State officials are cautioning Iowans not to burn leaves, even if their community still allows the practice. Brian Button is an air quality specialist at the Iowa Department of Natural Resources.who says leaf smoke contains tiny particles of soot and toxins that can harm lung tissue and cause breathing troubles for people with asthma and other respiratory problems. He says the number of leaf-burners in Iowa is on the decline.Button says people in rural areas should not burn leaves, even though there may not be another house around for miles. He says the particles still get into the air and can travel great distances.He urges people to consider composting, mulching or municipal leaf handling instead of burning.