HYDERABAD: Hyderabad may be seeing a gradual improvement in fine particulate pollution, but a long-term assessment of the city’s air quality has highlighted another concern: coarse dust levels are rising even as PM2.5 concentrations decline.
A seven-year analysis of air quality data from 2017 to 2023 found that PM2.5 levels fell by about 2.86 per cent annually. However, the city’s average PM2.5 concentration remained about 23% higher than its historical mean recorded between 2001 and 2022. Both PM2.5 and PM10 remained above national ambient air quality standards throughout the study period.
The findings, published in Environmental Science and Pollution Research International, are based on an assessment by scientists Venugopalan Nair Jayachandran and Thota Narayana Rao of the National Atmospheric Research Laboratory (NARL), Department of Space, Tirupati.
The researchers analysed data from six ground-based monitoring stations across Hyderabad, along with satellite-derived hybrid PM2.5 data and ERA5 meteorological reanalysis. They examined PM2.5, PM10, nitrogen dioxide (NO2), sulphur dioxide (SO2), carbon monoxide (CO) and ozone (O3) to understand long-term pollution trends and their drivers.
PM10 emerged as Hyderabad’s dominant particulate pollutant. The city recorded a mean fine-mode fraction of around 0.46, indicating that coarse particles accounted for more than half of the particulate burden.
Unlike PM2.5, NO2, SO2 and ozone, which showed overall declining trends, PM10 increased during the seven-year period.
The researchers linked the rise partly to changes in the daytime atmospheric boundary layer. A reduction in boundary layer height reduces the volume of air available to disperse pollutants, allowing coarse dust and other particles to remain concentrated closer to the surface. The finding is significant for a rapidly urbanising city such as Hyderabad, where construction activity, road dust, vehicular movement and other local activities continually generate and resuspend coarse particulate matter.
The role of local human activity became particularly evident during the Covid-19 lockdown. The researchers used the period, when movement and economic activity were sharply curtailed, to distinguish the contribution of local emissions from broader atmospheric influences. Their analysis indicated that local anthropogenic activities were an important contributor to day-to-day PM10 concentrations.
However, pollution sources can change during extreme episodes. While routine PM10 pollution is strongly influenced by local activities, exceptionally high pollution events can be driven predominantly by regional-scale advection, with winds transporting polluted air masses into Hyderabad from surrounding areas.
This suggests that severe pollution episodes cannot always be addressed through city-level measures alone and may require coordinated action to tackle regional pollution transport. Despite the decline in PM2.5, the city continues to face a significant particulate pollution burden. Gaseous pollutants, including NO2, SO2, CO and O3, remained within national regulatory limits during the study period.
