Air pollution from burning forests in Africa is wafting throughout the Southern Hemisphere, previously considered relatively clean compared with the heavily industrialized North, researchers said.
In a study analyzing satellite monitoring data and ground-based pollution measurements, four atmospheric scientists found elevated levels of carbon monoxide, methane and ozone at certain times of the year in Africa, Australia and Antartica.They said last week the seasonal increases in pollutant levels appear to be linked with widespread burning of forests in tropical and subtropical Africa during the dry season from August to October.
Using ground-based measuring devices, the scientists detected high ozone concentrations over the west coast of southern Africa and the adjacent Atlantic Ocean that coincide with the burning season.
Ozone in the lower atmosphere is considered a health-threatening pollutant, as opposed to "good" ozone in the upper atmosphere, which screens out harmful ultraviolet radiation from the sun.
The researchers also said satellite data - some collected by the space shuttle - show fire-related pollution is transported long distances by winds that disperse it throughout that hemisphere.
"Widespread air pollution has generally been regarded as a . . . phenomenon identifiable with industrialized nations, primarily in the Northern Hemisphere," the international team of scientists wrote in a paper published in the journal Science.
"These data suggest that even the most remote regions on this planet may be significantly more polluted than previously believed."
The paper was submitted by J. Fishman at the atmospheric sciences division of the National Aeronautics and Space Administration, K. Fakhruzzaman at ST Systems Corp., in Hampton, Va., and B. Cros and D. Nganga of the Laboratoire de Physique de l'Atmosphere at the Universite Maien Ngouabi in Brazzaville, Republic of Congo.
Among other supporting data, the scientists said satellite measurements of carbon monoxide taken by the space shuttle in November 1981 and October 1984 confirmed that large amounts of that pollutant came from Africa as a result of biomass burning.
Biomass burning includes the intentional burning of forests to clear farmland.
Subsequent analysis of those measurements found carbon monoxide originating in Africa had moved over the eastern Indian Ocean and then was transported more than 4,500 miles to the southeast, almost reaching Australia.
They argued their theory also was supported by monitoring data showing that peak atmospheric levels of carbon monoxide and methane occurred at roughly the same time - September and October - at locations in Australia, South Africa and Antarctica.