USGS Examines Aquatic Toxicity Of Aircraft Deicers, Anti-Icers

The U.S. Geological Survey (USGS) has been examining the relative toxicity to aquatic life from a variety of formulations used to remove or prevent dangerous ice buildup on aircraft. The latest USGS study, announced on Jan. 10, compared nine different formulations, finding that neither the primary ingredients (ethylene glycol and propylene glycol) nor the known additives accounted for all observed toxicity of these formulations.

Additives are included to improve a formulation's effectiveness. Those that are proprietary have compositions known only to the manufacturer. Although research conducted in the mid 1990s revealed the toxicity of proprietary additives, the latest study compared numerous deicers and anti-icers and confirmed that most still have toxic additives that have not been publicly identified.

"This study suggests that some deicers -- products that remove snow and ice buildup -- that are currently in use are safer for the environment than the deicers used in the 1990s," said Steve Corsi, USGS scientist and lead author of this study. "But the toxicity profiles of anti-icers -- products that prevent ice and snow buildup -- have not changed significantly."

For this study, completed in cooperation with Milwaukee's General Mitchell International Airport and the Dallas/Fort Worth International Airport, formulations were collected directly from storage tanks and deicing vehicles and tested on minnows, water fleas, green alga and marine bacterium. These organisms are near the bottom of the food chain and are common benchmark indicators of environmental health. The sensitivity of tested organisms varied according to a number of factors including formulation of the product. Concentrations of deicer and anti-icer components previously observed in airport effluents have, at times, exceeded the toxicity levels shown in results of this study.

Study results indicated that anti-icers are more toxic than deicers due to the larger percent of additives contained in anti-icers. The package of additives used in these fluids varies between manufacturer and type of formulation. In addition, some additives are of special concern not only due to the toxicity of the additive, but also because they can become increasingly toxic as they degrade in the environment.

"Airports in cold climates throughout the world use deicers or anti-icers nearly every day during the winter, and those in warmer climates also must use them periodically. The most intensive deicing and anti-icing application often occurs during extreme weather conditions including periods of snow, freezing rain and high winds. This occasionally makes it difficult to contain the spent fluids and they are released to the environment. While they are a necessity for aviation safety, these products are potential environmental contaminants," Corsi said.

EPA acknowledges that there is environmental impact from aircraft deicers and anti-icers and is studying possible guidelines in consideration of national regulation to limit its runoff from airports, USGS officials said. Many airports have implemented measures to reduce runoff of chemicals into the environment, so the fate of these substances varies depending on the individual airport and weather conditions during their use.

"Certainly, the primary concern of an airline passenger is a safe arrival at their destination," Corsi said. "Airports have improved spent deicer collection systems and airlines are considering application methods to reduce the amount of fluids applied. Ultimately, it will take a combined effort from fluid manufacturers, airlines, and airports to continue reducing the environmental impact of aircraft deicers and anti-icers while maintaining the highest level of safety."

The additives are used in deicers and anti-icers to facilitate product application, ensure that the product will adhere to aircraft wings and fuselage, and enhance its overall effectiveness.

More information on the report, "Aquatic Toxicity of Nine Aircraft Deicer and Anti-Icer Formulations and Relative Toxicity of Additive Package Ingredients Alkylphenol Ethoxylates and 4,5-Methyl-1H-benzotriazoles," is available at http://pubs.acs.org/cgi-bin/abstract.cgi/esthag/2006/40/i23/abs/es0603608.html.

This article originally appeared in the 01/01/2007 issue of Environmental Protection.

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