On March 15, 2021, north China suddenly experienced a serious sand and dust storm, which originated in Mongolia and was the biggest in the past decade. At least nine people, including one child, were directly killed by the sand and dust storm in Mongolia.

The devastating storm swept across northern China, covering 380 million hectares of land in 12 provinces. Schools in several cities were closed and more than 50 flights to and from Beijing, China were cancelled. PM10 concentrations in Beijing increased sharply to 8000 μg/m3 during the morning of March 15 due to the storm, and 24-h mean PM2·5 concentrations exceeded 200 μg/m3, which is far higher than the WHO guideline of 25 μg/m3. It has been estimated that such an increase in PM10 concentration could lead to an increase of 99·8% in daily all-cause mortality, which corresponds to at least 265 excess deaths per day in Beijing.1 This wave of sand and dust storms is a result of combined effects of dry cyclones from Mongolia and cold air from Siberia. Driven by the prevailing westerlies, dust particles in the deserts of Mongolia were lifted high into the air, travelling downwind from the source areas, and depositing in northern China and even South Korea.

Sand and dust storms are strongly related to climate change; their primary driver is dry conditions associated with a series of interlinked factors, such as global warming, El Niño phenomenon, deforestation, and climate anomalies. In the past three decades, Mongolia has experienced substantial impact from global warming, with average temperature in summer increasing by 2·5°C between 1981 and 2014, and a noteworthy downward trend in vegetation coverage.2, 3

On the other hand, decreased frequency and duration of stratiform rain events caused by the movement of cyclones and the change in El Niño were observed during the same time period.4 The combined effect of rising temperature and reduction in stratiform rain quickened the loss of soil moisture and led to severe desertification.3 The hot weather and anomalous cyclonic circulation could also be intensified by persistent water loss and soil erosion, leading to widespread drought and land degradation.2

Exposure to dust particles is linked to a wide range of health problems. The main component of sand and dust storms posing a threat to human health is PM10. Particles with a diameter greater than 10 μm can damage external organs such as skin and eyes, whereas coarse (PM2·5–10) and fine (PM2·5) particulate matter (PM) are associated with increasing all-cause mortality and morbidity, especially from respiratory and cardiovascular diseases. Sand and dust storms expose individuals not only to total suspended PM, but also to harmful combinations of microorganisms and potential allergens absorbed by dust particles during long-range atmospheric transport.5 For example, the UN Convention to Combat

Desertification suggested the epidemics of meningitis in Africa and Valley fever in the Americas are highly related to sand and dust storms. There is no doubt that health consequences of sand and dust storms are experienced worldwide. 151 countries experience the storms but only 45 (30%) of these are classified as sand and dust storm source areas.6 For example, 41% of the worst dust days in western USA in 2001 were attributed to transpacific sources that originated in Asia.7 Even for countries with no sand and dust storm activity or sand and dust deposition, they might still experience ramifications of the storms via their effect on the global climate.

An early warning system is essential to raise public awareness and help minimise losses of life and property from potentially devastating dust storms. Generally, people are advised by the American Thoracic Society to take direct measures to protect health when the dust storm occurs, including avoiding vigorous activities, staying indoors, and wearing dust masks. However, the indoor PM concentration can be close to that of outdoors as dust can penetrate into rooms through doors, windows, and ventilation systems.8 In schools, where students spend the majority of their time, the resuspension of PM due to high levels of activity could pose increased risks to children and adolescents.9 Thus, air purifiers with high-efficiency particulate absorbing (HEPA) filters and thorough cleaning of rooms are recommended to reduce indoor PM concentrations.

In the context of climate change, our earth will experience intensified droughts and greater occurrence of wind erosion and extreme weather events, resulting in increased intensity and frequency of sand and dust storms and their negative repercussions on the economy and health.10 Benefiting from large-scale ecological restoration programmes, China has seen remarkable reduction in frequency of sand and dust storms (appendix). However, this most recent wave of a sand and dust storm in China indicates that action in individual countries will not stop the occurrence of these storms. Global effort and commitment are required to tackle climate change and reduce the frequency and effect of sand and dust storms.