Date: March 15, 2026
Source: Johns Hopkins University
Scientists studying crops irrigated with treated wastewater discovered that trace pharmaceuticals often collect in plant leaves. Tomatoes, carrots, and lettuce absorbed medications such as antidepressants and seizure drugs during the experiment. However, the edible portions of tomatoes and carrots contained much lower levels than the leaves. The findings help researchers understand how crops process contaminants as wastewater reuse becomes more common.
The study, published in Environmental Science and Technology, is part of a broader effort to understand the safety of irrigating crops with municipal wastewater. In most cases, this water has already been processed through treatment facilities before being reused. “Farming practices place a high demand on freshwater resources. With limited rainfall and droughts threatening global water supplies, we're looking at a future with shortages that may only be met by repurposing treated wastewater, “ said Daniella Sanchez, a doctoral student at Johns Hopkins University and lead author on the study. “To continue to use wastewater safely, we need a more sophisticated understanding of where and how crop species metabolize, or break down, agents in the water.“
>> How Water Moves Drugs Through Plants
According to the researchers, the way water flows through plants likely helps explain the pattern. Water carries nutrients and other molecules throughout the plant, moving upward from the roots through the stem and into the leaves. Pharmaceutical compounds travel along with this flow. When water reaches the leaves, it evaporates through tiny openings known as stomata. As the water escapes, the remaining drug compounds are left behind in the leaf tissue. “Plants don't have a well-developed mechanism to excrete these drug compounds. They can't easily get rid of waste by peeing, like humans do, “ Sanchez said.
>> Why Plants Store Drug Compounds
Because plants cannot easily remove these substances, the compounds tend to remain inside their tissues. Some become embedded in the cell walls of leaves, while others are placed into structures called vacuoles, which act as storage compartments that hold unwanted materials inside cells. Over time, these pharmaceuticals and their byproducts can accumulate in the plant tissue since there is no efficient way for the plant to eliminate them.
