Effects of seasonal change on aryl hydrocarbon hydroxylase activity in human lymphocytes in a Japanese population

Although much effort has been made to determine the relationship between aryl hydrocarbon hydroxylase (AHH) activity and susceptibility to lung cancer, the results have not been very consistent. We examined the effects of seasonal changes on the AHH activity of lymphocytes in healthy male adults (n = 239). The subjects completed a short questionnaire on their current lifestyle characteristics. This included the frequency of some selected dietary and environmental factors, the number of cigarettes smoked per day, the heating system and ventilation in their home, and their residential area. When the subjects were divided into four seasons according to the date of blood collection, a significant seasonal variation emerged in non-induced and 3-methylcholanthrene (MC)-induced AHH activities, which were adjusted for age and some environmental factors. Both non-induced and MC-induced AHH activities were highest in summer and lowest in winter. AHH inducibility (MC-induced/non-induced AHH activity) was relatively stable. Since seasonal change may affect AHH activity, it should be considered, alongside age and environmental factors, in epidemiological studies on the association between AHH activity in human lymphocytes and lung cancer.