Indoor air pollution is a matter of serious concern in the mega cities which are grappling with poor air quality. There are very few reports available that discuss the indoor air quality of gaseous ammonia (NH3). This study reports the abundance and risk assessment of NH3 in two distinct urban households of Delhi city during July 2017 to June 2018. Results showed that the NH3 concentrations were consistently higher during entire sampling period at the Dwarka household (DH) site which represented the residential sector having an average value of 102.5 µg/m3, as compared to the Mayapuri household (MH) site which represented the industrial sector having an average value of 57.2 µg/m3. The spatio-temporal analysis suggested a characteristic seasonal influence as indoor concentrations were very high during monsoon season following the order, monsoon > summer > post-monsoon ≥ winter, at DH site but indoor NH3 at MH site did not show any remarkable seasonal variation except a sweeping increase during monsoons. Short term and long term health risk characterisation using multiple appropriate toxicological end limits for NH3 in the two households showed that at its present concentrations indoor NH3 cannot be a health hazard to the inmates. However, it does not fail to escape our notice that mushrooming urban areas with their complex problems such as poor sanitation, industrialisation, waste management, high vehicular traffic, high occupant density, etc. have become major hubs of continual rise in indoor ammonia.
