Toxicity Assessment of Aircraft De-Icier
In order to guarantee safety and regularity of air traffic at airports
located in cold climates, large amounts of de-icer and anti-icing fluids
(ADAF) are used on runways and aircrafts prior to take-off in order to
remove ice from the ground and airplanes' surfaces. Aircraft ADAF are
aqueous solutions of a glycol or mixture of glycols, with some proprietary
additives. Depending on the formulation required, the additives might
include a surfactant, polymer thickening agent, pH buffer, corrosion
inhibitor, flame retardant, or a dye. Most airports operate ADAF collection
systems and treat or recycle the spent fluids. But a portion of the ADAF
escapes through storm sewer systems to receiving surface waters, groundwater
systems, or are stored into snowbanks. The most known environmental effects
of the discharge of ADAFs in the environment are those associated with
glycols, thus causing a potential reduction of the dissolved oxygen in
receiving waters (because of an increased biochemical oxygen demand) and the
potential toxicity of ADAF additives. Still, the environmental route and
impact of many of the additives in the de-icing agents is poorly understood.
Recently, American scientists have taken samples from snowbanks and snowbank
runoff at a medium-size airport over a 4-year period in order to
characterise ADAF components and assessed their toxicity. They used
biosensor-based measurement systems for predicting the potential toxicity
The results suggest that the environmental risk of various Aircraft ADAF
components may be more difficult to assess than previously estimated. The
authors found that the toxicity associated with ADAF remained after glycol
had been removed during periods of warm weather when the snowbanks had
started to melt. This suggests that only part of the toxicity of ADAF can be
explained by these compounds, and therefore additional toxic additives exist
and need to be studied.
In the snowbank samples the authors identified alkylphenol ethoxylates,
nonionic surfactants that can be toxic to aquatic organisms and degrade into
the known endocrine disrupters nonylphenol and octylphenol. A second group
of additives was the toxic corrosion inhibitors benzotriazoles and
tolyltriazoles. These compounds have been detected in receiving waters near
investigated airports. Some forms of benzotriazole are not readily
biodegradable and are not adequately removed in wastewater treatment plants.
Overall, the results of the current study indicate that airports cannot
simply monitor glycol levels as an indicator for the fate of all the de-icer
components, because glycols do not provide a complete picture of the fate
and transport of ADAF additives. Further investigations have to be made
regarding this issue in order to minimise the potential impacts on the local
environment (around the airports).
Source: Corsi, S. R. et al (2006) Characterization of Aircraft Deicer and
Anti-Icer Components and Toxicity in Airport Snowbanks and Snowmelt Runoff
, Environ. Sci. Technol.; doi: 10.1021/es052028m.
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