在洛杉矶（美国）、希腊塞萨洛尼基和意大利米兰这几个城市中，我们考察了环境中与PM有关的致癌金属和多环芳烃（PAHs）对终身癌症风险的影响。这几个城市的地中海气候相似，但在城市排放源和空气质量监管方面存在差异。其中米兰和塞萨洛尼基的样本主要受生物质燃烧活动的影响，而洛杉矶收集的颗粒物则主要受交通排放的影响。我们分析了每个地点冷季和暖季PM样本中，镉（Cd）、六价铬（Cr(VI)）、镍（Ni）、铅（Pb）和13种PAH化合物的环境PM2.5质量浓度。铅在这三个城市中的年均浓度最高，其次是镍、砷、六价铬、镉和PAHs。我们根据室外污染物的三种不同渗透情况进行了癌症风险评估。塞萨洛尼基终身吸入砷、六价铬和PAHs的风险很高，风险值分别在（0.97-1.57）× 10-6、（1.80-2.91）× 10-6和（0.77-1.25）× 10-6的范围内。米兰计算出的最高癌症风险值显著超过美国环境保护署的标准，该城市终身暴露于砷、六价铬和PAHs的风险值分别在（1.29-2.08）× 10-6、（6.08-9.82）× 10-6和（1.10-1.77）× 10-6的范围内。相比之下，洛杉矶与PAHs和金属（除了六价铬）相关的风险估计值要远低于指导值，即使假定渗透因子达到峰值。洛杉矶对砷、镉、镍、铅和PAHs的终身癌症风险值在（0.04-0.33）× 10-6之间。这一观察结果突出了洛杉矶地方空气质量措施改善空气质量和降低癌症风险的影响，相比其他两个城市。

Lifetime cancer risk characterization of ambient PM-bound carcinogenic metals and polycyclic aromatic hydrocarbons (PAHs) were examined in the cities of Los Angeles (USA), Thessaloniki (Greece) and Milan (Italy), which share similar Mediterranean climates but are different in their urban emission sources and governing air quality regulations. The samples in Milan and Thessaloniki were mostly dominated by biomass burning activities whereas the particles collected in Los Angeles were primary impacted by traffic emissions. We analyzed the ambient PM2.5 mass concentration of Cadmium (Cd), Hexavalent Chromium (Cr(VI)), Nickel (Ni), Lead (Pb), as well as 13 PAH compounds in the PM samples, collected during both cold and warm periods at each location. Pb exhibited the highest annual average concentration in all three cities, followed by Ni, As, Cr(VI), Cd and PAHs, respectively. The cancer risk assessment based on outdoor pollutants was performed based on three different scenarios, with each scenario corresponding to a different level of infiltration of outdoor pollutants into the indoor environment. Thessaloniki exhibited a high risk associated with lifetime inhalation of As, Cr(VI), and PAHs, with values in the range of (0.97-1.57) × 10-6, (1.80-2.91) × 10-6, and (0.77-1.25) × 10-6, respectively. The highest cancer risk values were calculated in Milan, exceeding the US EPA standard by a considerable margin, where the lifetime risk values of exposure to As, Cr(VI), and PAHs were in the range of (1.29-2.08) × 10-6, (6.08-9.82) × 10-6, and (1.10-1.77) × 10-6, respectively. In contrast, the estimated risks associated with PAHs and metals, except Cr(VI), in Los Angeles were extremely lower than the guideline value, even when the infiltration factor was assumed to be at peak. The lifetime cancer risk values associated with As, Cd, Ni, Pb, and PAHs in Los Angeles were in the range of (0.04-0.33) × 10-6. This observation highlights the impact of local air quality measures in improving the air quality and lowering the cancer risks in Los Angeles compared to the other two cities.