Whole sediment Toxicity Identification Evaluation tools for pyrethroid insecticides: I. Piperonyl butoxide addition

Abstract

Piperonyl butoxide (PBO) is a synergist used in some pyrethroid and pyrethrin pesticide products and has been used in toxicity identification evaluations (TIEs) of water samples to indicate organophosphate or pyrethroid-related toxicity. Methods were developed and validated for use of PBO as a TIE tool in whole-sediment testing to help establish if pyrethroids are the cause of toxicity observed in field-collected sediments. Pyrethroid toxicity was increased slightly more than twofold in 10-d sediment toxicity tests with Hyalella azteca exposed to 25 g/L of PBO in the overlying water. This concentration was found to be effective for sediment TIE use, but it is well below that used in previous water and pore-water TIEs with PBO. The effect of PBO on the toxicity of several nonpyrethroids also was tested. Toxicity of the organophosphate chlorpyrifos was reduced by PBO, and the compound had no effect on toxicity of cadmium, DDT, or fluoranthene. Mixtures of the pyrethroid bifenthrin and chlorpyrifos were tested to determine the ability of PBO addition to identify pyrethroid toxicity when organophosphates were present in a sample. The PBO-induced increase in pyrethroid toxicity was not seen when chlorpyrifos was present at or above equitoxic concentrations with the pyrethroid. In the vast majority of field samples, however, the presence of chlorpyrifos does not interfere with use of PBO to identify pyrethroid toxicity. Eleven field sediments or soils containing pyrethroids and/or chlorpyrifos were used to validate the method. Characterization of the causative agent as determined by PBO addition was consistent with confirmation by chemical analysis and comparison to known toxicity thresholds in 10 of the 11 sediments.

Monitoring acute and chronic water column toxicity in the Northern Sacramento–San Joaquin Estuary, California, USA, using the euryhaline amphipod, Hyalella azteca: 2006 to 2007

“…Analytical detection limits (1-3 ng/L in the current study) are in the range of biological effect concentrations for H. azteca [33]. This may explain the large number of analytical nondetections in samples that showed negative PBO effects on amphipod growth, especially because PBO enhances pyrethroid toxicity to H. azteca by a factor of approximately 2 to 4 [19,34]. This problem can be exacerbated when multiple pyrethroids, whose toxic effects are nearly additive [34], are present at concentrations below detection limits, or when mixtures of contaminants lead to synergistic effects [35].…”

“…Concentrations detected were high enough to account for the observed effects on survival [33]. Although interpretation of these results remains difficult for the reasons outlined earlier, PBO effects on H. azteca survival are considered a reliable TIE tool [19]. Evaluating our results on growth differences between ambient and PBO-treated ambient water samples is more difficult.…”

“…Addition of the enzyme inhibitor PBO to ambient samples was intended to enhance our ability to detect the presence of bioavailable OP or pyrethroid insecticides in the water [19,20] and to address concerns over the potential loss of toxicity during sampling and testing [32]. Significant differences in amphipod survival were seen in just four samples from sites near the mouth of the Napa River (323, 340) and the lower Sacramento River (711, Hood), and chemical analysis confirmed the presence of two pyrethroids, cyfluthrin and esfenvalerate, in one sample (340).…”

“…All tests were conducted with and without PBO to synergize [19] or antagonize [20] toxicity of pyrethroid or OP insecticides, respectively, because of concerns that toxicity may be lost during sampling, transport, and storage, and to guide subsequent chemical analyses. Tests were initially conducted with 100 mg/L PBO, reduced to 50 mg/L as of May 2006.…”

Distribution and toxicity of sediment‐associated pesticides in urban and agricultural waterways from Illinois, USA

“…A TU is equal to the sediment concentration normalized to total organic carbon (TOC) divided by the organism 10-d median level lethal concentration (LC50) for each pesticide. The LC50 values used in the TU analysis were permethrin [4,6,15,16], fenpropathrin ¼ 1.1 mg/g OC, and tefluthrin ¼ 2.9 mg/g OC (Y. Ding, unpublished data). The chlorpyrifos LC50 value was the average of three current literature values ranging from 1.77 to 4.2 mg/g OC [15].…”