Unraveling the chemistry of polluted air 

Declining air quality is a major issue in many countries, including Saudi Arabia. Pollutants can be directly emitted from both natural sources —such as wind-blown mineral dust, transported soil particles, volcanic ash, wildfires, and pollen — and anthropogenic activities, including industrial and agricultural emissions, ship and automobile exhaust, cooking, and biomass burning. 

“However, many pollutants, termed secondary air pollutants, are formed in the atmosphere. For example, plants emit volatile organic compounds (VOCs), which can form significant amounts of secondary organic aerosols upon solar irradiation,” says Chak Chan, an expert in pollution chemistry whose research focuses on aerosol science and air quality. The group’s research integrates laboratory simulations of atmospheric reactions with field measurements to improve understanding of the sources and formation mechanisms of particulate matter (PM), a major component of air pollution. 

Although the health risks of this complex mixture of tiny solid particles and liquid droplets are receiving increasing attention, its formation pathways remain only partly understood. Atmospheric reactions can generate sulfate, nitrate, and organic compounds, which together account for the most significant fractions of PM. 

The finest particles are especially harmful, as they can penetrate deep into the respiratory system and are linked to respiratory and cardiovascular diseases, cancer, and neurological disorders. 

“With a better understanding of their formation mechanisms, policymakers can formulate targeted control strategies to effectively manage emissions of precursor pollutants, such as nitrogen dioxide, sulfur dioxide, and VOCs for controlling secondary pollutants such as PM and ozone,” says Chan. “Source-based emission control can subsequently reduce PM and ozone formation, lower atmospheric concentrations, improve air quality, and better safeguard public health,” he adds.