What does PM 1 mean?

A pipe and noose attached to the device atop the van sucks in the ambient air, which is analysed by a special software.

What are PM 1 particles?

These are extremely fine particulate matter (PM) particles of diameter less than 1 micron — significantly smaller than PM 2.5 (of diameter 2.5 microns) that have been at the centre of discussions on particulate matter in Delhi’s air. PM 10, PM 2.5 and PM 1 particles make up the total suspended particulate matter. These particles, byproducts of emissions from factories, vehicular pollution, construction activities and road dust, are not dispersed, and stay suspended in the air that we breathe. 1 micron is about a thousandth of a millimetre.

Why are PM 1 particles more harmful than PM 2.5 or PM 10?

The finer the particles, the more difficult they are to disperse — and the deeper they can penetrate into the blood stream, causing more harm. PM 10, which are smaller than 10 microns in diameter, enter the respiratory tract, and have been associated with risks like bronchitis, asthma, and upper respiratory tract infections. PM 10 aggravate symptoms of existing diseases more than triggering new conditions. PM 2.5 are considerably finer, penetrate into the lower respiratory tract or deeper in the respiratory tract, and the blood stream, causing cardiovascular problems. The spike in these particles over the last two years has prompted doctors to advise patients to leave Delhi temporarily.

PM 1, which are so much finer than PM 2.5, can penetrate the cardiovascular stream even further, and give rise to lasting conditions, such as predisposing people to heart diseases. Studies in the west have shown that PM 1 can lead to premature births and affect foetal development.

So why and how has Delhi begun measuring PM 1 concentrations?

On December 15, 2015, instrumentation company Nevco Engineers Pvt Ltd purchased from a New Zealand firm a new mobile air quality sampling machine called Airqual. The machine, installed on a mobile van, is supplying data to the Delhi Pollution Control Committee on six pollutants recognised by the US Environmental Protection Agency as vehicular pollutants that can impact human health. The technology has been brought to India for the first time — according to Delhi government officials, the machine was purchased to assess the impact of the odd-even road rationing policy based on spot monitoring by the mobile van. The machine uses technology by which the level of a pollutant is measured by the amount of light it scatters. While the data isn’t as accurate as that from stationary machines, it is faster — and accepted internationally. Also, the mobile van is venturing deep into colonies, going near construction sites, and to traffic signals. Stationary air quality monitoring machines are not close to residential areas, and often human exposure levels are higher than the levels indicated by these machines. The van collects data for 20 minutes at each location, and records the average. Data collected so far show wide variations even within small areas, which experts say points to the need for micro-level assessments of pollution sources.

Since when has data been collected?

Since January 1. The van is on the move from 10 am to 7 pm, and will collect data from some 210 locations spread over all 70 assembly constituencies until January 15. The government may release the PM 1 data after the impact of the odd-even policy is assessed. The Central Pollution Control Board is yet to prescribe safe standards for PM 1. According to India’s national Air Quality Index, PM 10 levels should not be higher than 100 micrograms per cubic metre, and PM 2.5 not more than 60 micrograms per cubic metre.