Brief Summary of Minutes of Annual Meeting

Objective 1: Identify, develop, and/or validate trace residue analytical methods, immunological procedures, and biomarkers 

Hawaii, Li: Exploring Adduct Formation between Human Serum Albumin and Eleven Organophosphate Ester Flame Retardants and Plasticizers using MALDI-TOF/TOF and LC-Q/TOF. Toxicant-protein adducts are valuable biomarkers for retrospective verification of exposure. In the present study, our goal was to determine whether organophosphate ester (OPE) flame retardants (OPE FRs) and plasticizers can covalently bind to human serum albumin (HSA) and can be used to evaluate their exposure. Eleven OPE FRs and plasticizers were examined in a HSA-adduct in vitro assay. Pure HSA was incubated with the target OPEs, as well as with an OP insecticide (profenofos) positive control. After enzymatic cleavage with pepsin or Glu-C, the digested albumin was analyzed by matrix-assisted laser desorption ionization tandem time-of-flight mass spectrometry and liquid chromatograph-quadrupole time-of-flight mass spectrometry. Under optimized HSA assay conditions, tyrosine adducts were formed at Y₄₁₁ and Y₁₄₈/Y₁₅₀ with a characteristic mass shift for phosphorylation (∆m/z 166) for the profenofos positive control. However, no such phosphorylated peptides were detected for the 11 target OPEs. This negative result suggests that these OPEs have very different affinities from the OP insecticide. They are less reactive or may specifically interact with other proteins.

Objective 2: Characterize abiotic and biotic reaction mechanisms, transformation rates, and fate in agricultural and natural ecosystems

Louisiana, Armbrust: Salinity Impacts on Pesticide Water Solubility and n-Octanol/Water Partition Coefficients. Salinity has been reported to influence the water solubility of organic chemicals entering marine ecosystems. However, there is limited data available on salinity impacts for chemicals potentially entering seawater. Impacts on water solubility would correspondingly impact chemical sorption as well as overall bioavailability and exposure estimates used in the regulatory assessment. The pesticides atrazine, fipronil, bifenthrin, cypermethrin, as well as the crude oil constituents dibenzothiophene and three of its alkyl derivatives all have different polarities and were selected as model compounds to demonstrate the impact of salinity on their solubility and partitioning behavior. The n-octanol/water partition coefficient (K_OW) was measured in both distilled-deionized water as well as artificial seawater (3.2‰). All compounds had diminished solubility and increased K_OW values in artificial seawater as compared to distilled-deionized water. A linear correlation curve estimated salinity may increase the log K_OW value 2.6% per one log unit increase in distilled water (R² = 0.968). Salinity appears to generally decrease the water solubility and increase partitioning potential. Environmental fate estimates based upon these parameters indicate elevated chemical sorption to sediment, overall bioavailability, and toxicity in artificial seawater. These dramatic differences suggest that salinity should be taken into account when conducting exposure estimates for marine organisms.

California, Gan: Degradation of Pyrethroids and Formation of 3-Phenoxybenzoic Acid on Urban Impervious Surfaces. Urban insecticide use including structural pest control and landscape maintenance accounts for a large fraction of the total insecticide use. For instance, in California, reported urban insecticide use in 2014 amounted to 1.8 million kg (as active ingredients), of which 1.77 × 10⁵ kg was synthetic pyrethroids. Pyrethroid use has been associated with acute toxicity to water column and benthic invertebrates in urban streams. Many pyrethroids may be transformed to a common intermediate, 3-phenoxybenzoic acid (3-PBA), an endocrine disrupting compound. However, little is known about the formation of 3-PBA from pyrethroids in urban settings. In this study, we examined the stability of five common pyrethroids, permethrin, lambda-cyhalothrin, deltamethrin, fenpropathrin, and esfenvalerate, on concrete surfaces and the derivation of 3-PBA under sunlight. Irreversible binding, hydrolysis, photolysis and volatilization led to rapid dissipation of pyrethroids on irradiated concrete. Formation of 3-PBA was almost instantaneous, reaching up to 3% of the initial level of pyrethroids within hours of exposure, and was caused mainly by hydrolysis, likely enhanced by the strong alkalinity of concrete. The formation of 3-PBA on concrete further varied among the different compounds, and was transient, with an average half-life of 4.2-6.7 h. Trace levels of 3-PBA were consistently found in two streams draining urban neighborhoods, suggesting that urban use of pyrethroids resulted in 3-PBA contamination of urban surface waters. Findings from this study suggested that urban hardscapes such as concrete pavement are reactive surfaces, highlighting the need to consider formation of biologically active intermediates such as 3-PBA from urban-use pesticides.

