Investigations into the effects of DEET found that in some instances frequent human users reported severe skin reactions, including blistering and burning sensations, as well as seizures and cognitive malfunctions—and, in a few cases, death. Lab tests on rodents resulted in neuron damage. Further studies proved that DEET is absorbed through the skin and, once in the body, it's ultimately eliminated through urine. DEET was also found to pose environmental problems, as its chemical composition is slow to break down, and it easily moves through soil to penetrate water sources. Despite such concerns, DEET lobbyists successfully negotiated a deal with the EPA that waived further testing requirements. To date, some countries, such as Canada, have banned repellents with heavy concentrations of the compound.