Several popular game fish were collected in Lake Norman, Mountain Island Lake, and Lake Wylie and analyzed for polychlorinated biphenyls (PCBs), mercury, arsenic, and selenium. The targeted fish species included blue catfish, channel catfish, flathead catfish, largemouth bass, spotted bass, white perch, and black crappie.
The study took place from July through December 2011. PCBs were detected in all samples that were collected, which is consistent with other fish tissue studies throughout the United States. A portion of the blue catfish samples from Mountain Island Lake and all of the largemouth bass samples from Lake Wylie had PCB levels that exceeded the fish consumption advisory action level set by the NC Department of Health and Human Services (NCDHHS). Mercury was also detected in all of the samples collected but was not above the NC fish consumption advisory action level. This is also consistent with other studies throughout the United States. Selenium was detected in some samples, but not at levels above the action level. Arsenic was not detected in any sample from any of the three lakes, and no exceedances of NC action levels were observed in any samples from Lake Norman.
PCBs were once widely used as coolants and lubricants in transformers, capacitors and other electrical equipment before being banned by the federal government in 1977 due to evidence that they build up in the environment and cause cancer and other negative health effects. Mercury, arsenic and selenium are metals that are found naturally in the environment at low levels but are released into the air through the burning of fossil fuels and other manufacturing processes. Like PCBs, these metals build up in the environment and can cause cancer and other negative health effects. PCBs and metals are absorbed into fish by ingestion of the food they eat, and exposure to water and sediments that contain the chemicals. The chemicals build up or bioaccumulate in the fish’s tissue over time. Due to bioaccumulation, the larger predator fish typically have the highest level of contaminants.
As a result of this study, the NCDHHS issued a fish consumption advisory on December 23, 2011 for largemouth bass due to PCBs in Lake Wylie. Additional testing of blue catfish will occur in Mountain Island Lake this summer. An advisory was previously issued for channel catfish in Mountain Island Lake on January 6, 2011 due to PCB contamination and a state-wide advisory for largemouth bass has been in effect since 2008 due to widespread mercury contamination.
For more information regarding fish consumption advisories in Mecklenburg County, visit the following website: http://charmeck.org/stormwater/creekslakesponds/Pages/FishConsumptionAdvisories.aspx
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Media Contact: David Caldwell, Storm Water Services Office: 704-336-5452 David.Caldwell@Mecklenburgcountync.gov