A historical cohort study was carried out in an agricultural research institute in the Republic of Ireland to investigate a perceived excess of cancer deaths among employees. The objectives of the study were (a) to confirm whether or not total or cause specific death rates among selected employees were higher than expected based on national figures, and to quantify any excess, and (b) to identify centres and employee grades associated with any excess risk. The cohort comprised all administrative, research, and technical staff employed for at least two years between 1960 and 1980, giving a final total for analysis of 1323 employees.Employment history was categorised by place of work and employment grade. Deaths among the cohort were identified and causes of deaths verified. Overall the cohort had a lower than expected mortality compared with national rates (OlE = 0.67). Female deaths were too few for analysis but, among the male employees, there was an excess of all cancers (OlE = 1-24; 95% confidence interval (95% CI) 0.8-1.9), in particular brain cancer (OlE = 4-69; 95% CI 1.2-11-4) and bladder cancer (OlE = 9-31, 95% CI 1-9-27-2). The pattern of brain tumour deaths was consistent with an occupational aetiology but it was not possible to identify specific exposures associated with the excess. All four cases occurred among research workers in the plant and soil science area. The pattern of bladder cancers was difficult to interpret. The authors are at present participating in a multicentre study to further investigate cancer risk in laboratory workers.

K. (1975One of the most consistent observations in studies of breast cancer in women has been the association between high parity and a reduced risk of developing the disease, and the interpretation of this epidemiological characteristic has been that pregnancy or a concomitant of pregnancy affords protection against breast cancer, and that the amount of protection is related to the total number of pregnancies. A recent collaborative international study has further elucidated the nature of the protective effect of pregnancy (Salber, Trichopoulos, and MacMahon, 1969;Valaoras et al., 1969;Lowe and MacMahon, 1970;MacMahon et al., 1970b;Yuasa and MacMahon, 1970). Analyses of data from all centres included in the study have shown a decreased risk of breast cancer strongly associated with age at first pregnancy. The association with high parity appears to reflect only an early start to childbearing, those women who had early first pregnancies tended ultimately to have large families. Since no study of the epidemiological features of breast cancer in the Republic of Ireland had previously been done, and in the light of the unusual demographic characteristics of late marriage and late first pregnancies associated with high fertility rates, this study was carried out in 1972-73. METHODAltogether 100 breast cancer cases selected randomly from the outpatient register of St Luke's Hospital, Dublin, were compared with a presenting sample of 200 controls attending the fracture clinics of St Vincent's and the Mater Misericordiae hospitals in Dublin during the same period. Breast cancer patients aged under 35 years were matched with controls who were within two years of the same age, and where cases were over 35 years of age controls were required to be over 35 years, but age-matching was not considered necessary. Cases and controls were interviewed by one of us (BH) and a precoded questionnaire was used to obtain detailed information of marital, reproductive, and family history, history of previous illness, and smoking habits. The height of cases and controls was measured and controls were examined to exclude the possibility of their having breast cancer. RESULTS AGE AND SOCIOECONOMIC STATUSAlthough age-matching of controls was carried out only for breast cancer patients who were aged under 35 years, the overall age distributions of cases and controls were similar, the mean age of both groups being 57'3 years. There were no significant differences in socioeconomic status as measured by mean duration of schooling (cases 10 3 years; controls 10 5 years; P=0-34), by father's occupation (P>010), and by husband's occupation (P>0 10) in the case of the evermarried women.