A mineral fish study shows people are not exposed to high levels of mercury in their diet after eating fish from Grand Lake, said a Harvard School of Public Health official on Thursday.

“We are not seeing high levels of mercury and methyl mercury in the fish caught in Grand Lake,” said James Shine.

Laurel Schaider, Zhao Dong and Shine, with the Harvard School of Public Health presented their findings on mercury at the 14th National Tar Creek Conference. The two-day conference concluded on Thursday.

Fetuses and babies are the most sensitive to mercury in connection with brain development and impaired motor skills and learning problems, Schaider said. “Most fish tested in Grand Lake Watershed are below the guideline values for mercury,” Schaider said. “The flathead catfish, largemouth bass, drum and blue catfish were the exception.”

The highest mercury level came from three largemouth bass samples from a pond, Schaider said.

“Catfish, crappie and bass are the most frequently eaten local fish,” Schaider said. “The largest contributors of dietary mercury are catfish and bass,” Schaider said.

Tuna is the largest non-local contributor, she said.

Mercury is measured with hair samples, which was tested five times over a 12-month period, she said. The general hair mercury levels in the study were low. Of the participants, 95 percent were below Environmental Protection Agency guidelines, Schaider said.

Hair mercury levels in the study population were similar compared to the general population, both regionally and nationally, she said. In the study, the mercury levels were higher in men compared to women and in older participants and in the fall season, Schaider said.

In an odd twist, fish consumption is generally the lowest in the fall and scientists could not explain for the higher levels of hair mercury during that season, she said.  

The study showed that 64 percent of the participants fished two to three times a month or once a week.

“The mercury levels in most fish species were not found to vary over locations,” Schaider said.  

Schaider said coal-fire power plants are a major source of mercury into the atmosphere. There are six coal-fired power plants within a 60-mile radius of Grand Lake.

The study, which is going into its fourth year, followed over 100 participants from 23 Grand Lake communities. A total of 1,403 fish samples from 20 types of fish were collected from Honey Creek, Elk River, Horse Creek, Neosho River, Spring River and Buffalo Creek.