According to the State Meteorological Agency, haze is a meteorological phenomenon in which we have a “suspension in the atmosphere of extremely small dry particles, invisible to the human eye, but numerous enough to give the sky an opalescent appearance. The term haze is used when reduced visibility and a relative humidity of less than 70% coincide. The degree of humidity is what differentiates it from mist, which is mainly made up of water droplets.”
What are those extremely small particles?
They receive the name of particulate material and are a mixture of tiny solid particles and liquid “droplets” from various materials such as acids, organic compounds, metals and soil or dust particles.
The way meteorologists classify this particulate is by its origin (contaminant gases, polluting particulate, dust and biological contaminants) and by its size, which is measured in microns, that is, one thousandth of a millimeter. As we can see, we are dealing with something very, very small.
This atmospheric particulate is designated by the letters PM (from English particulate matter or particulate matter) followed by numbers, such as PM2.5 or PM10, which refer to the size of these particles. Thus, a PM2.5 particle measures less than 2.5 microns and a PM10 particle measures 10 microns or less . To realize what this means, let’s think that the width of the silk thread of a spider’s web is 3 to 8 microns, and that of the transparent plastic that we have in the kitchen is, generally, between 10 to 12 microns.
From a health point of view, the particles of greatest concern are those of 10 microns or less. Why? Because the smaller they are, the more likely they are to pass through the different defenses that our body has and reach the interior of the lungs and the bloodstream.
The air we breathe always contains this type of particulate, which includes pollen, sea salt (especially if you live in a coastal area), the remains of car combustion and the dust that the air usually contains. We are not usually very aware of it, except when we have to clean it at home, but in the atmosphere of our home floats a deposit of more than 10 million tiny foreign objects per cubic meter : bits of melted tire, flakes of skin, sea salt , cement dust, sand from the deserts of the Earth and many more things that is what we know by the generic name of dust. All these particles take from hours to weeks to settle on furniture, shelves, books, televisions and floors, in a constant and practically imperceptible rain.
Why is PM10 so dangerous?
For several reasons. High levels of PM10 can irritate the eyes and throat, symptoms that often increase when a person with asthma or other lung conditions is exposed to PM10. Similarly, if you have heart disease, PM10 can exacerbate these symptoms. There is even research linking prolonged exposure to PM10 with lung cancer.
For these reasons, the existence of particulate matter in the atmosphere is one of the most serious environmental problems that large cities have and for which there is no clear solution except to limit the use of emission sources into the atmosphere, which are transport and different industrial processes.
In an article published by researchers Robert Laumbach, Qingyu Meng and Howard Kipen of Rutgers University on long-term exposure to PM10, they suggest the need to implement “emission reduction policies to preserve human health from exposure to pollutants in the environment”. air in urban areas such as restricting traffic.
At times when the air quality is poor – as it is happening these days – it is not advisable to exercise outdoors. Similarly, it is not advisable to do it in areas close to areas with high vehicle traffic or with high industrial emissions.
But not everything has to be bad news. This dust from the Sahara is an excellent source of micronutrients for terrestrial and, above all, marine ecosystems. According to the Atlantic Oceanographic and Meteorological Laboratory belonging to the well-known National Oceanic and Atmospheric Administration of the United States, “the iron and phosphorus that the dust transports benefit the production of marine biomass in parts of the oceans where there is a shortage of these elements” . This organization is dedicated to monitoring the so-called Saharan Air Layer, a very dry and dust-laden air mass that forms over the African desert in late spring, during summer and early fall, and moves towards the Ocean North Atlantic every 3 to 5 days. This causes the atmosphere to be filled annually with 182 million tons of Saharan dust. What we are experiencing today is a special situation as the tongue of dust in suspension that is affecting all of Europe has been propelled towards us by the Celia storm.
Consonni D, Carugno M, De Matteis S, Nordio F, Randi G, Bazzano M, Caporaso NE, Tucker MA, Bertazzi PA, Pesatori AC, Lubin JH, Landi MT. Outdoor particulate matter (PM10) exposure and lung cancer risk in the EAGLE study. PLoS One. 2018 Sep 14;13(9) doi: 10.1371/journal.pone.0203539
Laumbach R, Meng Q, Kipen H. What can individuals do to reduce personal health risks from air pollution?. J Thorac Dis. 2015;7(1):96–107. doi: 10.3978/j.issn.2072-1439.2014.12.21