Occupational lead exposure affects nerves, brain

Occupational lead exposure affects nerves, brain

CanWest News Service

1st August 2007

A new study suggests people who are better readers have more protection from some of the effects of lead poisoning than those who do not read as [so] well.

The study, involving 112 Belledune, N.B., smelter workers with similar exposure to lead, was reported in the July 31 issue of Neurology, the medical journal of the American Academy of Neurology.

Occupational lead exposure has negative effects on nerves and a number of areas of brain function.

Certain brain functions, however, seem to resist the effects of lead exposure better than others, the authors say.

One of these is reading ability, which is also an indicator of cognitive reserve -- or the brain's ability to function in spite of damage.

The study divided the workers into two groups based on education -- Grade 12 and higher and those with less than Grade 12. The authors measured each group's reading level, and participants were given tests to determine their degree of thinking and motor-skill impairment.

"Even though the two groups had similar lead exposure, the cognitive effects of lead were 2.5 times greater in workers with low reading ability," said author Margit L. Bleecker of the U.S.-based Center for Occupational and Environmental Neurology.

"In contrast, the effect of lead on motor speed was comparable in both groups." Bleecker said the findings suggest that greater cognitive reserve has a protective effect that allowed the workers to maintain their functioning, even though lead still affected their motor skills.

"This has been extensively studied in other neurological disorders -- Alzheimer's disease, stroke, other dementias, sleep apnea, traumatic brain injury. It's always the individuals with more cognitive reserve who are able to withstand the injury to the brain," she said.

Bleecker says there are several theories on how cognitive reserve protects against damage to the brain.

"These include an increased concentration of cortical synapses in larger brains that provide more brain capacity, a greater ease of using alternative brain circuits and the ability to process tasks more efficiently in current brain circuits," said Bleecker.

Exposure to lead can cause reduced cognitive ability, as well as nausea, abdominal pain, irritability, insomnia, paralysis, seizures and coma. It is also linked to anemia, and kidney and reproductive problems.

© The Vancouver Province 2007