Although scientists have not agreed on an exact percentage of vehicle exhausts' contribution to fine particulate matters in big cities, they do agree it is a major source of pollution.
尽管科学家们对于汽车尾气在大城市PM2.5(空气中的可吸入微小颗粒物)来源中所占百分比尚未达成一致意见,但他们一致认为汽车尾气是主要的空气污染源。
汽车尾气的英文表达是vehicle/automobile exhausts,它和soil dust(土壤尘)、fire coal(燃煤)、biomass burning(生物质燃烧)、waste incineration(垃圾焚烧)、industrial pollution(工业污染)一起被认为是北京PM2.5主要污染源。
目前为了减少汽车尾气,各大城市都开始实行restrictions on purchasing motor vehicles(机动车限购政策),同时通过charging higher prices for diesel fuel and parking(提高汽油价格和停车费)来提高机动车的usage costs(使用成本)。