Smog hangs over Beirut most days, a brownish cloud that darkens the city’s skyline of minarets and concrete towers. An estimated 8,000 diesel generators have been powering Lebanese cities since the nation’s economic collapse in 2019. The generators can be heard, smelled and seen on the streets, but their worst impact is on the air the city’s inhabitants are forced to breathe.

New research, to be published by scientists at American University of Beirut (AUB), has found that the Lebanese capital’s over-reliance on the diesel generators in the past five years has directly doubled the risk of developing cancer. Rates of positive diagnosis, oncologists say, are shooting up.

“The results are alarming,” says Najat Saliba, an atmospheric chemist who led the study. In the area of Makassed, one of the more densely populated parts of Beirut tested, levels of pollution from fine particulates – that is, less than 2.5 micrometres in diameter (PM2.5) – peaked at 60 micrograms a cubic metre, four times the 15 mcg/m³ level the World Health Organization says people should be not exposed to for more than 3-4 days a year.

Since 2017, the last time AUB took these measurements, the level of carcinogenic pollutants emitted into the atmosphere has doubled across three areas of Beirut. Saliba says calculations suggest cancer risk will have risen by approximately 50%.

“It’s directly related,” she says. “We calculate the cancer risk based on the carcinogen materials emitted from diesel generators, some of which are classified as category 1A carcinogens.”

Generators used to fill a three-hour gap in national grid provision. Then, in 2019, one of the world’s most catastrophic economic collapses since the mid-19th century began in Lebanon. Within months the state energy grid came close to collapse and the diesel generators took over. The explosion in August 2020, which killed more than 200 people and devastated Beirut’s commercial port, further brought the country to its knees.

Anecdotally, oncologists in Beirut now estimate that general cancer rates have been rising by 30% annually since 2020. There is a common observation – although as yet no definite data – that patients are getting younger and the tumours more aggressive.

Hani Nassar runs a cancer support association in the name of his late wife, Barbara Nassar. In his office in Beirut he points to a box of Lynparza, used to treat ovarian cancer. It is one of the medications not subsidised by the health ministry and costs $6,000 for a month’s supply. His association supports 40 women and he sometimes has to share one box among all of them.

Money is the biggest problem facing cancer patients in Lebanon, he says. The crisis has wreaked chaos. The average public sector salary is about $150 a month, far below the cost of chemotherapy.

“We have a lot of cancer patients who have not even begun any treatment,” says Hani. “They just end up saying, ‘OK, I will die – I don’t want to deprive my family of our house, our car, etc, just to pay for this.’”

In 2023, Human Rights Watch reported that lack of a reliable power supply had affected people’s right to electricity, and pointed to the Lebanese government continually adopting policies that entrenched oil dependency even as nations around the world try to transition to renewable energy.

“Diesel importers exert great influence, primarily because of the overlap between the shareholders of these companies and the political establishment,” the report noted.

Saliba says generator-owners and fuel importers are “making a fortune from burning diesel inside the city and suffocating people”. In 2017, Lebanon imported around $900m (£720m) worth of diesel for generators. By 2022, that figure was reported to have jumped to $1.9bn.

Lebanon’s government, paralysed politically and failing to enact anti-corruption measures that could unlock a bailout deal from the International Monetary Fund, has frozen ministry budgets, affecting all areas of life.

Lebanon is stuck in a “big vicious cycle” Saliba says. “We are a very poor country now, so we keep asking for all this money. But the trend across all sectors – and everything the government has handled over the past 10 years – is to take the money, install what needs installing, and then leave it without operating costs or any willingness to put the effort in to keep it running.”

The billions of dollars pumped into Lebanon by various international donors for infrastructure projects have not corrected the most basic issues, she says: “There is still no clean air, water or soil. There is nothing to show for any of it.”

Julien Jreissati from Greenpeace Middle East and North Africa says an inoperative air pollution monitor network is consistent with other environmental projects.

“At least it was used and was a useful source of information for a time,” Jreissati says. “Unlike in the waste-management sector – which has seen millions of dollars poured into infrastructure projects, by the EU and other funders, such as funding wastewater-treatment plants or recycling plants.”

Many of these internationally funded projects, he adds, were never operational and some were never connected to the wastewater network.

A 2020 Greenpeace study estimated that 2,700 people died prematurely in Lebanon because of air pollution in 2018 – the highest rate per capita in the Middle East, joint with Egypt. The report found that the economic cost of air pollution in Lebanon amounted to $1.4bn – 2% of its GDP. Now, with no systemic data, there is no way to estimate the premature deaths.

Oncologists interviewed by the Guardian were keen to stress that while diesel generators harm public health, there is no getting away from Lebanon’s tobacco consumption.

An estimated 70% of the adult population of Lebanon smoke regularly and 38% are full-time smokers.

Dr Fadlo Khuri, the president of AUB and an oncologist specialising in lung and neck cancer says what is happening in Beirut is “a confluence of circumstances”.

Lebanon only taxes imported tobacco products: a packet of 20 Marlboro Gold costs £2.20 (in the UK it costs about £15), while the local brand Cedars costs 60p for 20. The domestic tobacco industry, Khuri says dryly, is “probably the only remaining functional branch of the government, besides the armed forces”.

He also says the health effects caused by long-term exposure to the airborne carcinogens from the generators – such as emphysema, heart disease and cancers – could take years more to see.

“The AUB did measurements and mathematic modelling and found that 40% of daily exposure by people in Lebanon to airborne carcinogens comes from one source: diesel generators,” Khuri says. “You’re not going to see the impact of that on lung and neck and bladder cancer rates for years because these are diseases which take years of chronic exposure.”

For Pia Saadeh, 27, diagnosed with stage 2 breast cancer six months ago, the government does not take the link between Lebanon’s worsening environment and rising cancer rates seriously enough.

“Generators should be gone,” she says. “The government has to take back control over the electricity sector. Where can you hide from the pollution here? It’s in the water, it’s the air, it’s in what you eat, it’s everywhere.”