Skip to main content
eScholarship
Open Access Publications from the University of California

Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC Riverside Electronic Theses and Dissertations (2012)

Pyrethroids are synthetic derivatives of pyrethrin insecticides whose urban usage and continuous municipal wastewater discharge results in "pseudo-persistent" levels in Northern California waterways. Climate change causes warmer global temperatures which diminishes snowfall and reduces freshwater input into the San Francisco Bay Delta (SFBD) resulting in increased salinity over time. The SFBD and its drainage serve as spawning and rearing habitat for salmonid species and is under threat by multiple stressors including pesticide pollution.

Endocrine disrupting effects of bifenthrin at low-level exposures were investigated in laboratory and field experiments. 96-Hour laboratory exposures to bifenthrin (1 ng/L to 10 ug/L) showed no changes in plasma levels of the estrogenic biomarker, vitellogenin (VTG) protein, nor changes of the sex steroids testosterone (T), 11-ketotestosterone (11-KT), and 17beta-estradiol (E2) levels in two salmonid species: Oncorhynchus mykiss and Oncorhynchus tshawytscha. Field exposures using storm water containing bifenthrin, also showed no significant change in VTG or sex steroid levels in both fish species, suggesting short-term low dose exposure to bifenthrin does not result in estrogenic activity in salmonids.

To evaluate the impacts of hypersaline conditions on bifenthrin toxicity, a 14-day laboratory exposure was performed using two populations of O. mykiss acclimated to freshwater, 8 g/L, and 17g/L salinity and then exposed to 0, 0.1, and 1.5 ug/L bifenthrin. The first population (Jess Ranch) was previously treated as embryos with high levels of E2 to obtain uni-gender populations, while the second population (Nimbus Hatchery) was cultured without hormone treatment. Only Jess Ranch fish exhibited significant mortality following exposure to 1.5 ug/L bifenthrin in freshwater. No significant difference was observed in VTG levels in either population. Jess Ranch Fish showed no significant difference in T, 11-KT, or E2 levels. Nimbus fish only showed a significant increase in E2 following exposure to 1.5 ug/L bifenthrin in freshwater. In vitro biotransformation studies using livers were also performed. Saltwater acclimation significantly reduced conversion of bifenthrin to polar metabolites in Jess Ranch fish. This study suggests that embryonic exposure to estrogens can increase susceptibility to bifenthrin in freshwater fish and saline acclimation protects against acute lethality through an unknown mechanism.

    Cover page: Impacts of Hypersaline Conditions on the Biotransformation and Toxicity of the Pesticide Bifenthrin in Salmonid Species of the San Francisco Bay Delta
    • Article
    • Peer Reviewed
    UC Riverside Previously Published Works (2013)
    The pyrethroid insecticide bifenthrin is frequently detected at ng/L concentrations in tributaries of the San Francisco Bay Delta. The estuary is also experiencing increasing salinity through climate change and water redirection. To evaluate the impacts of hypersaline conditions on bifenthrin toxicity in anadromous salmonids of the San Francisco Bay Delta (CA, USA), a 14-d laboratory exposure was performed using 2 strains of Oncorhynchus mykiss (rainbow trout and steelhead) acclimated to freshwater and to 8 g/L and 17 g/L salinity. The fish were then exposed to nominal concentrations of 0 µg/L, 0.1 µg/L, and 1.5 µg/L bifenthrin. Rainbow trout exhibited significant mortality following exposure to 1.5 µg/L (1.07 ± 0.35 µg/L measured) bifenthrin in freshwater. Elevated levels of Na⁺ /K⁺ adenosine triphosphatase α1A mRNA subunit expression was observed in the gill of rainbow trout acclimated to hypersaline conditions relative to freshwater animals. No significant difference was noted in Na⁺ /K⁺ adenosine triphosphatase subunit levels in brains of either strain in freshwater or hypersaline conditions. Likewise, significant differences were not observed in plasma vitellogenin or steroid hormone concentrations in either strain whether maintained in freshwater or saltwater. Saltwater acclimation significantly reduced nicotinamide adenine dinucleotide phosphate-catalyzed biotransformation of bifenthrin in liver microsomes of rainbow trout but not of steelhead. The present study showed that, relative to steelhead, rainbow trout have different responses to bifenthrin acute toxicity as well as different rates of hepatic bifenthrin biotransformation and regulation of Na⁺ /K⁺ adenosine triphosphatase subunits in gills. These data indicate that significant differences exist between the strains and that animal life history may have important effects on the susceptibility of each strain to environmental contaminants.
      Cover page: Effects of salinity acclimation on the endocrine disruption and acute toxicity of bifenthrin in freshwater and euryhaline strains of Oncorhynchus mykiss
      Top