| Current Fish Consumption Advisories |
The primary contaminants of concern have been polychlorinated
biphenyl compounds (PCBs), the pesticide dieldrin and organic mercury.
PCBs are a class of aromatic compounds produced and marketed in the U.S. since 1929.
Before 1971, they were used as plastisizers, heat transfer fluids, lubricants and
wax extenders. Since 1971 PCBs have been limited to use in closed electrical systems
(capacitors and transformers). The production of PCBs was discontinued in the U.S.
in 1977, and their importation was greatly reduced in 1979 and completely stopped in 1982.
Before 1979 the disposal of PCB compounds was not subject to federal regulation. Of
the approximately 1.25 billion pounds purchased by U.S. industry, about 60% are still
in use in capacitors, 36 percent are in landfills of dumps and about 4 percent had been destroyed
by incineration or degraded by the environment.
Dieldrin was once widely applied to corn fields as a pest control agent, and it has been
used to treat wood products for termite protection. The legal use of dieldrin in the U.S. was halted
in 1974, except for its use as a means of subteranean termite control. In 1985 importation of dieldrin ceased,
and in 1987 its registration was cancelled. Dieldrin remains in the environment as it is extremely persistent.
This carcinogen is believed to eminate from both agriculture and urban runoff.
Mercury occurs naturally in the earth's soil, but is also present in the atmosphere from natural and man-induced sources.
Degassing of the earth crust can release up to 6000 pounds of mercury into the atmosphere annually, and emissions of mercury
from industrial discharges (chlorine alkali industry) and waste (coal and municipal refuse incinerators) also contribute. The
primary industrial uses of mercury are in the manufacture of batteries, vapor discharge lamps, rectifiers, flourescent bulbs, switches
thermometers, and industrial control instruments. The products usually end up in landfills or incinerators. Mercury also has been
used as a slimacide in the pulp and paper industry, as an antifouling and mildew-proofing agent in paints and as an antifungal seed dressing.
Of the existing sources of mercury, it is widely accepted that atmospheric depostion of both natural and man-induced mercury is the
major contributor both in our state and nation-wide. Cycling of mercury in the environment is facilitated by the volatile nature of its metallic
form and by bacterial transformation of metallic and inorganic forms to stable mercury compounds, particularly in bottom sedements. It is the stable
or organic mercury (methyl-mercury) that is detected in fish tissue and is harmful to humans.
How Great is the Risk?
Advisories for cancer-causing chemicals in fish are
issued when concentrations reach a risk level of 1 in 10,000.
This means under a worst-case scenario, the chemicals would
cause one additional case of cancer per 10,000 people eating
those fish. Theoretically, each of those 10,000 people would
have to eat five ounces of the fish every week for 70 years
to produce that one case of cancer. Thus these advisories are targeted
toward and effect a very smalllpart of tthe population of fish consumers
in the state. Mercury is not a cancer risk but because of the way it reacts
in the human body advisories for high mercury levels are targeted toward
pregnant and nursing women, infants and children under 15. As for the cancer causing
chemical advisory, mercury is also targeted toward people who consume high
amounts of fish caught from advisory waterbodies.