CHEMICAL OF THE MONTH - Mercury

By Caitlion O. Hunter, Esq.

A service program of RISE St. James; Caitlion O. Hunter, Esq.; Tim Schütz, PhD Researcher, Anthropology University of California, Irvine; and The Community Scientist (TCS) Research Team

Mercy, mercy me, 

Things ain't what they used to be

Oil wasted on the ocean and upon our seas

Fish full of mercury

Marvin Gaye, Mercy Mercy Me (The Ecology), 1971

Some of the environmental issues of 1971, like acid rain, ozone depletion, and DDT use, have been addressed or solved through a combination of activism, international diplomacy, and advances in science. But from 1971 through to 2024, the level of mercury found in tuna has remained the same, despite international attention and cooperation around reducing mercury use. Because mercury contamination can happen in the air, water, soil, and inside of living things, it has proved to be a difficult problem to solve.

Mercury is a metal, a silvery liquid at room temperature, which can take several forms. It can be found in its pure state, known as elemental mercury, like the liquid inside of old thermometers. Processing bauxite ore for aluminum, like at the Noranda aluminum plant, is a major source of elemental mercury. Elemental mercury reacts easily with other elements, like sulfur or oxygen, to form compounds. When mercury forms a compound with carbon, it is known as methylmercury or organic mercury, which is the most toxic form to humans and other life. Methylmercury is commonly emitted by coal fired plants, since there are often traces of mercury alongside the carbon-based coal. As of 2018, the three largest sources of anthropogenic (human made) mercury were small-scale gold mining, coal-fired power plants, and metal smelting.

The Noranda aluminum plant, previously owned by Kaiser, is one of the largest mercury emitting plants in the country. In 2022, Noranda released more than 11 pounds of elemental mercury into the air each week. For eight months of the year, prevailing winds blow the elemental mercury dust and vapor towards the Blind River and Lake Maurepas. The mercury is then deposited in water bodies, where it settles to the muddy bottom, and bacteria are able to convert the elemental mercury to the more dangerous methylmercury. Microorganisms like plankton absorb the methylmercury directly from the water. When bottom feeders, shellfish, and small fish eat the plankton, the mercury binds easily to their organs and begins to accumulate. Larger, long-lived predator fish like tuna and shark that eat these slightly mercury contaminated fish concentrate the mercury in their bodies over many years. Then, if the tuna or shark is eaten by a human, the toxic methylmercury in the fish enters into the human body, bloodstream, and brain.,

Mercury exposure has serious human health effects, whether through breathing, exposure to skin, or eating contaminated fish. Methylmercury exposure while in the womb or in early childhood is especially damaging, and can have a lifetime negative impact on cognitive thinking, memory, attention, language, fine motor skills, and visual/spatial skills. Breathing in elemental mercury can cause tremors, headaches, emotional changes, or impaired mental functioning. 

Since at least 1999, LDEQ has issued warnings that fish in the Blind River have high levels of mercury and should not be frequently consumed. And in April of 2024, LDEQ also issued a fish consumption advisory for Lake Maurepas due to high mercury levels. The liquid waste ponds at the Noranda aluminum are less than 2 miles away from the Blind River, and the winds often blow mercury-containing dust into the watershed as well. How this mercury got into the waterways is no mystery. For decades, Noranda emitted thousands of pounds per year of mercury- without a permit. Despite our state being home to one of the largest mercury emitting facilities in the country, the Louisiana Department of Health fails to recognize that Louisiana’s mercury problems stem from industrial activity. 

HOW TO REDUCE YOUR EXPOSURE TO MERCURY:

  • If you fish or eat locally caught freshwater fish, refer to the fish consumption advisories found at https://ldh.la.gov/page/health-fish-consumption-advisories-program-mercury-advisories 

  • The larger the fish, the greater the mercury content. Avoid tuna, shark, or swordfish, and choose oysters, shrimp, catfish, or crawfish instead. If you are pregnant or feeding small children, reducing mercury exposure is especially important.