Garth Rattray | The good, bad, and the ugly Saharan dust

Everyone hates dust, it settles on everything and requires that we constantly clean surfaces and equipment. It’s as if the Earth is attempting to slowly and inexorably bury us alive!

Aside from the inconvenience, ugliness, and dirtiness of dust, it can make some of us sick. A few may even die from respiratory complications. Those with allergy problems can suffer skin, eye, upper and/or lower respiratory problems. These can manifest as an annoying rash, conjunctivitis, rhinitis, sinusitis, a combination of the two, post-nasal draining, throat problems, asthma, and other lung troubles. They can occur as a direct result of environmental dust or as a result of trying to get rid of the dust. In other words, it can be a real nuisance and dangerous to a few susceptible individuals.

But dust is not all bad; in fact, there are more things that are good about it than there are things that are bad about dust. Here’s an interesting example that we take for granted every day. Since light travels in straight lines, if there were no dust particles for light beams to bounce off, and partially illuminate under furniture and other objects like awnings, shadows would appear pitch black even on the brightest day. Sometimes we would need flashlights to look into corners, and under tables and chairs during the daylight hours.

In fact, dust is essential for our survival. Atmospheric dust helps to absorb and scatter potentially harmful radiation that enters our atmosphere. Dust is also a source of nutrient particles and pollen; without it our ecosystem would collapse. Evaporating water molecules need dust particles on which to form precipitation. Without dust there would be no clouds in the sky, no snow and no rain.

PARTICULATE MATTER

As for the Sahara dust; it is particulate matter that comes around this time every year. It originates from the Sahara Desert in Northern Africa. It comes off the eastern side of the Atlantic Basin. High-speed winds produced by thunderstorms and cyclones propel the dust into the air and sometimes transport it thousands of kilometres around the globe … including to regions of Europe, the Caribbean, the United States of America, Central, and South America.

Sometimes the dust plumes are huge. If conditions permit, 180 million tons of dust form into a ‘Saharan air layer”. It is a ‘pancake’ of hot and dry air, between 1.5 and 4.5 kilometres above sea level, and over three kilometres thick. This usually occurs between late spring and early fall. But this plume of ‘dust’ also contains iron and phosphorus mineral fragments that nourish plants on land and phytoplankton in the sea. The dust also picks up pollen and is therefore essential for the fertility and health of innumerable plant life. In turn, the plants absorb carbon dioxide, produce oxygen, and provide food for several species of animals.

The phytoplankton drift in the hostile ocean. The Sahara dust provides nutrients so that the phytoplankton can carry out photosynthesis. Aside from food for some marine life, at least 50 to 85 per cent of the oxygen in our atmosphere is produced by phytoplankton. And, every year, they absorb about 30 per cent of the carbon dioxide produced by humans. Over 70 per cent of the iron needed by the essential phytoplankton in the Atlantic Ocean comes from the Saharan dust.

weather phenomena

As this dust passes over the open Atlantic Ocean and through the Caribbean Sea, it suppresses adverse weather phenomena by becoming a buffer between the searing heat from sunlight and the rapidly heating summer waters. The plume absorbs some of the heat energy that would have gone into starting or feeding weather phenomena (tropical storms/hurricanes).

Aside from reducing the risk of serious storms/hurricanes, I was fascinated to learn that the Saharan dust has been providing nourishment to the Amazon rainforest, some 9,000 Km away from Africa, for millions of years. The Amazon rainforest is considered to be the ‘lungs of the world’. It alone produces about 6 per cent (some say 9 per cent) of the entire world’s oxygen, and it absorbs 25 per cent of the carbon dioxide produced.

It is extremely biologically active and only some species of its plants have been identified. But the soil in the rainforest is known to be low in some of the elements needed for the survival of the flora there because the almost constant rain washes away the essential nutrients. Without the annual “rain of fertiliser” from the African dust, to replenish the crucial elements, the South American forest would perish. The impact on humanity would be nothing short of catastrophic.

As I see the dull, dust-laden sky, and layers of dust that accumulate daily on everything, as a physician I’m cognisant that exposure to the Saharan dust may be bad for your health. This is especially true for the very young, the very old, and people who suffer from allergies. Since the Saharan dust worsens the air quality, susceptible individuals should try to avoid outdoor activities, perhaps wear a dust mask when the air quality index is poor, and adhere to any prescribed medications given for allergies and other dust-related conditions. The Saharan dust has been linked to increases in Emergency Room visits.

However, as a scientist, I know that the Saharan dust is vital to Earth’s biology (ecology), climate, and our survival. The natural annual transplanting of African dust is what is keeping all of us alive.

n Garth A. Rattray is a medical doctor with a family practice. Send feedback to columns@gleanerjm.com and garthrattray@gmail.com