California Code, Health and Safety Code - HSC § 40451.5

On or before January 1, 2001, the south coast district shall revise its forecasting models to allow the district to predict, using state-of-the-science techniques, when the 24-hour federal ambient air standard for PM2.5, as adopted in July 1997, or any standard adopted by the United States Environmental Protection Agency that succeeds that standard, may be expected to be exceeded.