Studies of the neurobehavioral toxicity of mercury on children suggest that no level of mercury exposure can be considered safe, but pressure from the fish industry may be preventing safety limits from dropping further.
Nerves of Mercury
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No mercury level may be truly safe. This review on the adverse effects of mercury in fish suggested that “[E]ven slightly increased environmental exposure to methylmercury from fish could lead to adverse effects on nervous system development, just like…lead exposure.” No lead is the only good lead, and the same is true for mercury.
They point to this famous study, published in the Journal of Pediatrics a few years ago, showing delayed brainstem auditory evoked potential latencies in teens exposed to methylmercury as an objective measure of neurobehavioral toxicity in 14-year-old children with developmental exposure to methylmercury from fish.
It’s a measure of how well the nerves in your brain communicate. You take kids; you stick electrodes on their scalp, and headphones on their ears, and play a quick sound. And then, just measure how long it takes for that sound to be transmitted from the nerves in their ear to the auditory cortex in their brain. The longer the delay, the slower your nerve impulses are traveling.
And so, here’s the graph. This is delay versus mercury content in their hair. You’ll notice two things. The more mercury the kids had in their bodies, the longer the delay. That’s bad. Also, you’ll notice it’s basically a straight line. It doesn’t plateau out at the bottom end; the lower the mercury, the better.
Where do the official safety limits fit on this graph? In 1978, the World Health Organization started to realize how dangerous mercury was, so they said no greater than this level is safe. We didn’t know any better.
Decades later, the “safe” upper limit was moved down to here. Our government said no way, our children are much too precious for that, and placed our upper limit here, in 2001. As you can plainly see from this later data, though, if you push levels lower, get people to eat less fish, you get even less brain damage. Yet, as of 2012, the safety limit remains there.
As one former EPA toxicologist told the Wall Street Journal, “[Government regulators] really consider the fish industry to be their clients, rather than the U.S. public.”
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Serena Mylchreest.
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- Grandjean P, Satoh H, Murata K, Eto K. Adverse effects of methylmercury: environmental health research implications. Environ Health Perspect. 2010 Aug; 118(8):1137-45.
- Toyoda K, Ibayashi S, Yamamoto T, Kuwabara Y, Fujishima M. Auditory evoked neuromagnetic response in cerebrovascular diseases: a preliminary study. J Neurol Neurosurg Psychiatry. 1998 Jun; 64(6):777-84.
- Murata K, Weihe P, Budtz-Jørgensen E, Jørgensen PJ, Grandjean P. Delayed brainstem auditory evoked potential latencies in 14-year-old children exposed to methylmercury. J Pediatr. 2004 Feb; 144(2):177-83.
No mercury level may be truly safe. This review on the adverse effects of mercury in fish suggested that “[E]ven slightly increased environmental exposure to methylmercury from fish could lead to adverse effects on nervous system development, just like…lead exposure.” No lead is the only good lead, and the same is true for mercury.
They point to this famous study, published in the Journal of Pediatrics a few years ago, showing delayed brainstem auditory evoked potential latencies in teens exposed to methylmercury as an objective measure of neurobehavioral toxicity in 14-year-old children with developmental exposure to methylmercury from fish.
It’s a measure of how well the nerves in your brain communicate. You take kids; you stick electrodes on their scalp, and headphones on their ears, and play a quick sound. And then, just measure how long it takes for that sound to be transmitted from the nerves in their ear to the auditory cortex in their brain. The longer the delay, the slower your nerve impulses are traveling.
And so, here’s the graph. This is delay versus mercury content in their hair. You’ll notice two things. The more mercury the kids had in their bodies, the longer the delay. That’s bad. Also, you’ll notice it’s basically a straight line. It doesn’t plateau out at the bottom end; the lower the mercury, the better.
Where do the official safety limits fit on this graph? In 1978, the World Health Organization started to realize how dangerous mercury was, so they said no greater than this level is safe. We didn’t know any better.
Decades later, the “safe” upper limit was moved down to here. Our government said no way, our children are much too precious for that, and placed our upper limit here, in 2001. As you can plainly see from this later data, though, if you push levels lower, get people to eat less fish, you get even less brain damage. Yet, as of 2012, the safety limit remains there.
As one former EPA toxicologist told the Wall Street Journal, “[Government regulators] really consider the fish industry to be their clients, rather than the U.S. public.”
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Serena Mylchreest.
Please consider volunteering to help out on the site.
- Grandjean P, Satoh H, Murata K, Eto K. Adverse effects of methylmercury: environmental health research implications. Environ Health Perspect. 2010 Aug; 118(8):1137-45.
- Toyoda K, Ibayashi S, Yamamoto T, Kuwabara Y, Fujishima M. Auditory evoked neuromagnetic response in cerebrovascular diseases: a preliminary study. J Neurol Neurosurg Psychiatry. 1998 Jun; 64(6):777-84.
- Murata K, Weihe P, Budtz-Jørgensen E, Jørgensen PJ, Grandjean P. Delayed brainstem auditory evoked potential latencies in 14-year-old children exposed to methylmercury. J Pediatr. 2004 Feb; 144(2):177-83.
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Title
Nerves of Mercury
LicenseCreative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
Content URLDoctor's Note
This is the second of my three-part video series on the latest on the risks of mercury in fish. For part one, see Hair Testing for Mercury Before Considering Pregnancy, and for part three, see Which Brand of Tuna Has the Most Mercury? I have a bunch of other videos on mercury, including fish contamination and its consequences. For example, see The Effect of Canned Tuna on Future Wages. And check out my other videos on undue industry influence on our food supply. One can also be exposed to lead though dietary supplements (Some Ayurvedic Medicine Worse Than Lead Paint Exposure), and even protein powders too (Heavy Metals in Protein Powder Supplements).
For more context, check out my associated blog posts: Mercury Testing Recommended Before Pregnancy; Lead Poisoning Risk From Venison; Protecting Our Babies From Pollutants; and Schoolchildren Should Drink More Water.
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