Triple water rinsing does not always render waste plastic pesticide containers non-hazardous waste

After pesticide application onto crops, waste plastic pesticide containers (WPPC) may still contain residual active substances (AS) that are typically hazardous. Specific limits exist per pesticide active substance to classify WPPC as hazardous or non-hazardous wastes. The most frequent limit is 0.1% w/w (mass of active substance per mass of as received container). Triple rinsing is a widely used management technique to decontaminate WPPC and determine their downstream management. However, its efficiency needs to be evaluated for new types of pesticides. The goal of the work was to measure the residual contents of 15 new pesticide AS, widely used all over the world, before and after triple rinsing using 56 WPPC. In addition, the contents of pesticide AS sorbed onto the plastic containers are analyzed for the first time. Results show that all unrinsed WPPC had residual AS contents above the hazard limits except for four AS. Triple rinsing removed from 68.3% (minimum) to 99.9% (maximum) of the liquid contents of 15 active substances. However, due to high variances of the AS contents after triple rinsing, mean values before and after rinsing were statistically equal for 8 out of 14 AS. The sorbed AS contents ranged from 3% to 97% of the total AS content. Only Azoxystrobin’s total content (i.e. the sum of liquid and sorbed phases) slightly exceeded the hazard limit of 0.1% w/w. Conclusively, triple rinsing may not always lead to AS content reductions below hazard limits. The sorbed contents should be considered to check legal compliances.