One of the most readily available options for mulching and creating weed barriers around the home garden is cardboard. Placed at the bottom of a raised bed or lining a pathway, it can prevent unwanted plant growth and be the base of a new soil layer.
But if you use treated cardboard packaging, it may contain per- and poly-fluoroalkyl substances, or PFAS.
The glossy layer that makes boxes resistant to water, grease and food is created with these “forever chemicals,” so called because they are difficult to break down in the environment and the human body.
PFAS chemicals have been linked to health problems including cancers and kidney diseases.
Forever chemicals have received attention in Maine from contamination caused by past use of sludge containing PFAS as agricultural fertilizer. The chemicals are still used in everyday items like waterproof clothing and upholstery, nonstick cookware and dental floss.
The Food and Drug Administration ended sales of grease-proofing PFAS treatments for food containers this March, but the coatings are still allowed on other cardboards.
Uncoated corrugated cardboard is less likely to contain PFAS, according to the University of Maine Cooperative Extension. If you use it in the garden, any PFAS in it will likely be diluted by the surrounding soil, though there isn’t information to say for sure.
The extension also points out that even so, a home garden may be an insignificant source of the chemicals overall.
“If your garden is small, potential PFAS contributions from your home-grown produce may be very small compared to PFAS from other sources in your life,” associate extension professor Caragh Fitzgerald said in a recent newsletter.
The FDA is still researching what level of PFAS exposure in food causes health problems. If you are concerned about your garden soil, you can have it tested for the chemicals at several Maine laboratories.
