Carbon monoxide (CO) is a widely distributed air pollutant. It is a colorless, odorless, and tasteless gas that is poorly soluble in water. CO has a high affinity to hemoglobin and reacts readily by binding reversibly to one of the heme proteins to form carboxy-hemoglobin (COHb) in the human body and thus reduces oxygen-carrying capacity of the blood. In humans, COHb is a biomarker and indicates exposure to CO. Upon reaching the lungs, CO diffuses rapidly across the alveolar and capillary membranes into the bloodstream and readily crosses placental membranes. CO exposure is a significant cause of accidental poisonings and causes many deaths annually in Europe and the U.S. (World Health Organization [WHO], 2000).
Banjoko and coauthors (2008) investigated %COHb levels among smokers and nonsmokers in Ibadan city, Nigeria, and reported significantly different (p
There are an estimated 5,000 petrol stations in Nigeria with more than 100,000 filling station workers exposed to petrol fumes and air pollutants from vehicle exhaust as they dispense fuel into tanks of automobiles and trucks on a daily basis (Akintonwa & Oladele, 2003). According to the Government of Canada (2020), approximately 3,950 persons work as service station attendants in the province of Ontario, Canada, with nearly half (49%) of them working year-round. In comparison, the U.S. Bureau of Labor Statistics (2020) estimated the number of service station attendants in the U.S. at 20,070. These numbers raise a serious public health concern regarding concentrations of air pollutants that filling stations workers are exposed to and subsequent adverse health outcomes. These adverse outcomes are not easily determined due to the absence of pre-employment health examinations and routine medical checkups (Udonwa, Uko, Ikpeme, Ibanga, & Okon, 2009).
Limited information on ambient air quality in smaller cities/urban areas in less developed countries exists, especially with respect to specific outdoor work microenvironments and the health and safety of susceptible, vulnerable population subgroups. Therefore, this study assessed and provided information on the exposure levels of workers at filling stations (filling station attendants [FSAs]) to CO and the likelihood of these attendants developing adverse health outcomes, particularly acute symptoms, in Ibadan, Nigeria. Currently, there are no local standards or guidelines protecting occupational health and safety of FSAs in Nigeria. Additionally, Kuranchie and coauthors (2019) described neighboring Ghana's occupational safety and health laws for pump workers as weak.
In the U.S., the risk of exposure remains relevant, for example, in the State of New Jersey, where people must pay paid attendants to pump unleaded and diesel gas. In New Jersey, the Retail Gasoline Dispensing Safety Act and Regulations (Retail Gasoline Dispensing Safety, n.d.) is aimed at protecting FSAs in New Jersey and mitigating risks of exposure to hazardous conditions.
The study area was Ibadan North Local Government Area in Ibadan city, Nigeria. Ibadan (7[degrees]22'39" N; 3[degrees]54'21" E) is approximately 119 km (74 miles) northeast of Lagos and 120 km (75 miles) east of the Nigerian international border with the Republic of Benin. It lies completely within the tropical forest zone but close to the boundary between the forest and the savanna. The city ranges in elevation from 150-275 m above sea level. Ibadan has a tropical w et and dry climate with a lengthy wet season and relatively constant temperatures throughout the course of the year. The mean total rainfall for Ibadan is 1,420 mm. There are two peaks for rainfall, June and September. The mean maximum temperature is 26.5 [degrees]C, minimum is 21.4 [degrees]C, and the relative humidity is 74.6%.
Sampling and Selection of Filling Stations
We used a systematic sampling procedure to select filling stations for this study. We randomly selected a local government area and then chose 50% of the 40 active filling stations (at the time of the study) within the selected area for the study. Therefore, 20 active filling stations were selected for the study by selecting every other filling station on the list. We recruited 100 FSAs who were nonsmokers, approximately 50% of the total number of survey respondents, from the 20 selected filling stations for human exposure assessment using a convenience sampling method whereby only willing consenting persons were recruited.