During the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, cleanup crews applied millions of liters of dispersants to break up the oil. At the time, the public and some scientists worried about how long the chemicals would last in the deep sea. According to a new Environmental Protection Agency study, the key active ingredient in the dispersants degrades slowly at deep-sea temperatures. EPA oil spill expert Albert D. Venosa and coworkers ran tests on artificial seawater at 5 °C, about the temperature of deep Gulf water. The team inoculated flasks of the water with bacterial communities from the deep Gulf and then added an oil and dispersant mix. By using liquid chromatography/tandem mass spectrometry, the team tracked levels of the main surfactant in the Gulf dispersants. They didn’t see significant breakdown for almost a month, and some of the surfactant persisted at the end of the 42-day experiment (Environ. Sci. Technol., DOI: 10.1021/es303881h). The chemical’s persistence suggests more research is needed to understand potential toxicity in cold environments, the researchers say.