Carboxyhaemoglobin Levels among Traders Exposed to Vehicular Emissions in Three Motor Parks in Ibadan, Nigeria

Carbon monoxide (CO) remains a leading cause of work-related chemical poisoning. Vehicular emissions are the primary daily ambient source of CO in urban Nigerian motor parks, where there have been few human exposure studies. Using a cross-sectional comparative design, we assessed carboxyhaemoglobin levels (% COHb), a biomarker of CO exposure, among traders at three motor parks (AMP, IMP, and NMP) and other traders (nonmotor park workers) in Ibadan, Nigeria, using a noninvasive pulse CO-dosimeter (Rad 57). Ninety-three traders were proportionally allocated between motor parks; 93 other traders were selected based on specific study inclusion criteria. Mean ages of motor park traders and other traders were comparable, 37.8 ± 11.1 and 38.7 ± 9.6, respectively. Mean % COHb for traders (range 3–22) at AMP, IMP, and NMP was 11.2 ± 3.8, 11.6 ± 3.1, and 12.2 ± 3.3, respectively, while mean % COHb for other traders was about three times lower, 4.1 ± 1.7 (range 2–8). Overall, mean % COHb for motor park traders, 11.7 ± 3.3, was also significantly higher than for other traders (p < 0.05). Nevertheless, mean % COHb for both groups exceeded the current World Health Organization guideline, 2.5%. This study suggested that motor park traders have higher % COHb and thus are highly susceptible to exposure and more vulnerable to known risks of adverse health effects from exposure to CO.