Whether it’s an acre of greenery or a collection of pots on your balcony or windowsill, having a garden can provide you with your own slice of nature. And growing your own food is a pleasure that even access to a great Farmer’s Market can’t beat. A ripe strawberry or tomato freshly harvested and still warm from the sun offers the best flavor and burst of nutrients. It’s also a good way to increase the amount of organic, unpackaged food in your diet and to avoid toxic chemicals associated with industrial farming and food processing.
However, there are several potential sources of toxic chemicals in gardens that you need to be aware of so that you can avoid them. Toxic chemicals can find their way into your produce from soil to seed to harvest through use of pesticides or other toxic products, as well as from contaminants present in the soil or environment. Contaminants can also find their way into chickens and their eggs if you raise them.
In the next couple of blogs, I’ll discuss sources of toxic chemicals to watch out for in gardens and offer easy tips to reduce your exposure to them. In this first garden blog, I will focus on environmental sources of contamination and what might be present in your soil.
Where does your garden grow?
The first step in deciding whether it’s safe to grow produce in your garden is to make sure your soil and environment is relatively free of toxic chemicals. As a realtor might say, it’s all about location, location, location. Except for plants you grow on your windowsill indoors, there may be sources of contamination past or present that contaminate your garden with heavy metals, polycyclic aromatic hydrocarbons (PAHs), pesticides, or other toxic chemicals. It’s important to know the history of your land and sources of contamination nearby.
Potential sources of contamination to your soil:
- Past uses of the property, like an orchard that was treated with lead-arsenate, or industrial activities that might have left PCBs or mercury in the soil.
- If your house is old enough (pre-1980) to have lead-based paint, especially near wood windows that shed paint particles when they’re raised or lowered.
- Creosote-treated railroad ties.
You can have your soil tested for lead and other contaminants, though that can get expensive, especially for chemicals like PAHs, PCBs, and dioxins. Keep in mind, contamination may vary widely and it’s difficult to capture it all with a small number of samples, though you can mix subsamples from all the areas you’re going to grow produce in to get an average value. Here are some options:
- You may qualify to have your soil tested for lead for free at: https://www.360dustanalysis.com.
- Check with your local state university or agricultural extension agency to see if they offer free soil testing.
- You may also find a lab that is accredited by the EPA at: https://www.epa.gov/lead/national-lead-laboratory-accreditation-program-list
Potential sources of airborne toxic chemicals:
- Living next to busy roads, railroad routes, commercial properties where diesel trucks idle, farms where pesticides are sprayed, or in the flight path of airports.
- Hedges and buildings between the contaminant source and your garden can block some of the pollution (Säumel et al. 2012). However, if your home is in the flight path of an airport, it may not be advisable to plant produce since you can’t control what is deposited from directly above you (Miranda et al. 2011).
- Pesticide spraying by a neighbor, the homeowner’s association (HOA), or landlord.
- There is also the possibility of longer-range atmospheric transport and deposition of contaminants from sources like incinerators or industrial emissions.
- Check the EPA’s Toxics Release Inventory to see if your garden is located downwind of industries that emit toxic chemicals into the air that can then deposit on your yard. Planting a vegetative buffer like trees or tall bushes can help filter some of those contaminants out before they are deposited on your garden. And, if you’re so inclined, lobby your legislators and regulators to force nearby industries to clean up their emissions.
What about microplastics in the air and soil, as well as the toxic chemicals they contain or absorb? With widespread contamination from microplastics in the news (e.g. Shao et al. 2022), a reader asked whether her garden could be contaminated by those. Home gardens would have same issues as the rest of the planet with respect to atmospheric deposition of microplastics so yes, that’s possible. However, if you use plastic sheeting to combat weeds or as a greenhouse tent for early season plantings, these are likely a greater source of microplastics to your garden.
- You can replace plastic in your garden by adding mulch or straw to reduce weed growth and build hotbeds from old windows instead of plastic, as long as they aren’t from houses older than 1980 so that you avoid lead-based paint. Skip using newspapers, which may have toxic ink (Jadhav 2021).
- To reduce atmospheric deposition of microplastics to your garden, it might help to plant vegetative buffers like tall hedges or trees around your garden plot, though I haven’t seen data on whether this works.
For many of us, our gardens extend to greenspaces near and far that are covered in blackberry vines, fruit trees, or other produce. There are potential sources of toxic chemicals to watch for in these cases as well. Check to make sure they’re not adjacent to heavily traveled roads and or treated with pesticides by the municipality.
Bottom line
- If you’re not sure your soil is free of contamination, grow your plants in raised beds using clean soil and gravel over a liner at the base to prevent uptake of the toxic chemicals into your plants.
- If your garden is located near sources of toxic chemicals, plant a tall hedge or trees to filter out some of the contaminants or choose to not garden in this location. There may be a community garden in your area that is located in a cleaner area and has plots you can rent.
- Ask to be notified by your HOA or landlord if and when they plan to spray so you can cover your plants or request that they use less toxic ways to control weeds and pests.
References
- Shao, L. et al. 2022. Airborne microplastics: A review of current perspectives and environmental implications. J. Clean. Prod. 347:131048.
- Jadhav, S. et al. 2021. Health risks of newspaper ink when used as food packaging material. Lett. Appl. NanoBioScience 10:2614-23.
- Miranda, M. L. et al. 2011. A geospatial analysis of the effects of aviation gasoline on childhood blood levels. Environ. Health Perspect. 119:1513-16.
- Säumel, I. et al. 2012. How healthy is urban horticulture in high traffic areas? Trace metal concentrations in vegetable crops from plantings within inner city neighbourhoods in Berlin, Germany. Environ. Pollut. 165:124-32.
Picture attributes
- Blackberries and tomatoes – Laurel Standley
- Window: https://www.dreamstime.com/photos-images/peeling-paint-window-sill.html
- Crop duster: Fotolia
- Microplastics: oceanservices.noaa.gov
Dr. Laurel Standley 
One response to “Gardening, part 1. Avoiding toxic chemicals in your garden.”
[…] sure the garden where you’ll be planting produce is as free of toxic chemicals as possible (see prior post), the next step is to make sure products you use in the garden are also free of added pesticides or […]