Characterizing Association Between Outdoor and Indoor Particulate Matter in a Soot Polluted City

Background: The deposit of fine black particulate substances on outdoor and indoor surfaces in Port Harcourt metropolis since December 8, 2016 gave rise to agitation on the potential health effects thus, became a major public health concern. Objective: This study was carried out to determine the differential significance in the distribution of fine Particulate Matter (PM 2.5) in a soot polluted outdoor environment and indoor office environment in Port Harcourt, Nigeria. Materials and Method: A cross sectional study involving 2 hourly outdoor and indoor fine particulate matter (PM2.5) monitoring using Environmental Monitor series 7 (EVM-7) from April 11, 2017 to August 26th, 2018. A total of 6,048 measurements were conducted in 528 days. Result: The Outdoor measurements ranged from 6 to 420 µm3 while the Indoor measurement ranged from 1 to 136 µm3. The daily average for Outdoor and Indoor fine Particulate Matter (PM2.5) were 97.1µm3 and 25.6µm3 respectively. A statistical analysis (t-test) was performed to compare the daily average outdoor and indoor concentration for PM2.5 measurements. The statistical analysis showed t value to be 24.5287 and P was less than 0.0001. By conventional criteria therefore, this implies that there is statistically significant difference between outdoor and indoor PM2.5 daily average concentration. Conclusion: This implies that the outdoor average is in exceedance by more than two-fold. The indoor average however, is not in exceedance but higher than 50% of the benchmark which is significant enough for remedial actions. The statistical significance therefore implies that the indoor concentration is dependent, responsive and directly proportional to the ambience concentration. This direct proportionality therefore requires a wholistic approach to outdoor and indoor PM2.5 mitigation as there is a dominant effect of outdoor concentration on the indoor concentration.