It’s the bane of every car owner and the delight of the car-washing industry. But it may also present a risk to health.

Saharan dust was in the air for several days last week, a fairly frequent weather phenomenon that occurs mainly in spring.

The dreaded xita tal-ħamrija, rain laden with ‘soil’, leaves cars and rooftops coated with brown dust.

But these dust plumes can also affect the respiratory and cardiovascular systems.

An ongoing study, called Life Media, carried out among children suffering from asthma in Cyprus and Crete, has found that when they stayed indoors during such sandstorms they experienced a lesser impact on their respiratory system.

Research has shown that in Malta this dust, whipped up from the Sahara, makes up between 15 and 20 per cent of airborne particles.

Respiratory specialist Stephen Montefort recommends that people, especially those suffering from respiratory and even cardiovascular conditions, should be advised by the government to stay indoors when a dust occurrence is forecast.

“Sandstorms can make our respiratory and cardiovascular system deteriorate,” he said.

“As this is a natural thing and cannot be stopped, people can mitigate the impact by staying indoors, not exercising outdoors and having air purified,” he added.

Sandstorms can make our respiratory and cardiovascular system deteriorate

This topic was explored during a recent conference organised by the University of Malta’s Department of Respiratory Medicine together with the Universities of Cyprus, Israel and Crete. Titled  Air Quality and Health in Mediterranean Europe, experts from central Europe shared research on the matter.

According to the Meteorological Office, the Maltese islands experience Saharan dust when the winds are southerly-southwesterly. The island had 14 occurrences of dust in suspension in 2021 and seven in 2020.

Saharan component in particulates

In Malta, visibility is reduced significantly when the dust load is high.

When it rains, the dust in suspension gives rise to ‘blood rain’ which reduces the dust load by washing the dust out of the atmosphere.

Mark Scerri, a researcher from the Institute of Earth Systems at the University of Malta, said that while a lot of research into the impact of Saharan dust on health has been carried out in the western and eastern Mediterranean, there was not much in the central region.

Local dust samples which were taken during a series of studies he was involved in, back in 2012 and 2013, showed a high Saharan component – rich in aluminium and silicon – especially during spring.

This was found to contribute to 20 per cent of coarse particulate matter in the air.

In another study of samples taken in 2016, Saharan dust was a significant contributor to fine particulate matter, making up 15 per cent.

Coarse particles (PM10) are relatively large at 2.5 to 10 microns in diameter, about one-seventh the thickness of a human hair. Smaller airborne particulate matter is referred to as fine (PM2.5).

The finer airborne particles are, the more problematic they are as the deeper they penetrate into the respiratory tract, ending up in the lungs.

Saharan dust is considered coarse yet research has shown that it too has negative health effects.

All this reveals the need to take Saharan dust more seriously from a health perspective.

However, because it is considered a natural occurrence, it is not included in EU countries’ measurements of their particulate matter in the air, Scerri said.

The EU sets safety limits on the amount of particulate matter that a country should allow, and over the years Malta has generally stayed within these limits.

The annual average concentration of fine particulate matter stands at approximately 12 µg/m3 (12 micrograms of gaseous pollutant per cubic meter of ambient air). This is below the annual limit of 25 µg/m3 set by the air quality EC directive.

Natural dust in air

The EU sets the annual limit of large particulate matter at 40 µg/m3. In Malta’s air monitoring stations, the annual average was 25 µg/m3, with only Msida hitting the limit at 40 µg/m3.

But Scerri cautioned that European legislation allows member states to deduct natural contributions when calculating the legally binding limit values.

The natural contributions of interest to Malta are primarily Saharan dust and sea salt (from sea spray).

“This means that sometimes airborne dust levels can be very high due to natural causes,” he notes.

“Because these events occur rather frequently we should devise strategies to control the emissions of dust from the sources that we can control irrespective of whether we exceed the applicable limit value once the contribution of natural sources have been deducted.”

As the total concentration of airborne dust can be very high during an episode of Saharan dust, and because it poses a threat to human health, it needs to be quantified, he said.