An environmental concern: uptake of ivermectin from growing substrate to plant species

Abstract

Ivermectin (IVM) is an antiparasitic drug used worldwide. However, its high level of faecal elimination, its transfer to thesoil, and the use of manure for soil amendment, represents a potential environmental risk. Two trials were conducted to evaluate theuptake of IVM to: 1) a crop of ryegrass (Lolium multiflorum) and clover (Trifolium repens) growing for 120 days post treatment (dpt) inIVM-spiked soil at 3, 000 (High group, HG) and 90 ng/g (Low group, LG); 2) a crop of radish (Raphanus sativus) and lettuce (Lactucasativa) growing for 60 dpt in a mix of soil and 10% IVM-spiked manure at 3, 000 ng/g. Soil, soil-manure mix and plants were sampledstarting at 15 dpt and at different intervals. IVM concentration (IVMc) was quantified by HPLC. In the HG, IVMc in soil decreasedfrom 2, 154 to 225 ng/g; in ryegrass ranged between 378.65-21.74 ng/g. Strikingly, clover development was delayed; hence, samplingbegun 30 dpt. IVMc in clover ranged between 94.09-4.56 ng/g. Significant differences were detected between species (p=0.0374). In theLG, IVMc varied between 22.26-1.02 ng/g in ryegrass and between 10-1.02 ng/g in clover, differences being statistically not significantbetween species (p=0.8301). IVM was detected in both horticultural species at significant levels (p>0.05) in all sampling times and IVMcwas between 10-5 ng/g in radish and 17.70-6.55 ng/g in lettuce. In the substrate IVMc decreased from 1, 311 to 116 ng/g. Consequently,IVM in soil and in composted substrate is transferred to plants during its growth and could be incorporated into the food chain of bothlivestock and humans.