ARS | Publication request: Volatile organic compounds in pesticide formulations: Assessing methods to predict contributions to ground-level ozone

Submitted to: Atmospheric Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 7, 2011
Publication Date: May 1, 2011
Citation: Zeinali, M., Mcconnell, L.L., Hapeman, C.J., Nguyen, A., Schmidt, W.F., Howard, C. 2011. Volatile organic compounds in pesticide formulations: Assessing methods to predict contributions to ground-level ozone. Atmospheric Environment. 45:2404-2412.

Interpretive Summary: California currently experiences some of the worst ozone episodes in the United States. As volatile organic compounds (VOCs) are one of the precursors to ozone formation, California has deemed that all sources of VOC emissions must be reduced in order to alleviate this problem. Pesticide application is one such source of VOC emissions in California and the Department of Pesticide Regulation (CADPR) has determined that these emissions must be reduced by 10% in order to meet the ozone reduction goals. The amount of VOC emissions from pesticide application is currently determined through an experimental method known as thermogravimetric analysis (TGA). In this process, a known mass of pesticide is heated over a specific time period and the mass lost over time is set to the total VOC emissions for that pesticide type. This method does not account for the way in which the VOC reacts in the atmosphere (reactivity) nor does it account for its ability to transition from a liquid to a vapor at normal temperatures (volatility). In the current study, six pesticides were used in a case study to examine available methods to predict the volatility and the ozone formation potential of pesticide products. This work provides a critical analysis of these available methods and recommendations for future research needed to develop more effective air quality management practices.

Technical Abstract: Environmental scientists have primarily focused on the fate, transport, and toxicity of pesticide active ingredients, but relatively little research has been conducted to examine the environmental fate of pesticide inactive ingredients, sometimes termed formulants or inerts. Many formulants are volatile organic compounds that may contribute to ground-level ozone pollution. As many regions of the US come under greater regulatory pressure to reduce ozone, air quality managers may implement measures to reduce emissions of reactive VOCs. In California, a system of formulation testing using thermogravimetric analysis (TGA) is used to estimate VOC emission potential for pesticide products. In this work, we provide a critical analysis of several available methods for estimating VOC emissions and ozone formation potential (OFP) of pesticide products. The methods examined are TGA alone; TGA with calculated OFP from confidential formulation information; TGA-FTIR of evolved gases and calculation of OFP; and gas-chromatography-mass spectrometry and calculation of OFP. Results show that the use of TGA likely overestimates the VOC content of pesticide products as compared with GC-MS. VOC profiles measured by GC-MS were examined in a simple emissions model. Results indicate that for many products VOCs in pesticide formulations are emitted during the first 24 hours after application.