Factories have released toxic gasses into the air, which has resulted in the spread of air pollution across a number of cities. To best address this problem, an expert in which Earth system should be consulted?

Air pollution affects the atmosphere, the layer of gases surrounding Earth. Since the pollution comes from toxic gases released into the air and spreads through cities, an atmosphere expert would be best suited to address it. The hydrosphere concerns water, the geosphere concerns solid Earth, and the biosphere concerns living things.

AI-written and checked against the verified answer.