Luxury of clean air

The latest air-quality guidelines released by the World Health Organization (WHO) show air pollutants are harmful at much lower levels than believed so far. The WHO has recommended minimum air-quality standards for six kinds of hazards. These include particulate matter (PM), ozone, nitrogen dioxide, sulphur dioxide and carbon monoxide. Typically, air clean-up efforts measure and focus on particles in two groups: those up to 10 and 2.5 micrometres across. These can penetrate our lungs, and their tinier bits could even enter our bloodstream. The exposure levels considered safe for all pollutants have been lowered. For PM2.5, for example, we should risk no more than 15 micrograms per cubic metre within a 24-hour period, on average, down from 25 earlier. For PM10, no more than 45 micrograms, down from 50.

Readings of PM2.5 and PM10 levels in urban India show just how unhealthy the air is that we inhale. Several cities suffer dangerously high concentrations of these particles for prolonged periods. Assuring ourselves cleaner air is a matter of top urgency. Once-smog-laden big cities like Beijing managed to clean up. Delhi, in particular, still has a very long way to go.