By Susan Redden
BAXTER SPRINGS, Kan. —
When it comes to eating fish caught from Grand Lake in Oklahoma, letting the big one get away may not be a bad idea.
That’s according to a study of mercury levels in fish that was released Thursday during a meeting of a Spring River watershed group in Baxter Springs.
Study results, presented by Robert Lynch, with the Oklahoma University Health Sciences Center, suggested that fish from the Grand Lake watershed generally do not have high levels of mercury. But the study did find levels of mercury above federal guidelines for children and women of childbearing age in 3 percent of the roughly 1,000 fish tested. Those species included flathead catfish, largemouth bass, blue catfish and drum.
“Mercury accumulates over time, so the bigger fish had more mercury,” Lynch said.
The study started three years ago, and included analysis of fish taken from the lake and tests of hair samples from volunteers around the lake who eat fish.
Lynch reviewed study findings at a meeting of a group called Spring River Watershed Restoration and Protection Strategy of Southeast Kansas that attracted nearly 20 participants, primarily from Southeast Kansas and Northeast Oklahoma.
About 1,500 fish will have been analyzed when final elements of the study are completed in July, Lynch said. No significant differences in mercury levels were found in fish taken from different areas of the lake.
The study also involved about 150 participants recruited by the LEAD Agency in Miami, Okla. Those people completed questionnaires and kept diaries to track their fish consumption — 64 percent ate fish at least once a week, with 65 percent coming from local sources. They also permitted hair samples to be taken for testing.
Among the participants, 95 percent had mercury levels below Environmental Protection Agency guidelines. Five percent had levels above EPA guidelines of 1 part per million; 2 percent had levels above 2 parts per million. The findings are consistent with those from other parts of the U.S., Lynch said.
“If you want to reduce your mercury levels, eat smaller fish,” he said. “Or, when you catch a big one, you could just take a picture and let it loose.”
Two participants put that advice into practice and saw their mercury levels drop, said Rebecca Jim, executive director of the LEAD Agency.
“Their levels were elevated, and we asked them to eat smaller fish,” she said. “They did, and their levels came down. We also suggested that people who serve fish at fish fries keep flatheads and large fish separate, and not serve them to children.”
EPA guidelines are for children and women of childbearing age, since unborn and young children are the most sensitive to mercury, which can hurt the brain, spinal cord, kidneys and liver.
Flathead catfish longer than 30 inches registered the highest mercury levels, averaging 276 parts per million, while smaller flatheads averaged 188 parts per million. Drum averaged 118 parts per million, and largemouth bass averaged 84 parts per million. Based on the EPA guideline that mercury levels should not exceed 300 parts per million for sensitive populations, the study recommended that children or women of childbearing age eat large flathead catfish no more than twice a month, smaller catfish and drum no more than once a week, and largemouth bass no more than twice a week.
Some at the meeting asked about the impact of mercury levels on top of other heavy metal levels in the lake, a result of the region’s mining history.
“It’s really a double-whammy, because they’re both neurotoxins,” Jim said.
The study was sought to determine the impact of airborne mercury from coal-fired power plants falling into the lake and its watershed. Earl Hatley, with the LEAD Agency, said high bacterial levels in the water exacerbate the problem. When mercury interacts with nutrients and bacteria in the water, it converts to methyl mercury, which enters the food chain via algae eaten by small fish.
The Harvard School of Public Health also was involved in the study, which was funded by the National Institute of Environmental Health Sciences.
TWO PUBLIC PRESENTATIONS on the test results are set for June 12. One will start at 11:45 a.m. at the Wyandotte Tribal Nutrition Center in Wyandotte, Okla., and another will start at 3 p.m. at the GRDA Eco Center in Langley, Okla.
TWO PRESENTATIONS also are set for June 13. One will be at 9 a.m. at Grove (Okla.) City Hall, and another will be at 2 p.m. at the Peoria Tribal Office in Miami, Okla.