Access to protected sources of drinking water improved from 68% of the population in 1990 to 88% in 2008. However, only 26% of the slum population has access to safe drinking water, and 25% of the total population has drinking water on their premises. This problem is exacerbated by falling levels of groundwater caused mainly by increasing extraction for irrigation. Insufficient maintenance of the environment around water sources, groundwater pollution, excessive arsenic and fluoride in drinking water pose a major threat to India's health.