As Madison enters another season of holiday fireworks, the silence over their pollution is deafening.

Exhausted by the fight over Rhythm & Booms, stymied by the stonewalling of fireworks companies and lack of data over environmental effects, and driven by patriotism and tradition, Madison will host another big fireworks show as if the residue issue has disappeared.

But the heavy metals that give us the bright colors have not. These include strontium red, titanium silver, aluminum white, copper blue, barium green, potassium violet, sodium blue, etc.

Fireworks are made up of fuel, oxidizers and salts of those metals — copper chloride and strontium carbonate are two examples. According to Ken Kosanke, a Ph.D. chemist from Colorado, publisher of the Journal of Pyrotechnics and author of "The Illustrated Dictionary of Pyrotechnics," 5 to 15 percent of fireworks by weight are the metal salts. Depending on the molecule and atomic weight of the metal, one-third to one-half of those salts are the metals.

As we watch Shake the Lake this weekend, the colors will be created when electrons in the atoms of metal are “excited” by the heat. The light comes as the electrons release this excess energy and return to their normal, or ground, state.

While the salt molecules and much of the rocket burn up, the metal atoms do not disappear.

That means that for every ton of fireworks shot over our lakes, somewhere between 33 and 150 pounds of heavy metals fall into the water. A definitive calculation would require chemical details from fireworks contractors, who refuse to provide them. They call it proprietary information.

According to published reports, Rhythm & Booms exploded approximately five tons of fireworks in each 30-minute show. Each show, then, deposited 165 to 750 pounds of heavy metals. Thus, in its 20 years, Rhythm & Booms deposited 3,300 to 15,000 pounds of heavy metals in Warner Park’s wetland.

A Volkswagen Beetle, a popular standard for weight comparison, weighs 1,900 pounds.

So, in its 20 years, Rhythm & Booms deposited the equivalent of two to eight VW bugs into Warner’s wetland.

A Harley-Davidson Street 500 motorcycle weighs just under 500 pounds. Put another way, in 20 years, Rhythm & Booms deposited the equivalent of seven to 30 motorcycles into the public waters of Madison.

When I ran these calculations by Michael Hiskey, a former Los Alamos National Lab chemist and current professor at the University of Colorado in Colorado Springs, he called them “pretty close.”

“Different colors and effects will have varying metal contents, of course,” he wrote. “Chinese fireworks, which are used the most worldwide due to the low cost, are the worst offenders, containing arsenic, mercury and lead. You have to put this in perspective though, as a typical coal-fired power plant emits a lot more heavy metals on a daily basis (including radioactive metals) than a typical fireworks display does.”

We heard this from Madison health officials — that street runoff contributes far more pollution than fireworks. I find this argument specious, as if to say, what’s a little more in a dirty lake? We’ll see June 27 as we “shake” Monona, and July 4 on Mendota as Maple Bluff celebrates the Fest on the Fourth.

Jim Carrier is a science journalist and co-founder of Wild Warner.

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