Antimicrobial May Harm Developing Nervous System

[7/4]

Antimicrobial May Harm Developing Nervous System

By Megan Rauscher

NEW YORK (Reuters Health) - Prolonged exposure to a germ killer widely used in industry and in household and personal care products, stunts the growth of developing nerves in the brains of rats, according to new research.

The finding was described by Dr. Elias Aizenman on Sunday at the annual meeting of the American Society of Cell Biology in Washington, DC.

There haven't been many studies of the toxic effects of this compound, methyl-isothiazolinone or MIT, the researcher noted in a telephone interview with Reuters Health. "There are many documented instances of people being exposed to MIT in the workplace -- most of what one sees is contact burns or dermatitis or allergic sensitization," he said.

"I would be concerned that a pregnant woman working in such an environment could potentially be exposed to high enough concentrations of MIT to have some effects on the developing embryo, but we just don't know yet," he added.

In a previous study, Aizenman and his colleagues from the University of Pittsburgh School of Medicine found that exposing mature rat neurons to a high concentration of MIT causes a high proportion of the cells to die within 10 minutes.

In their latest experiments, the researchers saw that prolonged exposure (roughly 18 hours) to a much lower, sub-lethal concentration of MIT caused embryonic rat neurons to stop developing in the way they should.

Aizenman said he plans to conduct further studies of the toxic effects of MIT on nerves to better understand the "molecular mechanisms and the potential neurodevelopmental consequences."

[7/4]

Shampoo Preservative Concerns

Dec. 6, 2004

CBS

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.

"The experiments conducted with (MIT) on extracted rat nerve cells in laboratory containers do not remotely resemble the possible consumer exposure to this preservative," the CTFA statement says.

Aizenman says he became aware of MIT while researching the mechanisms associated with the death of brain cells. He found that the agent activated a novel pathway that promoted cell death in the laboratory setting, and showed in earlier work that adult rat brain cells died when exposed for short periods to MIT at high concentrations.

In their latest work, Aizenman and colleagues exposed immature, developing rat brain cells to very low concentrations of MIT — roughly 1/100 of the dose used in the previous study. Low-level exposure for 18 hours was found to slow down cell growth. The higher the dose the brain cells were exposed to, the more effect there was.

Aizenman acknowledges that it is "a big leap" to suggest that MIT exposure in the womb could play a role in the rise of developmental disabilities in children. But he adds that the questions raised by his research need to be answered.

"I would caution that based on our data, there very well could be neurodevelopmental consequences from MIT," he notes. "Clearly, more study is needed, with both scientists and government regulators equally engaged."

Sources: American Society for Cell Biology 44th Annual Meeting, Washington, D.C., Dec. 4-8, 2004. Elias Aizenman, PhD, professor of neurobiology, University of Pittsburgh School of Medicine. News release, Cosmetic, Toiletry, and Fragrance Association.

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Shampoo Ingredient Kills Rats' Brain Cells

The industry sees no harm to consumers from low concentrations of a chemical found in some common household products.

By Steven Reinberg

HealthDay Reporter

MONDAY, Dec. 6 (HealthDayNews) -- Experiments with the brain cells of rats show that contact with an ingredient found in shampoos, hand lotions and paint causes neurons to die.

The chemical, methylisothiazolinone (MIT), belongs to a class of compounds called biocides. These are used in the manufacture of many common household products and industrial water cooling systems to prevent bacteria from developing.

According to the National Institutes of Health, brands containing MIT include the shampoos Head and Shoulders, Suave, and Clairol, as well as Pantene hair conditioner and Revlon hair color.

"As far as I can tell, no neurodevelopmental testing has been done on MIT," said lead researcher Elias Aizenman, a professor of neurobiology at the University of Pittsburgh School of Medicine.

Aizenman said he is concerned that without such testing it is not known if, for example, a pregnant woman who is exposed to MIT could put her fetus at risk for abnormal brain development. People working directly with MIT are those most at risk, he said.

In earlier experiments with rat brain cells, Aizenman's team found that direct exposure to MIT in concentrations like those found in hand cream was enough to kill neurons. In the current series of experiments, also with rat cells, the researchers found that a long exposure to low concentrations of MIT caused a malfunction in the ways neurons communicate with each other.

"One of the things that this compound was very good at was preventing neurons from communicating with other neurons," he said.

Aizenman presented his findings Dec. 5 at the American Society for Cell Biology annual meeting in Washington, D.C.

