The presence of PAH in breast milk collected from 32 smoking and non-smoking lactating women, residing in urban and rural areas of Tuscany (Italy) was investigated. The results indicated a significant contribution of tobacco smoke to the PAH contamination of milk: the condensate contained in the cigarettes smoked daily by each subject was strongly related with the polynuclear hydrocarbon content (R(2)=0.92, P<0.005). An experiment carried out under controlled exposure conditions to cigarette smoke allowed to demonstrate that individual metabolic activity and smoking habits affect the PAH concentration in milk samples. Mothers living in rural environments showed significantly lower PAH concentrations than those observed in urban subjects. The risk evaluation due to PAH ingestion via breast milk was assessed on the basis of the acceptable daily intake of Benzo(a)pyrene in drinking water, evidencing that a hazard cannot be excluded for heavy smokers residing in urban areas.