Diurnal Variations of Halogen Gases and Particulate Matter in Refrigerator Maintenance Workshops: Implications for Occupational Air Quality in Mofor, Udu LGA, Delta State, Nigeria

This study assessed the diurnal variations of indoor air pollutants, specifically halogen gases and particulate matter fractions (PM0.3, PM0.5, PM1.0, PM3.0, PM5.0, PM10.0 µm), in selected refrigerator maintenance workshops within Udu Local Government Area, Delta State, Nigeria. Sampling was conducted across morning, afternoon, and evening periods to determine the temporal distribution of pollutants and their implications on occupational health. The concentration of halogen gases exhibited significant temporal variations, with afternoon periods recording the highest mean concentration (0.485 ± 0.014 ppm), followed by evening (0.367 ± 0.008 ppm) and morning (0.289 ± 0.008 ppm). Similarly, temperature readings peaked in the afternoon (36.54 ± 0.16°C), declining in the evening (31.49 ± 0.29°C), and lowest in the morning (27.66 ± 0.10°C). Particulate matter concentrations demonstrated a consistent diurnal pattern, where afternoon periods showed significantly higher values across all particle sizes. PM0.3 concentrations were highest in the afternoon (218.18 ± 2.55 µg/m³), compared to evening (180.15 ± 2.17 µg/m³) and morning (148.12 ± 1.64 µg/m³). For PM0.5, afternoon recorded 191.79 ± 3.22 µg/m³, evening 157.95 ± 3.13 µg/m³, and morning 123.32 ± 2.09 µg/m³. The PM1.0 values were 160.20 ± 2.41 µg/m³ (afternoon), 130.51 ± 2.75 µg/m³ (evening), and 100.22 ± 1.79 µg/m³ (morning). PM3.0, PM5.0, and PM10.0 followed similar trends, with afternoon concentrations of 137.47 ± 2.31 µg/m³, 117.98 ± 1.84 µg/m³, and 101.47 ± 2.10 µg/m³ respectively. The findings revealed that poor ventilation, intense mechanical activities, and lack of dust control measures significantly contributed to elevated pollutant levels during peak operation hours. It is recommended that workshops adopt engineering controls such as local exhaust ventilation systems, implement scheduled cleaning routines, and enforce personal protective equipment (PPE) usage to mitigate occupational exposure risks.