Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans (PCDD/Fs) Impurities in Pesticides: A Neglected Source of Contemporary Relevance

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) may be formed during the manufacture of chlorinated pesticides, and can remain in the products as impurities. However, the contemporary release of PCDD/Fs to the environment from pesticide use is poorly understood. For this study, 27 pesticide formulations were analyzed for PCDD/Fs (n = 23 registered for use in Australia). PCDD/F impurities were present in all samples, ranging from 0.020 to 2100 ng ΣPCDD/F g−1 active ingredient (AI). Among current use pesticides, pentachloronitrobenzene (PCNB) contained the highest impurity levels (up to 2000 ng ΣPCDD/F g−1 AI and 5.6 ng TEQ g−1 AI). The quantity of pesticide used in Australia and associated release of PCDD/Fs was estimated for PCNB and phenoxy herbicides (2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenoxybutyric acid (2,4-DB)) using a probabilistic approach. Input parameters to model pesticide use contributed the highest proportions to the variability of the estimated PCDD/F release, and were considered to have the highest uncertainty. Preliminary estimates of PCDD/F release suggest that contaminated pesticides represent an important ongoing PCDD/F source to the Australian environment (10th−90th percentiles for PCNB = 14−42 and 2,4-D/2,4-DB = 0.35−1.6 g TEQ annum−1). These results may have global relevance given that many of the pesticides analyzed were imported into Australia, and are used in high volumes in other countries.