Railroad tie leaching

Asked September 5, 2017, 2:00 PM EDT

We purchased my home 6 years ago, at that time I removed the old rotten railroad ties they had used for retaining walls and replaced with concrete blocks. In this area there are strawberries, and blueberries. The strawberries are still in this soil, will they ever be safe to eat? I moved the blueberries to a different part of my yard that is not contaminated. Uphill from area. It has been 3 years for them are they safe to eat now?

Clackamas County Oregon

1 Response

Thanks for your question about your soil's safety after railroad ties. The reason the EPA has made illegal the use of treated railroad ties in vegetable gardens is the fact that they are treated with coal tar creosote, a pesticide registered both with the EPA and the State of Oregon. The EPA's label warning is essentially "Don't touch the wood with bare skin; don't let animals or children near it; don't let it get near a water supply; don't inhale the dust; wear protective equipment when you handle it—including gloves that are "chemically impervious"; and don't burn it—the fumes can be deadly." (I quoted this from an article with a similar question to yours.)

So, then the question becomes: how long does creosote remain a risk in the soil? Although several writers indicate that plant roots do not absorb creosote, the EPA says: " If the soil in your yard was contaminated by creosote in the past, you should probably not grow food in it. You will need to wash your hands and any other exposed skin carefully after you are in contact with the contaminated soil or water outside." (Most of the dangerous exposure to creosote occurs when it leaches into the water, as well as consuming fish that have ingested it.)

So, you have a couple of options. You could have your soil tested (A & L Western Laboratories, e.g.), or you could remove the soil within a couple of feet or so of the old timbers, and replace it with uncontaminated topsoil. You could also consider building raised beds with 'clean' soil in them, with a protective net between the soil levels, which allows water and earthworms to pass through, suggested in this World Health Organization publication.

When you asked whether 'they' are safe to eat now, I'm not sure you are referring to the strawberries, the blueberries or both. However, this Extension article suggests that fruiting plants (except cucumbers and squash) are less likely to have absorbed contaminants than root crops.

Sorry I can't provide you with a simple, black-and-white answer, but environmental science research as it relates to us and our gardens is still in its infancy. Hope this is helpful. Good luck!