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OBJECTIVE--To investigate the association between bird keeping and risk of lung cancer. DESIGN--Case-control study asking detailed questions on exposure to domestic birds and other pets, smoking, and various demographic and potentially confounding variables. SETTING--District general hospital; current admissions interviewed in hospital or recent admissions interviewed at home. PATIENTS--143 patients with lung cancer, 143 controls with heart disease, and 143 controls with orthopaedic conditions individually matched for age, sex, date of admission, and current or past admission. MAIN OUTCOME MEASURES--Odds ratios for lung cancer in relation to various aspects of bird keeping, after adjustment for smoking and other relevant confounding variables. RESULTS--Risk of lung cancer was not significantly associated with household exposure to pet birds at any time or at various specific periods in life, or to keeping large numbers of birds. For specific types of birds no association was seen for living in households with budgerigars or canaries but risk was significantly associated with keeping pigeons (odds ratio 3.53, 95% confidence interval 1.56 to 7.98). This remained significant after regression analysis to account for confounding variables (3.9, 1.2 to 12.62) in both sexes and all age groups. CONCLUSION--Bird keeping may confer some risk of lung cancer but the relation is not as strong as previously reported.

Because short-term bacterial tests have previously shown that about one-third of substituted anthraquinones tested are capable of causing reverse mutation, and two-year feeding studies of three such dyestuffs in rats have shown an excess of hepatocellular carcinomas, a retrospective cohort mortality study was carried out on a population of 1975 male workers employed in a dyestuffs manufacturing plant in Scotland. The population was identified as having worked for more than six months within the factory during the decade 1 January 1956-31 December 1965, and their mortality experience was followed up to 30 June 1980. Age-standardised mortality rates did not show any excess in total or cancer-related mortality.