Medicines Are Turning Up in Food Crops Fertilized With Wastewater, Manure and Biosolids
As cities search for ways to conserve water and recycle nutrients, a hidden problem is emerging in the fields that feed them: traces of medicines can move from wastewater, animal manure and sewage-derived fertilizers into edible plants. A comprehensive review in Environmental Chemistry Letters finds that pharmaceutical residues are being detected across the water–soil–plant system, including in vegetables, fruits, roots and grains. The amounts reaching edible tissues are generally small—typically less than 1 percent of the total pharmaceutical load introduced into farmland—but the researchers warn that the apparent dilution does not eliminate concern. Some compounds persist in soil, some are readily absorbed by roots, and others are transformed inside plants into metabolites whose toxicity and behavior remain poorly understood. The findings place a new question at the center of agricultural water recycling: can circular farming systems close resource loops without quietly opening a pathway for drug residues into the food chain?
The pressure to reuse unconventional water and fertilizers is growing rapidly. Agriculture consumes roughly 70 percent of available freshwater worldwide, while climate change, urbanization and population growth are intensifying competition for water and arable land. Reclaimed wastewater is already widely used for irrigation in arid and semiarid regions; in Israel, it accounts for more than half of the water used in agricultural irrigation. Wastewater treatment also generates biosolids, while livestock farming produces manure rich in nutrients and organic matter. Applying these materials to soil can improve fertility, water retention and crop yields. Yet pharmaceuticals consumed by people and animals are not always completely removed or metabolized before reaching wastewater treatment plants, manure or sewage sludge. More than 11,000 pharmaceutical compounds are in use, and rising consumption of antidepressants, antidiabetic drugs, lipid regulators and other medicines means that agricultural systems may receive an increasingly diverse chemical mixture.
The review, by Lúcia H. M. L. M. Santos, Sara Rodríguez-Mozaz and Gianluigi Buttiglieri, brings together evidence from field studies rather than relying only on laboratory or hydroponic experiments. That distinction matters because real agricultural soils are chemically and biologically complex. Once a pharmaceutical enters a field, it may dissolve in soil pore water, bind to clay or organic matter, move with infiltrating water, break down through microbial or chemical reactions, or be absorbed by plant roots. The fraction available for uptake is therefore not simply the concentration measured in bulk soil. Soil pH, clay content, organic matter, moisture, temperature and microbial communities all influence whether a compound remains mobile or becomes temporarily trapped. Sorption can reduce uptake, but it is often reversible: a contaminant attached to soil particles may later be released into pore water during irrigation or rainfall, creating a delayed exposure route for crops planted months or years later.
The chemical structure of a drug also determines how readily it enters a plant. Neutral compounds generally cross root-cell membranes more easily than charged molecules, while polarity, water solubility, molecular size and hydrophobicity influence movement through plant tissues. Compounds with intermediate lipophilicity can be particularly mobile because they are soluble enough to travel in water but sufficiently compatible with cell membranes to pass into tissues. Carbamazepine, an antiepileptic and psychiatric drug, is a prominent example. It remains largely neutral across a broad pH range, has a logKow near 2.45–2.77, and can persist in soil for more than 60 days. Those properties help explain why it is repeatedly detected in crops irrigated with reclaimed water. Active transport may complicate the picture further: membrane proteins can sometimes carry ionic pharmaceuticals into cells even when passive diffusion would predict limited uptake.
The pattern of accumulation across a crop is uneven, but leafy vegetables appear to be the most exposed edible tissues. Across field studies involving reclaimed wastewater, the general order was leaves, then fruits, roots and cereal grains. Leafy greens such as lettuce, spinach, cabbage, leeks, parsley and arugula maintain extensive, actively transpiring tissues and are consumed directly, leaving little opportunity for contaminants to be excluded before harvest. In a survey of 445 commercial fields in Israel, leaves contained an average of about seven pharmaceutical compounds, compared with roughly six in roots, four in fruits and two in tubers. In vegetables irrigated with water dominated by treated wastewater in Jordan, total pharmaceutical concentrations reached 347 nanograms per gram dry weight in lettuce, 204 in parsley and 147 in arugula. Carbamazepine reached 215.7 nanograms per gram dry weight in lettuce. By contrast, cereal grains generally showed concentrations one to two orders of magnitude lower than other edible organs, although low accumulation does not mean zero exposure.
