ABsTRAcr A spillage of about 1200 gallons of benzene occurred during the loading of a ship, and 10 workers on a single shift were exposed to benzene. Shortly afterwards, an assay of the urine of these individuals showed that substantial amounts of phenol were being excreted. About three months after the incident samples of venous blood were taken from 10 individuals exposed to benzene and 11 men on a comparable shift who acted as controls. The lymphocytes were stimulated to divide in short term cultures. For each subject, 200 cells at metaphase were examined for chromosome damage using 48 h cultures, and sister chromatid exchanges (SCE) were analysed from about 30 cells in their second division, using 72 h cultures. The most frequent types of aberrations in all the individuals were chromatid gaps, with occasional breaks of chromatids and chromosomes. There were few exchanges within or between the arms of chromatids or chromosomes. More cells in the control than in the exposed group showed damage, an effect that was especially noticeable for chromatid gaps. All values, however, were considered to be within a normal range. There were slightly more SCE in some of the exposed individuals than in the controls and there was a trend towards a positive association between the frequency of SCE recorded for each individual and the maximum value for the excretion of phenol in the urine on the day after the incident. There is no evidence to indicate that benzene induced any type of lasting chromosome damage in the lymphocytes of the 10 exposed workers when cells were examined about three months after the incident.People exposed to benzene may be at an increased risk of developing leukaemia, pancytopaenia, and chromosomal aberrations compared with people not so exposed.' Men employed in factories where benzene had been used as a solvent had significantly more chromosome aberrations in their peripheral blood lymphocytes than those working in areas where toluene had been substituted for benzene.23 In these studies exposure to benzene took place over a long period, and it is impossible accurately to estimate details of exposure in retrospect, but exposure must be assumed to have been high.At Stanlow, Cheshire, on 8 January 1981 some 1200 gallons of benzene were accidentally released into the dock and on to the surrounding berth. TheReceived 22 December 1982 Accepted 15 March 1983 amount of phenol in the urine of some of the men had been estimated the day before, or on the day of the spillage. Shortly after the incident, assays of the urine of 10 workers on a single shift who were present on the dockside showed that substantial amounts of phenol were being excreted. These results confirmed that most of these men had been exposed briefly to a high concentration of benzene.4About three months after the incident, samples of peripheral blood were collected from these men and from 11 individuals from another shift at Stanlow and forwarded to the Shell Toxicology Laboratory. The lymphocytes were stimulated to divide in tissue cul...

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