Can railroad ties treated with creosote leach into the soil and contaminate vegetables and fruit? Is CCA-treated wood safe to use? Is glyphosate a safe herbicide? Master gardener Paul James offers his opinion on these controversial garden issues:
Railroad ties
Are railroad ties safe? At issue is creosote, a powerful preservative that's applied to railroad ties. Creosote is a thick, oily pungent-smelling liquid made from the distillation of wood or coal tar. It has been linked to a number of health problems--including skin and respiratory disorders. If you were to expose yourself for long periods of time to creosote--especially on a warm day when it's more volatile--there's a chance you could wind up needing medical attention.
"If you limit your exposure and wear protective clothing when working with railroad ties, I don't think there's any great cause for concern," says James. "I would, however, strongly suggest that you limit the use of railroad ties to things like retaining walls rather than raised beds--especially in vegetable gardens. Some chemicals in creosote can leach out of the railroad ties and into the surrounding soil--chemicals that have the potential of contaminating food crops."
CCA-Treated lumber
Another wood preservative--CCA (Copper-Chromates-Arsenic)--is also at the heart of a controversy. CCA-treated lumber is sold for all sorts of building projects. It is a preservative that is either applied to the surface of the wood or actually forced into the wood under pressure. CCA is toxic, but the question is whether the CCA ever leaves the wood, and if it does, under what conditions?
"After reading many articles on the subject by a variety of researchers, I'm convinced that the arsenic can be leached out of the wood," James says. "And it appears that certain food crops can absorb the arsenic." So if you're using CCA-treated lumber for raised beds in a veggie garden, take the following precautions:
- Either line the interior surface of the wood with plastic to avoid soil contamination or make sure that you plant at least six inches away from wood since arsenic can migrate at least that far into the soil.
- If you're planning on using CCA-treated lumber in a veggie garden, consider instead a naturally rot-resistant wood such as cedar, redwood or cypress or lumber treated with an arsenic-free preservative such as ACQ.
- When working with CCA-treated wood, make sure you wear a mask. Some studies suggest that ingesting or inhaling the sawdust can cause arsenic poisoning.
- Never burn CCA-treated lumber. It is illegal to do so in all 50 states. A single 12-foot, 2" x 6" section of it contains enough arsenic to kill 250 people, and burning the wood can release arsenic into the atmosphere. Also, don't handle the ash from a CCA treated-lumber fire, because a single tablespoon can be fatal.
Glyphosate
This controversy has to do with what is perhaps the most popular herbicide ever invented. Sold under several popular brand names, glyphosate is a non-selective herbicide, which means it kills anything green that it comes in contact with--weeds, turfgrass or plants. It's extremely effective, and James says it's arguably far safer to use than other commonly used herbicides such as 2,4-D, or 2, 4, 5-T or arsenic-based compounds. Opinions vary widely: it seems that glyphosate is either harmless or extremely hazardous.
To try to arrive at an answer, James analyzed research from dozens of sources, including the original manufacturer of glyphosate, the EPA, various independent laboratories and several environmental organizations, including some of the most radical. With all his collected information, he was more confused than enlightened. "I got the distinct feeling that both camps--pro and con--were seeking to profit from their findings," he says. "However, it's generally agreed that the acute toxicity of glyphosate is very low--in part because unlike other organophosphates found in various garden chemicals--it doesn't affect the nervous system."
Nevertheless, the claims and counterclaims regarding glyphosate continue, and gardeners are left to decide for themselves whether to use it. They clearly have decided to do just that, because sales of glyphosate worldwide total in the hundreds of millions of dollars.
The scientific jury is still out on the question of whether glyphosate is harmful to humans and other living things, and if so, in what doses. If you're concerned about its potential hazards, use safe alternative herbicides such as those made from potassium salts of fatty acids, straight vinegar, boiling water or a butane torch. Or you can just pull the weeds by hand.
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