Animal studies show that mercury binds to cells throughout the body, including neurons, and interferes with the signals being sent to the cells that control how they develop, replicate and die. (Duncan, 2009) It’s most famous for being a neurotoxin, but it can cause other health problems as well.
How mercury affects a child’s brain development
“Mercury’s toxicity derives from its ability to penetrate the blood-brain barrier and disrupt the central nervous system,” states Wesley Marx (1967, p. 62). Thus it can cause extreme neurological damage in children.
One study took hair samples from 5th and 6th graders living near an abandoned mine site where mercury exposure had occurred. It was found that the higher the mercury concentration in the hair, the lower a child’s verbal intelligence scores were. (Kennedy, 2005) Another found that for every 1,000 pounds of mercury released into the environment, autism rates rise by 61% and the need for special education increases by 43%. (Palmer, 2008) The closer children are to the source of exposure, the higher autism rates were.
Mercury exposure during pregnancy & its effects on fetal development
High levels of mercury exposure early in development can be especially devastating. Mercury will be passed from mother to child through the placenta or through nursing, and it irreversibly damages the developing brain. Because mercury accumulates in the umbilical cord, a baby can have mercury levels 1.7 times higher than that in the mother’s blood, according to EPA scientist Dr. Kathryn Mahaffery. (Shabecoff & Shabecoff, 2010)
The government has estimated that 7% of women of childbearing age are exposed to excessive mercury emissions. (Wolf & Groppe, 2014) Other reports state that as many as 630,000 babies born each year were exposed to high levels of mercury in utero, and approximately 1 in 6 newborns comes into this world with high levels of mercury in their system. “The science is really clear now,” says Dr. David Carpenter of the School of Public Health at the State University of New York, “that at those levels [that have been documented in hundreds of thousands of women of childbearing age] the child almost certainly would have a permanent IQ loss of anywhere from 5 to 7 points.” (Shabecoff & Shabecoff, 2010)
It’s estimated that mercury exposure causes an additional 1,566 children in the U.S. to be born mentally retarded each year. (ibid) It can also cause other serious birth defects. In Japan’s Minamata Bay, a group of women exposed to higher mercury levels (as a result of eating mercury-laden fish) “gave birth to babies with distorted limbs, mental retardation, cerebral palsy, and other horrible disorders.” (ibid, p. 19) It’s estimated that preventing the premature deaths and brain damage in young children that results from mercury exposure could be worth anywhere from $37 billion to $90 billion a year. (Wolf & Groppe, 2014)
Acute mercury poisoning
In high enough doses mercury can cause immediate and potentially deadly health effects. “Mere inhalation of organic mercury compounds can prove fatal,” says Wesley Marx. “In fact, most cases of organic mercury poisoning have involved farmers who were spreading fertilizers that contained mercury compounds.” (Marx, 1967, p. 62)
Mercury in the Environment
“Mercury is far more prevalent in our environment than anybody thought.”
– Ecologist David Evers, chief scientist at the nonprofit Biodiversity Research Institute (Neimark, 2013)
Most natural mercury in the environment originates from volcanoes, and is released during eruptions. Most man-made mercury in the environment comes from the burning of fossil fuels, either by coal-fired power plants or from factories and transportation.
Mercury then rains down to the ground during storms. An Aug. 2016 study by Holmes et al. in Environmental Science & Technology found that thunderstorms deliver 50% more mercury than other rain events, probably because they pull in mercury from the upper atmosphere. (Earth, Nov./Dec. 2016, p. 28)
This mercury contamination then gets into just about everything, including fish and wildlife populations. A study by David Evers and colleagues found high levels of mercury in the feathers of Saltmarsh Sparrows living in New York. (Niemark, 2013)