Current progress on tropospheric Ozone sources, biological effects and trends.

Elevated levels of tropospheric ozone (O3) caused by anthropogenic emissions of nitrogen oxides (NOx) and volatile organic compounds (VOCs) have a negative impact on human health, crops, and ecosystems. Therefore, estimation of ground-level ozone trends is necessary to determine the burden of ozone on human health. Its formation undergoes complex photochemical reactions and processes that are non-linearly related to its precursors. Despite a relatively clear understanding of the O3 formation mechanism, effectively characterizing and analyzing its source and distribution at precise spatio-temporal resolutions remains a significant challenge. The review summarizes the current knowledge of tropospheric O3 in recent years, including its sources, trends and biological effects. It contributes to the understanding of how ozone and its precursors are affected and the impact they have on the environment, which contributes to the effective assessment and control of surface ozone.