Thick brown air over Shanghai, China
Thick brown air over Shanghai, China. Photo: Lei Han / Flickr.

New data on urban air quality from the World Health Organization recently led Onitsha, Nigeria, to be given the title of “most polluted city” in the world. International media also singled out the “most polluted city” in their region, and highlighted countries such as India, which had several cities in the “top five”.

Of course, it’s important to highlight cities where pollution is a big concern. Air pollution is a “silent killer”, which can increase the risk of stroke, heart disease, lung cancer and respiratory diseases such as asthma. Often, poorer and more vulnerable groups, such as children and the elderly suffer these effects the most.

But this “name and shame” approach risks being inaccurate and misleading. For one thing, the pollutants that cause poor air quality can vary significantly between cities. Saying one city is more polluted than another is a bit like comparing apples and oranges – particularly when it comes to developing countries. To understand why, we need to dig down further into the data.

Source: The Conversation, UK