In the final weeks of the Clinton administration in January 2001, the administration ratified a new drinking water standard of 0.01 mg/L (10 parts per billion, or ppb) of arsenic, to take effect in January 2006. The old drinking water standard of 0.05 mg/L (equal to 50 ppb) arsenic had been in effect since 1942, and the EPA, since the late 1980s, had weighed the pros and cons of lowering the maximum contaminant level (MCL) of arsenic. The incoming Bush administration suspended the midnight regulation, but after months of research, the EPA approved the new 10 ppb arsenic standard to take effect in January 2006 as initially planned.