A drinking water standard of 0.05 mg/L (equal to 50 parts per billion, or ppb) arsenic was originally established in the United States by the Public Health Service in 1942. After the passage of the Safe Drinking Water Act of 1974 (SDWA), the Environmental Protection Agency (EPA) was given the power to set the maximum containment levels (MCLs) of contaminants in public water supplies. In 1996 Congress amended the SDWA and created a Drinking Water State Revolving Fund to provide loans for water supply improvements, which increased the EPA's power to set mandates. This amendment created the "costs and benefits rule" to determine whether the cost of implementing new MCLs outweighs the health benefits. To maximize the costs and benefits of setting new MLCs, the EPA began allowing more affordable technology to be substituted that did not fully meet MLC standards because it was more affordable.