Answer: Railroad ties are not recommended for vegetable gardens. Some forms of creosote and/or components of creosote are known human carcinogens, so contact with the compound is not recommended. Aged ties are less likely to have volatile components that can irritate the lungs and mucous membranes, but you should wear gloves and long-sleeved shirts to prevent skin contact at any rate. Some of the components of coal tar creosote, which is used for railroad ties, can leach into soil and groundwater, where they take a long time to biodegrade. Since you've already constructed your raised bed, you will want to line the insides with plastic to keep the chemicals from leaching into your garden soil. The grass won't pose a problem. Once you add topsoil the grass will die out.
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