In the study from Lund University in Sweden, researchers have investigated to what extent hairdressers are exposed to these aromatic amines in their work.
The study involved 295 hairdressers, 32 consumers who had recently dyed their hair and 60 control subjects who had not dyed their hair in the past year. All were female and non-smokers.
“We took blood samples and analysed them for eight different aromatic amines that are or are suspected of being carcinogenic and which have previously been reported in certain hair dyes. These included ortho-toluidine, which is classified as carcinogenic for humans”, said Maria Albin, a reader at Lund University and head of the research project.
In order to obtain a representative measurement of exposure over a long period of time, the researchers analysed levels of amines that had bound to haemoglobin in the red blood cells (known as adducts). They have a life-span of four months and show the level of amines the subject has been exposed to over the past four months.
“We found low levels of adducts, 0–0.2 nanograms per gram of haemoglobin, but we found measureable levels of ortho-toluidine in around half of the hairdressers, consumers and control subjects”, said Gabriella Johansson, a doctoral student at Lund University and first author of the study.
Among the hairdressers, the researchers observed that levels of ortho-toluidine increased with the number of treatments they performed using light hair dye and perming products. Levels of another amine, meta-toluidine, increased with the number of customers dyed with both light and dark dye, but not enough is known to say whether meta-toluidine can also cause cancer. For the other amines, the researchers found no link with treatments carried out.
“Our results suggest that hairdressers are exposed to ortho- and meta-toluidine from hair dyes and perming chemicals. Ortho-toluidine has been shown to cause cancer in humans and laboratory animals. Our view is therefore that this exposure must be eliminated if possible”, said Maria Albin.
Practical advice to hairdressers:
- Aromatic amines are absorbed into the blood through the skin. It is important to protect your skin to prevent contact with chemicals and water, in order to avoid the risk of eczema and allergies. Gloves used correctly also protect against the absorption of chemicals into the blood through the skin.
- We recommend using non-powdered disposable PVC gloves, because rubber gloves can produce problems with allergies. The gloves should be changed often and disposed of after use. This means that you should throw them away when you remove them after applying hair dye and that you should put on new gloves to rinse the hair afterwards.
- Newly dyed hair contains excess dye even after it has been rinsed, so it should be cut while wearing gloves. Many people find this difficult, in which case it is better to cut the hair before dyeing it.
Where is ortho-toluidine found? How dangerous is it?
- Occupational exposure to ortho-toluidine has been seen in the rubber industry and in the production of colouring pigment. It can also occur in laboratory work and has been found in wastewater. There is ortho-toluidine in cigarette smoke (10–100 nanograms/cigarette) and in certain local anaesthetics. A previous study in Turkey (2008) found varying levels of ortho-toluidine in 34 of 54 hair dyes tested.
- Studies of workers who manufacture colouring pigment have shown that exposure to ortho-toluidine can cause bladder cancer. Their levels of exposure were very high. There have been no previous studies measuring hairdressers’ exposure to ortho-toluidine. A comparison of ortho-toluidine exposure in smokers and non-smokers in Italy showed higher levels in both groups than were found in the present study on hairdressers. It may be the case that today’s levels in Sweden are lower, but differences in measurement methods could also be a factor.
- The researchers’ overall judgement is that even if the levels are low and therefore should not produce a significant risk, the exposure to ortho-toluidine that has been identified is undesirable because this is a substance that is carcinogenic. Exposure to such substances should be kept as low as possible. It is therefore important to try and find the source of the exposure. It is important to see whether it is present in hair dyes and perming products in Sweden so that possible measures can be discussed. In the meantime, what individual hairdressers can do is to protect themselves against absorption of dyes and other chemicals through the skin.
The study was made possible through a research grant from FORTE, the Swedish Research Council for Health, Working Life and Welfare.