American farmers have been ridiculing a proposal by U.S. regulators to reduce the amount of dust floating in rural air. "If there's ever been rural America, that's what rural America is," said Nebraska hog farmer Danny Kluthe. "You know? It's dirt out here, and with dirt you've got dust." The Environmental Protection Agency is looking to tighten standards for the amount of harmful particles in the air, facing opposition from U.S. farming groups who call it an unrealistic attempt to regulate dust. The EPA is reviewing its air quality standards to comply with the Clean Air Act that prescribes reevaluation every five years. The agency's scientific panel proposes either retaining or halving the current standard for coarse particles, commonly containing dust, ash and chemical pollutants--particles 10 microns or smaller in diameter, about one-tenth of human hair.