The route by which recycled material reaches a field appears to be as important as the concentration of the contaminants themselves. Reclaimed wastewater is applied repeatedly throughout a growing season, sometimes daily during hot summers, continuously adding pharmaceuticals in dissolved form—the form most accessible to roots. Biosolids and manure are usually applied once or twice a year, often before planting, and deliver contaminants largely bound to solid organic matter. That difference helps explain why crops grown in biosolid-amended soils generally contained fewer pharmaceuticals and lower concentrations than crops irrigated with reclaimed wastewater. Biosolids can increase organic matter, alter pH and stimulate microbial activity, creating additional sites for sorption and degradation. In some experiments, increasing the biosolid application rate reduced the uptake and movement of radiolabeled carbamazepine through edible vegetables. Even so, biosolids can also act as a long-term reservoir, gradually releasing residues as their organic components decompose.
Manure presents a different concern because veterinary medicines—especially antibiotics—are frequently excreted by livestock in urine and feces. Tetracyclines, sulfonamides and fluoroquinolones have been measured in manure at concentrations reaching 183,500, 32,700 and 24,700 nanograms per gram dry weight, respectively. Their strong attraction to soil can make agricultural land a persistent reservoir, while repeated applications may maintain exposure over many growing seasons. Field studies have detected antibiotics in lettuce, spinach, tomatoes, peanuts, cauliflower and other crops raised in manure-amended soils. The type of manure matters: crops grown with pig slurry or horse manure often contained higher antibiotic levels than those fertilized with poultry or cattle manure. In one comparison, norfloxacin concentrations ranged from 93.6 micrograms per kilogram dry weight in tomato fruit to 411 micrograms per kilogram in spinach leaves. Fruits sometimes showed the greatest bioaccumulation factors for antibiotics, while sex hormones reached a bioaccumulation factor of up to 30 in some root vegetables.
Perhaps the most unsettling finding is that measuring only the original drug may underestimate what is present in a crop. Plants are not passive filters; they metabolize foreign chemicals using enzyme systems that resemble detoxification pathways in other organisms. Phase I reactions such as oxidation, hydrolysis and hydroxylation can make a pharmaceutical more polar and mobile. Phase II reactions attach sugars, sulfates, glutathione or amino acids to the altered compound. Some conjugates are then locked into cell walls or vacuoles as so-called Phase III residues, becoming difficult to extract and detect. But these transformations do not automatically make a compound harmless. Carbamazepine metabolites, including 10,11-epoxycarbamazepine, are frequently found in crop tissues and can sometimes exceed the concentration of the parent drug. Certain metabolites retain biological activity, while others may be more persistent or toxic. Phase II conjugates can also be broken apart during digestion, potentially releasing the parent compound or an active intermediate. Because these substances occur at trace levels in chemically complicated plant tissues, advanced high-resolution mass spectrometry and non-targeted screening will be needed to find them reliably.
The review does not conclude that eating a particular vegetable is demonstrably dangerous, and the authors emphasize that field data remain limited compared with laboratory experiments. Instead, it identifies a monitoring gap that could become more important as water scarcity makes agricultural reuse unavoidable. Existing water-reuse standards often focus on conventional measures such as pathogens, suspended solids, pH and biochemical oxygen demand, while pharmaceuticals and other emerging contaminants may receive attention only when regulators judge that clear evidence of risk exists. The researchers argue for identifying compounds most likely to accumulate, developing models that predict concentrations in individual plant tissues, and prioritizing drugs or metabolites with low acceptable daily intakes or high toxicological concern. Drip irrigation can reduce direct contact between reclaimed water and edible plant surfaces, although it does not remove root uptake. Sprinkler systems may deposit residues on leaves and fruits, adding a second exposure route. Circular agriculture can still deliver major environmental benefits, but its safety depends on tracking not only what enters the field, but also what survives the journey from wastewater or manure into the food on our plates.
Subject of Research: Pharmaceutical uptake, accumulation and metabolism in edible crop plants grown with reclaimed wastewater, biosolids and manure.
Subject of Research: Chemistry
Article Title: Pharmaceutical contamination in edible plants grown on soils amended with wastewater, manure, and biosolids: a review
Article References: Santos, L. H. M. L. M., Rodríguez-Mozaz, S., & Buttiglieri, G. (2026). Pharmaceutical contamination in edible plants grown on soils amended with wastewater, manure, and biosolids: a review. Environmental Chemistry Letters, 24(1), 61-84. https://doi.org/10.1007/s10311-025-01878-9
Image Credits: AI Generated
DOI: 10.1007/s10311-025-01878-9
Keywords: pharmaceutical contamination, reclaimed wastewater, edible crops, biosolids, manure, plant uptake, bioaccumulation, pharmaceutical metabolites, food safety
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Gideon R. (August 29, 2026). Review Examines Pharmaceutical Contamination in Edible Plants Grown on Waste-Amended Soils. Scienmag. https://scienmag.com/review-examines-pharmaceutical-contamination-in-edible-plants-grown-on-waste-amended-soils/
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