Ambient Air Quality and Potential Inhalation Exposure Around Selected Waste Dumpsites in Port Harcourt Metropolis, Nigeria

values NO2 47–159.80 μg/m3; highest at L2 Respiratory irritation and aggravation of respiratory conditions Important potential respiratory concern, particularly at L2 IJGEM IJGEM IIARD International Journal of Geography & Environmental Management O3 19.60–117.60 μg/m3; highest mean at L3 Elevated exposure may impair respiratory function and aggravate asthma Potential concern, particularly at L3 and during elevated measurements Source: Field Measurements (2026); World Health Organization. Characteristics of Respondents and Exposure Patterns A total of 186 respondents participated in the exposure assessment, comprising 110 residents and 76 workers. Each monitoring location contributed 62 respondents, representing 33.3% of the total sample. This balanced distribution provided comparable respondent numbers across the three locations. Table 7: Distribution of Respondents by Location and Category Location Residents, n (%) Workers, n (%) Total, n (%) L1 38 24 62 (33.3) L2 35 27 62 (33.3) L3 37 25 62 (33.3) Total 110 76 186 (100.0) Source: Field Survey (2026). Duration of Exposure As shown in Table 8, 67 respondents (36.0%) had lived or worked in the vicinity of the dumpsites for 1–5 years, representing the largest exposure-duration category. This was followed by 53 respondents (28.5%) who reported 6–10 years of exposure. Twenty-eight respondents (15.1%) had less than one year of exposure, while 24 (12.9%) and 14 (7.5%) reported 11–15 years and more than 15 years, respectively. Table 8: Exposure Duration among Respondents Duration L1 (n) L2 (n) L3 (n) Total (n) % <1 year 9 11 8 28 15.1 1–5 years 22 24 21 67 36.0 6–10 years 18 16 19 53 28.5 11–15 years 8 7 9 24 12.9 >15 years 5 4 5 14 7.5 Total 62 62 62 186 100.0 Source: Field Survey (2026). Daily Exposure Time Table 9 indicates that 55 respondents (29.6%) spent 5–8 hours per day in the dumpsite vicinity, while 54 (29.0%) spent 2–4 hours. Thirty-six respondents (19.4%) reported more than 8 hours per day, and 41 (22.0%) reported less than 2 hours per day. IJGEM IJGEM IIARD International Journal of Geography & Environmental Management Table 9: Daily Exposure Time in the Dumpsite Vicinity Daily exposure time L1 (n) L2 (n) L3 (n) Total (n) % <2 hours 14 12 15 41 22.0 2–4 hours 19 17 18 54 29.0 5–8 hours 18 20 17 55 29.6 >8 hours 11 13 12 36 19.4 Total 62 62 62 186 100.0 Source: Field Survey (2026). Exposure Frequency Table 10 shows that 64 respondents (34.4%) reported spending 5–6 days per week in the dumpsite vicinity. Forty-five respondents (24.2%) reported exposure on 3–4 days per week, while another 45 (24.2%) reported exposure every day. Thirty-two respondents (17.2%) reported exposure on 1– 2 days per week. Table 10: Frequency of Exposure to the Dumpsite Vicinity Days per week L1 (n) L2 (n) L3 (n) Total (n) % 1–2 days 11 9 12 32 17.2 3–4 days 16 15 14 45 24.2 5–6 days 21 23 20 64 34.4 7 days 14 15 16 45 24.2 Total 62 62 62 186 100.0 Source: Field Survey (2026). Occupational and Exposure Categories Residents constituted the largest exposure category, accounting for 65 respondents (34.9%), followed by nearby traders with 33 (17.7%) and waste pickers with 28 (15.1%). Scavengers constituted 11.8%, while waste transporters and dumpsite workers each accounted for 7.0%. Table 11: Occupational and Exposure Categories of Respondents Category L1 (n) L2 (n) L3 (n) Total (n) % Waste picker 9 11 8 28 15.1 Scavenger 7 8 7 22 11.8 Waste transporter 4 5 4 13 7.0 Dumpsite worker 4 3 6 13 7.0 Nearby trader 12 10 11 33 17.7 Resident 22 21 22 65 34.9 Other 4 4 4 12 6.5 Total 62 62 62 186 100.0 Source: Field Survey (2026). Distance of Residence or Workplace from Dumpsite Table 12 indicates that 55 respondents (29.6%) lived or worked within 50 m of the dumpsites, while 48 (25.8%) were located 50–100 m away. Forty-two respondents (22.6%) were located 101– IJGEM IJGEM IIARD International Journal of Geography & Environmental Management 250 m away, 26 (14.0%) were 251–500 m away, and 15 (8.1%) were located more than 500 m from the dumpsites. Table 12: Distance