A new study by the U.S. Geological Survey (USGS) agency found that nine of 11 ice control product formulations commonly used at airports contain phosphorus in levels that can drive overgrowth of algae.
The six-year study analyzed areas around Mitchell International Airport in Milwaukee, Wisconsin, but the deicing products examined are extensively used at more than 200 airports in the U.S. that experience freezing conditions.
The deicing products have a high biochemical oxygen demand and chemical oxygen demand and can degrade aquatic ecosystems through oxygen depletion. Freezing point depressants such as propylene glycol and ethylene glycol, as well as additives in anti-icing fluids and pavement deicers, can also be toxic to aquatic organisms.
Airport deicers were found to contribute to total phosphorus (TP) in 84% of the water samples collected at downstream sites during deicing events, and TP concentrations at those sites exceeded aquatic life benchmarks in 70% of samples collected during deicing, the study found.
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“Monitoring ice control product runoff is an important part of an airport’s pollution prevention plan, and in many cases, these plans include monitoring of phosphorus runoff,” says USGS physical scientist and study co-author Owen Stefaniak, in a statement. “But accounting for the true source of phosphorus observed in airport runoff can be a real challenge for airport managers. Since these products contain proprietary ingredients not disclosed by the manufacturers, the airlines have no way to know how much phosphorus they are applying when they deice a plane.”
Milwaukee’s Mitchell International Airport uses extensive deicer collection systems such as deicing pads (areas that drain to recovery tanks) and vehicles with high-powered suction devices designed to capture ice control products from pavement. However, preventing all runoff from aircraft and runway deicing operations during inclement weather while maintaining flight schedules is not typically possible.
The study notes that ice control product applications occur during freezing weather and phosphorus may not have the same environmental impact as it would during warmer months, when plant and algae growth is much greater.
Use of deicing products is required by the Federal Aviation Administration during periods of ice and snow accumulation on aircraft. Stormwater runoff from airports is regulated by the states with guidance from the Environmental Protection Agency (EPA) and managed by airports. The EPA has designated spent deicers as regulated industrial wastewater.
“New airports are required by law to collect 60% of their [deicing] runoff while existing airports are handled by a site-specific permitting process. Any uncollected spent deicing products can run off to nearby surface waters or enter the local groundwater,” the study states.
The study, Airport Deicers: An Unrecognized Source of Phosphorus Loading in Receiving Waters, was published in the journal Environmental Science & Technology.
Traveling by plane this holiday season? ✈️❄️
A new USGS study found that airport ice control products may result in elevated phosphorus levels in waterways downstream from the airport despite airport efforts to contain these products.
— USGS (@USGS) December 21, 2023