Issue Brief from the Ornithological Council

Volume 1, Number 2

August 1997

MERCURY CONTAMINATION IN BIRDS AND HUMANS

THE ISSUE

Mercury emission rates from industry have tripled since the turn of the century and mercury levels in animal tissues are increasing, particularly in species that consume fish.

Consumption of mercury contaminated fish has been linked to health problems, nervous system disorders and death in humans, and causes similar problems in birds.
Mercury is deposited in fresh water where it accumulates in fish and is passed up the food chain often resulting in adverse impacts on fish-eating birds.

There are 1,740 lakes and rivers in the U.S. where people are advised to limit their fish consumption owing to high levels of contaminants. Fish consumption advisories have been issued by over 35 states suggesting that pregnant women not eat mercury-contaminated fish.

POLICY ISSUES

We do not know the full impacts of mercury toxicity to humans, birds, and other wildlife. Studies are needed in order to understand the full impacts of mercury on our lives and on birds.

Accountability issues are beginning to be raised about who is responsible for the deposition of mercury. This complicates the management of species.

BACKGROUND

Mercury in lakes and rivers originates from industry (coal burning operations, smelters, incineration of waste) and the inappropriate disposal of millions of mercury batteries. Coal industries in the U. S. release approximately 100 tons of mercury into the atmosphere each year and 3-5,000 tons are released worldwide. Once released into the air, mercury can be transported thousands of miles. When deposited, metals do not degrade in the environment and levels are rising each year. In the water, inorganic mercury is chemically altered and transformed into more toxic methylmercury. Methylmercury becomes more concentrated at each level up the food chain and has serious ramifications for animals at high levels in the food chain such as fish-eating birds and humans.

THE FACTS

An EPA report (1995) explains that areas highest in mercury contamination are the Northeast, Great Lakes, Florida, and the West. Because of the release of mercury by industries all over the world and mercury's mobility in the atmosphere, mercury emissions are an international problem. In any case, we still need research to determine the sources of mercury released into the atmosphere and to provide a biologically sound the basis for legislation regulating mercury emissions.

As a precautionary measure, the U.S. Food and Drug Administration discourages human consumption of fish containing mercury levels greater than or equal to 1.0 part per million (ppm). Consumption of mercury-contaminated fish by birds, such as eagles, and herons, results in the accumulation of methylmercury in their tissues where it continues to build up over the life of the bird. Neurological damage and reproductive failure from mercury poisoning have been found in birds. Bald eagle eggs have been killed by mercury concentrations over 1.0 ppm. Concentrations as high as 19.1 ppm have been found in feathers of eagle chicks and cause sterility. In other cases adult birds have been killed by high concentrations, eggs fail to hatch, flight is impaired, aberrant behavior and kidney lesions develop.

The adverse effects of mercury contamination - neurological impairment, decreased reproductive success, and physiological impairment in birds and humans - may go unnoticed for months and even years. Until research can be conducted to document the sources of mercury we cannot write supporting legislation to reduce levels. Children, pregnant women and sensitive species of wildlife, such as fish-eating birds, continue to remain at risk of mercury contamination.