Some 200 health organizations and more than 1,400 health professionals on Wednesday called on governments to forge a binding international agreement to phase out fossil fuels, which they say poses “a serious and escalating threat to human health.”

A letter proposing the “Fossil Fuel Non-Proliferation Treaty” said it could function similarly to the World Health Organization’s Framework Convention on Tobacco Control – except this time the harmful controlled substances would be coal, oil and gas.

WHO was among health organizations from around the world to sign the letter.

“The modern dependency on fossil fuels is not just an act of environmental vandalism. From a health perspective, it is an act of self-sabotage,” WHO chief Tedros Adhanom Ghebreyesus said in a statement.

The letter called on national governments to develop and implement a legally binding mechanism that would immediately halt any future fossil fuel expansion and phase out existing production.

It stressed that the transition should be carried out “in a fair and just manner” and that high-income countries should support lower-income countries to ensure that the transition “reduces poverty, rather than exacerbates it”.

Air pollution, mainly from burning fossil fuels, is linked to the deaths of seven million people a year.

Climate change has also led to more frequent and severe extreme weather events, which can have lasting health impacts beyond those initially affected by the disasters, including smoke from wildfires and disease spreading after floods.

The letter also highlighted the increased health risks faced by workers who extract, refine, transport and distribute fossil fuels and related products.

Phasing out fossil fuels would prevent 3.6 million deaths a year from air pollution alone, the letter said, adding that “the same cannot be said for proposed wrong solutions like carbon capture and storage.”

Diarmid Campbell-Lendrum, director of WHO’s climate change department, said that “from a health perspective, you cannot fix a disease without identifying the causes”.

The call for a deal is important because it is not “trying to use false balance sheets or imaginary solutions to further support fossil fuel burning,” he told AFP.

“We can either have fossil fuels or we can have health – we can’t have both.”

Courtney Howard, an emergency medical doctor in Canada’s subarctic region who signed the letter, said the city of Yellowknife had one of the worst air quality levels in the world when it was hit by wildfires in 2014.

“We had a doubling of visits to the emergency room for asthma, a 50 percent increase in pneumonia and one of our pharmacies ran out of ventilator medication,” Howard told AFP.

She said that phasing out fossil fuels “is something we need to do for everyone – for all the children”.

Jeni Miller, the executive director of the Global Climate and Health Alliance who helped coordinate the letter, called for international dialogue and negotiations to make the deal a reality.

“The costs of inaction are increasing,” she said.