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The ILSI Health and Environmental Sciences Institute (HESI) Risk Assessment in the Twenty-first Century (RISK21) project was initiated to address and catalyze improvements in human health risk assessment. RISK21 is a problem formulation-based conceptual roadmap and risk matrix visualization tool, facilitating transparent evaluation of both hazard and exposure components. The RISK21 roadmap is exposure-driven, that is, exposure is used as the second step (after problem formulation) to define and focus the assessment. This paper describes the exposure tiers of the RISK21 matrix and the approaches to adapt readily available information to more quickly inform exposure at a screening level. In particular, exposure look-up tables were developed from available exposure tools (European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) Targeted Risk Assessment (TRA) for worker exposure, ECETOC TRA, European Solvents Industry Group (ESIG) Generic Exposure Scenario (GES) Risk and Exposure Tool (EGRET) for consumer exposure, and USEtox® for indirect exposure to humans via the environment) and were tested in a hypothetical mosquito bed netting case study. A detailed WHO risk assessment for a similar mosquito net use served as a benchmark for the performance of the RISK21 approach. The case study demonstrated that the screening methodologies provided suitable conservative exposure estimates for risk assessment. The results of this effort showed that the RISK21 approach is useful for defining future assessment efforts, focusing assessment activities and visualizing results.

The HESI-led RISK21 effort has developed a framework supporting the use of twenty-first century technology in obtaining and using information for chemical risk assessment. This framework represents a problem formulation-based, exposure-driven, tiered data acquisition approach that leads to an informed decision on human health safety to be made when sufficient evidence is available. It provides a transparent and consistent approach to evaluate information in order to maximize the ability of assessments to inform decisions and to optimize the use of resources. To demonstrate the application of the framework’s roadmap and matrix, this case study evaluates a large number of chemicals that could be present in drinking water. The focus is to prioritize which of these should be considered for human health risk as individual contaminants. The example evaluates 20 potential drinking water contaminants, using the tiered RISK21 approach in combination with graphical representation of information at each step, using the RISK21 matrix. Utilizing the framework, 11 of the 20 chemicals were assigned low priority based on available exposure data alone, which demonstrated that exposure was extremely low. The remaining nine chemicals were further evaluated, using refined estimates of toxicity based on readily available data, with three deemed high priority for further evaluation. In the present case study, it was determined that the greatest value of additional information would be from improved exposure models and not from additional hazard characterization.

A 10-port manifold was developed for the injection of insecticides into a drip irrigation system for small plot bell pepper research trials. A 179.1 metric ft lb/s positive displacement Aquaflow® electric chemical metering pump was used to transfer liquid chemical treatments from an 18.9 liter polyethylene bottle through a 10-valve manifold that allowed both water and up to 10 separate chemical treatments to mix and flow into the drip irrigation line of each treatment plot. Because very small amounts of insecticides are injected for small-plot trials, a valve and discharge pipe were built into the manifold to allow for the complete rinse of the system between treatments. This system would be suitable for chemigation research trials in most row crop trials using drip irrigation with or without plastic mulch.

The aerobic biodegradation of [1,2-(14)C] 6:2 FTOH [F(CF(2))(6)(14)CH(2)(14)CH(2)OH] in a flow-through soil incubation system is described. Soil samples dosed with [1,2-(14)C] 6:2 FTOH were analyzed by liquid scintillation counting, LC/ARC (liquid chromatography/accurate radioisotope counting), LC/MS/MS, and thermal combustion to account for 6:2 FTOH and its transformation products over 84 d. Half of the [1,2-(14)C] 6:2 FTOH disappeared from soil in 1.3 d, undergoing simultaneous microbial degradation and partitioning of volatile transformation product(s) and the 6:2 FTOH precursor into the air phase. The overall (14)C (radioactivity) mass balance in live and sterile treatments was 77-87% over 84-d incubation. In the live test system, 36% of total (14)C dosed was captured in the airflow (headspace), 25% as soil-bound residues recovered via thermal combustion, and 16% as soil extractable. After 84 d, [(14)C] 5:2 sFTOH [F(CF(2))(5)CH(OH)(14)CH(3)] was the dominant transformation product with 16% molar yield and primarily detected in the airflow. The airflow also contained [1,2-(14)C] 6:2 FTOH and (14)CO(2) at 14% and 6% of total (14)C dosed, respectively. The other significant stable transformation products, all detected in soil, were 5:3 acid [F(CF(2))(5)CH(2)CH(2)COOH, 12%], PFHxA [F(CF(2))(5)COOH, 4.5%] and PFPeA [F(CF(2))(4)COOH, 4.2%]. Soil-bound residues as well as conjugates between fluorinated transformation products and dissolved soil components were only observed in the live test system and absent in the sterile soil, suggesting that such binding and complexation are microbially or enzymatically driven processes. At day 84, 5:3 acid is postulated to be the major transformation product in soil-bound residues, which may not be available for further biodegradation in soil environment.

