February 23, 1999
by Edmund Tsang
|Concentration of Mercury detected in Mobile Bay Sediments. Source: 1991 Annual Report to Alabama Geological Survey Project, "Sediment Distribution and Geological Framework of Coastal Alabama," by Wayne C. Isphording, University of South Alabama.|
Kohn said mercury is found in fish tissues all along the Gulf Coast that resulted in no-consumption advisories from Louisiana to Tampa Bay in Florida. Dr. Kohl added that he can document potential local sources of mercury in each case, and he believes owning up to the local sources is the first step to take if a community is serious about addressing the issues of mercury in the environment.
In Alabama, when the concentration of methyl-mercury in fish tissue exceeds 1 part per million (ppm), a no-consumption advisory is issued for that fish species, which means "everyone should avoid eating the designated species of fish in the defined area." In the neighboring states along the Gulf Coast of Florida, Mississippi, and Louisiana, the trigger levels are 0.5, 0.75, and 0.5 ppm, respectively. On the federal level, the Food and Drug Administration (FDA) uses a 1 ppm trigger to prohibit interstate shipment of commercial fish, and the Environmental Protection Agency
(EPA) sets a trigger level for pregnant women and children under 7 years old at 0.3-0.6 ppm.
Last July, when the Alabama Department of Public Health announced that largemouth bass caught in Fowl River had been added to the list of species in the no-consumption advisory for Mobile County, bringing the total number to five of bodies of water that flow into the Mobile Bay estuarine system with the warming, two articles were published in the Mobile daily within a period of three weeks identifying out-of-state coal-fired power plants as the culprits.
The first article, which was written by the environmental editor of the daily newspaper and published a day after the Alabama Department of Environmental Management (ADEM) issued a press release about the results of its fish-tissue monitoring program, repeated almost verbatim the ADEM press release but added the medical incinerator of the University of South Alabama as another source for the mercury found in elevated levels in fish caught in the waters of Lower Alabama. (Because the smokestack of a medical incinerator is much shorter than that of a utility power plant, the reasoning goes, the mercury in the air emission does not get carried as far away as a taller smokestack, and would be deposited closer to the point of origin. By the same reasoning, the mercury in the air emission from the taller smokestacks of power plants in lower Alabama becomes some other states' problem.) The ADEM press release identifies atmospheric deposition from out-of-state power plants as the likely source of mercury found in the fish tissues of its screening program.
Another article, written by Rick Wallace, an marine specialist with the Sea Grant Extension program at the Auburn University Marine Center, was titled "Mercury is natural part of environment," and was published soon afterwards in the Suburban Section of the Mobile daily. Wallace wrote, "In the absence of any identifiable source, such as a discharge, most mercury is deposited from the atmosphere."
In a telephone interview last summer, Mr. Wallace said he had not consulted the Mobile County Toxic Release Inventory (TRI) data and was not aware of any mercury emitted by local sources into the waters of Lower Alabama and the Gulf Coast, when he wrote the article that was published in the daily.
When informed that TRI data show that, as recently as the late 1980's, hundreds of pound of mercury were released into the waters that flow into Mobile Bay, Wallace discounted the likelihood that they could be a cause for the no-consumption advisory that was announced in Spring, 1998 regarding king mackerel over 39 inches long caught in the Mobile Bay section of the Gulf Coast. Under the Community Right-To-Know provision of the Superfund legislation passed by the U.S. Congress that became effective beginning 1987, TRI refers to the self- reported data on hazardous chemicals released by industries via water, air, and land.
A search of the Environmental Protection Agency's (EPA) on-line TRIS database showed that in 1989, Akzo Chemical located in Axis, Alabama released 1,000 pounds of mercury in fugitive air, 251 pounds via water, and 250 pounds via land. (The stack air released 750 pounds of mercury.) In the subsequent two years, the amounts of mercury emitted via water were cut down to five (5) and six (6) pounds, respectively in 1990 and 1991, while the amount released via fugitive air and land remained basically unchanged. In 1990, another Mobile County facility, Occidental Chemical Corp., released 450 pounds of mercury in fugitive air and 11 pounds in water. In 1988, Occidental released 1,475 pounds of mercury in fugitive air, 255 pounds via water, and 250 pounds via land. [See Table 2.]
