The toxicity associated with the fine particulate matter (PM_2.5) has not been well studied, particularly in relation to the emissions from on-road vehicles and other sources in low- and middle-income countries such as India. Thus, a study was conducted to examine the oxidative potential (OP) of PM_2.5 at a roadside (RS) site with heavy vehicular traffic and an urban background (BG) site in Mumbai using the dithiothreitol (DTT) assay. Simultaneous gravimetric PM_2.5 was measured at both sites and characterized for carbonaceous constituents and water-soluble trace elements and metals. Results depicted higher PM_2.5, elemental carbon (EC), and organic carbon (OC) concentrations on the RS than BG (by a factor of 1.7, 4.6, and 1.2, respectively), while BG had higher water-soluble organic carbon (WSOC) levels (by a factor of 1.4) and a higher WSOC to OC ratio (86%), likely due to the dominance of secondary aerosol formation. In contrast, the measured OP^DTTv at RS (8.9 ± 5.5 nmol/min^/m³) and BG (8.1 ± 6.4 nmol/min/m³) sites were similar. However, OP^DTTv at BG was higher during the afternoon, suggesting the influence of photochemical transformation on measured OP^DTTv at BG. At RS, OC and redox-active metals (Cu, Zn, Mn, and Fe) were significantly associated with measured OP (p < 0.05), while at BG, WSOC was most strongly associated (p < 0.05). The coefficient of divergence (COD) for PM_2.5, its chemical species, and OP^DTTv was >0.2, indicating spatial heterogeneity between the sites, and differences in emission sources and toxicity. The estimated hazard index (HI) was not associated with OP^DTTv, indicating that current PM_2.5 mass regulations may not adequately capture the health effects of PM_2.5. The study highlights the need for further studies examining PM_2.5 toxicity and developing toxicity-based air quality regulations.

与细颗粒​​物 (PM _2.5 ) 相关的毒性尚未得到充分研究，特别是与印度等低收入和中等收入国家的道路车辆和其他来源的排放相关的研究。因此，我们进行了一项研究，使用二硫苏糖醇 (DTT) 测定法检测孟买交通繁忙的路边 (RS) 地点和城市背景 (BG) 地点的PM _{2.5氧化电位 (OP)。}在两个地点同时测量了 PM _2.5重量，并表征了碳质成分以及水溶性微量元素和金属。结果显示，RS 上的 PM _2.5、元素碳 (EC) 和有机碳 (OC) 浓度高于 BG（分别为 1.7、4.6 和 1.2 倍），而 BG 的水溶性有机碳 (WSOC) 更高）水平（1.4 倍）和较高的 WSOC 与 OC 比率（86%），可能是由于二次气溶胶形成占主导地位。相反，在RS（8.9±5.5nmol/min ^/ m ³）和BG（8.1±6.4nmol/min/m ^{3 ）位点测量的OP DTTv}相似。然而，下午 BG 的OP ^DTTv较高，表明光化学转化对BG测量的 OP ^{DTTv的影响。}在 RS 中，OC 和氧化还原活性金属（Cu、Zn、Mn 和 Fe）与测量的 OP 显着相关（p < 0.05），而在 BG 中，WSOC 的相关性最强（p < 0.05）。_{PM 2.5}、其化学物质和 OP ^DTTv的发散系数 (COD) >0.2，表明站点之间的空间异质性以及排放源和毒性的差异。^{估计的危害指数 (HI) 与 OP DTTv}无关，表明当前的 PM _{2.5质量法规可能无法充分捕捉 PM 2.5}的健康影响。该研究强调需要进一步研究 PM _2.5毒性并制定基于毒性的空气质量法规。