of Residence or Workplace from Dumpsites Distance L1 (n) L2 (n) L3 (n) Total (n) % <50 m 18 21 16 55 29.6 50–100 m 16 15 17 48 25.8 101–250 m 14 13 15 42 22.6 251–500 m 9 8 9 26 14.0 >500 m 5 5 5 15 8.1 Total 62 62 62 186 100.0 Source: Field Survey (2026). Derived Exposure Parameters Midpoint estimates were used to derive representative exposure duration, daily exposure time and annual exposure frequency for the exposure-concentration calculations. The overall estimated exposure duration was 6.9 years, mean daily exposure time was 5.1 hours/day, and mean exposure frequency was 244 days/year. The corresponding time-activity factor was 0.142. Workers had the highest estimated time-activity factor (0.252), compared with 0.083 among residents. Respondents located within 100 m of the dumpsites had a time-activity factor of 0.173. Table 13: Derived Exposure Parameters Used for Time-Weighted Exposure Concentration Exposure group Mean ED Mean ET (h/day) Mean EF (days/year) Time-activity factor (ET/24 × EF/365) Overall 6.9 5.1 244 0.142 Workers 7.4 7.3 302 0.252 Residents 6.5 3.6 203 0.083 <100 m 7.1 5.8 261 0.173 Source: Calculated from Field Survey (2026). Note: ED = exposure duration; ET = exposure time; EF = exposure frequency. Estimated Time-Weighted Inhalation Exposure Concentrations Time-weighted exposure concentrations were estimated using: EC= C× ET 24 × EF 365 where EC is the estimated exposure concentration and C is the measured ambient concentration. Using the corrected overall pollutant means, the estimated exposure concentrations were 3.07 μg/m3 for PM2.5, 4.26 μg/m3 for PM10, 14.59 μg/m3 for NO2, 13.31 μg/m3 for O3, 0.107 mg/m3 for CO and 0.00 μg/m3 for SO2. IJGEM IJGEM IIARD International Journal of Geography & Environmental Management Table 14: Estimated Time-Weighted Inhalation Exposure Concentrations Pollutant Mean ambient concentration Overall exposure factor Estimated exposure concentration PM2.5 (μg/m3) 21.56 0.142 3.07 PM10 (μg/m3) 30.00 0.142 4.26 NO2 (μg/m3) 102.77 0.142 14.59 O3 (μg/m3) 93.64 0.142 13.30 CO (mg/m3) 0.75 0.142 0.107 SO2 (μg/m3) 0.00 0.142 0.00 Source: Calculated from Field Measurements and Field Survey data (2026). Estimated Inhalation Exposure by Exposure Group Table 15 presents estimated exposure concentrations according to exposure group. Workers had higher estimated exposure concentrations than residents for all pollutants because of their greater reported daily exposure time and exposure frequency. For example, estimated PM2.5 exposure was 5.46 μg/m3 among workers compared with 1.79 μg/m3 among residents. Among respondents located within 100 m of the dumpsites, the estimated PM2.5 exposure was 3.73 μg/m3. Table 15: Estimated Inhalation Exposure Concentrations by Exposure Group Pollutant Ambient mean Residents EC Workers EC <100 m EC PM2.5 (μg/m3) 21.56 1.79 5.45 3.73 PM10 (μg/m3) 30.00 2.49 7.56 5.19 NO2 (μg/m3) 102.77 8.53 25.90 17.78 O3 (μg/m3) 93.64 7.77 23.60 16.20 CO (mg/m3) 0.75 0.062 0.189 0.130 SO2 (μg/m3) 0.00 0.00 0.00 0.00 Source: Calculated from Field Measurements and Field Survey data (2026). EC = estimated exposure concentration. Hypothesis Testing H01: The mean concentrations of measured ambient air pollutants do not differ significantly from the applicable air-quality reference values. PM2.5 and NO2 showed the most consistent numerical elevation relative to the WHO reference values, with all nine observations exceeding the respective 24-hour guidelines. PM10 exhibited a single episodic exceedance (at L3). Five of the nine O3 readings were numerically higher than 100 μg/m3, although formal comparison with the 8-hour guideline is limited by the averaging-period mismatch. SO2 was not detected at any location, and CO concentrations remained well below the stated reference value at all sites. These patterns indicate that fine particulate matter and nitrogen dioxide are the pollutants of greatest potential concern under the conditions observed during the monitoring period. IJGEM IJGEM IIARD International Journal of Geography & Environmental Management Table 16: One-Sample t-Test of Ambient Air Pollutant Concentrations against Selected WHO Reference Values