“Everyone at or downwind of a pyrotechnic display is getting subjected to levels of these metals that aren’t natural levels,” said David E Chavez, a chemist at Los Alamos National Laboratory. “Whether that really is going to cause health effects is up for debate,” he added.

Generally the metals used for making the fireworks attractive and colourful turn poisonous as soon as they are heated. These chemicals include the perchlorates that are used as fuel in the fireworks.

Animal studies related to perchlorates, have shown that these cause thyroid problems. Repeated pyrotechnic displays, especially ones that occur every day at theme parks, can take their toll.

 “If you have a place where pyrotechnics are shot over and over again for years and years, you will have a build-up of these toxins in the environment,” said Chavez.