Ground floor residents breathe cleaner air: Upper floors in high-rise apartments record 40% more pollution and toxic air, study finds

Residents living on the upper floors of high-rise apartments may be exposed to considerably more air pollution than those living closer to the ground. A study by the Mumbai Ecological Research and Analysis Group (MERAG) has found that particulate pollution on higher floors can be up to 40% greater than on lower levels, challenging the assumption that moving away from street-level traffic means getting cleaner air, reports TOI's Mahiyar Patel.

The researchers monitored residential complexes in Mumbai's Wadala between February and May 2026, installing sensors from the second to the 26th floor. Their findings showed that pollution levels increased progressively with building height, with the difference between higher and lower floors reaching 40% in March. Researchers identified emissions from distant factories and swirling wind currents around clusters of tall buildings as possible reasons for the higher pollution at greater elevations.

Sensors tracked pollution from the 2nd to 26th floor

The research team installed continuous air-quality monitoring devices at multiple elevations in residential buildings. The equipment tracked fine particulate matter (PM2.5), coarse dust and gaseous indicators, while real-time wind tracking helped researchers examine how air currents moved around the buildings.


Monitoring covered floors from the second to the 26th. Researchers found that pollution levels increased progressively with elevation during the study.

A MERAG convener said the measurements showed a systematic rise in pollution with each successive floor.

The convener also said that a sensor installed on the 40th floor would likely have recorded even higher readings. However, the actual monitoring conducted for the study extended up to the 26th floor.

Why are upper floors recording higher pollution?

Researchers identified emissions from distant industrial sources and factory chimneys as possible reasons for the higher pollution readings.

Pollutants released by factories can travel horizontally through the atmosphere and reach residential towers at considerable heights. These emissions can directly reach upper floors without necessarily passing through the lower levels of the buildings.

The study also pointed to the movement of wind around clusters of tall buildings.

When wind encounters multiple high-rise structures, it can form micro-meteorological wind eddies. These are swirling or circular air currents that influence how pollutants move around buildings.

According to the research, these currents and air recirculation can trap smoke and fine dust at higher elevations instead of allowing them to disperse.

This combination of industrial emissions and wind movement could explain the higher particulate pollution recorded on upper floors.

March recorded the biggest difference between floor levels

One of the key findings was the difference in particulate pollution between higher and lower elevations.

In March, the ratio between the readings at higher and lower floors reached 1.40. This meant that particulate pollution at higher elevations was 40% greater than at lower levels.

The researchers tracked PM2.5, coarse dust and gaseous indicators throughout the February-May monitoring period.

The findings highlight the variation in pollution levels across different heights within the same residential environment.

The MERAG study focused on residential complexes in Wadala and used sensors installed across multiple floors to document how pollution levels changed with elevation.

(TOI inputs)