Better predicting of sand haze to limit exposure to atmospheric pollution
A natural phenomenon set to intensify
When a sandstorm occurs, large quantities of particles are lifted into the atmosphere. Once at a high altitude, they can travel hundreds or even thousands of kilometres before falling back to the ground. This means that a Saharan sandstorm can cause sand haze to occur in mainland France or the Caribbean, resulting in air pollution that is recognisable by the yellow-orange colour of the sky and visible deposits on the ground.
With climate change, the sand haze season is tending to grow longer while the frequency and intensity of sand haze, including in winter, are increasing.
An increase in levels of airborne particles
Depending on their intensity, episodes of sand haze can cause concentrations of particles in ambient air to increase to varying degrees.
“Based on the available data, even though these are limited, we have demonstrated the effects of sand haze on human health, including an increase in non-accidental deaths as well as visits to hospital emergency units, hospitalisations, and mortality from respiratory or cardiovascular issues. These effects are also observed during episodes of standard particulate pollution” explains Claire Dulong, coordinator of the scientific expert appraisal.
Reducing concentrations of particles when sand haze occurs
Air quality forecasts are available up to five days in advance, allowing sand haze to be predicted. When this happens, ANSES advises the authorities to address local sources of pollution – for example by limiting road traffic or reducing industrial emissions – to reduce the level of particles already present in the air when the phenomenon occurs.
Otherwise, the particles from the sand haze will be added to the anthropogenic pollution in the air, potentially exceeding the air quality thresholds intended to protect human health.
“Sand haze is a natural phenomenon that requires action to be taken where possible, addressing emissions caused by human activities, in order to reduce the total concentration of particles and therefore the population’s exposure to atmospheric pollution, whose health effects are now well established” stresses Dulong.
Varying effects on the environment
By supplying particles composed of organic and inorganic matter, sand haze can have beneficial effects on ecosystems (addition of phosphorus and/or iron to water, for example) or negative ones (contamination by metallic elements, introduction of pathogens, etc.). For example, sand haze is thought to be one of the factors contributing to the proliferation of Sargassum seaweed. Sand haze deposits can also be associated with accelerated snow and ice melt.
However, to date, few data are available on the consequences of sand haze for fauna, flora and the environment. The Agency therefore stresses the importance of carrying out further research to better understand its effects.