Saharan Dust - Friend or Foe

When we hear about Saharan Dust we automatically think about the health issues and the constant cleaning up until the plume passes. However, it appears that this natural phenomenon is having a more noticeable impact on our lives.




As recent as June 2020, Trinidad and Tobago experienced the highest concentration of saharan dust in recent history. Air Quality levels were reduced to HAZADOUS with calls the reduced outdoor activity and persons with respiratory challenges to take extra precautions:

    You may be surprised to know that despite it being a major hazard to human health, the Saharan dust feeds life itself and disrupts the formation of hurricanes and thunderstorms.

    Saharan dust embarks on a more than 10,000 km journey to do more than create runny noses, itchy eyes and sore throats. Saharan dust is transported across the Atlantic Ocean to South America and beyond to the Caribbean Sea and is the largest transport of dust on the planet. Dust clouds from the Sahara Desert are often so big they can be seen from space.

    There are two main causes of Saharan dust transport, depending on the time of year. Harmattan Winds bring mild to moderate outbreaks across Trinidad and Tobago from November to the middle of March.

    Thunderstorms across Central and Western Africa being mild to severe outbreaks across Trinidad and Tobago between April and November, with peak outbreaks occurring from June through August.

Here are some of the benefits and hazards of Saharan dust:




Benefits:

• Replenishes the Amazon Rainforest with much needed phosphorus.

• It is a significant contributor of iron to marine algae. Phytoplankton in the Caribbean and along the southeastern U.S. coast feeds on this iron as well. It allows these organisms to thrive and produce a significant amount of oxygen.

• It can also affect the formation of clouds as the layer of air in which Saharan dust is transported across the Atlantic is quite dry, suppressing cloud development. This dry air lay (Saharan Air Layer) also suppresses and hinders the development of tropical cyclones.

• With increased dust in the atmosphere, increased scattering of light occurs at sunset. This allows for more colorful sunsets.

Hazards

• High concentrations of dust with a diameter of fewer than 2.5 micrometers have been correlated with increases in emergency room admissions for respiratory and cardiovascular disease in North America, Asia, and Europe. The primary health concern associated with Saharan dust is particulate matter that can sidestep the lungs’ natural defenses can contribute to cardiovascular problems as well as respiratory diseases such as asthma, especially in children and the elderly.

• The dust particles also serve as a vehicle for the transport of known asthma triggers such as biological materials, including bacteria, viruses, fungal spores, and pollen. It has also been shown to transport various pollutants such as metals and pesticides. Dry skin and cracked lips are also typical symptoms of dense Saharan dust.

• Dust in our atmosphere ultimately causes hazy skies. Depending on the concentration, these hazy skies can significantly reduce visibility at airports, on the roadways, and on shipping lanes.

• Saharan dust has several implications with regards to the weather.

• The dust can reflect or block sunlight, causing lower than usual temperatures on the surface. However, this effect is only observed when concentrations are very unhealthy to hazardous.

• It can also affect the formation of clouds suppressing the development of tropical cyclones. The negative side of this is rising ocean temperatures, bleaching corals and impacting predominant ocean currents which as a number of knock-on effects. Additionally, tropical cyclones can attribute a significant amount of rainfall for areas in which freshwater access is limited.

• As the Saharan Air Layer is a well-mixed layer of dry air between 5,000 ft and 15,000 ft, this provides conditions to be favorable for higher instability and convective wind gusts at the surface in strong thunderstorms.

• The dust mixes with the rainfall, and when it lands on the surface, it becomes a layer of dust and mud when the dust is particularly thick.

• Pathogenic bacteria feed on the dust nutrients and create bacteria blooms which play a role in many diseased ocean organisms. Filter-feeding shellfish accumulate Vibrio parahaemolyticus and Vibrio vulnificus in their meat. This causes the majority of seafood-related sickness and death in the U.S. Other Vibrio species are known to be associated with diseased coral that is already facing so many other environmental stressors Vibrio disease and mortality have even placed an economic strain on the fishing and shrimp farming industries.