a Gradient , Cambridge , MA , USA.
b Gradient , Seattle , WA , USA.
Crit Rev Toxicol. 2018 Oct;48(9):713-737. doi: 10.1080/10408444.2018.1528208. Epub 2018 Dec 27.
The International Agency for Research on Cancer recently classified straight-run bitumens and associated emissions during road paving as possibly carcinogenic to humans (Group 2B), owing to potential exposures to polycyclic aromatic hydrocarbons. We examine existing chemistry, exposure, epidemiology, and animal toxicity data to explore quantitative cancer risk implications for paving workers exposed to asphalt emissions from the data used in identifying this qualitative hazard. Epidemiology studies show no consistent cancer risk elevation. One skin-painting mouse study of paving asphalt emission condensate found a single tumor at only the highest tested dose, as did one rat inhalation study. These studies were used to develop an upper bound on possible carcinogenic potency of emissions that are inhaled or dermally deposited. Extending earlier work on roofing asphalt, we conducted time-to-tumor modeling using the dose-time-response shape for several dose levels of benzo[a]pyrene (B[a]P) in concurrent bioassay controls to infer presumed parallel dose-time-response curves for paving-asphalt-emission condensate. In addition, we developed a scientific rationale, based on general scaling considerations and on dermal uptake, for the chosen means to scale observed dermal cancer potencies in mice to apply to dermal exposures in humans. The results indicate that paving asphalt emissions have a reduced dermal cancer potency compared to roofing asphalt, consistent with the lower levels of the multi-ringed PAHs implicated in cancer risks. Based on existing occupational exposure studies, cancer risks to pavers from both dermal and inhalation exposure to asphalt emissions is within a range typically acceptable within regulatory frameworks.
国际癌症研究机构最近将直馏沥青和道路铺设过程中的相关排放物归类为可能对人类致癌（2B 组），这是由于潜在的多环芳烃暴露。我们检查了现有的化学、暴露、流行病学和动物毒性数据，以探讨用于识别这种定性危害的数据中接触沥青排放物的铺路工人的定量癌症风险影响。流行病学研究没有显示出一致的癌症风险升高。一项关于铺路沥青排放冷凝物的皮肤涂抹小鼠研究发现，只有在最高测试剂量下才出现了一个肿瘤，一项大鼠吸入研究也是如此。这些研究被用于开发吸入或皮肤沉积排放物的潜在致癌效力的上限。我们扩展了先前对屋顶沥青的研究，使用苯并[a]芘（B[a]P）在同时进行的生物测定对照中的几个剂量水平的剂量-时间-反应形状进行了肿瘤发生时间建模，以推断假定的平行剂量-时间-反应曲线用于铺路沥青排放冷凝物。此外，我们基于一般比例考虑和皮肤吸收，为选择的方法开发了一个科学依据，将观察到的小鼠皮肤癌效力比例应用于人类的皮肤暴露。结果表明，与屋顶沥青相比，铺路沥青排放物的皮肤癌效力降低，这与癌症风险中涉及的多环芳烃的低水平一致。基于现有的职业暴露研究，从皮肤和吸入沥青排放物暴露两个方面来看，铺路工人的癌症风险在监管框架内通常可接受的范围内。
