Air pollution in a large tropical city with a high traffic density — results of measurements in Lagos, Nigeria

The joint project, ‘Environmental Monitoring and Impact Assessment in Nigeria’ consisted of universities from Nigeria, Germany and Great Britain, and was funded by the European Union. Within the context of this project, an air monitoring station was purchased and placed in Lagos, the former capital of Nigeria. In addition to these permanent measurements, single samples were taken at different places in Lagos. A northern wind, the so-called Harmattan, transports much dust from the Sahara. But most of the identified air pollution in Lagos is caused by the traffic which can even be recognized without measurements, by strong turbidity, bad smell and eye irritation. This pollution is caused by the combination of many strongly emitting vehicles and frequent traffic jams. Diesel vehicles emit plumes of black smoke consisting of soot. Many petrol engined cars exhaust blue smoke which is caused by unburnt oil; market places are established especially around bus stops, and many people are exposed to unhealthily high concentrations of aromatic hydrocarbons, CO and particles. The results of measurements at such places are presented here. The measured CO values, for instance, often exceed the limits set by WHO guidelines. These initial results show that drastic measures are necessary to protect the population against this high pollution. The measured benzene concentrations cause a raised carcinogenic risk.