Lahore?s air is unsafe and toxic. But just how toxic, few of us know. Air pollution is a silent, invisible and, until now, an unbeatable killer. India?s Delhi is grappling with the same public health emergency, smog - a thick, soupy mixture hanging over the city. Alarming readings, from across the border, of the PM 2.5 ? tiny particles that can get lodged in the lungs - underline the need for urgent regional measures. Pollution trackers estimate that breathing in Delhi is as bad as smoking 50 cigarettes a day. However, here, in Pakistan, the government-run Environment Protection Agency has shied away from releasing official data from its six air quality monitors.

Refusing to stay in the dark, citizens in Lahore have installed air quality stations at their homes, provided by AirVisual, an air pollution application, which offers people real-time access and hourly updates of the air quality readings in Lahore. Here is how harmful the air was this past week:

(Data via @LahoreSmog)

WHO guideline is 35 ?g/m³ per 24 hours.