sensitivity issue the agency faced in monitoring for PFAS . In 2022 , the agency demurred on taking action on TCP , in part because it had no data on how widespread the chemical was at these lower levels . The agency declined to comment on why it didn ’ t use more sensitive tests that were available .
As with PFAS , follow-up testing by states and local utilities have found more people exposed to TCP than was initially documented , according to the Environmental Working Group data . ProPublica ’ s analysis of the data shows that since the EPA stopped its monitoring , TCP has been found in water systems serving an additional six million people , though many states recorded few or no tests during that time period . While many of these detections were in California , which requires testing , Texas documented TCP contamination in water from Smithwick Mills and dozens of other utilities .
Alan Roberson , executive director at the Association of State Drinking Water Administrators , said the EPA should make a greater effort to provide final determinations on these contaminants of concern , including decisions to take them off its candidate list . There are three chemicals , for example , that have been on the list since 1996 without any final determination , according to the ProPublica review .
“ They need a process for having a more manageable list and then doing the research to move it forward ,” Roberson said . “ Let ’ s make sure we have the stuff we need to make decisions , either up or down , on a regular basis .”
Leadership Void
In the absence of direction from the federal government , some states have acted on their own . In 2018 , New Jersey joined Hawaii and California in regulating TCP . The limits vary widely , however . Hawaii ’ s TCP standard , which was enacted in the 1980s and revised 20 years ago , allows up to 600 parts per trillion in water .
Darrin Polhemus , deputy director of the division of drinking water with California ’ s State Water Resources Control Board , said the state ’ s laws allow it to be more aggressive in targeting health risks in drinking water . Unlike the EPA , which has to determine that the benefit of a drinking water standard outweighs the cost , California regulators are directed by state law to set a maximum level as low as possible , so long as most water systems can afford to implement the treatment .
“ That is why I like our system better than the federal government ’ s ,” he said . “ It can be incredibly hard to calculate the benefit of the health outcome .”
If Smithwick Mills had been in California , the water utility would have had to drastically reduce the levels of TCP in its water to comply with the state ’ s standard , either by installing treatment technology to remove the chemical or changing its water supply . At minimum , residents would have been notified of the contamination levels . But since the system is in Texas , the chemical ’ s presence went largely unnoticed until now . State officials said they have no plans to regulate TCP .
Paul , the Smithwick resident , said what ’ s most unsettling is that no one seems to know how TCP entered the community ’ s water supply . For years , Paul drank only bottled water because she didn ’ t like the taste of what came from the tap . But after learning about her town ’ s TCP test results , she stopped giving her dog water from the tap , and now uses bottled water even to make bird feed and water her plants . She uses tap water only for cleaning and bathing . “ I don ’ t trust it for anything else ,” she said .
This article was originally published by ProPublica and is reprinted here according to their guidelines .
40 x The Trial Lawyer