###### Abstract  
Nitropolycyclic aromatic hydrocarbons (NPAHs) are derivatives of PAHs and contain one or more nitro functional groups (-NO\({}_{2}\)). Some NPAHs are classified as possible or probable human carcinogens and are more mutagenic than PAHs. Although the atmospheric cancer risk is estimated as \(11\%\) from PAHs but \(17\%\) from NPAHs, many of the atmospheric behaviors of NPAHs are unknown. There are two major NPAH formation processes. Primary formation of NPAHs occurs directly during the combustion of organic materials. The secondary formation of NPAHs occurs through the transformation of PAHs after they have been released into the environment. The fate, transport, and health effects of NPAHs are considerably different from their parent PAHs because of these differing formation processes. However, the amount of research conducted on NPAHs is comparatively low relative to PAHs. This is primarily due to a lack of effective analytical method for NPAHs, which generally exist in the environment at concentrations one to three orders of magnitude lower than PAHs. However, with the development of more sensitive analytical methods, the number of research papers published on NPAHs has recently increased. The Western Pacific region, one of the post polluted areas in the world, is the most frequently studied area for NPAHs. Many of them reported that atmospheric concentrations of NPAHs were much lower than parent PAHs and oxygenated derivatives (OPAHs). In this article, recent research on sample treatment and analysis, as well as the sources and environmental fate of NPAHs, are discussed with PAHs and OPAHs. A notable achievement using NPAHs is the development of a new emission source analysis method, the NP method, whose features are also discussed in this review. nitropolycyclic aromatic hydrocarbon; environmental fate; analytical chemistry; source appointment; NP method +
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mutagenicity without S9 mix of airborne particulate extracts cannot be explained by eight NPAHs quantified [3]. The sources of PAHs and NPAHs include automobiles, factories, heating, landfills, open burning, forest fires, cooking and tobacco (Figure 1). Not only are the airborne concentrations of PAHs and NPAHs different in urban and rural areas, outdoors and indoors, but their composition also differs. However, little is known about the differences in the contribution of these sources to PAHs and NPAHs in individual air samples. The above combustion sources also directly emit hydroxylated PAHs (OHPAHs) and quinoid PAHs (QPAHs), some of which are secondary formed from PAHs and NPAHs in the atmosphere. Among PAHs and their derivatives, NPAHs have usually the lowest concentrations in the air, but they are much more mutagenic than the PAHs from which they are derived. Therefore, they are important PAH derivatives to be monitored. OHPAHs and QPAHs, whose formation is thought to be closely related to NPAHs, also show carcinogenicity or mutagenicity, as well as endocrine disrupting activity and reactive oxygen species production [4; 5; 6; 7]. They are associated with an increased risk of adverse health effects, such as lung cancer, asthma, and cardiovascular diseases [8]. On the other hand, PAHs and their derivatives are important contributors to brown carbon light absorption [9]. In earlier studies, the concentrations of NPAHs in the environment (which are at least two orders of magnitude lower than those of PAHs) could only be measured by HPLC-chemiluminescence (CL) detection method. However, in the last two decades, the introduction of HPLC with a high-sensitive fluorescence (FL) detector and GC-MS has greatly improved the sensitivity of detecting NPAHs in the environment. Since my previous review of analytical methods [10], the number of papers on environmental NPAHs and OPAHs has increased in the world, especially from the Western Pacific [11; 12; 13; 14; 15; 16]. As a result, there has been a greater amount of information on outdoor and indoor NPAHs exposures, which is necessary for estimating human health risks.