Excess carcinogen in hair straightening products

The amounts of formaldehyde, a recognised carcinogen, exceed the safe level in the majority of hair straightening products tested by a new NMR method developed by European scientists. Formaldehyde is banned as an active ingredient in hair straightening products in the EU, with a maximum allowable concentration of 0.2% when used as a preservative. However, 70% of commercial products bought in Germany contained higher amounts, ranging from 0.42-5.83%.

The novel NMR method, described in the International Journal of Cosmetic Science, is based on the fact the formaldehyde exists as methylene glycol in solution. ¹H NMR spectra of aqueous solutions revealed resonances at δ4.84-4.82 ppm originating from the CH₂ group which were used to estimate its concentration, which is directly related to the level of formaldehyde.

The amount of formaldehyde that escapes into the air when these products are in use in salons was estimated to be 6 ppm on average, well above the safe level of 0.1 ppm. At most risk are hair salon workers, who will be regularly exposed to formaldehyde emissions when this type of product is applied to customers.

On the basis of these results, the research group declared "we judge all limit exceeding formaldehyde-containing products as being not safe and not suitable to be placed on the market." This is more difficult than it sounds because the majority of these products are direct imports form non-EU countries that were purchased over the Internet, which is an unregulated market.