The changes to the monsoons were an unexpected side effect of the lockdowns that restricted human activity. With no vehicles plying the streets and with industrial activity slowing considerably, the reduced emissions led to a significant decrease in atmospheric aerosols. These are tiny solid and liquid droplets suspended in the atmosphere, and they include microscopic particulate matter (PM 10 and PM 2.5) harmful to human health. Aerosols include sulphur dioxide, from burning coal, and black carbon or soot. The latter is a byproduct of agricultural burning, which in India is often from wood fires commonly used in cooking.