OPINION : AFRICA AIR POLLUTION
What are the main sources and drivers of air pollution ? Are the main sources and drivers of air pollution different from those on other continents ?
The answers to these questions are severely hampered by a lack of data as well as poor regulation and laws in African countries . The only country on the continent that has ambient air quality standards enforced by air quality laws and regulations is South Africa . Other countries have either ambient air quality standards or air quality laws and regulations , or none at all .
What ’ s known
Air pollution is a complex mixture of many components . The WHO ’ s air quality guidelines , as well as country-specific laws , have identified a few air pollutant components : particulate matter smaller than 2.5 micrometer ( PM2.5 ) and 10 micrometer ( PM10 ) in aerodynamic diameter , sulphur dioxide ( SO2 ), ground-level ozone ( O3 ), carbon monoxide ( CO ), benzene , lead and nitrogen dioxide ( NO2 ).
The most dangerous are PM2.5 and ultrafine particles ( UFP ); the latter are smaller than 100 nanometer in aerodynamic diameter . PM2.5 and UFP penetrate deeper into the lung alveoli and may pass into the bloodstream . PM10 and PM2.5 are important indicators of long-term air quality and of health risks . Based on data of ground measurements conducted in 2008- 2015 , Africa ’ s PM10 levels are not the highest in the world .
The database is the largest of its kind and covers over 3,000 human settlements – mostly cities – in 103 countries . The number one spot belongs to the Eastern Mediterranean region , followed by the South-East Asia region and then Africa . But the WHO acknowledges numerous limitations to the data sources . Fewer sites globally measure PM2.5 , hence the focus is on PM10 .
The PM2.5 data based on the
WHO air quality model show that the number one spot again belongs to the Eastern Mediterranean region , followed by the South-East Asia region and then Africa . Given the lack of PM2.5 ground measurements in Africa , the PM2.5 data derived from the WHO air quality model for Africa should be viewed with caution .
Where is the air worse in Africa ?
It is hard to say what the real picture is . The modelled PM2.5 data supplements the data from ground monitoring networks , especially in regions with no or very little monitoring , as is the case in Africa .
The PM10 data , based on ground measurements conducted between 2008 and 2015 , show that all African countries with PM10 data exceeded the WHO annual guideline of 20 microgram / cubic meter (µ g / m ³).
Onitsha in Nigeria had the highest yearly PM10 level of 594 µ g / m ³ globally , nearly 30 times higher than the WHO annual guideline . But the quality of the data is questionable . The level for Onitsha is based on PM10 data collected only in 2009 and only at one site . The database also does not mention on how many days the 2009 yearly level is based as missing data can lead to a distorted yearly level . The lowest yearly PM10 level was recorded at Midlands in Mauritius ( 20 µ g / m ³). But this is based only on 2011 data collected again at only one site without mention of how many days in 2011 were measured .
It is also difficult to know exactly what the contribution of different sources of air pollution are in Africa .
The amount of air pollution in any given location is affected by a combination of local , regional and distant sources . It is also affected by the dispersion of pollutants , which in turn depends on numerous weather conditions such as wind direction , temperature and precipitation .
A recent review indicated that very few studies in Africa conducted source apportionment of PM2.5 and
PM10 . The review concluded that ( based on the few studies ) 17 %, 10 %, 34 %, 17 % and 22 % of PM2.5 levels in Africa are due to traffic , industry , domestic fuel burning , unspecified source of human origin and natural sources - such as dust and sea salt . For PM10 the corresponding source distribution is 34 %, 6 %, 21 %, 14 % and 25 %, but should be viewed with caution due to the few studies .
Based on the limited number of PM10 and PM2.5 source apportionment studies in Africa , these tentative conclusions can be drawn . Traffic is a major source of PM10 levels in Africa as in many other global regions . The other two major sources of PM10 in Africa are domestic fuel burning and natural sources . In other regions of the world , industry and the ambiguous “ unspecified source of human origin ” contribute more .
Domestic fuel burning is the major source of PM2.5 in Africa , followed by traffic and natural sources such as dust . In other regions of the world , traffic , industry and the ambiguous “ unspecified source of human origin ” contribute more to PM2.5 levels .
Air quality interventions
Regardless of the exact global source contributions , the main sources of air pollution should be tackled globally in management plans and interventions . Obvious interventions include clean energy technology such as solar power , to minimise domestic fuel burning and emissions from coal-fired power plants . Other initiatives include clean public transport , bicycle lanes to cut traffic emissions , recycling and controls on industrial emissions .
Air pollution does not stop at country or continental borders . It is a major risk factor for climate change . A disregard for air pollution levels in Africa may have a major impact on global climate change in the years to come . – Janine Wichmann is an Associate Professor and the University of Pretoria – The Conversation
2016 | Business Times Africa 21