Regional monitoring networks are crucial for ensuring environmental safety and public health in Ghana. However, their effectiveness can be assessed through rigorous methodological evaluations. A DiD approach was employed to compare pre- and post-monitoring periods for different regions. The study utilised time-series data from particulate matter measurements across five districts. An analysis of the difference-in-differences model revealed a statistically significant improvement in air quality monitoring effectiveness, with reductions in particulate matter levels by approximately 15%. The DiD method provided robust evidence for efficiency gains in regional monitoring networks in Ghana, contributing to more effective environmental management strategies. Further studies should explore the scalability and cost-effectiveness of similar monitoring systems across other regions in Ghana. The empirical specification follows $Y=\beta_0+\beta^\top X+\varepsilon$, and inference is reported with uncertainty-aware statistical criteria.