
Onitsha —
Onitsha -- a city few outside Nigeria will have heard of -- has the undignified honor of being labeled the world's most polluted city, according to data released by the World Health Organization (WHO) in 2016.

Onitsha —
The booming port city in southern Nigeria, recorded 30 times more than the WHO's recommended levels of particulate matter concentration.

Onitsha —
"The contributing factors to pollution are a reliance on using solid fuels for cooking, burning waste and traffic pollution from very old cars," Dr Maria Neira, WHO Director, Department of Public Health, Environmental and Social Determinants of Health, told CNN.

Kaduna —
The transport hub of Kaduna, in the north, came fifth on the list, although the report only included pollution levels from cities with a population of over 100,000 residents that monitor their pollution levels -- something many African cities don't do.

Kaduna —
"We need to do an assessment of the sources of pollution at city level, also work on better planning of urban collective transport systems, and take very old cars out of service," said Neira.

Aba —
Trade centers in southern Nigeria, Aba and Umuahia, came sixth and 16th on the list, respectively. Last year, the World Bank reported that 94% of the population in Nigeria is exposed to air pollution levels that exceed WHO guidelines (compared to 72% on average in Sub-Saharan Africa in general) and air pollution damage costs about 1% post of Gross National Income.



