London, Apr 29 (IANS): Levels of air pollutants such as fine particles (PM2.5) and nitrogen dioxide (NO2), both hazardous to health, are increasing in Kanpur and Delhi, according to scientists using observations from instruments on satellites that scan the global skies every day.

The findings, led by the University of Birmingham and University College London (UCL), showed that the rise in PM2.5 and NO2 reflect increasing vehicle ownership, industrialisation and the limited effect of air pollution policies to date.

This contrasts with trends in the UK's London and Birmingham, which show modest but ongoing declines in PM2.5 and NOx, reflecting the success of policies targeting sources that emit these pollutants.

The study, published in the journal Atmospheric Chemistry and Physics, also showed increases in the air pollutant formaldehyde in Delhi, Kanpur and London.

Formaldehyde is a marker for emissions of volatile organic compounds that include a large contribution from vehicle emissions in India, and, in the UK, an increasing contribution from personal care and cleaning products and a range of other household sources.

"We were surprised to see the increase in formaldehyde above Delhi, Kanpur and London -- a clue that emissions of other volatile organic compounds may be changing, potentially driven by economic development and changes in domestic behaviour. Our results emphasise the need to monitor our air for the unexpected, and the importance of ongoing enforcement of measures for cleaner air," said William Bloss, Professor from Birmingham University.

The team used a long record of data gathered by space-based instruments to estimate trends in a range of air pollutants for 2005 to 2018, timed to coincide with well-established air quality policies in the UK and rapid development in India.