Exploring the Toxicity of Secondary Organic Aerosol formed from Atmospheric Oxidation of Pesticides

2015年全球杀虫剂(针对害虫的所有制剂，包括杀虫剂、除草剂、杀菌剂和杀菌剂)的有效成分估计为410万吨，预计到2025年将增加25%。农药主要在喷洒过程中进入大气，其次是气体到颗粒的分配、表面的伏化和风流过程。它们在大气中的命运在很大程度上取决于它们的物理化学性质，如它们对大气氧化剂的反应性，它们的蒸气压力决定了它们对颗粒的分配，以及它们潜在的显著光解率。在过去的十年中，许多实验室和田间研究表明，当前使用的农药与大气氧化剂(如羟基自由基羟基和臭氧臭氧)的反应可以产生大量的二次有机气溶胶(SOA)。农药氧化产生的SOA可能产生更持久和/或更有毒的产品，并可能额外促进对流层臭氧的产生。水样中某些农药的紫外线处理副产物的毒性增加，这是由于产生了羟基的紫外线所致。同样，农药在大气中氧化生成的SOA也可能增加其毒性负担。近年来发现，生物来源的有机化合物在大气中的氧化会由于与羟基和臭氧的反应而增加毒性负担，因此有理由预计农药氧化生成的有机氧化物会影响人类和动物的健康。我们建议结合前沿的大气模拟实验室(曼彻斯特气溶胶室，MAC)、氧化流动反应器(OFR)化学和细胞生物学的方法，从当前使用的农药(即在存在羟基和臭氧的情况下)的光氧化作用来探索有机污染物的形成和毒性。MAC和OFR可以在与大气相关的环境条件下提供受控环境，可用于模拟农药的大气氧化。农药将通过喷洒的方式引入MAC和OFR中，这一过程与作物中使用的过程类似。随后，小室的灯将被打开，启动光化学和氧化剂的产生，导致SOA的形成。MAC光源提供了与真实大气相似的光化通量谱，但强度较低，因此形成了较低的SOA质量。OFR广泛的紫外线光源可以产生高浓度的氧化剂，产生高水平的SOA质量，这是后续毒理学测试所必需的。最先进的质谱学技术将被用来对OFR和MAC产生的SOA成分进行基准测试，并监测产生的SOA的物理和化学性质。这将进一步使研究小组能够探索它们的关键特性--提供关于它们在大气中的寿命和命运的信息。OFR SOA将通过撞击在模拟细胞外液(SEF)中进行采样，并将使用等量的样本来评估其心脏毒性，使用细胞系和完整心脏的方法来评估心脏功能的关键方面和功能障碍的标志。我们建议在我们独特的设施中进行一系列跨学科实验，以探索我们是否有能力提供必要的信息，以了解当前使用的杀虫剂产生的SOA的大气命运、特性和毒性。这些信息对于向决策者、杀虫剂制造商和使用者提供制定适当准则和可持续产品的信息至关重要。项目合作伙伴Ian Mudway的参与将通过他与NIHR健康保护研究单位在农药方面的工作，通过UKHSA向政府提供一条途径。

Global usage of pesticides (all agents that target pests and including insecticides, herbicides, fungicides, and bactericides) was estimated at 4.1 million tonnes of active ingredient in 2015 and is expected to increase by 25% by 2025. Pesticides mainly enter the atmosphere during the spraying application followed by gas-to-particle partitioning, volatisation from surfaces and wind drifting processes. Their atmospheric fate is largely dependent on their physicochemical properties such as their reactivity towards atmospheric oxidants, their vapour pressure dictating their partitioning to particles as well as their potentially significant photolysis rates. Over the past decade, a number of laboratory and field studies have shown that the reaction of current-use pesticides with atmospheric oxidants (such as the hydroxyl radical, OH and ozone, O3) can yield to significant amounts of secondary organic aerosol (SOA) mass. The SOA produced from the oxidation of pesticides can yield products that are potentially more persistent and/or more toxic and can additionally contribute to tropospheric O3 production. Such an increase in the toxicity of the by-products of UV treatment of certain pesticides in water samples has been shown, effected by the UV generation of OH. Similarly, SOA formation from the atmospheric oxidation of pesticides may also increase the toxicity burden. The atmospheric oxidation of organic compounds from biogenic sources have recently found to increase to toxicity burden due to the reactions with OH and O3, and it is reasonable to expect that the SOA formed from the oxidation of the pesticides could affect human and animal health.We propose to combine cutting-edge, atmospheric simulation chamber (the Manchester Aerosol Chamber, MAC), oxidation flow reactor (OFR) chemistry and cell biology approaches to explore the SOA formation and toxicity from the photo-oxidation of current-use pesticides (i.e. in the presence of OH and O3). The MAC and OFR can provide a controlled environment under atmospherically-relevant environmental conditions that can be used to simulate the atmospheric oxidation of pesticides. Pesticides will be introduced into MAC and OFR by spraying, a process similar to that used in the crops. Subsequently, the lights of the chambers will be switched on, initiating the photochemistry and oxidant production, leading to SOA formation. MAC light sources provide similar actinic flux spectrum to that of the real atmosphere, yet with lower intensity thus resulting to low SOA mass formed. OFR's extensive UV light sources can generate high concentrations of oxidants, yielding high levels of SOA mass that is necessary for the subsequent toxicological assays. State-of-the-science mass spectrometry techniques will be used to benchmark the SOA composition generated from the OFR against those from the MAC, as well as to monitor the physical and chemical properties of the generated SOA. This will further enable the research team to explore their key-properties providing information about their atmospheric lifetimes and fate. The OFR SOA will be sampled in simulated extracellular fluid (SEF) by impingment and aliquots of the samples will be used to assess their cardiac toxicity using a combination of cell lines and intact hearts approaches to evaluate key aspects of cardiac function and markers of dysfunction. Our proposed series of interdisciplinary experiments in our unique facilities will explore our capability to provide information essential to understanding the atmospheric fate, properties and toxicity of SOA generated from the current-use pesticides. Such information is essential in informing policy makers, pesticide manufacturers and users in the development of adequate guidelines and sustainable products. Involvement of project partner Ian Mudway will provide a pathway through to Government via UKHSA through his work on pesticides with the NIHR Health Protection Research Unit.