Atmospheric particulate matter, also known as particulate matter (PM) or particulates are microscopic solid or liquid matter suspended in Earth's atmosphere. This Complex mixture includes both organic and inorganic particles such as dust, pollen, soot, smoke and liquid droplets which are hazardous.  Sources of particulate matter can be natural or anthropogenic. They have impacts on climate and precipitation that adversely affect human health CITATION Wik l 1033 (Wikipedia). These particles vary greatly in size, composition, and origin. CITATION Gre l 1033 (Green facts)

Atmospheric particulate matter is a central component of the atmospheric chemical and climate system, a major air pollutant harmful to human health, and a component of biological systems and global biogeochemical cycles CITATION Blo l 1033 (Bloss).

Abundance:

PM₁₀ and PM_2.5, denoting the concentration of PM with aerodynamic diameters below ca. 10 and 2.5 micro-m respectively, which correspond roughly to adult human inhalable (thoracic) and respirable (alveolar) particle sizes respectively is the most legislative PM. Typical urban atmospheric loading of PM range from tens to hundreds of micro-g m^-3 for PM_10.

Updated WHO Air Quality Guideline values

Importance and impacts of PM

Human health impacts

Inhalation of PM in an urban atmospheric context is associated with enhanced respiratory and cardiovascular disease (marked by an increase in hospital admissions) and increased associated mortality. The figures are not trivial: studies find a 1 to 4 % increase in cardiovascular mortality per 10 micro g m^-3 increase in PM₁₀.

Impacts on climate and atmosphere:

Atmospheric PM loading contributes to the reduction in visibility associated with poor air quality, and both directly and indirectly affects atmospheric radiation transmission and hence climate. These effects (mainly but not exclusively cooling in nature) are among the largest, and least well quantified, terms in climate models and could potentially substantially alter the magnitude of the calculated warming. Aerosol particles also play important roles in atmospheric chemistry, providing a reaction site for heterogeneous reactions that would not otherwise occur. Dust transport is an important component of the biogeochemical cycles for crustal minerals, notably iron, representing a major route for their input into marine ecosystems.

Status of PM and its adversities in Nepal

Ambient (outdoor) air pollution causes over 9,000 deaths every year, with coronary artery disease and strokes each killing more than 3,000 people in Nepal, according to findings by the World Health Organization  (Shahi, 2016). The new analysis of 103 countries found that 36 people out of every 100,000 die in Nepal from outdoor air pollution leading to heart diseases, lung cancer, chronic obstructive pulmonary disease and stroke. Various scientific reports and findings, including the Environment Performance Index (EPI) 2016 prepared by the Yale University, listed Nepal among the top four worst performers in protecting the human health and environment from degrading air quality. Outdoor air pollution, mostly the PM2.5 and PM10 pollutants, kill around three million people every year, mainly from non-communicable diseases.

Dust particles suspended in the air from construction works and vehicular emissions are the key causes of the increasing cases of respiratory and other health problems related to air pollution in Nepal. The Kathmandu Valley?s ambient air has been found to be polluted with particulate air pollution. Environment Performance Index (EPI) ranks Nepal 177 among 180 countries in terms of air quality.



Air quality monitoring in brick kilns indicates very high concentrations of airborne particulate matter. Air pollution from brick kilns poses an enhanced threat to the environment and to human health.

Government's role

Monitoring of gaseous pollutants such as nitrogen dioxide, sulphur dioxide and carbon monoxide showed that their concentrations too exceeded national and WHO limits. The Department of Environment under the Ministry of Science, Technology and Environment in association with the International Centre for Integrated Mountain Development (Icimod) has installed air quality monitoring equipment at Ratna Park, Pulchok and Dhulikhel.

The major sources of particulate air pollution in the Valley are dust re-suspension from vehicular movement and human activity, and emissions from old motor vehicles and cement and brick factories. Several studies have also shown an association between PM pollution and health effects in Nepal CITATION Ray16 l 1033 (Rayamajhi, 2016).

Bibliography

BIBLIOGRAPHY Bloss, W. ECG Environmental Briefs. Royal Society of Chemistry.

Green facts. Air Pollution Particulate Matter.

Rayamajhi, B. (2016). Problem in the air. The Kathmandu Post.

Wikipedia. Particulates.