Fireworks can unleash a shower of toxins into soil and water, and scientists are only beginning to figure out what that means for human health.

This patriotic season, consider the effects of the chemicals and propellants used in the production of the firework display exploding before your eyes. Think about the rain of chemicals, unseen, wafting through the air, to land on you, your children, the land and the water around you.

The colour and brilliance in fireworks comes from a variety of chemicals and metallic materials, many of which are toxic to humans and other animals. From the gunpowder that fuels their flight to the metallic compounds that color their explosions, fireworks often contain carcinogenic or hormone-disrupting substances that can seep into soil and water, not to mention the lung-clogging smoke they release and the plastic debris they scatter.

There hasn’t been much in the way of research on how fireworks and their constituents can affect environmental or human health. While they haven’t been linked to any widespread outbreaks of disease, it’s not always easy to pin down why someone developed hypothyroidism , anemia or cancer.

For fireworks and other pyrotechnics to blow up, they use a blend of charcoal and sulphur fuel. They also need an oxidizer to speed up the explosion, which historically has been potassium nitrate. These three chemicals are mixed together into a sooty substance known as gunpowder. In modern propellants, however perchlorates are often used instead of nitrates for ease of handling.

Perchlorates may introduce their own problem, though. In sufficiently high doses, they limit the human thyroid gland’s ability to take iodine from the bloodstream, potentially resulting in hypothyroidism. Children, infants and especially fetuses suffer the worst from hypothyroidism, since thyroid hormones are crucial for normal growth.

The smoke from fireworks’ burned charcoal and sulphur fuel also contains particulate matter that can get lodged in people’s lungs, an immediate danger for those with asthma or chemical sensitivities. Air-quality monitors reportedly spike for about three hours after a fireworks show, until the particulates drift away or settle out.

One good thing for both perchlorates and particulates is that they most likely don’t pose a long-term health risk. Particulates fade away after a few hours, and perchlorates tend to dissipate several days after being released. Unfortunately, the same can’t be said about some other chemicals that help light up the sky.

In addition to gunpowder, fireworks are packed with heavy metals and other toxins that produce their array of colors. Like perchlorates, the exact effect of fireworks’ heavy-metal fallout is still mainly a mystery, but scientists do know that the various metals themselves can wreak havoc in the human body in sufficient doses. Unlike perchlorates, the metals linger and some can even accumulate, building up a toxic dose over time.

Some of the heavy metals released include strontium, which provides a strong red colour and can impair bone growth in children. Other metals include aluminum, which burns white, with a possible link to Alzheimer’s disease, blue-burning copper, which can jump-start the formation of dioxins, barium, which burns green, and is linked to some gastrointestinal disorders in high doses, and then there’s cadmium, which produces a range of colours and is a known carcinogen.

Fireworks shows are intermittent point sources of some very toxic materials. Whether the quantities involved are enough to be an actual health risk is unknown at this time. The use of heavy metals that can accumulate is of some concern, though. While the coloured explosions are definitely awe-inspiring, perhaps more research needs to be done into what the effects of fireworks and their residues are on their audiences.


Fireworks can unleash a shower of toxins into soil and water, and scientists are only beginning to figure out what that means for human health.