In May, World Health Organisation declared New Delhi the most polluted city in the world, based on air quality data published by official Indian agencies. But that might just be the tip of the iceberg. India actually has no way of accurately measuring how polluted its cities are, The Economic Times reported this week.

Therefore, India’s air pollution might be worse, much worse, than official figures let on. This massive underestimation, the report says, is a combination of three key factors, among others.

Cheap, dodgy equipment

India uses machines called high-volume samplers to measure PM 2.5, tiny and dangerous airborne particles that are less than 2.5 microns in size and are fine enough to enter deep into the lungs and the bloodstream. But most states choose the cheapest manufacturers who make machines using poor quality material and their readings cannot be trusted. The Central Pollution Control Board compared international samplers with Indian ones and found massive inconsistencies in the data.

India does not have a process of certification for these machines.

Even when it comes to imported machines, the data collection is suspect. “In most cases, these stations are manned by a daily wager, who might have studied only till the 8th or 10th grade. It is not clear if they followed the stipulated process,” a former member-secretary of CPCB told ET.

Data manipulation

Most state pollution boards present outdated data. For example, Odisha has 2006 data on its website. Gujarat gives an annual average for 2009-10. Most states give average figures, instead of real-time data; they have no incentive to report accurate readings because it alarms people and raises difficult questions.

“Every time readings spike, we receive Parliament questions,” an unnamed senior official from the Delhi Pollution Control Committee official told ET. “It’s why states don’t share their data or use their instruments.”

In most of the states, data is often collected for only a handful of pollutants because they have limited resources.

Western standards for Asian conditions

India asks its companies to follow norms set by US Environmental Protection Agency, even though the nature of environment pollution in the South Asian country is entirely different. As a result, India has ended up with many irrelevant norms and imported machines that are not fit for local conditions. For example, some of the machines only work when the temperature is between 25 and 35 degrees, singularly unsuitable for a tropical country like India.

This post originally appeared on Qz.com.