Tomatoes, carrots and lettuce store pharmaceutical byproducts in their leaves.

A Johns Hopkins lab study found that four common psychoactive drugs and their byproducts concentrated mainly in the leaves of tomatoes, carrots and lettuce, with tomato leaves holding more than 200 times the concentration found in fruits.

Researchers at Johns Hopkins examined how four psychoactive medications commonly detected in treated municipal wastewater move through and are metabolized by tomatoes, carrots and lettuce. Plants were grown in a temperature-controlled chamber and supplied for up to 45 days with a liquid growth solution that included one of the drugs. Tissues were sampled and analyzed to identify parent drugs and the byproducts the plants produced. The work aims to build a clearer picture of where compounds from recycled water end up in crop species and to inform which substances might merit further assessment. Key findings: - Pharmaceuticals and their byproducts tended to accumulate in leaves rather than in edible fruits or roots. - Tomato leaves contained more than 200 times the drug concentration measured in tomato fruits. - Carrot leaves had roughly seven times the concentrations found in the edible roots. - Among the four drugs studied (carbamazepine, lamotrigine, amitriptyline and fluoxetine), carbamazepine accumulated at higher levels across tissues, while lamotrigine and its byproducts were found at low concentrations. - The researchers reported that water transport to leaves and evaporation through stomata likely concentrate these compounds there, and that plants sequester them in cell walls or vacuoles. - The study was supported by U.S. EPA National Priorities grant R840247. Summary: The study provides a tissue-level map showing that tested medications and their byproducts concentrate in leaves of tomatoes, carrots and lettuce, with variation by compound. Authors said those patterns could help identify which compounds to assess further for potential regulatory review. Undetermined at this time.