DELHI>> The trucks have lumbered through the capital for years, dumping loads of hot, acrid ash from thousands of tons of incinerated garbage close to playgrounds and schools.

Residents in the soot-stained homes nearby know what to expect: stinging eyes, constant migraines, hacking coughs of black spittle and shallow, labored breaths.

Burning the garbage was supposed to help solve one of Delhi’s most startling environmental crises: the giant mountains of trash that soar nearly 200 feet into the air and eclipse the capital’s skyline — putrid, 20-story slopes of waste that collapse and crush people, or catch fire in noxious blazes that last for days.

The government pushed a revolutionary plan. It promised to incinerate the trash safely in a state-of-the-art plant, turning the waste into electricity in an ingenious bid to tackle two major problems at once.

Instead, the government’s answer to its bursting landfills and boundless need for energy is exposing as many as 1 million people to toxic smoke and ash, according to air and soil samples collected by The New York Times over a five-year period.

Residents call it a mass poisoning.

The smoke billowing from the plant and the ashes dumped near homes have been found to be toxic, and Indian officials are well aware of the dangers.

Internal government reports found that the plant pumped as much as 10 times the legal amount of dioxins — a key ingredient in the notorious Agent Orange herbicide deployed by the U.S. military in the Vietnam War — into the skies above Delhi. Yet, the government has doubled down on its strategy nonetheless, breaking the law by dumping toxic ash right near homes and vowing to build similar facilities in dozens of cities where tens of millions of people live.

Having surpassed China as the world’s most populous nation, India has nearly 60 cities with 1 million residents or more, making “waste to energy” plants such as the one in Delhi a model of what the government calls its “Green Growth” future.

The plant, run with one of India’s biggest family business empires, even managed to get certified by the United Nations in 2011, earning the right to sell carbon credits on the global market because it uses trash, instead of fossil fuels, to generate electricity.

The problem is, many current and former workers at the plant say, there is nothing green about it.

“The plant was never regulated, and the government knows,” Rakesh Kumar Aggarwal, a former manager at the plant, told the Times before he died in 2020, months after we started reporting this article and collecting samples for testing. He said basic safety measures were routinely skipped to save money and emissions from the facility went untreated, spewing dangerous chemicals into the heart of Delhi.

“On paper, it looks fine — it’s burning tons of trash each day,” he added. “But it’s killing people.”

Independent lab tests commissioned by the Times found that in the central Delhi neighborhood where the plant sits, the average amount of hazardous chemicals and heavy metals in the air drastically exceeded safety standards.

The Times collected about 150 air and soil samples from 2019 through 2023 around the plant, in neighborhoods where the ash was dumped illegally and in other parts of the capital. We worked with experts at the Indian Institute of Technology Delhi, one of the country’s premier universities, to test the samples, and analyzed the findings with scientists at Johns Hopkins University in Baltimore.

Experts called the levels of heavy metals we found alarming. In all, as many as 1 million people live in what scientists considered the possible contamination zones.

“I am the living example,” said Shailendra Bhadoriya, a cardiologist who moved into a leafy neighborhood in 2011. He loved its proximity to good schools and parks for his young children, and wanted to be able to walk to work at the Fortis Escorts Heart Institute, one of the largest cardiac hospitals in Asia, where he directed the intensive care unit.

He described watching the waste-to-energy plant being built about 150 yards from his home.

Then, soon after it opened in 2012, Bhadoriya said, he noticed something worrisome: He and his family were constantly sick. His neighbors started to complain, too.

In one of the most unequal cities in the world, the problems stalk the wealthy and poor alike. The facility, named the Timarpur-Okhla Waste to Energy Plant, sits squarely in the center of the capital and burns as much as 3,000 tons of garbage a day, generating a small amount of electricity for a power-starved country.

Many of the trucks have climbed to the top of a knoll overlooking hundreds of homes, a playground and a Hindu temple. From there, the soot has come hurtling down toward the neighborhood below in black clouds, seeping into homes.

“The dust is like a bedsheet,” said Rohit Mishra, 19, wiping down his desk and schoolbooks. Plumes of soot swirled in the air of his home. His mother sweeps and sweeps again. Still, the family is plagued by hacking coughs of black phlegm, the color of their lives since the trucks started coming.

There is so much ash that the government has even leveled it, with a school, a clinic, a wedding hall and a park built atop the poisonous ground. Incongruously, one of the dump sites is in an “eco park.”

When the plant opened, the government promised an innovative solution to a seemingly intractable problem. Delhi’s trash mountains and landfills are so enormous that they spanned more than 150 acres last year, with waste weighing about 16 million tons.