air pollution
　　Air pollution is the human introduction into the atmosphere of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or damages the natural environment. Air pollution causes deaths and respiratory disease. Air pollution is often identified with major stationary sources, but the greatest source of emissions is mobile sources, mainly automobiles. Gases such as carbon dioxide, which contribute to global warming, have recently gained recognition as pollutants by climate scientists, while they also recognize that carbon dioxide is essential for plant life through photosynthesis.
　　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.
　　【参考译文】
　　空气污染是人类引入化学物质到大气中,颗粒物,或生物材料对人类造成伤害或不适或其他生物体,或破坏自然环境。空气污染导致的死亡和呼吸道疾病。空气污染通常是与主要的固定污染源,但排放的来源是移动来源主要是汽车。气体如二氧化碳,导致全球变暖,最近获得了识别污染物的气候科学家,同时他们也认识到二氧化碳是植物通过光合作用所必需的。
　　大气是一个复杂的、动态的天然气体系统,以支持地球上的生命是至关重要的。平流层臭氧损耗由于空气污染一直被认为是威胁人类健康以及地球的生态系统。