Chile's main environmental problems are deforestation and the resulting soil erosion, and the pollution of its air, water, and land. Air pollution from industry and transportation and water pollution are especially acute in urban centers, where the population has doubled in the last 30 years. In 1996, Chile's industrial carbon dioxide emissions totaled 48.7 million metric tons. Untreated sewage poses the major threat to the nation's water quality. As of 2001, Chile had 928 cu km of renewable water resources. While 99% of its urban dwellers have pure drinking water, only 58% of its rural dwellers have the same access.