While the area around Dyal Singh college in Kasturba Nagar recorded PM10 levels of 149 micrograms per cubic metre, levels crossed 500 microgams per cubic metre in areas such as Patparganj in East Delhi. The safe limits, as defined by the National Air Quality Index (AQI) for PM 10, is 100 micrograms per cubic metre and 60 micrograms per cubic metre for PM 2.5.

Near Kamala Nehru College in South Delhi, where sources said the data was collected Friday evening, PM 2.5 levels was the highest at 226 micrograms per cubic metre. Delhi Public School in East of Kailash in South Delhi also recorded PM 2.5 levels of 217 micrograms per cubic metre.

The Institute of Human Behaviour and Allied Sciences in Seemapuri in Northeast Delhi recorded PM 10 levels of 266 and PM 2.5 of 133 micrograms per cubic metre. Dyal Singh College area recorded the lowest PM 2.5 value of 109 micrograms per cubic metre.

According to the Delhi Pollution Control Committee (DPCC), on an average, PM 2.5 hovered around 250 micrograms per cubic metre in all locations and ranged between 109-226 micrograms per cubic metre. PM 10 was in the range of 149-503 micrograms per cubic metre, according to data from the mobile machines.

Scientists said the first 24 hours of monitoring showed the odd-even policy has had a “definite impact” on the first day.

“This data has been calculated on the basis of a hand-held sampling device and a mobile van which uses light scattering principle. While this may not be as accurate as the beta attenuation mechanism used in fixed machines, it shows that for some time periods, there is a definite dip in levels of particulates,”

said Dr M P George, senior scientist at DPCC.

In the fixed machines, where beta rays are passed on filters before and after dust collection, and then calibrated for their difference in weight, only hourly data can be calculated. In the light scattering method, the scattering of light due to the suspended particles is captured, and data to the tune of seconds can be collected, said Dr George.

AnumitaRoychowdhury, head of CSE’s air pollution programme, said it was too early to celebrate, though there were “positive indications”.

“Weather played spoilsport on the first day, so considering that, even a 10-15 per cent drop in particulate level is very positive. What is interesting is that this spot-monitoring is already throwing up interesting colony-wise monitoring data. For areas near AnandVihar, the levels are expected to be high. But even in some colonies in South Delhi like near Kamala Nehru College, the high levels show that human exposure is much higher than the levels recorded by stationary ambient air quality machines. In many assemblies, there are stark differences in the data of different colonies,” said Roychowdhury. She added that these variations were expected and indicate hyper-local sources of pollution. “It depends on the wind situation of that area and local emission sources. They is also a good opportunity of micro-environment planning,” said Roychowdhury.

According to the Delhi government, areas such as Rohtas Nagar, Patparganj and Kondli, which border Uttar Pradesh, are showing higher levels of pollution as compared to areas near central parts of Delhi. Border areas such as AnandVihar, which according to government officials, “bear the brunt of vehicular pollution”, including entry of trucks from Uttar Pradesh, also show higher pollution levels.

In a statement, the Delhi government said Saturday evening that governments of states in the National Capital Region (NCR) “need to take immediate steps to supplement the efforts of Delhi government.”