With calm winds, seasonal crop burns, and the usual vehicle and industrial emissions, an extremely thick, toxic fog of pollution has settled on Delhi, choking and sickening residents.

Pollution measurements and indexes have exceeded charted ranges, blowing past the highest categorized levels dubbed “severe” and hazardous to health. In some areas of the gigantic metropolitan area, measurements of certain pollutants were around 30 times the levels considered safe by the World Health Organization. Local journalists reported that the smog is causing throat irritation, wheezing, nausea, vomiting, and extreme fatigue.

Delhi’s chief minister, Arvind Kejriwal, took to Twitter to call the city a “gas chamber.”

In a series of Facebook videos, the president of the Indian Medical Association, Dr. K.K. Aggarwal, called the pollution a “public health emergency.” He warned residents to rest “completely,” meaning no walking or going outside, citing concerns for asthma attacks, lung and heart damage, and sudden cardiac arrest. “The pollution levels are very, very, very toxic to the lungs and to the heart,” he emphasized.

Clinical and epidemiological studies over the years have linked air pollution to increased risk of lung and cardiovascular conditions—including stroke, heart disease, lung cancer, asthma, and chronic obstructive pulmonary—as well as death and low birth weights. In 2015, researchers estimated that outdoor air pollution kills more than six million people worldwide per year.

2.5

Smog’s harmfulness stems from the potpourri of toxic substances it contains, including ozone, sulfur dioxide, nitrogen dioxide, and fine airborne particulate matter. The latter category encompasses particles with diameters of 2.5 microns or less (PM), which are mainly generated by various types of combustion. These particles are of particular concern because they can reach deep into the lungs. The tiniest fractions may even enter the bloodstream and infiltrate organs, such as the brain

According to WHO air quality guidelines, a safe mean PM 2.5 level over 24-hour period is 25 micrograms per cubic meter. India’s country-specific air quality index (AQI) considers the PM 2.5 ranges from 0-60 µg/m3 to be good to satisfactory and those between 251 and 300 µg/m3 to be severe. On Thursday, the Indian Institute of Tropical Meteorology reported that the 24-hour mean PM 2.5 levels in Delhi hit 640 µg/m3 on Wednesday. But some areas of the city reported higher levels, reaching into the 800s.









The country’s AQI—which encompasses measurements of a range of pollutants, including PM 2.5 —uses a scale of 0 to 500 to convey “good” to “severe” air-quality ratings. On Wednesday, Delhi's AQI rating reached toward the 800s, with some areas seeing an AQI of 999.

Local officials have enacted emergency measures to try to cut through the pollution and reduce exposure to residents. Officials closed thousands of schools, raised parking rates, halted construction, and restricted vehicle traffic around the city.