پایگاه آموزش زبان انگليسي معصوم پور

Air pollution is the introduction of chemicals, particulate matter, or 
biological materials that cause harm or discomfort to humans or other living
organisms, or damages the natural environment, into the atmosphere.
The atmosphere is a complex, dynamic natural gaseous system that is essential to
support life on planet Earth. Stratospheric ozone depletion due to air pollution
has long been recognized as a threat to human health as well as to the Earth's
ecosystems.