Measurement of human CYP1A2 induction by inhalation exposure to benzo(a)pyrene based on in vivo isotope breath method

Cytochrome P450 1A2 (CYP1A2) is an enzyme involved in the metabolic activation of certain carcinogens, and inducible by toxic substrates. To date, few studies have investigated in vivo CYP1A2 induction in humans and its relationship to polycylic aromatic hydrocarbons (PAHs) like benzo(a)pyrene (BaP). Non-smoking healthy male coke-oven workers (n = 30) were recruited as 'exposure' group, and non-smoking healthy office workers in the same city (n = 10) were selected as 'control' group, to test whether high inhalation exposure to PAHs can induce CYP1A2 activity in human livers. Significantly higher inhalation exposure of PAHs were found among the exposure group compared to the control. Inhalation BaP exposure concentration in the exposure group was more than 30 times higher than the control group (p < 0.001). However, the exposure group did not exhale significant higher levels of 13CO2/12CO2 in breath samples (p = 0.81), and no significant relationship was found between the inhaled BaP concentration and the 13CO2/12CO2 ratio (p = 0.91). A significant association was found between the 13CO2/12CO2 exhalation and dietary BaP intake level. Hepatic CYP1A2 activity/induction level was not effected by inhaled BaP but was altered by ingestion of BaP.