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aberration was 8.5%. Chromatid breaks were the predominant type ofaberration and represented 61.2% of all breaks. Chromosome breaks,dicentric chromosomes and acentric fragments were also present. Theresults of the micronucleus and chromosome aberration assays werecomparable. Increasing numbers of micronuclei per binucleated cell andincreased numbers of cells with more than one micronucleus were followedby a higher percentage of chromosome aberrations or more severechromosomal damages. Sister chromatid exchange frequencies were alsoincreased, with a mean group value of 9.2 per cell. Individual range ofsister chromatid exchange frequencies was 4 to 27 per cell. [Fucic A etal; Mutation Research 242 (4): 265-70 (1990)]**PEER REVIEWED**The methods and results of a collaborative study, coordinated by theInternational Agency for Research on Cancer and conducted in many researchcenters in Europe, were examined. The study examined the cancer incidenceand mortality among vinyl chloride workers. A total of 14,351 subjectswere contributed to the combined data base. The results indicated thatvinyl chloride is associated with an increase in liver cancer incidence.An exposure response relationship was noted for both ranked and estimatedcumulative exposure. The relationship was even more evident when onlyliver angiosarcoma was analyzed. No significant excess of mortality wasobserved for the other sites suspected a-priori to be affected by vinylchloride exposure. While the incidence of lung cancer was slightlyincreased, neither it nor lung cancer mortality appeared to be associatedwith any of the exposure variables. Brain cancer and lymphosarcomamortality, while demonstrating slight increases, did not appear to beconsistently associated with exposure, although the small numbersprohibited firm conclusions. An increased risk of bladder cancer andmelanoma of the skin was detected which did not appear to be related toexposure in that the association with employment in the vinyl chlorideindustry was confined to one country only. No increased mortality wasobserved for the other main causes of death. [Simonato L et al;Scandinavian Journal of Work, Environment and Health 17 (3): 159-69(1991)]**PEER REVIEWED**Sister chromatid exchanges and micronuclei frequency in workers exposed tovinyl chloride monomer were measured to determine which of the twoendpoints was the most selective in this occupational setting. Bloodsamples were obtained from 93 human males, all of whom were nonsmokers.The occupationally exposed group, 52 workers, was divided into twosubgroups based on workplace and the vinyl chloride monomer concentrationin the air during the 4 weeks prior to sampling. One subgroup, exposed toconcentrations of 1.3 to 16.69 ppm, consisted of 31 workers aged 24 to 54yr at a manufacturing facility. The other subgroup contained 21 workerswho were exposed to concentrations of 0.3 to 7.3 ppm on the polymerizationcontrol lines. The comparison group included 41 unexposed men. Both sisterchromatid exchange and micronuclei were increased among exposed workers.The sister chromatid exchanges frequency was increased 61.8% abovecomparisons. It was possible to discriminate between the high exposure andlow exposure subgroups using sister chromatid exchanges. A significantincrease in micronuclei frequency was seen in the exposed group; there wasa significant difference between the high exposure and low exposuresubgroups, but not between the comparison group and the low exposuresubgroup. Sister chromatid exchange was the more sensitive endpoint forindicating a biological response. However, the authors point out thatmethods for restricting the micromuclei analysis to only cells at riskwere not used. [Sinues B et al; Toxicology and Applied Pharmacology 108