Yellowstone River fish contamination source still unknown

The advisory was issued last fall for the Yellowstone River between Reed Point and Laurel after an estimated 420,000 pounds of asphalt was released into the river when train cars crashed off a bridge.

The fish consumption advisory was made out of an “abundance of caution to ensure public health is protected” after various species of fish that were captured and tested had high enough levels of polycyclic aromatic hydrocarbons (PAHs) to warrant concern, Moira Davin, public relations specialist for the Montana Department of Environmental Quality, wrote in an email.

Davin’s email was in response to a series of questions the Billings Gazette sent to DEQ. To formulate answers, the agency shared the query with officials in the Montana Department of Public Health and Human Services and the Department of Fish, Wildlife & Parks, all of which have representatives on the Fish Consumption Advisory Board.

“The agencies are developing a plan for additional sampling in the spring to help delineate the extent of PAHs for human consumption concerns and confirm whether continuing the advisory is warranted,” Davin wrote.

Polycyclic aromatic hydrocarbons, a group of more than 100 different chemicals, are everywhere. They are generated by combustion and oil, and therefore can be found in the steak you char on the barbecue grill, in cigarette smoke, wastewater and industrial effluents. They are also released by oil production and automobiles — essentially anything where carbon is burned. PAHs can also naturally occur in the environment, like in oil-producing shales or coal deposits.

Testing for PAHs has occurred around the world, with scientists finding contamination in water, fish and sediments. Microplastics are also believed to help transport PAHs into ecosystems. Invertebrates seem to build up higher concentrations of PAHs than fish, due to their slower metabolism. The chemicals’ presence in ecosystems also seems to be increasing over time.

According to the Centers for Disease Control and Prevention, “Human health effects from indirect exposure to low levels of PAHs are unknown.” Yet PAHs are known to cause cancer and at higher levels of exposure can lead to birth defects in lab tests on mice.

“Health-based levels, determined using EPA risk assessment guidance and conservative assumptions, vary depending on the PAH and degree of toxicity,” Davin wrote. “Concentrations in fish tissue are compared to these health-based levels to identify whether there are any human health concerns.”

In general, Davin noted, children 6 years old and younger are more sensitive to chemical exposure because their bodies are still developing.

Mike Ruggles, the Region 5 supervisor for Fish, Wildlife & Parks in Billings, said a second round of fish sampling in the Yellowstone River did little to answer the agency’s questions about the source of PAHs identified in fish tissue.

“Trying to decide what it came from is not as easy as it sounds,” he said.

Water and sediment samples showed low or no levels of the chemicals, unlike the 2011 oil spill at Laurel when PAHs were detected in the water and fish downstream of a ruptured oil pipeline.

This time, testing of fish found contamination in different species of different sizes. With some other contaminants, like mercury, chemicals will build up, or bioaccumulate, in larger, predatory fish like brown trout. That’s not what FWP is seeing with the PAHs in the Yellowstone River. Fish have some accumulation of PAHs, but its not magnifying.

The chemicals were also found in fish above and below the asphalt spill, further confounding where the contamination may be coming from.

Ruggles said he’s not sure if that connection will ever be made.

“Our endpoint may be, ‘Yep, it’s there,’” and to provide people with that information, he said. “If it was glaring, we would have come out and said so.”

In Montana, testing for PAHs is not routine “but may be sampled if potential human caused sources are present,” Davin wrote. “Montana DEQ studied hydrocarbons and other pollutants in 18 streams and one lake in areas of active oil and gas development (extraction) across Montana from 2012-2016. Of the data that passed quality control review during this study, there were no results above water quality standards.”

Montana has water quality standards for many PAHs.

“Because there are many types of PAHs and a long list of laboratory analysis can get expensive, screening analysis for extractable or volatile petroleum hydrocarbons (EPH, VPH) or other measures is often needed,” Davin said. “If screening results are elevated, individual PAH parameters may be prioritized for analysis.”

Stay tuned. FWP and DEQ are promising more information later this spring as fish analysis continues.