Only a carcinogen in some countries
Substances that are likely to be injurious to health are often assessed quite differently in different countries. This has been demonstrated in a study from a researcher at KTH. Eighteen countries and 1300 subjects were studied, and a substance may be considered a carcinogen in one country and 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.
She points to another example - halothane - where values are also markedly different. Halothane is an anaesthetic used for general anaesthesia purposes; an American organization consisting of occupational hygienists (named ACGIH) has set a limit value of 50 ppm. In Sweden the limit value is 5 ppm while Australia only allows 0.5 ppm. 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 kind of glue. This glue is used in the construction industry and the electronics industry. In Sweden the allowed limit is 10 ppm, the previously mentioned American organization has set the limit at 0.1 ppm.
"Phenyl glycidyl ether is irritating to mucous membranes and can cause contact allergies. "Many organizations, including the International Agency for Research on Cancer, IARC has also determined that phenyl glycidyl ether is probably carcinogenic to humans," says Linda 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 thirty years old and based on knowledge from that time. But 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 Linda Schenk.
She adds that the limits should be consistent and equitable, it is a question of ethics.
For more information, contact Linda Schenk at 070-746 67 77 or schenk@kthse
Peter Larsson