By Kim Krisberg
2,4-Dichlorophenoxyacetic acid—otherwise known as 2,4-D—is the active ingredient in a variety of weed killers and one of the most common, widely used herbicides in the world. Studies in lab animals have found that high doses of 2,4-D are associated with negative health effects. Research on human exposure is more of a mixed bag.
According to the Agency for Toxic Substances and Disease Registry, it doesn’t appear that contact with small amounts of 2,4-D is harmful to people. Some studies on workers with relatively high exposure rates, such as professional herbicide applicators, have identified a possible link to cancers of the lymph system. Other studies found no strong evidence linking 2,4-D to cancers. The US Environmental Protection Agency (EPA) says there’s not enough evidence to either refute or support 2,4-D as a human carcinogen, while the International Agency for Research on Cancer has deemed 2,4-D as “possibly carcinogenic” based on “inadequate evidence.” In other words, we need more research.
One place where that research is happening is inside the public health labs of Arizona, Colorado, New Mexico and Utah, where a collaborative known as the Four Corners States Biomonitoring Consortium (4CSBC) hopes to gather new insights into environmental exposures that could impact people’s health. With funding from the Centers for Disease Control and Prevention’s (CDC) National Biomonitoring Program, 4CSBC began its work in 2014, building on the previous efforts of the Rocky Mountain Biomonitoring Consortium, of which all four states had been a member. The collaborative’s mission is to generate the data on environmental conditions and contaminants that can inform protective public health actions. It’s also an exercise in optimizing public health lab capacity toward regional environmental health risks and shared concerns regarding air and water quality.
“I think this is one of the most relevant grant-funded projects we do,” said Eric Petty, chemistry program manager within the Colorado Department of Public Health and Environment’s Laboratory Services Division and his state’s lead for 4CSBC. “It produces so much meaningful data and it’s pretty unlimited regarding the number of studies we can design. There’s so much out there that hasn’t been looked at.”
The consortium is focused on three main studies: heavy metal exposure from private well drinking water; pesticide, herbicide and phthalates exposure; and the San Luis Valley (Colorado) Children’s Study, which assesses hazardous chemical exposure among children ages 3 to 13. In each state, public health labs partner with environmental health workers and epidemiologists to find residents who want to take part, collect water and urine samples for testing, and eventually reconnect with residents to discuss results and any health-protective recommendations. The 4CSBC labs spread out the testing responsibilities according to capacity, so as to not burden any one state—for example, every state does its own metals testing; New Mexico and Utah test for metabolites of pyrethroids, a group of chemicals found in certain pesticides; Arizona handles all the testing for phthalate metabolites; and Colorado tests for 2,4-Dichlorophenol and 2,5-Dichlorophenol, the latter of which is found in household products. However, testing duties can change depending on circumstances and capacity. Testing results are interpreted, in part, by using baseline data from CDC’s National Health and Nutrition Examination Survey.
“We have similar geological settings, we all have a legacy of mining in heavy metals, we’re agricultural states, our populations can be sparse, we have common problems regarding arsenic and pesticides,” said Sanwat Chaudhuri, PhD, 4CSBC’s principal investigator and scientific advisor for chemical and environmental services at the Utah Public Health Laboratory. “It just makes more sense that we work together to try to solve our problems.”
To date, Chaudhuri said the consortium has tested more than 900 urine samples and about 500 water samples. Labs work closely with their state colleagues in epidemiology and environmental health—or in Utah and New Mexico, with CDC-funded participants in the National Environmental Public Health Tracking Program—in determining where in the states to focus their biomonitoring efforts and what kind of data gaps the consortium can help fill. Chaudhuri added that the consortium leverages its unique work to help particularly vulnerable communities reduce their risk of harmful exposure. 4CSBC’s focus on private well drinking water is a good example of that. Because such water often goes unregulated, 4CSBC can help alert residents to potential contaminants, while collecting the data that allow health officials to measure changes in environmental risk.
If lab technicians detect a particularly high concentration of a contaminant—like naturally occurring uranium that can seep into private well water—residents are notified and offered guidance about how to fix or mitigate the problem. In some instances, Chaudhuri said, local health officials are engaged and notified. 4CSBC teams regularly share data with each other, evaluate their progress and plan for the future during monthly phone calls and at two face-to-face meetings each year.
“We couldn’t have stretched [the CDC biomonitoring funds] across four states if wasn’t for our collaborations,” Chaudhuri said. “We get so much in-kind support from our environmental health and tracking partners—who else can better appreciate the need for biomonitoring data?”
On the ground, the biomonitoring collaborative not only hopes to offer new insights, but to boost capacity for more traditional public health responsibilities, such as safeguarding drinking water quality. For example, in New Mexico, about 20 percent of residents depend on drinking water sources—like private wells—that aren’t regulated by either federal or state oversight. At the same time, said Heidi Krapfl, MS, chief of the New Mexico Department of Health’s Environmental Health Epidemiology Bureau, the state’s geology means private well water drinkers may be at heightened risk of harmful arsenic and uranium exposures. Urine uranium concentrations above a certain threshold are already a notifiable condition in New Mexico.
To better understand that risk, New Mexico’s 4CSBC team partners closely with the state’s environmental health tracking program to collect and analyze water samples. To date, according to Barbara Toth, PhD, MS, epidemiologist supervisor at the New Mexico Department of Health, the biomonitoring effort in New Mexico has collected about 150 household water samples for heavy metal testing and just more than 200 urine samples for heavy metal and phthalate testing. If researchers find troubling levels in any of the specimens, they or their partners follow up with residents. So far, Toth said they haven’t detected any levels that would be deemed harmful.
“Tracking is about exposure and health outcomes,” Toth said, “and biomonitoring is the method by which we understand that exposure.”
Krapfl added: “Those three legs of the stool—tracking, biomonitoring and private well water testing—provide a strong foundation for taking supporting public health actions in the state. You really need all three.”
One of the 4CSBC’s main projects—the San Luis Valley Children’s Study—is focused on a specific community of children in Colorado. According to Petty, the 4CSBC lead in Colorado, the area has a particularly shallow water table and has a history of agricultural use. To get a clearer picture of the risk, 4SCBC is partnering with a researcher from the University of Colorado who’s already begun studying children’s exposure in the San Luis Valley. The researcher conducts the field work and collects samples, while the Colorado public health lab does the testing—to date, Petty said the lab has tested more than 200 urine samples and 100 water samples.
“The consortium is a great way to consolidate resources,” Petty said. “Ultimately, there’s so much information these studies can provide in the future.”
Well water quality is a priority issue in Arizona too, according to Jason Mihalic, chief of the Chemistry Office at the Arizona Department of Health Services and the state’s principal 4CSBC investigator. Any Arizona resident who uses well water can take part in the biomonitoring effort. But to sweeten the deal—and attract as many participants as possible—the Arizona lab offers a free water analysis for 19 metals using an EPA-approved method. The Arizona 4CSBC effort is also partnering with existing well water programs at the University of Arizona to spread word about the biomonitoring effort—for example, news of the biomonitoring testing even made it onto a local master gardener listserv®.
For many of the compounds included in 4CSBC testing—such as pyrethroid insecticides used to reduce risk of tick-borne diseases like Rocky Mountain spotted fever or the plastic chemicals known as phthalates that are now ubiquitous in our environment—biomonitoring will produce the first regional baseline data available, Mihalic noted.
And more precise data means public health can be even more effective in protecting communities against potentially harmful exposures.
“I love biomonitoring,” Mihalic said. “It’s a wonderful way for the public health lab and epidemiology to work together in tackling real-world problems.”