Only a carcinogen in some countries

Linda Schenk, researcher at KTH.

Eighteen countries and 1300 subjects were studied, and it was found that while a substance may be considered a carcinogen in one country, it might be considered merely an annoyance in another.

One example is the substance paradichlorobenzene, (used in devices such as air and toilet fresheners in Europe) which has been classified as a carcinogen in some places but not others.
"What is surprising is that the differences are so great from one country to the next," says Linda Schenk, researcher and PhD student at KTH.

Massive difference

She points to another example - halothane - where values are also markedly different. Halothane is an anaesthetic used for general anaesthesia purposes; an American organisation consisting of occupational hygienists (named ACGIH) has set a limit value of 50ppm. In Sweden the limit value is 5ppm while Australia only allows 0.5ppm. There is a difference by a factor of 100, which is a lot.

"The higher threshold for halothane is directed at industry, other limit values for the same substance are directed at hospital staff. " Are those who work in the industry more resistant than nurses and doctors?" questions Linda Schenk.
Some of the substances Linda Schenk has studied are not used in Sweden, but one of those that is used is phenyl glycidyl ether which is used to dilute epoxy resin, a glue used in the construction industry and the electronics industry. In Sweden the allowed limit is 10ppm, the previously mentioned American organisation has set the limit at 0.1ppm.

Limits rarely updated

"Phenyl glycidyl ether is irritating to mucous membranes and can cause contact allergies. " Many organisations, including the International Agency for Research on Cancer, IARC has also determined that phenyl glycidyl ether is probably carcinogenic to humans," says Schenk.

Altogether there are about 14 different substances in which limit values differ by a factor of 100. Linda Schenks has a theory as to why this happens.

"An important factor is that the limits are rarely updated, several of the high limit values in this study were more than 30 years old and based on knowledge from that time. However, another important factor is that there are differences between different groups of experts as to which parts of available research material about a substance is taken into account. "What is required for greater consensus is a process that is transparent and systematic, where it states the grounds upon which the expert groups set limits," says Schenk.

She adds that the limits should be consistent and equitable, it is a question of ethics.

Source: KTH - Royal Institute of Technology