According to the World Health Organisation, Air pollution is responsible for the deaths of about 6.5 million people globally. Air pollution in Uganda has reached worrying levels and exposes people to health risks, especially in Kampala. The number of respiratory tract infections in Kampala has soared in the recent past – a warning that air pollution is rapidly becoming a serious environmental threat.

Several studies have linked mounting respiratory tract infections such as asthma and chronic bronchitis to air pollution. The effects can be extremely serious. Research shows a connection between air pollution and lung cancer, and suggests it may contribute to childhood mortality.

Cycling to work in certain highly polluted cities could be more dangerous to your health than not doing it at all, reads a study originally published in the journal, Preventive Medicine.
This study, carried out in more than 10 cities globally, shows that the level of toxins in the air causes harm to human health.
From the study, harm will occur to you depending on how long you spend either walking, jogging or even cycling on the road.

Kampala City tops the list for cities with the most polluted air in East, Central and Southern Africa. Here, 90 minutes of exposure to the fumes are enough to cause damage to your health. 
Other cities in Africa include Bamenda in Cameroon, where 45 minutes on the road are enough to cause harm.
And, after 105 minutes in Kaduna, Nigeria, you are likely to catch complications from dangerous gases in the air.

Nevertheless, there are some preventive measures(some already implemented while others may take some time to be achieved)  such as; tightening the noose on importation of used cars, greening the city, promoting e-mobility and improving the methods of checking for air quality .

http://www.who.int/airpollution/en/

http://www.monitor.co.ug/SpecialReports/Quality-Kampala-air-deathtrap/688342-4310794-11eynt/index.html

http://www.dw.com/en/five-ways-to-improve-air-quality-in-our-cities/a-37149216