As millions of Americans head out for their annual Fourth of July fireworks, they might not realize the chemical that makes the shows so bright also poses an environmental threat. But researchers are developing new, greener pyrotechnics that already are being used at Disneyland and some indoor concerts.

The new fireworks use alternatives to perchlorate, a salt that provides oxygen to the combustible elements in fireworks so they can burn.

The chemical is considered particularly harmful to pregnant women and small children because of its ability to block absorption of iodine in the thyroid, a gland that controls metabolism and growth. The threat isn't considered sufficient for the government to ban the mostly Chinese-made pyrotechnics that use it, but the Environmental Protection Agency is studying the impact and plans to develop regulatory standards.

"It's definitely a problem," said John Conkling, an adjunct professor of chemistry at Washington College in Chestertown and an industry consultant. "How big a problem, no one can say. We need some more good science."

In the past five years, researchers have discovered that perchlorate can concentrate not only in the ground and water where fireworks are made, but also where they are launched. Duds can pose a particular problem, Conkling said, because properly working fireworks burn much of their perchlorate.

One recent study published in the American Chemical Society's journal Environmental Science & Technology found after fireworks displays from 2004 to 2006 on a lake in Oklahoma that perchlorate was found in the lake, fish and groundwater. It only dissipated in surface water, and only after several weeks.

Researchers at Los Alamos National Laboratory began looking into ways to make less polluting pyrotechnics at the request of the Walt Disney Co., which had been fielding complaints from neighbors about the smoke from nightly displays at Disneyland.

A team of chemists began developing fuel that used less carbon and more nitrogen atoms. As a gas, it created less smoke and allowed for lower amounts of metal coloring agents, also an environmental problem. But the high-tech solution would be too costly for mass use.

Two of the researchers formed a company, DMD Systems, and sell the new pyrotechnics to Disney, as well as many small, indoor venues where smoke and pollution are more of an issue.

But David E. Chavez, who remains a Los Alamos chemist, said research continues at his lab and elsewhere into environmentally friendly oxidizers and fuel ingredients that could be used eventually in big fireworks displays - and by the military, which uses much larger amounts of perchlorate in its missiles and rockets.

"To my knowledge, there are no green products sold for large Fourth of July-type displays, in large part due to the cost," he said. "I believe the products are closing in on being cost-competitive, though. We tried to get a collaborative effort between DMD Systems, [the lab] and the city of Los Alamos to become the first city to go perchlorate free, on the Fourth, but the deal was not approved."

Conkling said a lower-end municipal fireworks display can cost $50,000. That's what Baltimore averages for shows launched from barges in the Inner Harbor, though this year's show will cost slightly less because there will be live rather than choreographed music. Baltimore County plans to spend $60,000 on entertainment and fireworks.

A major city spectacle, however, can cost hundreds of thousands of dollars, and the high-tech pyrotechnics would likely cost many times that because the ingredients aren't readily available. Buyers have pressured manufacturers to begin scaling back their use of perchlorate, just as they had done to rid fireworks of lead, mercury and arsenic. Manufacturers have responded by subbing some perchlorate with nitrates, or common fertilizer, which Conkling says is better.

Until the really green stuff becomes commonplace, Conkling has some advice. "For anyone watching a Fourth of July fireworks show, the primary concern should be to stay behind the safety barriers. If smoke is blowing your way, move to get out of the way because there is no smoke that is good for the human lung, from exhaust or fireworks."

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