The former are suspended particulates largely produced by factories or power plants burning coal or other fossil fuels. The latter originate primarily in automobile exhaust. When dissolved in water, these anthropogenic pollutants become sulfuric acid and nitric acid, furthering the acidification of rainwater.
前者多半來自工廠或電廠燃燒煤炭或化石燃料而產生的懸浮微粒，後者則常源自汽機車排放的廢氣，這些人為污染物質統稱「酸雨前驅物」，溶於水後會形成硫酸或硝酸，將使原本已呈弱酸性的雨水持續酸化。