The Federal Institute for Risk Assessment says more studies are needed on styrene, a substance commonly used to produce food packaging and other materials.
The findings could have implications for plant workers who are involved in making packaging and other products that use styrene.
Enzyme not present in the lungs
Styrene is a liquid which is mainly used in the production of plastics. The German government's Federal Institute for Risk Assessment (BfR) yesterday said its research into the risks posed by the substance indicate that a human enzyme found in the lung could convert styrene to styrene oxide, which is known to be tumorigenic, or a cancer-causing agent.
"Studies on styrene by the manufacturing industry had indicated that this enzyme is not present in the human lung," the BfR stated. "The results of a research project conducted by BfR and the Emil von Behring Clinic in Heckeshorn in a large number of human lung samples now indicate the contrary: both enzymes can be detected in the human lung."
The BfR notes that the question whether the enzymes occur at a level which is sufficient for the formation of tumours cannot be definitively answered on the basis of the available data, indicating that more research needs to be done to come to a conclusion.
"The new findings could be relevant particularly for people involved in production processes in which styrene is used as the basic chemical," the BfR stated.
Paul-Michael Bever, a spokesperson for PlasticsEurope, said industry was "surprised" by the BfR statement as an ongoing EU-level risk assessment of the chemical had found any cancer-causing effects in animal studies "not relevant to humans at relevant levels of exposure".
Bever, who is the industry association's expert spokesperson on styrene, told FoodProductionDaily.com that PlasticsEurope would be issuing a statement on the BfR research later today.
The European Chemicals Bureau, an EU agency, is currently completing a risk assessment of styrene, which Bever said the industry supports.
So far, the working group overseeing the risk assessment has maintained that styrene should not be reclassified as a potential cancer-causing agent.
The group did conclude that styrene can cause respiratory tract irritation, and has proposed an amendment to reflect the finding.
Tumours in mice
The BfR study notes that previous research into styrene has found that after inhalation of styrene, tumours form in the lungs of mice. The substance styrene oxid is formed in the cells of the lung tissue under the influence of specific enzymes. Up to now, these enzymes have not been detected in rats, nor has styrene oxide or the tumours described in mice, the BfR stated.
"So far, it has been assumed that the enzymes required for the conversion of styrene to styrene oxide are not present in humans either or are not present in sufficient amounts to permit the formation of tumours," the BfR stated in a press release. "Results from experimental research at the Federal Institute for Risk Assessment (BfR) seem to indicate that this assumption may be wrong."
BfR claims its scientists have succeeded in detecting the enzymes involved in styrene conversion in human lung tissue, which have an effect comparable to that of the mouse.
"The tumorigenic styrene oxide could, therefore, also be formed in the human lung," the agency stated.
Metabolites the real danger
The chemical itself may not necessarily be toxic, the BfR noted. Its metabolites - substances formed during the conversion of the chemical in the body - may also trigger toxic effects, the agency suggests.
The BfR said its research was into the findings about why styrene leads to lung tumours in mice but not in rats and which of the effects should be taken as the basis for the assessment of the risk to consumers.
One major contributory factor to tumorigenic action in mice is the conversion of styrene to the toxicologically active degradation product styrene oxid in the lung. This is done with the help of two enzymes.
"The occurrence of the two enzymes responsible for the conversion of styrene to styrene oxid is an indication that a tumorigenic effect is also possible in humans," the BfR stated. - (Decision News Media, September 2006)