Sanitation trucks that run on natural gas and not diesel fuel are on display at Bronx Community College, where they are being touted Wednesday as a potential ally in the fight to curb asthma in the borough.The $50,000 cleaner air trucks are parked outside of the Center for Sustainable Energy, where they are being displayed by Clean Energy, the company promoting them. Clean Energy officials are in talks with private sanitation companies and the city, trying to convince waste managers to buy these trucks over those that run on diesel fuel. Richard Kassel, of the Natural Resources Defense Council, says diesel fuel can emit a type of pollutant that worsens asthma symptoms. One in five Bronx children suffer from asthma bad enough to keep them out of school and from growing up healthy, according to Kassel.The city has expressed concerns over the price of the trucks. Clean Energy has countered by pointing out the overall benefit to public health, as well as the fact that these trucks might lessen dependence on foreign oil.