However, air quality data over the last two years shows that monsoon air pollution levels are still significantly worse than those recommended by the World Health Organization (WHO). Although monsoon air is cleaner than air during other seasons, air-pollution levels are worse than what is considered safe and remain a risk to public health.
To understand seasonal air pollution, we examined air quality data published by the US embassy in New Delhi and its consulates in Mumbai, Chennai, Hyderabad and Kolkata. We broke down the data between June 2014 and June 2016 into four seasons: winter (December to February), summer (March to June), monsoon (July to September) and post-monsoon (October to November). We then calculated the average PM 2.5 levels for each season. PM 2.5 measures particulate matter that is less than 2.5 micrometres in diameter—particles so small they can penetrate deep into the respiratory system and pose significant health risks.