Air pollution occurs both naturally and through human activity. Natural air pollution mostly comes in the form of dust storms — currents of wind rustling up huge sheets of particles that can fill lungs with bacteria and other pathogens. Man-made air pollution mostly comes from the burning of fossil fuels, whether by vehicles or factories.
When these two sources combine, the air can become so laced with pollutants that people can’t even venture outside.
That’s what’s happening in Tehran right now.
Iran’s capital is in the dry, northern region of the country, surrounded by mountains that prevent fresh blasts of air from dispersing the dust. The air is further souped by the millions of cars that bustle through the streets on a daily basis and the petroleum refinement plants that churn out smog.
Read More: Almost 1 in 7 Children Is Breathing Toxic Air Right Now
Over the past week, the air has become too dangerous for people with respiratory illnesses to go outside, and on two of the worst days, the air was so contaminated that even the healthiest of people were warned to stay inside.
Over the past 23 days, 412 deaths have been attributed to the heightened pollution. The rising death toll has spurred the government to declare a state of emergency and close all the schools.
Air pollution, considered the worst environmental carcinogen, kills in many ways, including heart disease, cancer, and acute lung infections. More than 6.5 million people die from air pollution around the world each year, and this total is only expected to rise as climate change intensifies. In another Iranian city, Zabol, for example, what was once merely debilitating air pollution from regular dust storms became catastrophic when a nearby wetland dried out from overuse and extended drought. Zabol is considered to have the worst air in the world by the World Health Organization.
Read More: Air pollution is killing 6.5 million people each year
Many of the world's most polluted cities, including Beijing, are similarly surrounded by mountains that keep stagnant air from leaving.
The people of Tehran face crippling pollution every year, but the recent deterioration of air quality has provoked new levels of outrage. Newspapers throughout the city are mourning the loss of the environment and blaming the government for failing to take strong enough measures.
Perhaps this latest emergency will spur the government to act more decisively, finding ways to limit vehicles on the road and factory emissions. If they don't, people will have no choice but to leave.
Tehran Air Pollution.#illustrationpic.twitter.com/NbrAkIhyXI— Marj Illustration (@MarjaSadeqi) November 15, 2016
Tehran air pollution summarized in one picture— Sobhan Hassanvand (@Hassanvand) November 14, 2016
Mount Damavand's peak seems a clean place to breathe in pic.twitter.com/frrFzN4BFR
#Iran: Due to Air Pollution, 412 People Died in #Tehran in Less Than a Month. https://t.co/vvrQzattH7#FreeIran#No2Rouhanipic.twitter.com/h1L7gCgB2V— NCRI-FAC (@iran_policy) November 17, 2016
Tehran, like Delhi and Beijing, suffocates under toxic, deadly smog. Air pollution 4th leading cause of death https://t.co/AZaJ5xUERC— Celia W. Dugger (@celiadugger) November 16, 2016
Children who do not know a blue sky.— Sidewalk Lyrics (@pedestrian) November 14, 2016
Schools closed tomorrow in #Tehran due to air pollution. pic.twitter.com/Yp35ygbis5
Air pollution hits #Tehran, AGAIN pic.twitter.com/6pNGAvJyVg— Sobhan Hassanvand (@Hassanvand) November 13, 2016