News Coverage
Wash that MIT out of your hair?
Published December 6, 2004
Everyone knows what it feels like to have a bad hair day.
Perhaps your curly locks shriveled into a frizzy bird's nest. Or maybe your silky and luxurious mane deflated into a lifeless mop.
At catastrophic moments like these, a dose of sodium laureth sulfate mixed with tocopheral and cocamide DEA could help -- and don't forget the cyclopentasiloxane.
These are just a few of the unrecognizable chemicals in the alphabet soup of ingredients found in almost every hair product.
Your revitalizing daily shampoo might have been formulated to add volume and shine, but consumer watchdogs say the scads of chemicals used in cosmetics aren't adequately assessed for safety by either the federal government or the manufacturers.
Similar health concerns were echoed in a study presented Sunday by University of Pittsburgh School of Medicine neurobiologists at the annual meeting of the American Society for Cell Biology in Washington, D.C.
In tests on rats' brains, Pitt researchers have found that prolonged exposure to low levels of a common shampoo ingredient called methylisothiazolinone (pronounced METHYL-lie-so-THY-a-zole-a-nohn) dramatically restricts the growth of neurons.
Methylisothiazolinone -- shortened to MIT for obvious reasons -- is often added to water-based shampoos and hand lotions to prevent bacteria growth, said Pitt neurobiologist Elias Aizenman, the study's senior author. The chemical also is used widely as an antimicrobial agent to kill germs in industrial water storage tanks and cooling units.
Just because MIT is all around doesn't necessarily make it risk-free -- or mean that the right tests have been conducted to gauge its safety, according to Aizenman.
There is mounting evidence that neurodegenerative diseases such as Parkinson's or Alzheimer's could be exacerbated by exposure to chemicals in the environment, but there is little evidence about the potential effect on the brain of many commonly used substances, Aizenman said.
"It's disturbing, but when I started reading about methylisothiazolinone a few years ago, I found that there was no neurotoxicology data available for it," Aizenman said. "The (Environmental Protection Agency) apparently doesn't require this kind of testing for a lot of compounds that get approved."
Consequently, Aizenman and his colleagues began to look at the effects of MIT on the rodent brain.
In 2002, they reported in The Journal of Neuroscience that a 10-minute exposure to high concentrations of MIT was deadly to rat cortical neurons.
In their follow-up study presented at yesterday's meeting, the researchers showed that chronic exposure to much lower doses of the chemical doesn't kill rat brain cells, but it inhibits the growth of structures called neurites required for transmitting signals between neurons, Aizenman said.
So do this mean you need to find a new favorite shampoo that's MIT-free?
Not yet.
"It's too soon to tell if you need to be worried about exposure by using cosmetics that contain this compound," Aizenman said.
To address the question, Aizenman is planning further research to better understand the molecular mechanisms underlying MIT's neurotoxic effects on cells and studies involving whole animals.
The Cosmetic Ingredient Review panel, the personal care product industry's voluntary oversight body, has labeled MIT "safe with qualifications."
The panel deems the ingredient safe to use in personal care products that you rinse off, such as shampoo, if it is below concentrations of 15 parts per million. This corresponds to the concentration of MIT that Aizenman found to be deadly to rat nerve cells in the short-term.
In lotions and other "leave-on" products, the CIR-recommended dose is less than 7.5 parts for each million -- about 15 times as high as the amount found to inhibit neurite outgrowth in the long-term experiment.
Cosmetics industry representatives said it is too early tell from Aizenman's data whether MIT poses any significant risk to users of personal care products.
"When someone says I took cells out of an animal and applied something to them, it has absolutely no relationship to any kind of exposure that a consumer would get," said Gerald McEwen, vice president of science for the Cosmetic, Toiletry and Fragrance Association, a Washington, D.C.-based trade organization with about 600 member companies. "You have to look at how a chemical is actually used, what is the likely consumer exposure and whether an experiment is relevant to that exposure."
Published research that raises safety concerns about chemical ingredients in products on the shelf is evaluated seriously by the cosmetics industry, McEwen said. But in general, the public shouldn't worry about any hidden dangers in their hair spray or lip gloss, he said.
"I really believe that these products are very, very safe," McEwen said. "I think the overall data prove that there's not something lurking here."
Consumer activists disagree, arguing the safety levels set by the Cosmetic Ingredient Review panel for chemicals such as MIT are arbitrary and cosmetics should be subject to the same federal regulation food and drugs receive.
"There is not a safety standard in place that requires any testing to be done whatsoever in any cosmetic product," said toxicologist Timothy Kropp, a senior scientist with the Washington-based Environmental Working Group.
Last summer, the nonprofit public interest research organization released the results of its "Skin Deep" study (www.ewg.org/reports/skindeep/) that used a complex formula to assign a health-risk rating to 7,500 personal care products -- 382 of which contain MIT. For example, Neutrogena T-Gel Shampoo merits a whopping 8.9 score in the investigation, with 10 being the highest risk level. A safer choice, according to the report, would be Terressentials Fragrance-free Pure Earth Hair Wash, with a score of just 2.3.
"Our study is cause for concern, but not for alarm," Kropp said. "We don't know the concentrations of chemicals inside the products, so we can't say that these are levels that are going to cause harm. But we also don't know if they are safe."
Without the advanced chemistry degree required to understand shampoo labels, many hair stylists say they don't much care what's in the bottle as long as it works.
"We usually buy products based on how they function," said Michele Abijanac, owner of Hairdressers II salon in Shadyside. "I would definitely not use something if it was going to harm someone, but you would really have to have more information to say we're going to throw out all of these shampoos."
Regardless of whether MIT ends up posing a health risk to cosmetics users or to those with neurodegenerative diseases, it's not too early to worry about exposure in people who manufacture the chemical or work with it in an industrial setting -- especially pregnant women, Aizenman said. These individuals are exposed to MIT in much higher doses for longer periods of time.
"I have more concerns about occupational exposure rather than daily exposure through cosmetics," Aizenman said. "And my most immediate concern is if this stuff gets into the fetus. That could have terrible consequences on a developing nervous system."
About MIT
* Methylisothiszolinone (pronounced METHYL-lie-so-THY-a-zole-a-nohn) -- MIT for short -- is an antimicrobial preservative widely used in industrial applications and cosmetics to kill bacteria.
* Commercially, it is available as Kathon CG, manufactured by Philadelphia-based chemical maker Rohm and Haas Co. The chemical is actually a mixture of MIT, which is a cyclic, sulfur-containing molecule, and a chlorinated version of the same compound. At high concentrations, Kathon CG can cause skin irritation and severe eye damage.
* MIT was listed as an ingredient in 382 -- or about 5 percent -- of the 7,500 personal care products cataloged this summer by a consumer watchdog organization.
* It also is commonly used as a biocide in water storage tanks, dehumidifiers and cooling units in industries as varied as mining and energy production.
