Practice question

Sulfur oxides and nitrogen oxides are atmospheric precursors of acid rain. Sulfur dioxide is oxidised to sulfuric acid, while nitric oxide is converted through nitrogen dioxide and other reactions to nitric acid. These acids dissolve in cloud droplets or deposit as gases and particles. Carbon dioxide creates normal weak rain acidity, whereas methane, sodium chloride, and the other listed pairings do not explain anthropogenic acid deposition. Sound classification links the source, atmospheric fate, exposure route, and mechanism of toxicity rather than relying only on the pollutant's name. Effective management combines cleaner fuels, emission standards, monitoring, urban planning, and protection of populations with high exposure or physiological vulnerability. The distinction is ecologically important because emission control must target either the directly released precursor or the product formed after atmospheric transport and reaction. Exposure depends on concentration, duration, ventilation, weather, and individual susceptibility, so a pollutant's presence alone does not fully predict biological harm.