Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, S.A.S. Nagar, Manauli PO, Punjab 140306, India.
Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, S.A.S. Nagar, Manauli PO, Punjab 140306, India.
Environ Int. 2016 Mar;88:187-197. doi: 10.1016/j.envint.2015.12.025. Epub 2016 Jan 4.
In the north west Indo-Gangetic Plain (N.W.IGP), large scale post-harvest paddy residue fires occur every year during the months of October-November. This anthropogenic perturbation causes contamination of the atmospheric environment with adverse impacts on regional air quality posing health risks for the population exposed to high concentrations of carcinogens such as benzene and toxic VOCs such as isocyanic acid. These gases and carbon monoxide are known to be emitted from biomass fires along with acetonitrile. Yet no long-term in-situ measurements quantifying the impact of this activity have been carried out in the N.W. IGP. Using high quality continuous online in-situ measurements of these gases at a strategic downwind site over a three year period from 2012 to 2014, we demonstrate the strong impact of this anthropogenic emission activity on ambient concentrations of these gases. In contrast to the pre-paddy harvest period, excellent correlation of benzenoids, isocyanic acid and CO with acetonitrile (a biomass burning chemical tracer); (r≥0.82) and distinct VOC/acetonitrile emission ratios were observed for the post-paddy harvest period which was also characterized by high ambient concentrations of these species. The average concentrations of acetonitrile (1.62±0.18ppb), benzene (2.51±0.28ppb), toluene (3.72±0.41ppb), C8-aromatics (2.88±0.30ppb), C9-aromatics (1.55±0.19ppb) and CO (552±113ppb) in the post-paddy harvest periods were about 1.5 times higher than the annual average concentrations. For isocyanic acid, a compound with both primary and secondary sources, the concentration in the post-paddy harvest period was 0.97±0.17ppb. The annual average concentrations of benzene, a class A carcinogen, exceeded the annual exposure limit of 1.6ppb at NTP mandated by the National Ambient Air Quality Standard of India (NAAQS). We show that mitigating the post-harvest paddy residue fires can lower the annual average concentration of benzene and ensure compliance with the NAAQS. Calculations of excessive lifetime cancer risk due to benzene amount to 25 and 10 per million inhabitants for children and adults, respectively, exceeding the USEPA threshold of 1 per million inhabitants. Annual exposure to isocyanic acid was close to 1ppb, the concentration considered to be sufficient to enhance risks for cardiovascular diseases and cataracts. This study makes a case for urgent mitigation of post-harvest paddy residue fires as the unknown synergistic effect of multi-pollutant exposure due to emissions from this anthropogenic source may be posing grave health risks to the population of the N.W. IGP.
在印度西北部恒河平原（NWIGP），每年 10 月至 11 月，都会发生大规模的水稻收获后残茬火灾。这种人为干扰导致大气环境受到污染，对区域空气质量造成不利影响，使暴露于高浓度致癌物（如苯）和有毒 VOC（如异氰酸）的人群面临健康风险。这些气体和一氧化碳已知是从生物质火灾中与乙腈一起排放的。然而，在 NWIGP 还没有进行过长期的现场测量来量化这种活动的影响。在 2012 年至 2014 年的三年期间，我们在一个战略性的下风地点使用高质量的连续在线现场测量，证明了这种人为排放活动对这些气体环境浓度的强烈影响。与收获前相比，苯类、异氰酸和 CO 与乙腈（生物质燃烧化学示踪剂）具有极好的相关性（r≥0.82），并且在后收获期还观察到了明显的 VOC/乙腈排放比，后收获期这些物质的环境浓度也很高。乙腈（1.62±0.18ppb）、苯（2.51±0.28ppb）、甲苯（3.72±0.41ppb）、C8-芳烃（2.88±0.30ppb）、C9-芳烃（1.55±0.19ppb）和 CO（552±113ppb）的平均浓度在后收获期约为每年平均浓度的 1.5 倍。对于异氰酸，这是一种具有主要和次要来源的化合物，在后收获期的浓度为 0.97±0.17ppb。作为一种 A 类致癌物，苯的年平均浓度超过了印度国家空气质量标准（NAAQS）规定的国家有毒物质和疾病登记署（NTP）每年 1.6ppb 的暴露限值。我们表明，减轻收获后水稻残茬火灾可以降低苯的年平均浓度，并确保符合 NAAQS。由于苯导致的终生癌症风险过高，儿童和成年人分别达到 25 和 10 每百万居民，超过了美国环保署规定的每百万居民 1 的阈值。异氰酸的年暴露量接近 1ppb，这一浓度被认为足以增加心血管疾病和白内障的风险。这项研究表明，迫切需要减轻收获后水稻残茬火灾，因为这种人为排放源排放的多种污染物的未知协同效应可能对 NWIGP 地区的人口造成严重的健康风险。
