Anderson Brian S, Phillips Bryn M, Voorhees Jennifer P, Petersen Megan A, Jennings Lydia L, Fojut Tessa L, Vasquez Martice E, Siegler Catherine, Tjeerdema Ronald S
Department of Environmental Toxicology, University of California, Davis, California.
Integr Environ Assess Manag. 2015 Apr;11(2):319-28. doi: 10.1002/ieam.1609. Epub 2015 Jan 30.
Many watersheds in the Central Valley region of California are listed as impaired due to pyrethroid-associated sediment toxicity. The Central Valley Regional Water Quality Control Board is developing numeric sediment quality criteria for pyrethroids, beginning with bifenthrin. Criteria are being developed using existing data, along with data from 10 d and 28 d toxicity tests with Hyalella azteca conducted as part of the current study. A single range-finder and 2 definitive tests were conducted for each test duration. Median lethal concentrations (LC50s), as well as LC20s and inhibition concentrations (IC20s) were calculated based on measured whole sediment bifenthrin concentrations and interstitial water concentrations. Sediment LC50s were also corrected for organic C content. Average LC50s were not significantly different in 10 d versus 28 d tests with H. azteca: 9.1 and 9.6 ng/g bifenthrin for 10 d and 28 d tests, respectively. Average LC20 values were also similar with concentrations at 7.1 and 7.0 for 10 d and 28 d tests, respectively. Bifenthrin inhibition concentrations (IC20s) based on amphipod growth were variable, particularly in the 28 d tests, where a clear dose-response relationship was observed in only 1 of the definitive experiments. Average amphipod growth IC20s were 3.9 and 9.0 ng/g for 10 d and 28 d tests, respectively. Amphipod growth calculated as biomass resulted in IC20s of 4.1 and 6.3 ng/g for the 10 d and 28 d tests, respectively. Lack of a clear growth effect in the longer term test may be related to the lack of food adjustment to account for amphipod mortality in whole sediment exposures. The average C-corrected LC50s were 1.03 and 1.09 μg/g OC for the 10 d and 28 d tests, respectively. Interstitial water LC50s were determined as the measured dissolved concentration of bifenthrin relative to interstitial water dissolved organic carbon. The average LC50s for dissolved interstitial water bifenthrin were 4.23 and 4.28 ng/L for the 10 d and 28 d tests, respectively. In addition, a set of 10 d and 28 d tests were conducted at 15 °C to assess the relative toxicity of bifenthrin at a lower temperature than the standard 23 °C test temperature. These results showed that bifenthrin was more toxic at the lower temperature, with LC50s of 5.1 and 3.4 ng/g bifenthrin in 10 d and 28 d tests, respectively. Amphipod growth at 15 °C after a 28 d exposure resulted in the lowest effect concentration of all experiments conducted (IC20 = 0.61 ng/g). This article discusses how bifenthrin dose-response data from 10 d and 28 d exposures inform development of sediment quality criteria for this pesticide for California Central Valley watersheds.
加利福尼亚中央谷地地区的许多流域因拟除虫菊酯相关的沉积物毒性而被列为水质受损区域。中央谷地区域水质控制委员会正在制定拟除虫菊酯的沉积物质量数值标准，首先从联苯菊酯开始。标准的制定使用了现有数据，以及作为本研究一部分进行的为期10天和28天的阿氏摇蚊毒性试验数据。每个试验持续时间都进行了一次预试验和2次正式试验。根据测得的沉积物中联苯菊酯的总浓度和间隙水浓度计算出半数致死浓度（LC50），以及LC20和抑制浓度（IC20）。沉积物的LC50也根据有机碳含量进行了校正。在对阿氏摇蚊进行的10天和28天试验中，平均LC50没有显著差异：10天试验中联苯菊酯的平均LC50为9.1 ng/g，28天试验中为9.6 ng/g。平均LC20值也相似，10天试验和28天试验中的浓度分别为7.1和7.0。基于双足类动物生长的联苯菊酯抑制浓度（IC20）各不相同，特别是在28天试验中，只有1次正式试验观察到了明确的剂量-反应关系。10天和28天试验中双足类动物生长的平均IC20分别为3.9和9.0 ng/g。以生物量计算的双足类动物生长在10天和28天试验中的IC20分别为4.1和6.3 ng/g。长期试验中缺乏明显的生长效应可能与在沉积物整体暴露中未对双足类动物死亡率进行食物调整有关。10天和28天试验中经碳校正后的平均LC50分别为1.03和1.09 μg/g有机碳。间隙水LC50被确定为相对于间隙水溶解有机碳测得的联苯菊酯溶解浓度。10天和28天试验中溶解在间隙水中的联苯菊酯的平均LC50分别为4.23和4.28 ng/L。此外，在15°C下进行了一组10天和28天的试验，以评估联苯菊酯在低于标准23°C试验温度下的相对毒性。这些结果表明，联苯菊酯在较低温度下毒性更大，10天和28天试验中联苯菊酯的LC50分别为5.1和3.4 ng/g。在15°C下暴露28天后双足类动物的生长导致了所有进行的试验中的最低效应浓度（IC20 = 0.61 ng/g）。本文讨论了10天和28天暴露的联苯菊酯剂量-反应数据如何为加利福尼亚中央谷地流域该农药的沉积物质量标准制定提供信息。
