Sand haze

Unique identifier / Notation

MH0019

Synonyms

Dust haze.

Sand haze is haze caused by the suspension in the atmosphere of small sand or dust particles, raised from the ground prior to the time of observation by a sandstorm or dust storm (WMO, 1992).

Primary reference(s)

WMO, 1992. International Meteorological Vocabulary, WMO-No. 182. World Meteorological Organization (WMO). Accessed 13 October 2020.

Additional scientific description

Sand haze is reduced visibility in the atmospheric boundary layer which is caused by suspended particles of soil, mixed into the air during strong winds. It is particularly prevalent in desert regions where there is little moisture and few plants to hold the sand grains to the surface (AMS, 2012).

After a sandstorm the larger sand grains fall out of the air quickly, leaving a sand haze of medium-sized particles (1–100 μm diameter, including silt and fine sand) and small particles (< 1 μm diameter, including clay particles) (AMS, 2012).

Metrics and numeric limits

Not available.

Key relevant UN convention / multilateral treaty

Not available.

Examples of drivers, outcomes and risk management

Sand haze can be considered as one of many causes of air pollution. Air pollution is a major environmental risk to health. By reducing air pollution levels, countries can reduce the burden of disease from stroke, heart disease, lung cancer, and both chronic and acute respiratory diseases, including asthma. The lower the levels of air pollution, the better the cardiovascular and respiratory health of the population, both long- and short-term. The World Health Organization has published an assessment of health effects of air pollution and thresholds for health-harmful pollution levels (WHO, 2018).

Sand haze contains particulate matter, which is a common proxy for air pollution. The major components of atmospheric particulates are sulphates, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water. It consists of a complex mixture of solid and liquid particles of organic and inorganic substances suspended in the air. While particles with a diameter of 10 microns or less (≤ PM10) can penetrate and lodge deep inside the lungs, the even more health-damaging particles are those with a diameter of 2.5 microns or less (≤ PM2.5). The latter can penetrate the lung barrier and enter the blood system. Chronic exposure to particles contributes to the risk of developing cardiovascular and respiratory diseases, as well as lung cancer (WHO, 2018).

Small particulate pollution has health impacts even at very low concentrations – and no threshold has been identified below which no damage to health is observed. Therefore, the WHO 2005 guideline limits aim to achieve the lowest concentrations of particulate matter possible (WHO, 2018).