The things that make our air dirty can be put down to three main activities… Manufacturing industries, power generation and to a smaller extent, automotive sector. Of course, we cannot ignore the less, and many times natural sources such as ashes and chemicals from volcanic eruptions.
It’s hard to turn raw materials around to produce the good and items that make like a bit more comfortable without spitting stuff into the air. They surely will involve some physical and chemical mixtures that are set off by burning or heating raw materials. Look at any manufacturing plant and you cannot miss a chimney or tower that emits something into the air as by-products. The content of these emissions is what is most disturbing.
Energy plants that refine fossil fuels such as oil, natural gas and coal, or produce electricity are also big players in air pollution. The high level of smoke they produce contain pollutants such as sulphur oxide, carbon monoxides and oxides of nitrogen. “The burning of fossil fuels and biomass is the most significant source of air pollutants such as SO2, CO, certain nitrous oxides such as NO and NO2 (known collectively as NOx), SPM, volatile organic compounds (VOCs) and some heavy metals“1
Next to those are all the auto traffic emissions that occur in cities all over the world.
Unfortunately, air is fluid and does not stay in one place. This means air from a polluted area may travel long distances, and the other people may suffer the consequences.
Construction / Minning / Demolition
Other minor sources of pollutants include construction and demolition work, such as roads and farms, together with mining that also emits lots of particles such as dust, soot and gaseous chemicals into the air. Mechanical work tends to produce coarser particles, whiles chemical processes tend to create finer particles.
Many of these pollutants are able to react with moisture or other chemicals in the air to produce secondary or further toxic pollutants.
1. Air pollution and air quality, UNEP, www.unep.org/geo/geo3/english/366.htm