Plant Triclosan (TCS) Accumulation From Biosolids-Amended Soils.

Triclosan (TCS) is an antimicrobial compound used in many personal care products that routinely enters domestic wastewater treatment plants. The solid product of treatment is biosolids, which is often land applied. A recent greenhouse study found significant TCS accumulation [bioconcentration factor (BCF) = 3 to 6.5) in plant parts of a single crop (soybean) grown in soil amended with TCS spiked liquid biosolids. The study suggested potential risks to humans and other species consuming these plants. Accumulation may vary with the plant species and type of biosolids (liquid vs cake) utilized. Our objective was to quantify the phytoaccumulation of TCS in multiple crops. We utilized a soil amended once with biosolids at 228 Mg ha^-1 and equilibrated in the field for 2 years, resulting in a final soil TCS concentration of ~1 mg kg^-1. Crops evaluated included lettuce (Lactuca sativa), radish (Raphanus sativus), and bahia grass (Paspalum notatum), representing monocotyledons (monocots), dicotyledons (dicots), above-ground (leaves), and below-ground (roots) biomass. The plants were either grown under growth chamber or greenhouse conditions. The TCS concentration utilized in the study did not adversely affect crop growth (dry matter yields). Phytoaccumulation was negligible in radish [bioaccumulation factor (BAF) = <0.001] and bahia grass leaves (BAF = <0.001), minimal in lettuce leaves (BAF = 0.01), but greater in radish roots (BAF = 0.10). Dicots (radish, lettuce) accumulated more TCS than monocot (bahia grass). The BAF values suggest some accumulation in below-ground biomass (roots), but minimal translocation to above-ground biomass (leaves). Further, corn leaf and soybean grain samples obtained from another field amended with biosolids for multiple years (soil TCS concentration = 0.55 mg kg^-1) had a maximum BAF value of 0.16. Preliminary risk assessments suggest the pathway of plant consumption by human and animals presents minimal risk from biosolids-borne TCS.