Center for Environmental Nanoscience and Risk, Department of Environmental Health Sciences, Arnold School of Public Health , University of South Carolina , Columbia South Carolina 29208 , United States.
Department of Chemistry , Louisiana State University , Baton Rouge , Louisiana 70803 , United States.
Environ Sci Technol. 2018 Mar 6;52(5):2468-2481. doi: 10.1021/acs.est.7b04439. Epub 2018 Feb 22.
Environmentally persistent free radicals, EPFRs, exist in significant concentration in atmospheric particulate matter (PM). EPFRs are primarily emitted from combustion and thermal processing of organic materials, in which the organic combustion byproducts interact with transition metal-containing particles to form a free radical-particle pollutant. While the existence of persistent free radicals in combustion has been known for over half-a-century, only recently that their presence in environmental matrices and health effects have started significant research, but still in its infancy. Most of the experimental studies conducted to understand the origin and nature of EPFRs have focused primarily on nanoparticles that are supported on a larger micrometer-sized particle that mimics incidental nanoparticles formed during combustion. Less is known on the extent by which EPFRs may form on engineered nanomaterials (ENMs) during combustion or thermal treatment. In this critical and timely review, we summarize important findings on EPFRs and discuss their potential to form on pristine ENMs as a new research direction. ENMs may form EPFRs that may differ in type and concentration compared to nanoparticles that are supported on larger particles. The lack of basic data and fundamental knowledge about the interaction of combustion byproducts with ENMs under high-temperature and oxidative conditions present an unknown environmental and health burden. Studying the extent of ENMs on catalyzing EPFRs is important to address the hazards of atmospheric PM fully from these emerging environmental contaminants.
环境持久性自由基（EPFRs）在大气颗粒物（PM）中存在着显著的浓度。EPFRs 主要是从有机物质的燃烧和热加工中排放出来的，其中有机燃烧副产物与含有过渡金属的颗粒相互作用，形成自由基-颗粒污染物。尽管燃烧中持久性自由基的存在已经有半个多世纪了，但直到最近，它们在环境基质中的存在及其对健康的影响才开始引起人们的关注，但仍处于起步阶段。为了了解 EPFRs 的起源和性质，大多数实验研究主要集中在纳米颗粒上，这些纳米颗粒是负载在更大的微米级颗粒上的，模拟了燃烧过程中形成的偶然纳米颗粒。对于 EPFRs 在工程纳米材料（ENMs）燃烧或热处理过程中形成的程度，人们了解得较少。在这篇重要而及时的综述中，我们总结了关于 EPFRs 的重要发现，并讨论了它们在原始 ENMs 上形成的可能性，这是一个新的研究方向。ENMs 可能会形成 EPFRs，与负载在较大颗粒上的纳米颗粒相比，EPFRs 的类型和浓度可能有所不同。由于缺乏高温和氧化条件下燃烧副产物与 ENMs 相互作用的基本数据和基础知识，因此存在着未知的环境和健康负担。研究 ENMs 在催化 EPFRs 方面的程度，对于全面了解大气 PM 中这些新兴环境污染物的危害非常重要。
