particulate matters (PM)
Particulate Matter consists of airborne particles in solid or liquid form. PM may be classified as primary or secondary, depending on the compounds and processes involved during its formation. Primary PM is emitted at the emissions source in particle form from the traffic or the smokestack of an industrial or domestic combustion process or a recently tilled field subject to wind erosion.
Secondary PM formation results from a series of chemical and physical reactions involving different precursor gases, such as sulphur and nitrogen oxides, and ammonia reacting to form sulphate, nitrate and ammonium particulate matter.
Numerous studies have linked PM to aggravated cardiac and respiratory diseases such as asthma, bronchitis and emphysema and to various forms of heart disease. PM can also have adverse effects on vegetation and structures, and contributes to visibility deterioration and regional haze.