The California Farm Bureau has filed suit to block the Environmental Protection Agency from ending the industry´s longtime exemption from federal air pollution regulations. The Farm Bureau wants the exemption continued another three years so more studies can determine how much farms pollute. The EPA settled a lawsuit in May to begin holding farms accountable for pollution from diesel water pumps and animal waste. Farms have had a break from Clean Air Act regulations for more than 25 years. The California Air Resources Board says agriculture contributes more than a quarter of the smog in the San Joaquin Valley during the summer and most of the soot pollution the rest of the year.