Toxicity of Formulated Glycol Deicers and Ethylene and Propylene Glycol to Lactuca sativa, Lolium perenne, Selenastrum capricornutum, and Lemna minor

Abstract.

Laboratory studies were conducted to determine the toxicity of ethylene glycol (EG) and propylene glycol (PG) as well as two formulated glycol aircraft deicing/anti-icing fluids (ADAFs) to lettuce (Lactuca sativa), perennial ryegrass (Lolium perenne), a green alga (Selenastrum capricornutum), and duckweed (Lemna minor). Seedling emergence, root length, and shoot length were measured in lettuce and ryegrass; cell growth of the alga and frond growth, chlorophyll a, and pheophytin a of the duckweed were measured. While both the ADAFs and pure glycols were toxic to the test species, there were substantial differences in how the organisms responded to the test materials. ADAFs affected emergence in ryegrass more than in lettuce. However, when considering the sublethal endpoints of root and shoot length, the ADAFs were significantly more toxic to lettuce. The root length 120-h IC₂₅s for lettuce were 2,710 and 21,270 mg EG/L for the ADAF and pure EG compound, respectively; the root length 120-h IC₂₅s for ryegrass were 4,150 and 3,620 mg EG/L for the ADAF and pure EG compound, respectively. EG and PG ADAFs were more toxic than pure EG or PG to L. minor. To S. capricornutum, EG ADAF toxicity was similar to EG toxicity, however, PG ADAF was substantially more toxic to the alga than pure PG. The greater toxicity of ADAFs is reflective of other studies using animals and suggests that although glycols no doubt contribute to toxicity in deicer formulations, other compounds in the mixtures also contribute to the toxicity of the deicers. However, differences in responses between the four plant species suggest differences in modes of action and/or how the plants metabolize the compounds.