People in India’s capital Delhi woke up to a thick layer of smog as the air quality deteriorated to severe levels in the city.

Delhi and its neighbouring cities are experiencing pollution levels that are at least 30-35 times the safe limit recommended by the World Health Organization (WHO).

Every year, Delhi and northern states battle hazardous air during the winter months of October to January due to plummeting temperatures, smoke, dust, low wind speed, vehicular emissions and crop stubble burning.

This time, experts say that the condition is likely to get worse in the coming days.

According to the Swiss Air Quality Index (AQI) monitoring system, pollution levels in several parts of Delhi touched the 500 mark on Wednesday morning.

AQI measures the levels of particulate matter, also called PM 2.5, in the air. These tiny particles can enter the lungs and cause a host of diseases.

As per WHO, air with AQI values at or below 100 is considered to be satisfactory for breathing, while readings in the 400-500 range denote that pollution levels are “severe” in an area.

The satellite cities of Noida and Gurgaon also registered AQI levels touching the 500 mark.

Several northern states have been experiencing toxic air and poor visibility over the past few weeks. There have been reports of flights to and from Delhi being cancelled or delayed due to low visibility.

So thick is the smog that it is visible even from space. A few days ago, Nasa shared satellite images of a blanket of smog engulfing parts of northern India and neighbouring Pakistan.

The toxic air is also impacting people’s health.

A survey by LocalCircles, an online community platform, in Delhi and nearby cities revealed that 81% of families reported at least one member suffering from health issues due to pollution in the last three weeks. Over a third of respondents said they had purchased cough syrup during that time.

The Delhi government has enacted its Graded Response Action Plan – which bans all activities that involve the use of coal and firewood, as well as diesel generator use for non-emergency services – but that has not saved the city from experiencing toxic levels of pollution.

Authorities have also urged residents to stay indoors as much as possible and to use public transport to cut vehicular emissions.

Delhi was the most polluted capital city in the world in 2023, according to a Swiss-based air-quality monitoring group.

India was also ranked as the world’s third-most polluted country after neighbours Bangladesh and Pakistan, IQAir said.

Air pollution is a serious problem in several Indian cities.

Experts say that rapid industrialisation coupled with weak enforcement of environmental laws have played a role in increasing pollution in the country.

India has seen a lot of development in the past few decades, but poor industrial regulation means that factories do not follow pollution-control measures. Rapid construction has also contributed to rising levels of pollution.