A new study says that electric are often more environmentally hazardous than their combustion-engine counterparts. The research, conducted by the Norwegian University of Science and Technology, looked at the entire life of the cars—from production, to usage, to end-of-life breakdown—to determine their total impact on the environment. If coal was used to create the electricity in cars, the study found, greenhouse-gas emissions rose greatly. The toxic waste created in production of electric cars—from nickel, copper, and aluminum—was also much greater than in conventional-car production. According to the study, "The global warming potential from electric vehicle production is about twice that of conventional vehicles." However, if the electric car is produced using low-carbon sources, there is still potential for it to reduce emissions on the whole. "If you are considering purchasing an electric vehicle for its environmental benefits,” said the study’s co-author professor Anders Hammer Stromman, “first check your electricity source and second look closely at the warranty on the batteries."