Along with the vibrant colors and occasional loud bangs, fireworks produce a tremendous amount of smoke.
Iowa air quality experts, including the DNR's Brian Hutchins, monitor the atmosphere to make sure the buildup of smoke does not exceed federal standards.
Hutchins said humid conditions add to the concern.
"Typically we'll see some spikes in and around the Fourth of July and in some cases we actually exceed the standards," he said. "We have often conditions that have essentially led to stagnant air and the smoke just builds up at ground level and is kind of persistent."
Hutchins advised family and friends who suffer from asthma or other respiratory conditions to stand upwind from the displays or view them from a distance when possible.