Originally published September 23 2005
Naturally-occurring marine toxin could harm unborn babies
by Mike Adams, the Health Ranger, NaturalNews Editor
Domoic acid, a naturally-occurring and potentially deadly marine toxin that humans are sometimes exposed to through contaminated shellfish, has been found to be toxic to unborn rats at levels deemed safe for adult humans, suggesting unborn human babies may also be at risk for cognitive damage at low levels of exposure and that fisheries should regulate the toxin more strictly.
The researchers saw behavioral effects of the toxin in animals after prenatal exposure to domoic acid levels below those generally deemed safe for adults, said Edward Levin, Ph.D.
Those effects --- including an increased susceptibility to disruptions of memory -- persisted into adulthood, he said.
The findings in rats, therefore, imply that the toxin might negatively affect unborn children at levels that do not cause symptoms in expectant mothers, said Levin.
While the researchers note that eating seafood offers significant health benefits, they said their findings suggest that the current threshold of toxin at which affected fisheries are closed should perhaps be lowered.
"A single administration of domoic acid to pregnant rats had a lasting affect on the performance of their offspring as adults," Levin said.
"The findings suggest we may need to re-evaluate monitoring of waters, shellfish and fish to make sure that the most sensitive parts of the human population are protected from toxic exposure to domoic acid," he continued.
The researchers reported their findings in a forthcoming special issue dedicated to research on marine toxins of Neurotoxicology and Teratology.
In severe cases, the toxin leads to neurological damage, characterized by headaches, confusion, coma and even death.
Exposure can also cause amnesic shellfish poisoning, characterized by permanent loss of short-term memory.
More recent reports examining the effects of a range of doses have found highly reproducible behavioral consequences of sublethal doses of the marine toxin, including impairments to spatial memory.
Rats with a history of domoic acid exposure showed greater initial activity in a maze test than control rats, followed by a rapid decline.
Moreover, domoic acid exposure affected cognitive function in complex ways, the researchers reported.
Exposed rats of both sexes also showed greater susceptibility to a chemical that induces amnesia by compromising particular brain receptors, suggesting that the animals had less functional reserve with which to solve memory tasks, the researchers said.
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