Living on Earth, from Public Radio International, has the answer for you:
Every year we celebrate Americas independence by sending combustible cocktails called fireworks into the sky. And every year some environmentalists object. This year, a lawyer representing a coastal conservation group in California won a suit that would force locals wanting to light-up to first file an environmental impact report with the state. It nearly kept the towns fireworks show grounded. Living on Earths Ike Sriskandarajah looks at the chemistry of what goes up and what comes down.
An excerpt from the transcript:
SRISKANDARAJAH: Gonzalez is the lawyer for the Coastal Environmental Rights Foundation, or
CERF. For a decade he has been suing to make firework shows accountable for their environmental impact. This year, he won. A judge ruled the San Diego and
La Jolla fireworks violate the California Environmental Quality Act.
GONZALEZ: A lot of people dont know what goes into fireworks, what makes those bright lights, and what really falls down once they explode.
SRISKANDARAJAH: But Swisher does know. That rockets red glare
SWISHER: Typical ingredients for that would be 60% potassium chlorate, 20% strontium carbonate, 15% resin - like red gum or shellac - and 5% dextrin.
SRISKANDARAJAH: And those bombs bursting in air
SWISHER: Thats a salute - those are created with a material called flash powder and thats usually a mixture of some oxidizer with powdered aluminum.
SRISKANDARAJAH: If enough metals like aluminum fall into the water, they could be eaten by small fish and work their way up the food chain. That could be toxic in fish eaten by humans.
And the most common oxidizer is perchlorate - that can cause thyroid problems in high enough quantities. But Swisher says there arent enough active ingredients to do damage.
Read the entire interview here.