Researchers to tackle short list of endocrine disrupters
Pharmaceuticals and endocrine-disrupting compounds are ubiquitous in waters, and researchers are trying to put these findings in perspective.
It’s no surprise that trace concentrations of pharmaceuticals and endocrine-disrupting compounds are showing up everywhere researchers look—in rivers, lakes, groundwater, and even treated drinking water. But what is the relevance of these trace levels for human health, particularly in areas like the arid western U.S., where wastewater—a primary source of these contaminants—is increasingly being recycled and used to augment drinking-water supplies?
“We can’t remove everything to zero, because the analytical methods are too good,” says Shane Snyder, an environmental toxicologist at the Southern Nevada Water Authority. “So we have to put a line in the sand, so to speak, and say, ‘This is a safe level, and this is an unsafe level.’ There’s going to be some level of contamination that I think we’re all just going to have to accept.”
To give state regulators some answers as soon as possible, as well as help them establish meaningful treatment and detection goals, Snyder and his colleagues have narrowed the universe of emerging contaminants to a list of roughly 30 compounds, a draft of which was presented at the WateReuse Association’s annual meeting in September. These include chemicals that the researchers expect have the highest toxicity levels or that are most likely to occur in drinking water. Snyder said that he and his colleagues plan to conduct occurrence monitoring for these chemicals at as many as 20 drinking-water utilities nationwide and develop provisional reference doses for those with sufficient toxicological data; this would follow the U.S. EPA’s standard human health risk assessment process. They also plan to screen for these chemicals in some foods and bottled beverages, particularly milks and fruit juices that contain natural phytoestrogens, such as soy.
Previously, Snyder and other researchers have argued that the human health threat of these trace contaminants in drinking water has been overblown. Now, Snyder hopes to back up this assertion with real data.
Snyder and his colleagues predict that the concentrations and bioactivity from contaminants could be higher in many of the foods and bottled beverages than in wastewater effluents. “I fully understand that we’ll open up a can of worms and probably create more questions than answers,” Snyder notes. However, “I truly believe we need to get started, because there are so many monitoring programs and so many people just going after treatment [of microcontaminants in wastewater].” The fallacy, says Snyder, is that such efforts may not change overall exposure levels, because these contaminants are probably in things we consume other than drinking water.
EPA is also working toward developing regulations for such contaminants in drinking water through its Endocrine Disruptor Screening Program. However, with an estimated 86,000 chemicals in line to be tested, the agency “is very far behind, because the assays have to be validated, reproducible, and transferable,” Snyder told conference attendees.
In devising their list, Snyder and his colleagues began with the top 200 most prescribed pharmaceuticals and selected those that carried potential health risk at low concentrations, were most likely to be present in drinking water in an active form, and represented different drug classes. Those chosen included substances that have effects on each of the major classes of endocrine function—estrogenic, androgenic, and thyroidal—and meet the criteria of “most likely to occur”, “most powerful at each of the endpoints”, and “availability of toxicity data”. Their efforts will focus on parent drug compounds only, not metabolites. To screen compounds, the researchers will use an estrogen-responsive cellular bioassay.
“I think we’ve done a fair job of balancing the chemicals we think are representative with [Snyder’s] ability to detect them,” says Richard Pleus, director of Intertox, a health-science consulting and research firm, and head of the toxicology portion of the study.
“It’s quite an ambitious project,” much larger in scale and more systematic than other studies to date, says Charles Staples, president of Assessment Technologies, Inc., and a member of the project’s advisory committee. “The program’s overall strength is [in] putting these low detection levels in perspective.”
David Sedlak, an environmental chemist at the University of California, Berkeley, who studies chemical contaminants in water reuse systems, agrees. “I think [this] study will start an interesting series of discussions,” Sedlak says, noting that drinking-water standards don’t usually take into account exposure from other sources.
More of this balance “is what we’re seeking,” adds Pankaj Parekh, director of water-quality compliance for the Los Angeles Department of Water and Power and a member of the project’s advisory committee. “If we truly want to address public-health issues, we have to make sure we look at these compounds in all of their environmental elements.”
