a naturally occurring element that is present throughout the
environment. It becomes a toxic air pollutant when
released into the air, water and soil by human activity.
Reactive, inorganic mercury is emitted to the atmosphere
primarily from coal-burning power plants and incinerators that
combust mercury-containing wastes.
Air currents and
rainfall convey this mercury from the atmosphere to the
earth's surface. Some of the deposited mercury ends up
in wetlands, lakes, and streams where bacteria convert a
portion of it into methylmercury, a toxic form that builds up
(bioaccumulates) in the tissues of animals at each link in the
Mercury may accumulate in sport fish to
levels that would be toxic if eaten by humans over a prolonged
period of time or by wildlife that prey upon those fish.
This effect occurs worldwide but is particularly acute in the
marshes of the Florida Everglades. There, largemouth
bass, which feed primarily on other fish in the food chain,
have been found with five times the level of mercury
considered safe for human consumption, and wading birds are
ingesting amounts of mercury close to levels that could reduce
beings are believed to have some tolerance for mercury.
Based on this, the Florida Department of Health has
established the following guidelines. Fish that have
more than 1.5 parts per million of mercury in the edible flesh
are considered unsafe for any consumption. Those
containing less than 0.5 parts per million are considered safe
for unlimited consumption. Consumption should be limited
for fish with concentrations from 0.5 to 1.5 parts per million
of mercury in edible flesh. Women of childbearing age
and children should limit consumption of these fish to a
single serving per month. Other adults should limit
consumption of these fish to a single serving per week.
These values are based on a body weight of 156 pounds and an
8-ounce (half-pound) serving of fish. If a person weighs
less, it would be safer to consume less. A conservative
approach for eating largemouth bass from untested waters would
be to follow the advice given for limited consumption - one
serving per month for women of childbearing age and children,
and one serving per week for other adults.
August 04, 2014