Islamabad, Pakistan
CNN
—

A smog-plagued province in eastern Pakistan has made a rare plea for cross-border cooperation with India as major cities in both countries suffer from severe air pollution that threatens the health of millions of people.

Officials in Punjab, Pakistan’s most populous province with 127 million people, have written a letter to the Indian government to open a dialogue on the issue, Punjabi Environment and Climate Change Minister Raja Jahangir Anwar said on Monday.

“We need climate diplomacy as a regional and global issue,” Anwar told CNN, just days after the megacity of Lahore in Punjab, about 25 kilometers (15 miles) from the Indian border, recorded its highest air pollution ever.

“We are suffering in some ways in Lahore from the easterly wind corridor from India,” he said. “We don’t blame anyone, it’s a natural phenomenon.”

Pollution in northern India and East Pakistan increases every winter when an ominous yellow haze covers the sky, due to a combination of farmers burning agricultural waste, coal-fired power plants, traffic and windless days.

India and Pakistan have had tense and sometimes hostile relations for decades, but as the problem of toxic air worsens, the neighbors are being forced to confront their shared responsibilities – and fate – when it comes to climate.

In Lahore, home to more than 14 million people, the air quality index exceeded a record 1,900 in one part of the city on Saturday, according to IQAir, which measures global air quality. That is more than six times the amount considered harmful to health.

The extreme pollution prompted Lahore authorities to close primary schools for a week and restrict barbecue restaurants, motorcycle rickshaws and construction activities.

In India, air quality in Delhi – which often trades places with Lahore as the world’s most polluted city – reached dangerous air quality levels of over 500 on Saturday and Sunday, partly because people flouted a local fireworks ban while celebrating Diwali Hindu festival, celebrated festival of lights. However, the warmer and windier weather helped alleviate the smog.

According to the World Health Organization, breathing polluted air increases the risk of a variety of diseases, including lung cancer, stroke and heart disease. Experts say air pollution in India is so bad that the smog could take years away from the lives of hundreds of millions of people.

“This is not just a political issue but a humanitarian issue,” Punjab Chief Minister Maryam Nawaz said last week. “The winds don’t know that there is a boundary in the middle.”

Air quality worsens in winter because colder, drier air traps pollutants instead of carrying them away as warm air does.

The start of winter also coincides with stubble burning season, a time when farmers intentionally set fire to crop residue to clear their fields, sending smoke billowing into the sky.

Both India and Pakistan have tried to crack down on the practice, but it is still widespread.

Last month, India’s Supreme Court condemned the governments of India’s Punjab and Haryana states for failing to crack down on illegal stubble burning. Local officials claim they have significantly reduced the practice in recent years.

The Pakistani state of Punjab is providing farmers with subsidized superseeders to provide alternative methods of disposing of crop residues.