Toxic Dust Delivered to You by Air Mail

    As a person allergic to dust and concerned about pollution of our environment, I found the article "The Global Transport of Dust" (Griffin et al., 2002, American Scientist, 90, 228-235) rather disturbing. The authors document how two billion metric tons of dust are carried into the Earth's atmosphere every year. These days this dust contains not only soil but also a toxic mix of chemicals, bacterial, viruses, fungi, and pollen. These toxins are carried far from their sources and deposited elsewhere around the world.

    The most troublesome sources of toxic dust are arid regions, which having been increasing in size. Consider Mali, southwest of Algeria in the Sahel region of Northern Africa. Mali is one of the poorest nations in the world. The Niger river is a sewer, full of feces, excreted drugs, and pathogenic micro-organisms. Once a year this river floods and deposits fine sediment in the floodplain. Citizens of Mali plant their gardens on this sediment, treat the gardens with herbicides and pesticides, and burn their garbage on it (in an attempt to fertilize the soil). In the past this garbage consisted of organic waste, but in the past 20 years much of the garbage has been tires and plastic, which produce rather nasty toxins when burned. The toxins stick to fine particles of the clay soil and then are carried into the atmosphere by strong winds. This toxic dust, also laden with pathogenic microbes, is carried across the Atlantic and deposited in the Americas. During the last 20 years there has been an increase in the amount of African dust deposited in the Caribbean. During this same period of time the incidence of asthma in the Caribbean has increased 17 fold! African toxins are poisoning the Americas. Some of the dust particles are so fine that once inhaled they cannot be exhaled. They lodge in the lungs next to capillary beds, where their toxins are released into the blood supply. Not only humans are affected. Material carried in the winds from Africa has been implicated in causing diseases in various crops, red tide algal blooms in coastal waters, and damage to coral reefs.

    Do not think that the only source of this toxic dust in Africa and the only victim the Americas. African dust frequently affects air quality in Europe and toxic dust from the Gobi desert in China is blown across North America to Europe. Its a small world after all.