Pollutant n Mean ± SD (μg/m3 or mg/m3) Min– Max WHO Reference Value Number (%) of observations above WHO value Mean / WHO ratio Screening interpretation PM10 9 30.00 ± 11.68 22–60 45 μg/m3 (24 h) 1 (11 %) 0.67 Mean below reference; one episodic exceedance (L3) PM2.5 9 21.56 ± 3.75 17–28 15 μg/m3 (24 h) 9 (100 %) 1.44 All observations above reference SO2 9 0.00 ± 0.00 0–0 40 μg/m3 (24 h) 0 (0 %) 0.00 Not detected; all values well below reference CO 9 0.75 ± 0.98 mg/m3 0–2.63 4 mg/m3 (24 h) 0 (0 %) 0.19 All observations below reference NO2 9 102.77 ± 32.78 47– 159.80 25 μg/m3 (24 h) 9 (100 %) 4.11 All observations above reference; highest values at L2 O3 9 93.64 ± 37.67 19.60– 117.60 100 μg/m3 (8 h) 5 (56 %) 0.94 Five individual readings above the numerical value of the 8-h guideline Source: Calculated from Field Measurements (2026). Summary of Key Findings The monitoring results demonstrated spatial and temporal variation in ambient air quality across the three selected waste dumpsites. PM10 concentrations ranged from 22 to 60 μg/m3, while PM2.5 ranged from 17 to 28 μg/m3. Location 3 recorded the highest mean PM10 concentration, whereas PM2.5 concentrations were relatively similar across the three locations. Among the gaseous pollutants, NO2 recorded the highest mean concentration at Location 2, while O3 recorded its highest mean concentration at Location 3. SO2 was not detected throughout the monitoring period, and CO concentrations were relatively low. The exposure assessment showed that respondents had substantial contact with the dumpsite environment. More than half of the respondents reported spending at least five hours per day in the vicinity, while approximately 59% reported exposure on at least five days per week. Nearly 56% of respondents lived or worked within 100 m of the dumpsites. Workers had a higher estimated time-activity factor than residents, indicating greater time-weighted exposure under the assumptions used in the exposure assessment. The exposure-adjusted concentrations provide an estimate of potential inhalation exposure but should not be interpreted as individual absorbed doses or as direct evidence of disease. The screening assessment indicates that PM2.5 and NO2 warrant particular attention because their IJGEM IJGEM IIARD International Journal of Geography & Environmental Management measured concentrations were consistently elevated relative to the stated WHO reference values. Further assessment incorporating individual-level exposure data, longer monitoring periods and health-outcome information would strengthen inference regarding the health effects associated with exposure to pollutants around the dumpsites. 4. Discussion The study showed spatial and temporal variations in ambient air quality around the selected waste dumpsites. PM10 concentrations ranged from 22–60 μg/m3, while PM2.5 ranged from 17–28 μg/m3. Although most PM10 values were below the WHO 24-hour guideline, all PM2.5 measurements exceeded the WHO guideline of 15 μg/m3. The mean PM2.5 concentration was significantly higher than the reference value (21.56 ± 3.75 μg/m3; t = 5.25, p < .001), indicating persistent fine-particle pollution around the dumpsites. Similar concerns have been reported in Port Harcourt, where air- quality assessments around dumpsites identified particulate pollution as an important environmental concern (Alilonu et al., 2023; Uche, 2021). The higher PM10 concentration recorded at L3 also suggests localized differences in waste activities, dispersion and site conditions. NO2 was another major pollutant of concern. Concentrations ranged from 47.00–159.80 μg/m3, with all observations exceeding the WHO 24-hour guideline of 25 μg/m3 and three exceeding the Nigerian reference value of 120 μg/m3. The overall mean concentration of 102.77 ± 32.78 μg/m3 was significantly above the WHO reference value (t = 7.13, p < .001). L2 recorded the highest mean NO2 concentration, suggesting possible differences in emission sources and atmospheric dispersion among the locations. Previous investigations of dumpsite environments in Port Harcourt have similarly identified air-quality concerns associated with