No abstract

Removal of pesticide residues from fresh produce is important to reduce pesticide exposure to humans. This study investigated the effectiveness of commercial and homemade washing agents in the removal of surface and internalized pesticide residues from apples. Surface-enhanced Raman scattering (SERS) mapping and liquid chromatography tandem mass spectrometry (LC-MS/MS) methods were used to determine the effectiveness of different washing agents in removing pesticide residues. Surface pesticide residues were most effectively removed by sodium bicarbonate (baking soda, NaHCO) solution when compared to either tap water or Clorox bleach. Using a 10 mg/mL NaHCO washing solution, it took 12 and 15 min to completely remove thiabendazole or phosmet surface residues, respectively, following a 24 h exposure to these pesticides, which were applied at a concentration of 125 ng/cm. LC-MS/MS results showed, however, that 20% of applied thiabendazole and 4.4% of applied phosmet had penetrated into the apples following the 24 h exposure. Thiabendazole, a systemic pesticide, penetrated 4-fold deeper into the apple peel than did phosmet, a non-systemic pesticide, which led to more thiabendazole residues inside the apples, which could not be washed away using the NaHCO washing solution. This study gives us the information that the standard postharvest washing method using Clorox bleach solution for 2 min is not an effective means to completely remove pesticide residues on the surface of apples. The NaHCO method is more effective in removing surface pesticide residues on apples. In the presence of NaHCO, thiabendazole and phosmet can degrade, which assists the physical removal force of washing. However, the NaHCO method was not completely effective in removing residues that have penetrated into the apple peel. The overall effectiveness of the method to remove all pesticide residues diminished as pesticides penetrated deeper into the fruit. In practical application, washing apples with NaHCO solution can reduce pesticides mostly from the surface. Peeling is more effective to remove the penetrated pesticides; however, bioactive compounds in the peels will become lost too.

4,4'-dichlorodiphenyltrichloroethane (DDT) has been re-recommended by the World Health Organization for malaria mosquito control. Previous DDT use has resulted in resistance, and with continued use resistance will increase in terms of level and extent. Drosophila melanogaster is a model dipteran that has many available genetic tools, numerous studies done on insecticide resistance mechanisms, and is related to malaria mosquitoes allowing for extrapolation. The 91-R strain of D. melanogaster is highly resistant to DDT (>1500-fold), however, there is no mechanistic scheme that accounts for this level of resistance. Recently, reduced penetration, increased detoxification, and direct excretion have been identified as resistance mechanisms in the 91-R strain. Their interactions, however, remain unclear. Use of UAS-RNAi transgenic lines of D. melanogaster allowed for the targeted knockdown of genes putatively involved in DDT resistance and has validated the role of several cuticular proteins (Cyp4g1 and Lcp1), cytochrome P450 monooxygenases (Cyp6g1 and Cyp12d1), and ATP binding cassette transporters (Mdr50, Mdr65, and Mrp1) involved in DDT resistance. Further, increased sensitivity to DDT in the 91-R strain after intra-abdominal dsRNA injection for Mdr50, Mdr65, and Mrp1 was determined by a DDT contact bioassay, directly implicating these genes in DDT efflux and resistance.

BACKGROUND: Drinking water contamination related to the use of aqueous film-forming foam (AFFF) has been documented at hundreds of military bases, airports, and firefighter training facilities. AFFF has historically contained high levels of long-chain per-and polyfluoroalkyl substances (PFAS), which pose serious health concerns. However, the composition and toxicity of legacy AFFF mixtures are unknown, presenting great uncertainties in risk assessment and affected communities. OBJECTIVES: This study aimed to determine the fluorinated and nonfluorinated chemical composition of a legacy AFFF sample and its toxicity in zebrafish embryos. METHODS: A sample of legacy AFFF (3% application formulation, manufactured before 2001) was provided by the Massachusetts Department of Environmental Protection. High resolution mass spectrometry (HRMS) was used to identify PFAS and nonfluorinated compounds, and a commercial laboratory measured 24 PFAS by a modified U.S. EPA Method 537.1. AFFF toxicity was assessed in zebrafish embryos in comparison with four major constituents: perfluorooctanesulfonic acid (PFOS); perfluorohexanesulfonic acid (PFHxS); sodium dodecyl sulfate (SDS); and sodium tetradecyl sulfate (TDS). End points included LC 50 values, and sublethal effects on growth, yolk utilization, and pancreas and liver development. RESULTS: We identified more than 100 PFAS. Of the PFAS detected, PFOS was measured at the highest concentration (9,410 mg=L) followed by PFHxS (1,500 mg=L). Fourteen nonfluorinated compounds were identified with dodecyl sulfate and tetradecyl sulfate the most abundant at 547.8 and 496:4 mg=L, respectively. An LC 50 of 7:41 × 10 −4 % AFFF was calculated, representing a dilution of the 3% formulation. TDS was the most toxic of the constituents tested but could not predict the AFFF phenotype in larval zebrafish. PFOS exposure recapitulated the reduction in length but could not predict effects on development of the liver, which was the tissue most sensitive to AFFF. DISCUSSION: To our knowledge, this research is the first characterization of the chemical composition and toxicity of legacy AFFF, which has important implications for regulatory toxicology.

Exposure of golfers to pesticides following their application to turfgrass is of concern to regulators, turfgrass professionals, and consumers. Multipathway exposures were evaluated for golfers on turfgrass treated with chlorpyrifos and carbaryl. Air concentrations and transferable foliar residues (TFRs) were measured to assess potential respiratory and dermal exposures, respectively. At the same time, exposure to individuals simulating the play of golf was determined by dosimetry and urinary biomonitoring. Individual golfer exposure was determined in 76 rounds of golf following eight applications of chlorpyrifos and two applications of carbaryl. Estimated exposures to golfers following full course and full rate applications of chlorpyrifos and carbaryl were 19-68 times below current U.S. EPA acute reference dose (Rfd) values, indicating safe exposures under U.S. EPA hazard quotient criteria. Dermal exposure was determined to be the dominant exposure pathway to golfers, accounting for approximately 60% of the chlorpyrifos absorbed dose and 100% of the carbaryl absorbed dose. This study also provides a set of transfer factors (TFs) that may be used to determine dermal exposure of golfers to pesticides using transferable residue data.