Cancer Risk Assessment of Airborne PAHs Based on <i>in Vitro</i> Mixture Potency Factors

Complex mixtures of polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants associated with adverse human health effects including cancer. However, the risk of exposure to mixtures is difficult to estimate, and risk assessment by whole mixture potency evaluations has been suggested. To facilitate this, reliable <i>in vitro</i> based testing systems are necessary. Here, we investigated if activation of DNA damage signaling <i>in vitro</i> could be an endpoint for developing whole mixture potency factors (MPFs) for airborne PAHs. Activation of DNA damage signaling was assessed by phosphorylation of Chk1 and H2AX using Western blotting. To validate the <i>in vitro</i> approach, potency factors were determined for seven individual PAHs which were in very good agreement with established potency factors based on cancer data <i>in vivo.</i> Applying the method using Stockholm air PAH samples indicated MPFs with orders of magnitude higher carcinogenic potency than predicted by established <i>in vivo</i>-based potency factors. Applying the MPFs in cancer risk assessment suggested that 45.4 (6% of all) cancer cases per year in Stockholm are due to airborne PAHs. Applying established models resulted in <1 cancer case per year, which is far from expected levels. We conclude that our <i>in vitro</i> based approach for establishing MPFs could be a novel method to assess whole mixture samples of airborne PAHs to improve health risk assessment

Detection of Benz[<i>j</i>]aceanthrylene in Urban Air and Evaluation of Its Genotoxic Potential

Benz­[<i>j</i>]­aceanthrylene (B­[<i>j</i>]­A) is a cyclopenta-fused polycyclic aromatic hydrocarbon with strong mutagenic and carcinogenic effects. We have identified B­[<i>j</i>]­A in air particulate matter (PM) in samples collected in Stockholm, Sweden and in Limeira, Brazil using LC–GC/MS analysis. Determined concentrations ranged between 1.57 and 12.7 and 19.6–30.2 pg/m³ in Stockholm and Limeira, respectively, which was 11–30 times less than benzo­[<i>a</i>]­pyrene (B­[<i>a</i>]­P) concentrations. Activation of the DNA damage response was evaluated after exposure to B­[<i>j</i>]­A in HepG2 cells in comparison to B­[<i>a</i>]­P. We found that significantly lower concentrations of B­[<i>j</i>]­A were needed for an effect on cell viability compared to B­[<i>a</i>]­P, and equimolar exposure resulted in significant more DNA damage with B­[<i>j</i>]­A. Additionally, levels of γH2AX, pChk1, p53, pp53, and p21 proteins were higher in response to B­[<i>j</i>]­A than B­[<i>a</i>]­P. On the basis of dose response induction of pChk1 and γH2AX, B­[<i>j</i>]­A potency was 12.5- and 33.3-fold higher than B­[<i>a</i>]­P, respectively. Although B­[<i>j</i>]­A levels in air were low, including B­[<i>j</i>]­A in the estimation of excess lifetime cancer risk increased the risk up to 2-fold depending on which potency factor for B­[<i>j</i>]­A was applied. Together, our results show that B­[<i>j</i>]­A could be an important contributor to the cancer risk of air PM