Which air pollutant is typically found in the highest concentrations in urban environments?

Carbon monoxide is typically found in the highest concentrations in urban environments primarily due to its direct association with vehicular emissions. In cities, the high density of traffic and the operation of internal combustion engines result in significant releases of carbon monoxide as a byproduct of fuel combustion. This pollutant is especially prevalent in areas with heavy traffic, such as busy intersections and crowded roadways, where incomplete combustion occurs more frequently.

While sulfur dioxide and nitrogen oxides are also significant air pollutants associated with industrial activities and vehicle emissions, their concentrations tend to be lower than those of carbon monoxide in urban settings. Ozone, although it can reach high levels in urban areas as a secondary pollutant formed from the reaction of sunlight with nitrogen oxides and volatile organic compounds, typically does not have the same direct emission sources as carbon monoxide.

Understanding the sources and behaviors of air pollutants in urban environments helps prioritize monitoring and mitigation strategies to protect public health and the environment.