Benzotriazole concentrations in airport runoff are reduced following changes in airport deicer formulations
Authors: Olds Hayley T. , Corsi Steven R. , Rutter Troy D. 
Published: May 2021

Abstract
A comparison of the presence of additives in airport deicers commonly used in the United States and in airport runoff was conducted with data collected before and after changes in deicer formulations. Three isomers of benzotriazoles (BTs)—4-methyl-1H-benzotriazole (4-MeBT), 5-methyl-1H-benzotriazole (5-MeBT), and 1H-benzotriazole (1H-BT)—are corrosion inhibitors added to some formulations of airport deicers and are reported to be a source of aquatic toxicity in streams receiving airport runoff. Concentrations of BT in aircraft deicers and anti-icing fluids (ADAF) were reduced over time but were not reduced in potassium acetate airfield-pavement deicer material (PDM) that was used throughout the study period. Streams receiving runoff from Milwaukee Mitchell International Airport, Milwaukee, Wisconsin, USA, were monitored from 2004 to 2019 for BTs, with concentrations of 4-MeBT varying from &lt;0.35 to 4600 µg/L, 5-MeBT varying from &lt;0.25 to 6600 µg/L, and 1H-BT varying from &lt;0.25 to 150 µg/L. Median 4-MeBT concentrations at sites downstream from the airport decreased by approximately 74%, 5-MeBT by 69%, and 1H-BT by 82% following reduction in BTs in ADAF formulations, resulting in a reduction in the potential for aquatic toxicity in receiving streams. A change in residuals from regression analysis between freezing point depressants and BTs indicate that the reduction in BT concentrations in airport runoff was a result of BT reduction in ADAF formulations, but PDM may still be a substantial source of BTs in airport runoff. Because BTs are a source of aquatic toxicity in airport deicers, the reductions in BTs in the common deicers observed in this study can be used to demonstrate the potential for a reduction in the effects to aquatic organisms in airport runoff, resulting in greater likelihood of meeting aquatic toxicity requirements in airport stormwater permits, and potentially driving airports, airlines, and permit holders to advocate further reduction or elimination of BTs and other harmful contaminants in airport deicers. Integr Environ Assess Manag 2022;18:245–257. Published 2021. This article is a U.S. Government work and is in the public domain in the USA. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC)
KEY POINTS
Analysis of benzotriazoles (BTs) in aircraft deicers and anti-icing fluids (ADAF) and airfield-pavement deicer material (PDM) formulations from 2019 showed that BT was removed or substantially reduced since analysis in 2006 and 2009 in ADAF, but concentrations in PDM formulations were not reduced. Median 4-methyl-1H-benzotriazole (4-MeBT) concentrations at sites downstream from the airport decreased by approximately 74%, 5-methyl-1H-benzotriazole (5-MeBT) by 69%, and 1H-benzotriazole (1H-BT) by 82% following the reduction of BTs of ADAF formulations. A change in residuals from regression analysis between freezing point depressants and BTs indicated that the reduction in BT concentrations in airport runoff was a result of BT reduction in ADAF formulations, and this change was found to occur in 2013 for 4- and 5-MeBT, and 2010 for 1H-BT. The frequency of exceedance of water quality benchmarks has been reduced since 2013, indicating that the potential hazard level for aquatic organisms has been reduced as a result of the removal of BTs from ADAFs, but some hazard may remain due to the presence of BTs in PDM formulations.