了解沙尘暴对健康的影响

Understanding the healthimpacts of sand andduststorms Technical brief Key messages Sand and dust storms (SDS) result from turbulent winds that raise large quantities of particlesfrom the ground into the air in emission areas. Emission areas are typically semi-arid and aridwith limited vegetation cover, as bare ground is most susceptible to sediment entrainment by thewind. During SDS, large amounts of particles of a broad range of sizes and chemical compositionare uplifted from the soil. SDS have significant impacts on the environment, climate, weather,ecosystems and human health. They are a significant concern that warrants multisectoral actionwith public health authorities. SDS are recognized as a climatic impact-driver, meaning that theycan be considered as a climate hazard in risk assessments. SDS activity varies widely depending on geographical location, climate conditions and localenvironmental factors. Major sources include large deserts in North Africa, the Middle East andAsia. Local sources are disturbed landscapes caused by climate factors (such as drought or icecover reduction), agricultural practices, overgrazing and deforestation. Larger sand particles remain relatively close to the ground in the emission area, while finer dustparticles can be lifted kilometres high into the atmosphere and potentially travel thousands ofkilometres to receptor areas. Receptor areas can be located close to or far away from SDS emissionareas. The air in receptor areas contains a mix of dust particles and non-dust particles, which areemitted from both natural and anthropogenic sources, from both receptor and emission areas andduring transport of dust air mases. SDS can last over various time periods with particulate matter(PM) concentrations exceeding 10000μg/m3during SDS events close to the sources and exceeding1000μg/m3in receptor areas. Studies on the health effects of SDS have associated short-term exposure with increased mortality, aswell as a higher incidence of respiratory and cardiovascular diseases, among other healthconditions. However, there is a significant gap in understanding the long-term effects, as no studies havefocused on chronic exposure. Detailed measurements on the PM concentrations, chemicalcomposition and size distribution are needed for advancing on the assessment of the healthimpacts of SDS. Standardized research protocols are needed to enhance the consistencyand robustness of future studies, particularly in the source regions of the Saharan belt andtheMiddle East. Overview What are sand and dust storms? In this document, SDS refer to weather and environment related phenomena associated withstrong winds that lift large amounts of sand and dust particles from bare, dry soils into theatmosphere. SDS vary in duration and extent based on meteorological and environmentalfactors. They can last from a few hours to several days, with localized storms coveringsmall areas (haboobs) and large-scale events spanning thousands of kilometres (e.g. theHarmattan in the Sahel). Dust sources are primarily located in arid and semi-arid regions where loose, fine sedimentsare exposed to strong winds. Major sources include the Sahara Desert (largest global dustcontributor), the Middle East, Central Asia (e.g. the Aral Sea basin) and the Gobi Desert in EastAsia(1). These regions often feature dry lake beds, alluvial plains and deserts with minimalvegetation. Overall, global dust emissions from major sources (i.e. deserts) are approximately22–29 billion kg per year, with North African source regions contributing roughly 50%(2).Human activities such as overgrazing, deforestation and unsustainable land use practicesexacerbate dust emissions by disturbing the soil surface and increasing the susceptibility ofthese areas to wind erosion(3). Agricultural areas in Eastern Europe and drying landscapeswithin the southern United States are also sources of SDS(4). See SPS1:Agriculture – sectoral solutions for air pollution and health During SDS, large amounts of particles of a broad range of sizes and chemical compositionare uplifted from the soil. Sand and dust are categorized by the size of the particles involvedin SDS: •Sand refers to coarse particles (with diameters of ≥ 60μm).•Dust refers to finer particles (with diameters of < 60μm), including silt and clay. Sand and dust particles are a conglomerate of different components, including largeproportions of minerals such as quartz, clay, carbonate, feldspar and iron oxide, and variableproportions of salts such as gypsum. The proportion of different minerals depends on theorigin of the dust (i.e. soil source). SDS can be considered a type of dust event. This is because sand, the larger coarseparticle,is mainly found near sources in the emission areas and has a very limited lifetimein the atmosphere. On the other hand, dust, the smaller particle, can remain suspendedin the air for extended periods in the emission area and travel long distances to receptorarea