Particulates or atmospheric particulate matter see below for other names are microscopic particles of solid or liquid matter suspended in the air. Airborne particulate matter is a Group 1 carcinogen. Worldwide, exposure to PM 2. Some types of dust, e. Those with sharp edges may be even more problematic. The number, shapes, stickiness, etc. Human-made anthropogenic aerosols account for about 10 percent of the total mass of aerosols in the atmosphere as estimated in The remaining 90 percent comes from natural sources such as volcanoes , dust storms , forest and grassland fires, living vegetation and sea spray , emitting particulates such as volcanic ash, desert dust, soot and sea salt.
In the United Kingdom domestic combustion is the largest single source of PM 2. There are a few ways to reduce wood smoke, e. The composition and toxicity of aerosols , including particles, depends on their source and atmospheric chemistry and varies widely. Wind-blown mineral dust [ 64 ] tends to be made of mineral oxides and other material blown from the Earth's crust ; this particulate is light-absorbing.
In addition, sea spray aerosols may contain organic compounds like fatty acids and sugars, which influence their chemistry. Some secondary particles derive from the oxidation of primary gases such as sulfur and nitrogen oxides into sulfuric acid liquid and nitric acid gaseous or from biogenic emissions. The precursors for these aerosolsβi. In the presence of ammonia , secondary aerosols often take the form of ammonium salts; i. Secondary sulfate and nitrate aerosols are strong light-scatterers.
Organic matter OM found in aerosols can be either primary or secondary, the latter part deriving from the oxidation of volatile organic compounds VOCs ; organic material in the atmosphere may either be biogenic or anthropogenic. Organic matter influences the atmospheric radiation field by both scattering and absorption.
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Some aerosols are predicted to include strongly light-absorbing material and are thought to yield large positive radiative forcing. Some secondary organic aerosols SOAs resulting from combustion products of internal combustion engines, have been identified as a danger to health.
