I’m using an old pair of windows to build a cold frame. Lately I’ve noticed that the paint on the window is starting to chip. Since I don’t know how old the windows are, I’m not sure if they have lead paint or not.
Is it possible that I’m accidentally introducing lead into my plants and soil? Would this be enough lead to worry about? Sometimes the paint chips end up on the soil of the plants in the cold frame and on the sides of the containers.
Your concern about the chipping paint from those old window frames is something you should take seriously. The real issue here is that you don't know how old these windows are, and that uncertainty matters a lot because it changes the risk level significantly.
Here's why the age of the windows is so critical. Lead-based paint for residential use was banned in the United States in 1978, which means any windows installed or painted before that date very likely contain lead. The problem is that you are not certain of their age, so you must assume they might be older and potentially contain lead.
How paint chips introduce lead into soil
When paint chips fall off those windows and land on your soil or containers, they're depositing lead directly where your plants are growing. This is how lead gets into a garden because the particles are there where you're handling soil and touching plants.
What makes your situation particularly concerning is that you're reusing the same soil and containers every year. This means that any lead that's already gotten into your soil is staying there and potentially accumulating as more paint chips fall.
When you reuse contaminated soil season after season, the lead concentration can increase over time. So even if the amount of lead from paint chips seems small each year, it adds up. And because you're uncertain about whether the paint contains lead at all, you can't even know if you're currently dealing with lead contamination or not.
How much lead is too much?
The real question is whether the amount of lead you’re introducing is enough to worry about. Soil with less than about 200 to 400 parts per million of lead is generally safe for growing vegetables if you're following good practices like washing produce and not letting children play in the soil.
Once soil gets above 400 parts per million, you should stop growing leafy greens and root crops directly in that soil. If it gets above 1,000 parts per million, you really shouldn't be growing food in it at all.
Testing your soil
You have several reasonable options to consider. One approach is to have your soil tested to see if any lead contamination has already happened. If the test comes back showing low lead levels, you could then make an informed decision about whether to keep using the windows. If it shows high levels, you'll know you need to remove the windows and replace the soil. See OSU Extension soil testing resources listed at the end.
Removing the source
Another approach is to remove the windows. Since you don't know the age of the windows and you can already see the paint is chipping, removing that source of uncertainty eliminates the risk entirely. You could build a new frame using untreated lumber, or if you want to keep using wood frames, make sure any paint on them was applied after 1978.
How lead exposure happens in the garden
The main way lead gets into your body from a garden is through your hands and the surface of vegetables, not so much by the plant taking up lead from the soil through its roots. So, when you touch contaminated soil while gardening, then eat a snack, or when you pick lettuce and don’t wash it thoroughly, that’s where the exposure happens.
If you continue gardening for now
If you want to keep gardening in your cold frame right now while you’re deciding what to do about the windows, you could minimize your risk by being very careful about what you grow. Focus on growing things like tomatoes, peppers, and beans, which accumulate less lead on their surface than leafy greens do.
Always wash your hands thoroughly after gardening and before handling food and wash all produce under running water right before you eat it. Peel any root vegetables and remove the outer leaves of any lettuce or greens.
If you decide to test your soil and it comes back with high lead levels, replacing the soil and using a certified clean planting mix instead is recommended.
Bottom line
When you have uncertainty about whether a potential lead source is present in your garden, preventing contamination by removing that source is far better than trying to manage it after it's already in your garden.
For more information about lead in soil, consult the OSU Extension Catalog resources below.
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