Why are petroleum, chromated copper arsenate and radon bad for the soil?

As outlined in our February 15, 2019 Soil Matter blog, natural soil is uncontaminated. Use by humans, especially in cities, can cause some unintended consequences. Long-term exposure to items like petroleum products, chromated copper arsenate and radon can cause problems for humans – and other plants and animals dependent on healthy soils.


The most common petroleum products we might think of to contaminate soils are gas and oil products. These can run off onto the soil after rainfall or snowmelt, or they can seep into soil from leaking gas tanks and abandoned gas station lots.

Shiny petroleum products on a driveway
Making sure your car is tuned and gaskets are leak-free can help prevent petroleum products from running off onto soil – or groundwater sources. Credit: SV Fisk

Petroleum products can harm humans. Soils contaminated by petroleum hydrocarbons can affect soil health. And it can affect soil health at much lower concentrations compared to the effects on human health. They can harm soil microorganisms, reducing their number and activity. To learn more about petroleum contamination of soils and some solutions, visit https://www.soils.org/discover-soils/soils-in-the-city/soil-contaminants/petroleum-products.

Chromated Copper Arsenate

Before 2004, chromated copper arsenate was a commonly-used inorganic chemical that helped preserve wood. But, in 2004, legislation was passed limiting its use.

Deck falling to the right and made with green treated wood
This deck has two problems – 1) it’s sinking into the poorly supported soil beneath it and 2) it’s made with chromated copper arsenate wood, used before 2004. This chemical treatment does help weather-proof the wood, but it is toxic. Credit: SV Fisk

The arsenic portion of chromated copper arsenate is water soluble. This means it can soak into the soil, and anyone playing or gardening near it can get contaminated. If any structures in your yard are made with wood and have a green tint, they could be contaminated. If not properly sealed (or removed), they can cause a hazard. To learn more about solutions to the problems caused by chromated copper arsenate, and another common wood preservative, creosote, visit https://www.soils.org/discover-soils/soils-in-the-city/soil-contaminants/CCA-and-creosote.


Radon is a gas – so what is it doing in soil? Well, it’s a natural by-product of the radioactive decay of radium. And, radium is a naturally-occurring substance, so this soil contaminant is not human-generated. But the problems with radon building up – in homes and other structures – are human-made. Managing this soil contaminant is more about reducing the problems caused by radon, versus getting rid of it completely.

Man sealing cracks in basement wtih a caulk gun
Sealing any cracks in your basement floors and walls can prevent radon gas from seeping into your home. Photo provided by National Radon Program Services at Kansas State University.

Radon levels in homes depend on a lot of factors. The type of bedrock under your house is one. Your foundation and home structure also have a lot to do with it. So, just because your neighbor’s home recently got a passing radon test, that doesn’t mean your home is safe. And, radon gas is colorless and odorless. The only way to detect its presence is through testing. To learn more about testing for radon and lowering high levels of radon, visit https://www.soils.org/discover-soils/soils-in-the-city/soil-contaminants/radon.

The Soil Science Society of America’s public information pages, Discover Soils, has more information about these common soil contaminants. Visit https://www.soils.org/discover-soils/soils-in-the-city/soil-contaminants to start learning more today!

By Aaron Daigh, North Dakota State University

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