Whether long-term exposure to products containing MIT is dangerous is not known, Aizenman said. "Can I say that these products are safe to use? No," he said. "Can I say that these products are unsafe to use? No."

Aizenman believes that testing needs to be done to determine if MIT is harmful to humans in the concentrations found in household products.

"It appears that the Environmental Protection Agency [EPA] does not require neurodevelopmental testing," Aizenman said. "That is bothersome. Maybe there are substances that have made it into general use that could be damaging to the nervous system. Regulators need to take a hard look this and require more tests."

The work that Aizenman has been doing "is important in understanding the things that people are exposed to on a chronic, daily basis," said Beth Ann McLaughlin, an assistant professor of pharmacology at Vanderbilt University.

McLaughlin added that people using products containing MIT should be skeptical. "There is a healthy dose of skepticism that needs to come when using any products or being intensely exposed to any compound," she said.

"These findings are expected," said Gerald McEwen, vice president for science at the Cosmetic, Toiletry and Fragrance Association. "MIT is a biocide. The purpose of it is to kill bacteria. You would expect it to be detrimental to any type of cells."

McEwen said that direct exposure to high concentrations of MIT will be irritating to the skin, because it can damage skin cells. However, he doesn't believe that MIT poses any dangers to consumers in the low concentrations found in household products.

"The ability of MIT to cause neurotoxicity has been studied," McEwen said. In animals exposed to MIT, there has been no hint of neuro-damage, because MIT affects only the cells it touches and there is no way for it to get into the bloodstream and go to the brain, he said.

"It can't get to your brain cells, period," he emphasized.

MIT has been approved as a biocide by the EPA, which looked at the neurological effects, McEwen added. This information was published by the Cosmetic Ingredient Review, an industry program that reviews the safety of cosmetic ingredients, he explained.

However, McLaughlin remains concerned. "The quantity of compounds that we can make that make the quality of life wonderful, in the short term, is growing," she said. "But we are lagging in our understanding of what those compounds can do to our health and our children's health."

More information

The National Institutes of Health has a list of household products containing MIT (householdproducts.nlm.nih.gov ).

Copyright © 2004 ScoutNews LLC. All rights reserved.

Last Updated: December 06, 2004

[BruceH]

I you trying to frighten us?

[DrJ]

OK, mildly interesting stuff, but there are literally DOZENS of equally scary-seeming test-tube studies published EVERY WEEK out there...and obviously 99.9% of these things never pan out in clinical studies to be of concern. Hey I'm up for caution as much as anyone, but this type of stuff always amazes me the way it's portrayed in the popular media as a real major, pressing concern.

Pouring a chemical (one that's intended to kill bacteria at that) directly on to developing nerve cells is a LONG way off from concluding that shampooing with it is an issue...that would mean very high concentrations would need to somehow cross into your blood stream, which seems HIGHLY unlikely.

A great example of the way science is routinely botched in the press.

Classic quote from one of the articles from the scientist: "Can I say that these products are safe to use? No," he said. "Can I say that these products are unsafe to use? No."

Gee. Thanks.

Another telling comment: Again, Aizenman is quick to point out that there is no direct evidence linking MIT to (any of) these disorders.

And this classic from some Assistant Professor at Vanderbilt: "There is a healthy dose of skepticism that needs to come when using any products or being intensely exposed to any compound," she said.

Uh, OK - could we be any more sweepingly vague?

OK. So given that time and money are limited at the governmental and every other level, hows about we worry about really PRESSING, proven health issues rather than fretting about stuff that will likely never pan out to be remotely important?

My personal favorite, other than test tube studies like this one being made to sound like they're clinical studies, is when they quote observational studies (you know, the kind that finds associations between some exposure and some bad medical outcome) as if they are firm evidence, when in fact they are weak and can NEVER confidently be used to infer causality in the association (the exposure CAUSED the outcome). One not too long ago about television watching and ADHD just killed me; no way to determine whether TV "caused" or contributed to the ADHD or if parents (either in desperation, or due to neglect, or whatever) simply parked the kids with ADHD behaviors in front of the TV more than those of non-ADHD kids. Classic chicken or egg thing.

Everyone who's interested in this type of ruse needs to read the DAMN LIES AND STATISTICS couplet of books, readily available on Amazon.

Edited December 7, 2004 by DrJ

[Jazzmoose]

Maybe so, DrJ., but I'm taking no chances. I'll never shampoo a rat again!

[DrJ]

Oh, you can shampoo him alright, just make sure you lather up his SCALP, not his BRAIN.

Edited December 7, 2004 by DrJ