Burning coal is not only a vast source of pollution — the mining process has all kinds of nasty side effects, too.

One of those is that coal dust ends up all over the place and severely clogs nearby ecosystems. An international team of researchers has found that the impacts, such as harming trees’ ability to clean the air, are worse than previously thought.

What’s happening?

A common type of coal extraction, called open-cast or open-pit mining, involves digging a wide pit right at the Earth’s surface to access top-layer coal deposits. The thing is, this gaping mine is left uncovered, and coal dust containing aluminum, silica, and iron deposits is spewed all over the surrounding area.