Soil erosion and deforestation are among Panama's most significant environmental concerns. Soil erosion is occurring at a rate of 2,000 tons per year. During 1990-1995, the annual average rate of deforestation was 2.15%. Air pollution is also a problem in urban centers due to emissions from industry and transportation. In 1996, industrial carbon dioxide emissions totaled 6.6 million metric tons. Only 79% of rural dwellers have pure drinking water. Pesticides, sewage, and pollution from the oil industry cause much of the pollution. Agencies with environmental responsibilities include the Ministry of Health and Ministry of Rural Development. The Smithsonian Tropical Research Institute, in Balboa, conducts studies on the conservation of natural resources. The nation's fish resources are threatened by water pollution. As of 2001, 17 of Panama's mammal species are endangered, and 10 of the nation's bird species are also endangered. Of the nation's plant species, a total of 1,018 are threatened with extinction. Endangered species include the red-backed squirrel monkey, tundra peregrine falcon, spectacled caiman, American crocodile, and four species of sea turtle (green sea, hawksbill, olive ridley, and leatherback).