Submitted to: Journal of Environmental Science and Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2007
Publication Date: 4/1/2007
Citation: Goel, A., Mcconnell, L.L., Torrents, A. 2007. Determination of Vapor Pressure-Temperature Relationships of Current Use Pesticides and Transformation Products. Journal of Environmental Science and Health, Part B. 42:343-349. Interpretive Summary: Vapor pressure is a fundamental chemical property related to volatility. This paper presents measurements of the vapor pressure-temperature relationships of some current use pesticides and degradation products. Vapor pressure data for many pesticides is only available at one temperature, and many degradation products have no published vapor pressure values. This data is critical in accurately predicting the environmental fate of these chemicals and assessing risk to humans and wildlife. Results of this work indicate that previously published estimates of vapor pressure may be drastically different than experimentally derived values. Further research on the fundamental properties of pesticides and especially their degradation products is needed to aid in mitigation and remediation efforts for current use and legacy pesticides.
Technical Abstract: Sub-cooled liquid vapor pressures of current use organochlorine and organophosphate pesticides (chlorothalonil, chlorpyrifos methyl, diazinon, fipronil) and selected transformation products (chlorpyrifos oxon, heptachlor epoxide, oxychlordane, 3,5,6-trichloro-2-pyridinol) were determined at multiple temperatures using the gas chromatography retention time technique. Results were utilized to determine vapor pressure-temperature relationships and to calculate enthalpies of vaporization. While results for chlorothalonil and diazinon were comparable with published values, some of the experimentally measured vapor pressure values differed by up to 4 orders of magnitude from previously published values. For example, fipronil has the lowest reported vapor pressure of all the test compounds (3.7 x 10-7 Pa); however, the measured value (1.82 x 10-6 Pa) is almost an order of magnitude higher than the reported literature value. The availability of enthalpy of vaporization values for these chemicals will aid in pesticide risk assessment development and improve the effectiveness of contaminant mitigation and remediation efforts.