When Jenny Linden, an air quality scientist, tried to measure the pollution in Burkina Faso’s capital city, one of her instruments clogged up. It was designed for road dust in Arizona, but the dust in Ouagadougou far exceeded the machine’s limit, and it had to be sent to the United States for repair.
The instrument “could not take the level of pollutants they had there,” recalled Dr. Linden, who took measurements in Ouagadougou between 2003 and 2007 and is now a research associate in urban climatology at the University of Mainz, in Germany. So intense was the dust, she added, that “you don’t have a cold but you have an irritated nose the whole time.”
Air pollution in Asia and Europe has grabbed headlines. But as Dr. Linden’s experience suggests, the problem is pervasive across Africa as well. Africa is urbanizing quickly, and pollution from sources like vehicle exhaust, wood burning and dusty dirt roads has reached worrisome levels in many cities. Equally or more troubling is air pollution inside homes, caused by cooking with wood or other sooty fuels. But few nations outside South Africa have imposed regulations to address the problem, experts say.
“We do know that in Africa, there’s a very major problem with indoor air pollution,” said Dr. Carlos Dora, an official with the World Health Organization’s Department for Public Health and Environment. Data for outdoor air pollution in cities, he added, is less available and may not capture the scope of the problem.
Dirty air can cause lung damage as well as heart disease, strokes and cancer. Last month the W.H.O. estimated that one in eight deaths worldwide resulted from air pollution. The organization found that air pollution in African homes contributed to nearly 600,000 deaths in 2012. Africa had the third highest level of deaths per capita from indoor air pollution of any region of the world, though it was still well behind areas of the western Pacific region (including China) and Southeast Asia.
The W.H.O. figures for deaths per capita from outdoor air pollution in Africa are well below the world average, but the lack of data is a barrier. Pollution monitoring is minimal on a continent that is mostly focused on other problems. Instruments are expensive, and academics say they often struggle to get grants to study the problem. The W.H.O. assesses outdoor pollution in Africa by drawing from satellite data, inventories of pollution sources, air-current modeling and occasional ground monitors, Dr. Dora said. Continentwide data is stronger than that for individual countries, he added.
In Nairobi, the Kenyan capital, normal levels of fine dust (meaning particles less than 2.5 micrometers in diameter, about 1/30 of the width of a human hair and a significant health threat) are usually five times as high as those in Gothenburg, Sweden, according to Johan Boman, a professor of atmospheric science at the University of Gothenburg. The Nairobi pollution doubles near the central business district, he said, reflecting high pollution from vehicle exhaust.
“It’s certainly not as bad as what we see from China,” he said. “On the other hand, in China it’s very much seasonal,” whereas Nairobi, with its relatively stable climate, has less variation.
A survey several years ago by the W.H.O. showed Gaborone, Botswana, as having the eighth-highest level of particulate pollution (particles of up to 10 micrometers in diameter) among a list of world cities. But the W.H.O. stresses that it is an incomplete list, since many cities did not provide data — including some of the most polluted.
The outdoor pollution problem is growing, as more Africans move to cities. Ms. Linden, who did research in Burkina Faso until 2007, said that “the situation is likely worse now” because Ouagadougou’s population has swelled by more than 50 percent since then. Major outdoor sources of pollution include old vehicles; the burning of wood and trash; industrial activities; and even dust from dirt roads, a serious issue in Ouagadougou. In West Africa, a wind called the harmattan adds to the problem in the winter, coating the region in Saharan desert dust.
One recent study, published in the journal Environmental Research Letters, estimated that Africa could generate 20 percent to 30 percent of the world’s combustion-driven sulfur dioxide and nitrogen oxides by 2030, up from about 5 percent each in 2005. Other pollutants are growing too: Organic carbon from Africa could rise to over 50 percent of the world’s combustion output, from 20 percent, the study said. The authors did their calculations using estimates about fuel consumption, growth and other emissions factors, and warned of “a considerable increase in emissions from Africa” in the absence of regulations.