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Aerosols affecting West Africa

Busy streets in Accra, capital of Ghana Busy streets in Accra, capital of Ghana Sura Nualpradid
28 Aug
2015
Unchecked pollution from West African cities could harm health, affect food production, and even change the monsoon season warn scientists

On 12 October 2005, the population of Lagos woke up to thick, toxic smog. During the six-hour incident there was widespread panic. Afterwards, it rang alarm bells for the West African atmosphere.

As the sixth largest city in the world, Nigeria’s Lagos has a burgeoning manufacturing sector and produces large amounts of anthropogenic particulates. A lack of intra-rail systems means the city’s 21 million inhabitants mainly travel by road, upping the emissions of the inner city. While the 2005 smog has been considered a major incident, Lagos is just one of many West African cities that suffer from atmospheric pollution.

aerosol Satellites pick up on the thickness along the cities of the Guinea coast (Image: Nature)

 

RAPID URBANISATION

Africa’s urban population is growing faster than any other region in the world, it is estimated that by 2030 over half the continent’s population will be urban. The vastly expanding cities such as Lagos in Nigeria, Accra in Ghana and Abidjan in the Ivory Coast produce escalating amounts of industrial pollutants and traffic emissions. Burning biomass, either in open-air incinerators or at dump sites, pumps even more particulates into the air.

At a local level, the pollutants endanger the population – with asthmatics most at risk from choking fumes. On a regional scale, a new report by the African and European research group, Dynamics-aerosol-chemistry-cloud interactions in West Africa (DACCIWA), looks to the greater impact the pollution might have on the pollution-sensitive monsoon season, which dictates the temperature, clouds, wind and rain needed to produce food in the surrounding countryside.

The report, published in Nature, detailed how burning biomass adds carbon aerosols to the air that can change the reflectivity of clouds. Meanwhile, volatile organic compounds such as carbon monoxide can indirectly change the climate by altering ozone and methane concentrations. ‘How that manifests itself with something like rainfall, which is what really matters, is much more complicated,’ said Mat Evans, an atmospheric chemist at the University of York and one of the authors of the study. ‘The environmental degradation may be local, but the implications can be regional and global.’

He fears that a changing monsoon could trigger widespread migration. ‘If people have no food because the climate is changing in their region, then they will move. There are knock-on effects.’

cotonou-traffic copyCotonou’s Dantokpa market where DACCIWA will measure traffic emissions (Image: DACCIWA)

 

DATA VACUUM IN WEST AFRICA

Small-scale observational studies on the West African cities, conducted by the United Nations Environmental Programme, suggest that the pollutants are already substantially above World Health Organization guidelines. However, the DACCIWA report states that there is a total lack of data in the region.

Unlike many European cities (London’s records have a satellite resolution of 30 metres), there are no emissions inventories for African locations. ‘Given the short lifetime of many pollutants, this makes estimating human exposure very challenging,’ reads the report.

‘Ultimately, what we want to be able to do is make predictions about what we think will happen on a five, ten and 50-year timescale,’ says Evans. He fears that neglecting the issue could further endanger health and food security in the future.

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