Just in time for the Fourth of July comes some news that might put a damper on your celebrations: A new study says exploding fireworks create toxic air pollution that could be harmful to your health. Happy Independence Day, everyone.

A study by federal scientists from the National Oceanic and Atmospheric Administration published in the journal Atmospheric Environment says the thousands of Fourth of July firework celebrations we set off around the country is contributing to air pollution, releasing tiny particles called particulates into the atmosphere.

Those particulates can affect your health because they travel into your respiratory tract and enter the lungs. Other particulate matter includes dust, dirt, soot smoke and liquid droplets, notes USA Today. They’re measured in micrometers, which is one-millionth of a meter.

In this study, particulates from fireworks were 2.5 micrometers in size. Whether you’re breathing them in often or only in the short-term, the particulates are linked to health effects like coughing, wheezing, shortness of breath, asthma attacks and even heart attack and stroke. It could contribute to premature death in people with heart or lung disease, the study says.

When it comes to the Fourth of July, the air will be at its most particulate-laden between 9 and 10 p.m. — which makes sense as that’s when it gets dark in the summer and many cities around the nation shoot off their fireworks. By noon on July 5, levels drop back down.

“These results will help improve air quality predictions, which currently don’t account for fireworks as a source of air pollution,” said Dian Seidel, NOAA scientist and study lead author. “The study is also another wake up call for those who may be particularly sensitive to the effects of fine particulate matter.”

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