Red, white and blue aside, how green will this weekend’s firework festivities be? Not very, argue some.

The dazzling displays owe their colors to traces of metal compounds: strontium for red, aluminum or magnesium for white, copper for blue and barium for green.

What happens when these chemicals come raining down on rivers, lakes and people? “Everyone at or downwind of a pyrotechnic display is getting subjected to levels of these metals that aren’t natural,” Los Alamos Natural Laboratory chemist David Chavez recently told Discovery News.

Waterways, often selected as launching sties to help decrease fire risk, show a spike in perchlorates (up from .08 to 44.2 micrograms per liter) after Fourth of July, a 2007 U.S. Environmental Protection Agency (EPA) study found. Perchlorates, which are used to help the fireworks’ fuel burn, were named in an EPA health advisory earlier this year (which recommended a maximum of 15 micrograms per liter of drinking water), as they have been linked to disruption of the thyroid gland.

Not to rain on your patriotic parade plans any more, but you can’t count on recycling the smoky remnants either: “Fireworks after they’re shot off are usually pretty dirty,” a policy analyst for the Oregon Department of Environmental Quality told Oregon Public Broadcasting.

Researchers still don’t know exactly what—if any—lasting ill effects fireworks may have on the Earth or the body. If anything, the biggest health concerns remain the same: choking on smoke and blasting off a finger. So set off—or observe—those fireworks with caution. 

Read more about what makes fireworks go bang in our Ask the Experts about how they work.

Image courtesy of RKHawaii via Flickr