What is the “acid rain” in the wake of US bombings in Iran?

What is the “acid rain” in the wake of US bombings in Iran?

By Gabriel da Silva & The Conversation US

The following essay is reproduced with permission from The Conversation, an online publication covering the latest research.

Reports are emerging of black rain falling across parts of Iran in the hours after US-Israeli airstrikes on oil depots over the weekend, with some outlets describing it as “acid rain”.

Iranian residents have reported headaches, breathing difficulties and oil-contaminated rain falling on buildings and cars. Iran’s Red Crescent Society warned that rainfall after the strikes could be “very dangerous and acidic”.

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As an atmospheric chemist and chemical engineer who researches air pollution, these reports are deeply concerning, and indicate much more than just acid rain.

This rain will include acids, but probably also a number of other pollutants that are harmful to people and the environment in the short and long term. It may even be worse than the term “acid rain” conveys.

More generally, the thick clouds of toxic smoke over densely populated areas in Iran are also a major problem for anyone breathing this air right now.

What could this “acid rain” be?

One of the most important ways air pollutants are removed from the atmosphere is through rain. When you have significant levels of pollutants in the air, they will be picked up by falling water droplets and “rained out” of the atmosphere.

That’s why we get these reports of black rain falling from the sky after the oil depots were hit – proof of how polluted the local air must be.

To me, this black rain indicates toxic pollutants such as hydrocarbons, ultrafine particles known as PM2.5, and cancer-causing compounds called polycyclic aromatic hydrocarbons (PAHs) have entered the rain.

On top of this there will be a mixture of other unknown chemicals, likely including heavy metals and inorganic compounds from the building materials and anything else caught up in the initial explosions and subsequent fires.

The smoke from the bombed oil depots would also contain sulfur dioxide and nitrogen dioxide, which are precursors to the formation of sulfuric acid and nitric acid in the air. This acid then enters water droplets, and is responsible for what we conventionally call acid rain.

The acid rain we heard so much about in recent decades was primarily caused by sulfur dioxide produced by burning fossil fuels. Sulfur is naturally present in crude oil, but is now mostly removed at the refining stage.

Apart from the rain, it is worth remembering that all smoke is poisonous; if you can smell it, it may be at levels that harm you.

So the level of black smoke seen over densely populated areas in Iran is extremely concerning and could cause chronic short- and long-term health problems.

What are the potential health risks?

In the short term, people exposed to this black smoke in Iran may have headaches or difficulty breathing, especially if they have asthma or lung disease.

Vulnerable populations – such as the elderly, young children and the disabled – are more at risk. Exposure to toxic air pollution during pregnancy can also lead to lower birth weights.

In the longer term, exposure to the compounds in the air and in this black rain will potentially increase people’s cancer risk. When ultrafine particles (PM2.5) are inhaled, they can enter the bloodstream. This has been linked to a number of health effects, including cancer, neurological conditions (such as cognitive impairment) and various cardiovascular conditions.

Once these highly polluted air floods have their pollutants rained into natural waterways, they can also begin to affect aquatic life, as well as human drinking water sources.

Another problem is that this black rain deposits these compounds on buildings, roads and surfaces, meaning they can get back into the air when disturbed by strong winds.

A legacy of war

There has been increasing attention to the environmental impact of conflicts worldwide. Part of this has emerged in the wake of previous wars in Iraq and Kuwait, where there was large-scale deconstruction of oil wells and the use of burn pits.

We now know that there are long-term health consequences for returning service members, including Australians. So we can assume that local people are also deeply affected.

In the short term, people exposed to this smoke and black rain in Iran should try to wear masks or face coverings, seek refuge from it, stay indoors, close doors and windows, and try to keep the air out. It is also important to clean hard surfaces where possible, especially indoors, to reduce exposure to deposited contaminants.

On the ground, this can of course be very difficult to achieve in the chaos of war.

This article was originally published on The conversation. Read original article.

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