There will be patriotism in the air this weekend—but there could be toxic pollution too, according to a new study published in the journal Atmospheric Environment.

The National Oceanic and Atmospheric Administration's Dian Seidel and her colleague Abigail Birnbaum analyzed 315 locations across the United States. They found that the amount of microscopic "particulate matter" in the air—including dirt, dust, liquid droplets, soot, and smoke—was more than twice the average amount between 9 p.m. and 10 p.m. on July 4th, largely because of fireworks. Those levels decreased overnight and returned to normal by 12 p.m. on July 5th.

The researchers note that short-term and long-term exposure to such particles have been linked to negative health effects, including an increased risk of asthma attacks, coughing, heart attack, stroke, shortness of breath, wheezing, and premature death for people with lung or heart disease.

Four in 10 Americans live in places with unhealthy air. Do you?

However, the study did not analyze any direct health effects from the temporary Independence Day increase in the particles.

In response to the study, the Environmental Protection Agency (EPA) on Tuesday said that people with lung disease, older adults, and children—who likely are especially sensitive to particle pollution—should limit their risk of negative health effects by viewing fireworks from upwind.

EPA said, "We want everyone to enjoy their local fireworks displays" (Ritter, AP/Minneapolis Star Tribune, 6/30; Rice, USA Today, 6/30; Bruggers, Louisville Courier-Journal, 7/1).