Simulated leachability of pesticides from recycled pesticide‐container plastics

Abstract

The rate of leaching of pesticides from fence posts made with recycled high‐density polyethylene plastics from pesticide containers was determined. Posts were 7.5 cm in diameter and contained 100, 50, or 25% pesticide‐container plastics, with pesticide‐free sources of low‐density polyethylene used as the diluent. As posts are manufactured in a number of diameters, results are reported as μg/m2. The 7.5‐cm posts had a surface area of about 0.5 m2. Trifluralin was the only pesticide detected in the leachates. Total amounts of trifluralin leached from these three products, using well water, were 17, 234, and 90 μg/m2 of the surface area of the posts, respectively. Total amounts leached using simulated acid rain were 85, 196, and 84 μg/m2 respectively. Weathering of posts for 1 year resulted in significantly lower concentrations of trifluralin in the leachate using simulated acid rain, total amounts of trifluralin leached were 4, 6, and 6 μg/m2 for the 100, 50, and 25% contents, respectively. The amount of trifluralin released in all instances was judged to be insufficient to cause injury to sensitive plants and did not exceed Canadian guidelines for the protection of drinking water for humans or livestock. Trifluralin levels in the leachate did exceed Canadian guidelines for the protection of aquatic life in some cases, suggesting caution in the use of the products in aquatic environments.