A massive cloud of hazardous dust blowing across the Atlantic from the Sahara Desert darkened much of Cuba and Puerto Rico on Wednesday and began to affect air quality in Florida.
It also sparked warnings to people with respiratory illnesses to stay home.
The dust cloud swept across the Atlantic from Africa over the past week, covering the Caribbean island of Puerto Rico since Sunday and hitting south Florida in the United States on Wednesday, authorities said.
Conditions over the Cuban capital Havana are expected to worsen on Thursday, specialists on the Communist-run island reported.
Francisco Duran, head of Epidemiology at the Ministry of Health, said the cloud is likely to “increase respiratory and allergic conditions”.
Air quality in Miami is currently “moderate” the city’s health department said, asking people with respiratory problems to stay home.
Powered by strong winds, dust from the Sahara travels across the Atlantic Ocean from West Africa during the boreal spring.
But the density of the current dust cloud over Cuba “is well above normal levels,” said Cuban meteorologist Jose Rubiera.
“The highest concentration over the capital will occur tomorrow,” he said.
In Havana, scientist Eugenio Mojena said the phenomenon “causes an appreciable deterioration in air quality.”
Mojena said the dust clouds are loaded with material that is “highly harmful to human health.”
Mojena listed “minerals such as iron, calcium, phosphorous, silicon and mercury” in the dust, and said the clouds also carried “viruses, bacteria, fungi, pathogenic mites, staphylococci and organic pollutants.”
According to the Institute of Meteorolgy, temperatures in Cuba’s eastern province of Guantanamo reached a record for the time of year of 37.4 degrees Celsius on Wednesday.
In a report by NASA in 2013, the tons of blown across the Atlantic Ocean by the Sahara helps build beaches in the Caribbean and fertilize soils in the Amazon.
Some meteorologists have speculated that a particularly dry and dusty Saharan Air Layer could suppress hurricane formation in the North Atlantic.
Dry air masses from Africa can sap the moisture-collecting energy of storm systems over the ocean.
More dust can also mean fewer storms because it blocks incoming sunlight, leading to cooler ocean temperatures.