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Many materials in contact with food, including printing inks, the lack of deeper knowledge about possible toxic effects is a problem. Furthermore, some of these substances are not only produced for packaging of foods, they are produced for a variety of purposes and are not meant to come into direct contact with foodstuffs. Two examples on such chemicals in printing inks are benzophenone and 4-methylbenzophenone. Recently, authorities reported that high levels of the photoinitiator 4-methylbenzophenone had been detected in cereal products. Based on this information we have studied 4-methylbenzophenone and the chemically similar benzophenone using the micronucleus assay in vivo and in vitro. To increase the sensitivity we have used the in vivo flow cytomer-based micronucleus assay in mouse. Although doses up to lethality were used and an average of hundred thousand young erythrocytes, polychromatic erythrocytes, analysed from each animal, no genotoxic effect occurred. The 4-methylbenzophenone was also analysed in the in vitro micronucleus assay, using human lymphocytes. The result does not show any dose-related effect. These results show that the occurrence of 4-methylbenzophenone that so far has been detected in foodstuff does not increase the cancer risk through chromosome breaks or mal-distribution of chromosomes.

Furan, a potential human carcinogen, is formed during heat-treatment of food. Previous studies of the genotoxicity of furan have given disparate results. Hence, there is a need for complementary data to clarify the mechanism behind the carcinogenicity of furan. In this study, we have used the flow cytometer-based micronucleus assay in mice and the cytokinesis-block micronucleus assay in human lymphocytes to investigate the genotoxic potential of furan. Three in vivo experiments were performed: intraperitoneal or subcutaneous injection of furan in male Balb/C mice (0-300 and 0-275 mg/kg body weight, respectively) and intraperitoneal injection of male CBA mice (0 and 225 mg/kg body weight). No increased level of micronucleated erythrocytes was detected in any of the in vivo experiments. In the in vitro setup, human lymphocytes from two donors were treated with furan in concentrations from 0 to 100 mM, either with or without metabolic activation (liver homogenate from rat). In parity with the in vivo results there was no significant increase in the frequency of micronucleated cells here either. As neither the in vivo nor the in vitro studies disclose any significant increase in the micronucleus frequency after treatment with furan, our results support that the carcinogenicity of furan is caused by a non-genotoxic mechanism.