Dr. Barry Kohl, who consults for the Louisiana Department of Environmental Qualify, said he is not surprised by Wallace's reaction to data that suggest a possible local source for the mercury found in fish tissues, because that attitude is also prevalent among state officials in Louisiana. "It's just politics because they think that's something they can't do anything about," Dr. Kohl said in a telephone interview last month. "Perhaps he [Wallace] is not aware that larger king mackerels probably feed on the smaller fish from the tributaries that flow into Mobile Bay and the Gulf, and consequently concentrates the level of mercury up the food chain."
In a way, Dr. Kohl said, the passage of mercury into the natural environment reflected the rapid industrialization of America, especially after World War II, and up until the 1970s, when awareness coupled with environmental disasters resulted in guidelines in the disposal of hazardous wastes. "During that big resurgence of industrialization, there were no controls governing the use as well as air and water emissions of hazardous materials," Kohl said.
"Until the chemical were banned in 1965 and its use reduced to zero in 1973, many paper mills, including those all along the Gulf Coast, used a mercury-based slimicide to preserve wood pulp in the 1950s and 60s," Kohl said. He estimates that five to twelve percent of the mercury used in the pulping process was discharged in the effluent into waterways. Several of the chemical plants along the Gulf area used mercury as an electrode to produce chlorine, caustic soda, and potash. For fifty years, the oil and gas industries used pumps and gauges that contained mercury, and many were abandoned in the Gulf and became broken, discharging the mercury," Kohl said. "Even the Coast Guard had contributed to the mercury problem because they used to dump their batteries along coastal waters. So, the evidence suggest there are local sources to the mercury build-up in predatory fish in the Gulf Coast area."
Dr. Kohl cautioned that using only TRI data might not lead to the identification of all possible local sources of mercury. "TRI did not come on-line until the late 80s, by which time many industries were no longer discharging mercury directly into the environment. Many of the uses of mercury were banned in the 70s or being phased out, and these discharges in the 60s and 70s wouldn't show up in the TRI either," Kohl said. "And until this year, the utility industry was exempted from having to report TRI because of their lobbying power," Kohl said. "Now, how many power plants do we have in the Gulf Coast area?"
Kohl said the agriculture sector also contributes to the environmental problem of mercury contamination, and one example is mercury-based organic and inorganic fungicides are used to control turf-grass disease in golf courses, parks, cemeteries, and lawns. Mercury contamination can come from leaking landfills that have broken fluorescent lamps, which contain 50 to 100 ppm mercury.
In January 1998, EPA placed Mobile Bay on the list of 96 watersheds "whose sediment may be contaminated at levels that may adversely affect aquatic life and human health." One of the contaminants is mercury. Because of the overall high concentration in the sediments, the fact that some of the mercury found is in the harmless inorganic form may not offer any reprieve in the long term. According to a fact sheet published by the U.S. Geological Survey titled "Mercury Contamination of Aquatic Ecosystems," some bacteria can ingest the harmless inorganic mercury and convert it into the harmful organic form --methyl-mercury. "The methylmercury- containing bacteria may be consumed by the next higher level in the food chain, or the bacteria may release the methylmercury to the water where it can quickly absorb to plankton, which are then consumed by the next level in the food chain," the report continues. "Organisms higher on the food chain are progressively more concentrated in mercury and other contaminants, thus magnifying bioaccumulation rates at the top of the food chain."
In a 1991 report to the U.S. Geological Survey titled "Organic And Heavy Metal Chemistry of Mobile Bay," Dr. Wayne Isphording, a professor of geology at the University of South Alabama, concluded that the results indicate "(1) significant increase in heavy metals and certain organic compounds occur towards the head of Mobile Bay, (2) partitioning data indicate that, unlike some other estuaries in the northern Gulf of Mexico, most metals held in Mobile bottom sediments are in forms that allow not only their release back into the water column, but also their extraction by bottom feeding organisms." The heavy metals referred to in Dr. Isphording's report include mercury.
|Fugitive air release||1,475||1,000|
|Stack air release||814||750|
|Fugitive air release||1,000|
|Stack air release||750|
|Fugitive air release||1,000|
|Stack air release||750|
|Fugitive air release||450||750|
|Stack air release||87||750|
|Fugitive air release||450||490|
|Stack air release||87||350|
SOURCE: Environmental Protection Agency, TRIS database.