In the eastern Mediterranean area there is desert dust in the air almost all year round, and not only in spring or autumn as is commonly thought. Why is this important?
What is a "dust storm"? Even for Tel Aviv University researchers it is difficult to define the phenomenon precisely.
A new study by Tel Aviv University conducted on behalf of Israel found that it is difficult to define the phenomenon precisely. Half of the days on which dust storms occurred, or on which there was a high presence of dust particles in the air - were not identified as such by the ground stations. These "uncontaminated" days are not included in the assessment of the impact of dust on morbidity, and as a result, the epidemiological study is misleading.
The researchers emphasize that these significant "misses" may harm the health of the public, who is not aware that there is a high concentration of dust particles in the air and a dust storm in the sky, and especially populations at risk.
The research was conducted under the leadership of doctoral student Irina Rogozovsky under the guidance of Prof. Alexandra Chodnovsky from the Air Quality Research Laboratory fromThe Porter School of Environment and Earth Sciences at Tel Aviv University, in collaboration with Dr. Albert Ansman from the Leibniz Institute for Tropospheric Research in Leipzig, Germany. The results of the research were published in the journal Science of the Total Environment.
Prof. Alexandra Chodnovsky
Wow, how much dust there is here
"It is difficult to impossible to define days with the presence of dust," explains Prof. Chodnovsky. "No existing definition captures", adds Irena Rogozovsky and emphasizes that approximately 50% of the days with dust are missed and defined as days without dust, or as days with anthropogenic pollution - that is, days with man-made air pollution.
Rogozovsky: "These two sources of air pollution have consequences for human health, but other consequences that are examined separately. There are different definitions for dust storms, which are mainly based on measurements of particles of different sizes at ground stations. According to what is measured at the stations, they try to decide if there is a dust storm that matches a certain definition that has been chosen In a specific research field or by the authorities, we tested about 20 different definitions from different research fields, and none of them fully matched to the actual situation".
In general, air quality stations measure the concentration of particles (micrograms per cubic meter), with a diameter of 2.5 and 10 microns, known as PM2.5 and- PM10. Particles with a diameter of 10 microns can penetrate the nose and upper respiratory tract, but usually do not reach the lungs. In contrast, particles with a diameter of 2.5 microns can penetrate deeper into the lungs. A dust storm refers to particles of the PM10 type. During a dust storm, the concentration of particles in the air can rise to very high levels, reaching concentrations that endanger the health, especially of children, the elderly and people with breathing problems. However, in Israel, not only is dust present almost all year round, it also contains anthropogenic pollution, so it is very difficult if at all to separate the two.
"There are several methods by which it is possible to distinguish between a dust storm and anthropogenic pollution," says Prof. Chodnovsky. "For example, optical analysis that allows to identify the optical parameters of the particles - such as reflection and polarization. Another method is Analysis of the source of air masses (Back-Trajectory Analysis), which allows tracing the source of the air that brought the particles to the measurement point. In our research, we used both methods." In 2019, a poly-lidar (LiDAR) type system was installed on the roof of the Kaplon building on the Tel Aviv University campus, which illuminates the target - in this case different layers of the atmosphere - with a laser beam, and measures the time it takes for the beam to return to the receiver. The system installed on campus was built at the Tropos Institute in Leipzig, and is one of the few systems in the entire world that can monitor air pollution vertically In the atmosphere up to a height of 15 km.
"It is a laser beam that is sent every second into the atmosphere," says Prof. Chodnovsky, "and according to the speed of the reflection, you can see where there are particles, which sources of pollution are involved, and most importantly: at what height is this layer of particles. The ground stations miss the layering of the sky. In fact, we found that ground measurements indicating anthropogenic air pollution miss layers of dust above the anthropogenic air pollution layers, or They both mix, and therefore do not define these days as dust chemicals - even though there is a high presence of dust particles in the air."
Irina Rogozovsky collected data from 2019 and almost until today in 2024, and showed that in the eastern Mediterranean region there is desert dust in the air almost all year round, and not only in spring or autumn as is commonly thought, and that these layers of pollution are diverse in their structure. Why is all this important? Because without accurate information it will be difficult to assess the various health effects, especially on populations at risk. For example, we know how to say that during dust storms there are more hospitalizations of asthmatics in hospitals, higher morbidity of heart diseases and more. To build an epidemiological model of dust exposure, we need to define the phenomenon. This means that the health effects of exposure to dust or pollution may appear lower than they actually are, and this is how model bias is caused."
Does a dust storm heat or cool?
"And there are other applications for our research," adds Prof. Chodnovsky. "For example, what are the consequences of dust storms on climate change, since the dust reflects back some of the solar radiation, and traps some of the solar radiation here. So does a dust storm warm or cool? While desert dust may cause local cooling by reflecting sunlight, anthropogenic pollution can lead Differentiation between these sources allows for a better understanding of their impact on climate change, and on local ecosystems Ours is another step on the way to a deeper understanding of the atmosphere, and human effects on it."
Dust of natural origin often contains natural mineral particles, while anthropogenic pollution contains substances such as heavy metals and harmful chemical compounds, originating from industry and transportation. Therefore the health impact can be very different between the two types of infection, and an accurate definition will allow better prediction of the health risks and their treatment. In addition, dust storm days often require different responses, such as issuing health alerts to populations at risk, while anthropogenic pollution requires more lasting solutions such as transportation and industrial planning to reduce emissions. An accurate definition will help decision makers to implement appropriate measures at the right time. Furthermore, accurate identification of dust storms versus anthropogenic pollution is essential for improving air quality forecasting models, since errors in the identification of dust days may cause biases in measurements and forecasts.
More of the topic in Hayadan:
