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Occupational Exposure to Additive Is Bigger Worry, Researcher Says

WebMD Health News

Study Raises Concerns About Shampoo Safety

Dec. 5, 2004 -- New research is raising concerns about the safety of a preservative that is commonly found in shampoos and other commercially available cosmetics. But cosmetics industry officials say the additive has been proven safe over years of use.

In laboratory studies, the bacteria-killing agent methylisothiazolinone (MIT) was shown to restrict the growth of immature rat nerve cells. Studies in live animals are needed to confirm the findings. But researchers say the early test tube evidence suggests that prolonged exposure to MIT, or exposure to the chemical at high concentrations, could damage the nervous system.

The research was presented Sunday at the annual meeting of the American Society for Cell Biology in Washington D.C.

Fetal Development a Concern

The biggest potential concern, says lead researcher Elias Aizenman, PhD, of the University of Pittsburgh School of Medicine, is for the fetuses of pregnant women exposed to high doses of MIT on the job. The agent is widely used in industrial settings.

"If the data that I am seeing does translate into some sort of neurodevelopmental problem in people, then the risk to the developing fetus of a woman who is exposed to this agent in [its concentrated form] may be significant," Aizenman tells WebMD.

Another concern is that occupational exposure or routine use of commercial products that contain MIT could trigger nerve-damaging diseases such as Parkinson's or Alzheimer's. Again, Aizenman is quick to point out that there is no direct evidence linking MIT to these disorders. But he adds that live animal studies are needed to clarify the risk.

"It is very difficult to find shampoos and conditioners that do not contain MIT, and it is in many other cosmetics, as well," he says. "I can't tell you that using shampoo is unsafe, but I can't tell you it is safe, either."

Cosmetics Industry Responds

A statement issued Friday by the nation's largest cosmetics industry trade group called the University of Pittsburgh research "meaningless for safety evaluation purposes."

A Cosmetic, Toiletry, and Fragrance Association spokesperson pointed out that the level of MIT in shampoos and other commercial products is extremely low.

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