Nevada, Miller: Grindelia squarrosa: A Potential Arid Lands Biofuel Plant. Gumweed (Grindelia squarrosa) is an arid lands plant that contains approximately 12-14% acetone extractable hydrocarbons. Gumweed is a naturally occurring plant of the intermountain west that can be grown with very limited additional irrigation water on arid lands not suitable for most food crops. The acetone extract of mature, ground gumweed produces a biocrude that is approximately 52% grindelic acid, a C₂₀ diterpene acid. When the biocrude is pyrolyzed and distilled, the distillate contains a variety of compounds that can potentially be utilized as a biofuel. The crude distillate obtained from pyrolysis (heating slowly from 200^oC to 450^oC in 3-4 hours) was further fractionated into three fractions, based on their boiling points. The first cut (73-134^oC) was light yellow and consisted of cycloalkenes, alkyl benzenes and trace amounts of alcohols with comparatively lower freezing point but higher acid number. The second cut (134-172^oC) was light green and consisted of two tetralin compounds, 1,1,6-trimethyl-1,2,3,4-tetrahydronapthalene (C₁₃H₁₈) and 5,6,7,8-tetramethyl-1,2,3,4-tetrahydronapthalene (C₁₄H₂₀) which constitutes about 29 percent of the biocrude by weight. The third cut (172-213 ^oC) was a darker green and consists of 5,6,7,8-tetramethyl-1,2,3,4-tetrahydronapthalene (C₁₄H₂₀) as major constituent and other higher molecular weight hydrocarbons with relatively higher freezing point but lower acid number. These tetralins have properties that can potentially qualify them as biojet fuels, based the branched structure of the molecules, freezing point, cloud point, density, heating value and acid number. The average biannual production of those second and third cut biofuel fractions was 570 liters per hectare (l/ha) (61 gallons per acre (gal/ac)) with the range of 475 l/ha (51 gal/ac) to 664 l/ha (71 gal/ac) when gumweed was cultivated in plots at the Nevada Agricultural Experiment Station.

Objective 3: Determine adverse impacts from agrochemical exposure to cells, organisms, and ecosystems

Montana, Peterson: Risks to Pollinating Bees from Adult Mosquito Management. The insecticides currently used for management of adult mosquitoes are broad-spectrum and highly toxic to most bees, but toxicity is not the same thing as risk. In addition, risk information is not available for real-world exposures of bee pollinator species to insecticides used for mosquitoes. Therefore, we are conducting insecticide susceptibility research on the honey bee (Apis mellifera) and the alfalfa leafcutting bee (Megachile rotundata), an important non-honey bee pollinator in the western U.S. that may also serve as a surrogate for other solitary bees. This two-year research study encompasses three primary objectives that are providing knowledge about the risks to bees from exposure to insecticides. The objectives are to determine: (1) LD₅₀ values (the dose that causes 50% mortality) for alfalfa leafcutting bees when exposed to three pyrethroid insecticides; (2) the effects on foraging alfalfa leafcutting bees and honey bees the day after field applications of pyrethroids; and (3) the effects on populations of alfalfa leafcutting bees after field applications of etofenprox directly on nest shelters. Results from 2015 and 2106 are presented here. LD₅₀ values for female alfalfa leafcutting bees were 0.051 µg/bee for etofenprox, 0.057 µg/bee for permethrin, and 0.0016 µg/bee for deltamethrin. These LD₅₀ values for permethrin and etofenprox were more than twice the values for honey bee, indicating that alfalfa leafcutting bees may be approximately twice as tolerant. We also characterized respiration rates after dosing at the LD₅₀ level. Respiration rates comparing each active ingredient to control groups were statistically different (P<0.0001) as well as rates between each active ingredient (P<0.0001). There was no significant increase in mortality of alfalfa leafcutting bees or honey bees after exposure of alfalfa leaves and flowers to maximum label rates of permethrin, etofenprox, and deltamethrin. Effects on populations after direct treatment with etofenprox have not been observed. Results analyzed to date indicate no significant differences in percentages of survivorship (p=0.78), unknown mortality (p=0.18), parasitoid mortality (p=0.94), or pollen ball mortality (p=0.36) between untreated nest shelters and nest shelters treated with etofenprox.

Indiana, Sepulveda: Uptake and Depuration of Four Perfluoroalkyl Acids (PFAAs) in the Northern Leopard Frog Lithobates pipiens Tadpoles. Per/polyfluoroalkyl acids (PFAAs) are an emerging group of persistent organic contaminants that are ubiquitous in surface waters. To date, their effects on aquatic systems, especially amphibians, are poorly understood. We examined the uptake and depuration of perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), perfluorooctanoic acid (PFOA), and 6:2 telomer sulfonate (6:2 FTS) in northern leopard frog (Lithobates pipiens) tadpoles. We quantified whole-body concentrations every 10 days during constant aqueous exposure at 10, 100, and 1000 µg/L for a total of 40 days, followed by 30 days of depuration. We also examined effects on length and development. PFOS accumulated to the highest levels with whole-body bioconcentration factor (BCF) values at day 40 ranging from 19.6 to 119.3. The other three PFAAs were not found to bioconcentrate (BCF < 1.0 at day 40). Furthermore, some BCF values decreased during the exposure phase, suggesting dilution due to growth and/or changes in toxicokinetics over ontogeny. In depuration studies, half-lives ranged from

 Objective 4: Develop technologies that mitigate adverse human and environmental impacts

 Oregon, Jenkins: The Evaluation of Methods/models to Improve Pesticide Dietary Risk Assessment in Thailand. This research aims to improve pesticide dietary risk assessment in Thailand. Dietary risk assessment methods and models were evaluated to facilitate a more efficient and accurate dietary exposure assessments in Thailand that support risk managers in their decision making on food safety, including risk assessment of pesticide residues on agricultural commodities at farm level and evaluating results of market basket surveys. Improved dietary risk assessment also supports compliance with the World Trade Organization (WTO) Agreement on the Application of Sanitary and Phytosanitary Measures, which includes the establishment of the national MRLs for pesticides based on the international guidelines; compliance with the WTO SPS is critical to international trade.