MARSHALLTOWN — Iowa authorities say 15 agricultural workers were exposed to a herbicide while working north of Conrad in Grundy County. The workers were in a field when herbicide from a ground sprayer blew onto them Thursday afternoon. They were taken to Central Iowa Healthcare in Marshalltown, where a decontamination area was set up in the hospital parking lot. Many of the workers complained of sore throats and itchy eyes. They were then taken inside for emergency treatment.