After attacks on Iran’s oil facilities, toxic black rain threatens the public

Clouds of toxic smoke from US-Israeli airstrikes on Iranian oil facilities returned dangerously to Earth in the form of “black rain”, prompting international health officials to warn the public of serious risks.

Residents of Tehran complained of burning eyes and breathing difficulties last week when black and oily rain fell near the Iranian capital after several fuel oil depots and a refinery were hit.

Plumes of dark smoke can be seen in other parts of the region as Iran retaliates against US-Israeli airstrikes by firing drones and missiles at its Persian Gulf neighbour’s oil and natural gas facilities, two weeks into the war.

Experts say rain washes hazardous chemicals out of the atmosphere in a relatively short period of time, but people exposed to black rain should take precautions to avoid short- and long-term health risks.

Here’s what to know:

This happens when soot, ash and toxic chemicals combine with water droplets in the atmosphere, which then fall back to Earth when it rains. It is common after oil refineries or oil fields catch fire, and can also be caused by forest fires, volcanic eruptions, and industrial pollution.

In Iran, microscopic soot forms when hydrocarbons in fuel oil burn incompletely, experts said. Burning oil forms compounds called polycyclic aromatic hydrocarbons, or PAHs, as well as toxic gases such as sulfur dioxide and nitrogen oxides that cause acid rain, said Peter Adams, professor of civil and environmental engineering at Carnegie Mellon University.

Micro-soot, whose particles are 40 times smaller than the width of a human hair, can lodge deep in the lungs and enter the bloodstream, causing breathing and heart problems that can lead to premature death, experts said. Exposure to PAHs may increase the risk of cancer.

In Iran, the World Health Organization and the country’s health and environmental authorities advised people to stay indoors and wear masks. Rain is highly acidic and can burn skin and cause lung damage, he warned.

“We can definitely expect severe health consequences from this type of event,” said Columbia University chemical engineering professor V.

Even regular air pollution events can trigger health problems and lead to more hospitalizations, especially among the elderly, children and people who already have health problems, he said. “But this is a high level, so health problems are likely to occur now.”

Some Iranians fear that polluted rain containing heavy metals could contaminate drinking water reservoirs and waterways.

It usually only takes hours for fuel tanks to burn out. But — as happened in Kuwait during the Gulf War 25 years ago — oil fields can burn for months, Adams said.

For fires that burn more quickly, more soot and chemicals are airborne and washed out of the atmosphere in about three to seven days, Adams said.

“So if we don’t create more problems, at least what’s in the atmosphere will go away,” even if there aren’t long-term health risks, Adams said.

“But we don’t know what’s going to happen with future strikes and whether other tanks will be hit or oil fields will be hit,” he said. “I’m less concerned about long-term or regional issues, but it’s a real mess for people in the immediate vicinity.”

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