Mutagenic activity of overnight urine from healthy non-smoking subjects.

Urinary mutagenicity was evaluated in relation to environmental mutagen exposure (i.e., diet, indoor/outdoor activities, residential area etc.) on the day prior to sample collection, and also considering factors that contribute to the variability of Salmonella mutagenicity assay results. Overnight urine samples from 283 healthy non-smoking residents of northeast Italy (46% males, 20-62 years) were analyzed for mutagenicity on sensitive Salmonella typhimurium strain YG1024 with S9 mix employing the preincubation version of the plate incorporation assay (i.e., the Salmonella reverse mutation test). Urinary mutagenicity varied between 0.02 and 9.84 rev/ equiv. ml, and 7% of samples were positive (i.e., sample elicited a two-fold increase in revertants). There was an evident increase in mutagenicity in subjects with increased intake of mutagen-rich meals (n = 80) (P < 0.01 and positive urine 13% vs. 5%, P = 0.025). Indoor-exposed subjects (n = 65) also showed a higher percentage of positive urine (14% vs. 5%, P = 0.015). In particular, those subjects exposed to cooking fumes the previous evening (n = 28) revealed higher urinary mutagenicity (P = 0.035, positive urine 25% vs. 5%, P < 0.001) than non-indoor exposed. The sources of variability of the mutagenicity assay, mainly the histidine content of the urine concentrate (z = 4.06, P < 0.0001), and to a lesser extent bacterial inoculum size (z = 2.33, P = 0.019), also significantly influenced urinary mutagenicity values. In a linear multiple regression analysis, their effects were still significant (i.e., histidine content P = 0.026 and inoculum size P = 0.021), but the effects of diet, indoor exposure, and other environmental exposures (i.e., traffic and heating system exhausts, residential area) were not. It is concluded that the previous day's exposure to mutagen-rich meals and cooking fumes may influence the presence of mutagenic activity in the overnight urine of non-smoking subjects. This mutagenic activity, which remains in contact with bladder mucosa for several hours, could be considered risk factors for colorectal adenoma and possibly other cancers (i.e., bladder) in non-smokers. Accurate control of histidine content and bacterial inoculum size is strongly recommended when investigating the mutagenic activity of urine from non-smokers.

Determinants of anti-benzo[a]pyrene diol epoxide-DNA adduct formation in lymphomonocytes of the general population.

We evaluated determinants of anti-benzo[a]pyrenediolepoxide-(B[a]PDE)-DNA adduct formation (adduct induced by the ultimate carcinogenic metabolite of B[a]P) in lymphomonocytes of subjects environmentally exposed to low doses of polycyclic aromatic hydrocarbons (PAHs) (B[a]P). Our study population consisted of 585 Caucasian subjects, all municipal workers living in North-East Italy and recruited during their periodic check-ups after informed consent. PAH (B[a]P) exposure was assessed by questionnaire. Anti-B[a]PDE-DNA levels were measured by HPLC fluorescence analysis. We found that cigarette smoking (smokers (22%) versus non-smokers, p<0.0001), dietary intake of PAH-rich meals (> or =52 (38%) versus <52 times/year, p<0.0001), and outdoor exposure (> or =4 (19%) versus <4h/day; p=0.0115) significantly influenced adduct levels. Indoor exposure significantly increased the frequency of positive subjects (> or =0.5 adducts/10(8) nucleotides; chi(2) for linear trend, p=0.051). In linear multiple regression analysis the major determinants of increased DNA adduct levels (ln values) were smoking (t=6.362, p<0.0001) and diet (t=4.035, p<0.0001). In this statistical analysis, indoor and outdoor exposure like other factors of PAH exposure had no influence. In non-smokers, the influence of diet (p<0.0001) and high indoor exposure (p=0.016) on anti-B[a]PDE-DNA adduct formation became more evident, but not that of outdoor exposure, as was confirmed by linear multiple regression analysis (diet, t=3.997, p<0.0001 and high indoor exposure, t=2.522, p=0.012). This study indicates that anti-B[a]PDE-DNA adducts can be detected in the general population and are modulated by PAH (B[a]P) exposure not only with smoking - information already known from studies with limited number of subjects - but also with dietary habits and high indoor exposure. In non-smokers, these two factors are the principal determinants of DNA adduct formation. The information provided here seems to be important, since DNA adduct formation in surrogate tissue is an index of genotoxic exposure also in target organs (e.g., lung) and their increase may also be predictive of higher risk for PAH-related cancers.