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Physical & Chemical properties

Vapour pressure

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Description of key information

Some potential for volatilization and vapour drift under (dry) field conditions, extrapolated experimental value (isothermal thermogravimetric effusion method, 40 to 70 °C)

Key value for chemical safety assessment

Vapour pressure:
4.05 Pa
at the temperature of:
20 °C

Additional information

The vapour pressure of the submission item Dimethyl itaconate (CAS 617-52-7) was investigated in a GLP-compliant study (Brekelmans 2010 NOTOX Report no. 492870) using the isothermal thermogravimetric effusion method according to the OECD TG 104 (2006) and EU A.4 (2009) protocols. The experiment can be considered relevant and adequate for the endpoint. Therefore it is deemed conclusive and was rated „reliable without restrictions“, i.e. “Klimisch 1” according to the scale of Klimisch et al. (1997).

The method bases on the assumption that the vapour pressure is a function of the temperature. The evaporation rates (vT) at elevated temperatures were determined for five reference substances of known vapour pressure at 20 °C, i.e. Benzo(ghi)perylene (CAS 191-24-2, 1.33 · 10^-8 Pa), Chrysene (CAS 218-01-9, 8.40 · 10^-7 Pa), Hexachlorobenzene (CAS 118-74-1, 1.47 · 10^-3 Pa), Naphthalene (CAS 91-20-3, 7.20 · 10^0 Pa) and Water (CAS 7732-18-5, 2.34 · 10^3 Pa) using a temperature program specific for each reference substance. Plots of the Log vT obtained at elevated temperatures and 1/T were used to determine the logarithms of the evaporation rate at 20 °C (Log vT, 20). The latter values were plotted against the vapour pressure at 20 °C in Pascal units (Log PT, 20). Linear regression analysis using the least squares method yielded an equation of the vapour pressure regression curve of Log PT, 20 = 1.04 · Log vT, 20 + 4.32. The correlation coefficient (r) of this calibration curve was 0.993 and the coefficient of determination (r²) was 0.986 demonstrating the reliability of the method in the calibration range from vapour pressures of 0.000'000'0133 to 2'340 Pa.

The determination was performed in duplicate with an amount of 20.8 or 21.6 mg of the test item. The isothermal weight loss was measured using an isothermal Thermographic Analyzer with the following temperature program: Start temperature 30 °C, Isothermal intervals of 10 minutes, Increment steps of 10 °C and an End temperature 100 °C. Weight losses during the isothermal intervals were determined at 40, 50, 60 and 70 °C. The corresponding evaporation rates (Log vT) were calculated according to the formula given in the test guidance and a linear regression analysis of Log vT as function of 1/T was performed using a least squares method. Thus the Log vT at 20 °C value of ca. -3.58 of the test item was obtained by extrapolation of the evaporation rate curve, which corresponds to a Log PT at 20 °C of ca. 0.6 according to the calibration curve function. The non-logarithmic value of the vapour pressure was thus determined to be 4.05 Pa = 3.04 · 10^-2 mm Hg.

The measured vapour pressure is a guide to volatility and to the probability of movement into the atmosphere. A volatility classification based solely on vapour pressure is best suited to dry, non-adsorbing surfaces. According to a classification system cited in White (2009, table 1, p 8, which is taken from p 25 of Guideline OPPTS 835.6100 of 2008) substances with vapour pressures ≥ 5.2·10^-3 at 25 °C are considered to show “intermediate to high volatility under field conditions”. Thus the vapour pressure of the submission item indicates some potential for volatilization and vapour drift. According to the reference values used in the study of Brekelmans (2010) the vapour pressure is comparable to the reference substance Naphthalene and three orders of magnitude lower than the one of water.

  • Klimisch HJ, Andreae M, Tillmann U (1997). A Systematic Approach for Evaluating the Quality of Experimental Toxicological and Ecotoxicological Data. DOI 10.1006/rtph.1996.1076 PMID 9056496 Regul Toxicol Pharmacol 25:1-5.
  • OPPTS Office of Prevention, Pesticides and Toxic Substances (2008). OPPTS 835.6100. Terrestrial Field Dissipation. Self-published, United States Environmental Protection Agency, Fate, Transport and Transformation Test Guidelines, Document Reference EPA 712-C-08-020, Washington, DC, U.S.A., in October. 48 p.
  • White K (2009). Guidance for Reporting on the Environmental Fate and Transport of the Stressors of Concern in Problem Formulations for Registration Review, Registration Review Risk Assessments, Listed Species Litigation Assessments, New Chemical Risk Assessments, and Other Relevant Risk Assessment. U.S. EPA, Office of Pesticide Programs, Environmental Fate and Effects Division, published 14 December 14. 19 p. URL