Mercury on your Dinner Plate

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This past July, for the first time, utilities were required to report their use of toxic chemicals reportable under the “Toxic Release Inventory” (TRI). TRI reporting affects manufacturing facilities that have 10 or more full-time employees, and meet the established thresholds for manufacturing, processing, or otherwise using listed chemicals. These companies must report their releases, transfers, and waste management activities for the listed chemicals. Thresholds for manufacturing and processing are currently 25,000 pounds, while the threshold for otherwise use is 10,000 pounds for each covered chemical.

Coal and oil fired utilities account for almost 33% of the releases of one particular reportable chemical, mercury. A product of combustion, it is emitted as elemental mercury, usually in vapor form, but it also rides on particles. The Environmental Protection Agency (EPA), for good reason, is now test-monitoring for mercury emissions and investigating control technologies. The concern is due to widespread contamination of water bodies primarily from air-borne mercury. For example, the EPA estimates that 80% of the mercury entering the Delaware Bay comes from the air. Unfortunately, mercury continues to recycle itself back into the atmosphere adding to the new emissions of mercury. For example, most inorganic mercury, (formed when the elemental mercury reacts with such things as ozone in the atmosphere) does not settle to the bottom when it falls into the ocean with rain or snow. Instead it re-releases as its elemental form back into the air.

Some mercury, particularly in lakes with appropriate conditions such as high carbon content, moderate temperatures and low pH, provide conditions where bacteria interact with the mercury to create organic methylmercury. This is the most toxic form of the three types of environmental mercury. The methylmercury becomes part of the food chain accumulating in the tissue of various organisms but accumulating more in some fish than others depending on diet and longevity of the fish.

Most states have fish advisories, but it is up to the state. Some advisories are based on EPA recommendations and some on the FDA’s so called “action level.” The EPA’s “reference dose” is many times more stringent than the FDA’s level of 1ppm, which in any case seems to be largely ignored by the FDA.

Particularly sensitive populations are pregnant women, women of child bearing age and children. Methylmercury is a developmental toxin especially damaging to a developing fetus and can cause mental retardation, visual loss and cerebral palsy. Although many people may not even be aware of the fish advisories for particular lakes, even fewer people seem to be aware that ocean fish rank high on the contamination table.

Of the top10 types of fish consumed by U.S. residents, tuna comes in at the top of the list for mercury contamination. On average, an 8-ounce can of tuna contains enough mercury to exceed the EPA’s recommended daily consumption level for an adult. A new guide in Vermont recommends that pregnant women eat no swordfish or shark and limit tuna to seven ounces per week and this to be the only fish eaten in that week. The Maine Department of Health advises that pregnant women, nursing mothers, women who may be pregnant and children under eight not eat any warm water fish; limit consumption of cold water fish to one meal/month; and avoid eating older, cold water fish.

Ocean fish that have comparatively lower levels of mercury include some species of flounder, pollock, cod, salmon, shrimp and scallops. Fresh water fish will depend upon the lake where it is caught.

As utilities are weighing compliance options, they should take a comprehensive approach to reduce all the major pollutants they emit, including mercury. Some scientists believe that if we stop all new mercury releases into the environment today, it would take at least 50 years before the fish would be safe to eat because the mercury cycle is so pervasive.(1) Mercury pollution is a problem that has been swept under the rug for much too long and must be addressed now in the most rigorous fashion.

(1) Mercury Atmospheric Processes: A Synthesis Report. Prepared by: Expert Panel on Mercury Processes. Convened March, 1994, Tampa Fla.

by Suzanne Seppi, GASP Executive Director