Pentachloronitrobenzene (PCNB) is a fungicide that effectively controls diseases in turf, potatoes, and other crops . The lack of resistance makes it a useful tool in Integrated Pest Management. The US EPA has developed the KABAM model that is used, with its default assumptions, to conduct unrefined tier 2 aquatic food web bioaccumulation risk assessments. KABAM is based on work by Arnot & Gobas (2008). The US EPA's application of KABAM typically includes several key conservative default assumptions: no biotransformation of the pesticide in the water column; the dissolved oxygen content; the lipid content of the aquatic organisms; and steady state conditions. This set of default assumptions yielded a BCF whole fish value that was approximately 4.8X the experimental determinations for total PCNB (basically, PCNB plus the metabolite PCTA). Use of a more appropriate lipid content, without changing the other default values, yields a BCF that is approximately 9X the experimental determinations. The lab studies also demonstrate the rapid metabolism and depuration of PCNB and PCTA: biotransformation of PCNB to PCTA in small fish is measured in hours; the overall total PCNB (PCNB + PCTA) depuration t1/2 is approximately nine days; and the t1/2 for total PCNB metabolism in fish is estimated to be 15-16 days. The EPA's modeling system PRZM-EXAMS was used to conservatively calculate 21-day and 60-day average concentrations in a hypothetical pond, to bracket a time-to-reach steady state of 37 days. Ultimately, the KABAM output is used to calculate risk quotients, which can be used to drive the regulatory process. An intensive, refined assessment yielded some lessons learned, some of which are described herein, and others are described in Part 2 of this work.

Bioaccumulation risk assessment of pentachloronitrobenzene 1: Basis for lessons learned

248th National Meeting (2014)

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