(hack! coff!) El Centro! (hack! coff!)

Dear Matthew:

Could you please tell us if the huge, thick, gray, billowing clouds of smoke that seem to be two to three miles from Interstate 8, between Seeley and El Centro, are set on purpose or not? And if they are, why?

-- Ellen Sumler, San Diego

Smoky El Centro has been a hacking and coughing battleground lately. Since the EPA instituted the Clean Air Act in 1976, the Imperial Valley has been exempt from its provisions, and farmers could continue the practice of burning off harvested fields to prepare for planting. But as a result of a Sierra Club lawsuit, that could be coming to an end next month. The area is also plagued with fires in the huge stacks of baled hay you see in the fields. Most arson, some spontaneous combustion. They can burn for days.