waste disposal activities (Chukwu- Okeah et al., 2021; Uche, 2021). O3 concentrations varied considerably, with individual measurements reaching 117.60 μg/m3. However, the overall mean of 93.64 ± 37.67 μg/m3 was not significantly different from the adopted reference value (t = −0.51, p = .313). Thus, the elevated individual observations should be interpreted as episodic rather than evidence of sustained exceedance. In contrast, SO2 was not detected during monitoring, while CO concentrations remained relatively low and were significantly below the reference value. These findings indicate that pollution around the study sites was more strongly characterized by particulate matter and NO2 than by SO2 or CO. The exposure assessment further demonstrated potential for repeated contact with polluted air. More than half of respondents were exposed for at least five hours daily, approximately 59% reported exposure on five or more days per week, and 55.4% lived or worked within 100 m of a dumpsite. Workers had higher estimated time-activity factors and exposure- adjusted concentrations than residents, indicating greater potential inhalation exposure among occupationally exposed groups. Similar concerns have been reported for populations living or working near waste facilities, where landfill-related air pollution has been associated with perceived and potential health risks (Gumede & Gumede, 2025). Evidence from Yu et al. (2018) also linked exposure to air pollution around a municipal solid-waste landfill with adverse respiratory and immune-related outcomes among children, although the present study did not directly assess health outcomes. Overall, the findings indicate that PM2.5 and NO2 were the principal air-quality concerns around the selected dumpsites. The results support the need for continuous air-quality monitoring, improved waste-management practices and measures to reduce exposure among workers and nearby residents. However, the exposure-adjusted concentrations represent estimates of potential inhalation exposure rather than absorbed doses or direct evidence IJGEM IJGEM IIARD International Journal of Geography & Environmental Management of disease. Further studies incorporating longer-term monitoring, personal exposure assessment and health-outcome measurements would strengthen assessment of the associated health risks. 5. Conclusion The study found considerable variation in ambient air quality around the selected waste dumpsites, with PM2.5 and NO2 emerging as the major pollutants of concern. PM2.5 and NO2 concentrations were significantly higher than the WHO reference values, while PM10 showed occasional elevation. SO2 was not detected and CO concentrations remained low. Exposure patterns indicated substantial potential for repeated inhalation exposure, particularly among dumpsite workers and individuals living or working close to the dumpsites. More than half of respondents were exposed for at least five hours daily, while 55.4% were located within 100 m of a dumpsite. Workers had higher estimated exposure levels than residents. Overall, the findings highlight the need for regular air-quality monitoring, improved solid-waste management and measures to reduce exposure around dumpsites. However, the exposure estimates represent potential inhalation exposure rather than absorbed doses or confirmed health effects. Longer-term monitoring incorporating personal exposure and health-outcome assessment is therefore recommended. 6. Recommendations Regular monitoring of ambient air quality around waste dumpsites should be strengthened, with priority given to PM2.5 and NO2. Improved waste-management practices and exposure-control measures should also be implemented to protect nearby residents and dumpsite workers. IJGEM IJGEM IIARD International Journal of Geography & Environmental Management References Abarca Guerrero, L., Maas, G., & Hogland, W. (2013). Solid waste management challenges for cities in developing countries. Waste Management, 33(1), 220–232. https://doi.org/10.1016/j.wasman.2012.09.008 Alilonu, E. C., Obafemi, A. A., & Eludoyin, O. S. (2023). 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