The first studies to explore 6-2 fluorotelomer alcohol [6-2 FTOH, F(CF(2))(6)CH(2)CH(2)OH] aerobic biodegradation are described. Biodegradation yields and metabolite concentrations were determined in mixed bacterial culture (90d) and aerobic soil (180d). 6-2 FTOH primary degradation half-life was less than 2d in both. The overall mass balance in mixed bacterial culture (day 90) was approximately 60%. At day 90, the molar yield was 6% for 6-2 FTA [F(CF(2))(6)CH(2)COOH], 23% for 6-2 FTUA [F(CF(2))(5)CFCHCOOH], 16% for 5-2 sFTOH [F(CF(2))(5)CHOHCH(3)], 6% for 5-3 acid [F(CF(2))(5)CH(2)CH(2)COOH], and 5% for PFHxA [F(CF(2))(5)COOH]. The overall mass balance in aerobic soil was approximately 67% (day 180). At day 180, the major terminal metabolites were PFPeA, [F(CF(2))(4)COOH, 30%], PFHxA (8%), PFBA [F(CF(2))(3)COOH, 2%], and 5-3 acid (15%). A new metabolite 4-3 acid [F(CF(2))(4)CH(2)CH(2)COOH] accounted for 1%, 6-2 FTOH for 3%, and 5-2 sFTOH for 7%. Based on 8-2 FTOH aerobic biodegradation pathways, PFHxA was expected in greatest yield from 6-2 FTOH degradation. However, PFPeA was observed in greatest yield in soil, suggesting a preference for alternate degradation pathways. Selected metabolites were also studied in aerobic soil. 5-3 Acid degraded to only 4-3 acid with a molar yield of 2.3%. 5-2 sFTOH degraded to PFPeA and PFHxA, and 5-2 FT Ketone [F(CF(2))(5)COCH(3)] degraded to 5-2 sFTOH, suggesting that 5-2 sFTOH is the direct precursor to PFPeA and PFHxA. Another new metabolite, 5-3 ketone aldehyde [F(CF(2))(5)COCH(2)CHO] was also identified in mixed bacterial culture. The formation of PFBA, PFPeA, and 4-3 acid indicates that multiple -CF(2)- groups in 6-2 FTOH were removed during microbial biodegradation.

Sorption of substituted phenols and carboxylic acids by soils was measured from methanol/water solutions. These data were used to assess a cosolvency model that incorporated changes in organic acid speciation as a function of soil-solution pH and the conditional pK a values observed in mixed solvents. For the chlorophenols, the cosolvency model with speciation adequately described the log-linear decrease in sorption with increasing volume fraction cosolvent (f c )

Determination des effets de l'addition de boue residuaire sur la sorption et la degradation du pentachlorophenol a des teneurs proches observees dans des sols ayant recus des boues

A greenhouse study was conducted to determine the effects of sludge on plant uptake of {sup 14}C-pentachlorophenol (PCP). Plants included tall fescue (Festuca arundinacea Schreb.), lettuce (Latuca sativa L.), carrot (Daucus carota L.), and chile pepper (Capsicum annum L.). Minimal intact PCP was detected in the fescue and lettuce by gas chromatography/mass spectrometry (GC/MS) analysis. No intact PCP was detected in the carrot tissue extracts. Chile pepper was not analyzed for intact PCP because methylene chloride extracts contained minimal {sup 14}C. The GC/MS analysis of soil extracts at harvest suggests a half-life of PCP of about 10 d independent of sludge rate or PCP loading rate. Rapid degradation of PCP in the soil apparently limited PCP availability to the plant. Bioconcentration factors (dry plant wt./initial soil PCP concentration) based on intact PCP were

Rynaxypyr™ is a highly potent and selective activator of insect ryanodine receptors with exceptional activity on a broad range of Lepidoptera. A strong correlation between insecticidal activity and ryanodine receptor activation is observed along with selective activity against insect over mammalian receptors. The synthesis and biological results are presented.