There are many environmental problems such as water pollution, thermal pollution, soil pollution, air pollution, light pollution,etc, but I would like to write about air pollution. Here are some causes making the air polluted. Firstly, the wastes and poisons from industries. Factories and enterprises have emitted tons of carbon dioxide every day,... not only polluting the air but also warming the Earth and changing the climate. Secondly, the increasing of traffic, vehicles like cars, motorcycles,... have dumped lots of pollutant gases. Thirdly, domestic waste from cooking mainly also emits bunch of harmful gases. Finally, air pollution is also caused by nature, forest fires, volcanic activities,... Because of those reasons above, we have to protect and improve the clean air as soon as possible. We should do something like planting trees, using clean energy (solar energy, hydroelectricity) instead of coal and oil, using environmentally friendly means of transport, buses, bicycles,... In short, air pollution is a matter of concern, we have to protect it.