Mechanisms and Pathways for Coordinated Control of Fine Particulate Matter and Ozone

Abstract

Purpose of Review Fine particulate matter (PM 2.5 ) and ground-level ozone (O 3 ) pose a significant risk to human health. The World Health Organization (WHO) has recently revised healthy thresholds for both pollutants. The formation and evolution of PM 2.5 and O 3 are however governed by complex physical and multiphase chemical processes, and therefore, it is extremely challenging to mitigate both pollutants simultaneously. Here, we review mechanisms and discuss the science-informed pathways for effective and simultaneous mitigation of PM 2.5 and O 3 . Recent Findings Global warming has led to a general increase in biogenic emissions, which can enhance the formation of O 3 and secondary organic aerosols. Reductions in anthropogenic emissions during the COVID-19 lockdown reduced PM 2.5 ; however, O 3 was enhanced in several polluted regions. This was attributed to more intense sunlight due to low aerosol loading and non-linear response of O 3 to NO x . Such contrasting physical and chemical interactions hinder the formulation of a clear roadmap for clean air over such regions. Summary Atmospheric chemistry including the role of biogenic emissions, aerosol-radiation interactions, boundary layer, and regional-scale transport are the key aspects that need to be carefully considered in the formulation of mitigation pathways. Therefore, a thorough understanding of the chemical effects of the emission reductions, changes in photolytic rates and boundary layer due to perturbation of solar radiation, and the effect of meteorological/seasonal changes are needed on a regional basis. Statistical emulators and machine learning approaches can aid the cumbersome process of multi-sector multi-species source attribution.

Assessment of Air Pollution Changes during COVID-19 Pandemic in Jiangsu Province of China from 2018 to 2021

“…Plausible reasons for this increase of O3 during this period in the urban regions are because of the VOC-limited chemical regime. Its increase can also be linked to the increased insolation caused because of the decrease in particulate matter (38.4 %) concentration in the atmosphere during the restricted travel in the lockdown period (33). In July 2021, COVID cases again began to increase, which resulted in regional lockdowns, during which AQI and all pollutants, including O3, decreased by 18.6 %.…”

Impact of electric and clean-fuel vehicles on future PM2.5 and ozone pollution over Delhi

“…This is true in particular for surface ozone, which is a pollutant not directly emitted but formed in the atmosphere through complex reactions involving carbon monoxide (CO), methane (CH 4 ), nitrogen oxides (NO x ) and volatile organic compounds (VOCs). The relationship between ozone and its precursors is characterized by high non-linearity, and reducing emissions of some precursors (which are also precursors for PM 2.5 ) may have the unwanted effect of increasing ozone levels (Ojha et al 2022). Typically in location downwind of urban and suburban areas, ozone production increases with NO x concentrations but does not depend on concentrations of VOCs and CO (NO x -limited regime).…”

Association of Short-Term Co-Exposure to Particulate Matter and Ozone with Mortality Risk

“…3−5 As research continues, synergistic control of multiple pollutants (especially PM and O 3 ) is gaining widespread attention and is more effective than single pollutant control strategies. 6 In many parts of the world, the phenomenon of PM−O 3 complex pollution has gradually come to the forefront and has become a major feature of air pollution. 7−9 Therefore, attention to the synergistic control of PM and O 3 is essential to reduce the burden of disease.…”

“…In 2019, environmental pollution caused 9 million premature deaths, with air pollution being the primary cause . Increasing conclusive evidence has demonstrated the positive associations of short-term exposure to air pollutants with all-cause and cause-specific mortality. − As research continues, synergistic control of multiple pollutants (especially PM and O 3 ) is gaining widespread attention and is more effective than single pollutant control strategies . In many parts of the world, the phenomenon of PM–O 3 complex pollution has gradually come to the forefront and has become a major feature of air pollution. − Therefore, attention to the synergistic control of PM and O 3 is essential to reduce the burden of disease.…”