MDH

Interestingly enough, back in October, this story actually made the New York Times:

https://www.nytimes....-fireworks.html

Environmentally friendly pyrotechnics as they are now are less an issue of what we know will produce results, a more a matter of industrial feasibility - think long-term storage, stability and affordability. Nitrogen rich pyrotechnic fuels, for instance, are excellent light producers, but are not cheap.

If you go to google scholar you can explore many journals dedicated to pyrotechnics, propellants and energetic materials which concern environmentally friendly pyrotechnics. Refine the search results to research published within the last five years and use specific names of the agent you want to explore.

If I look up Pyrotechnics Perchlorate Alternatives, I see this on the first page of results, from 2016:

https://onlinelibrar.../prep.201600084

Similar results can be found through Google Patents, when searching for barium alternatives:

https://patents.goog.../US9938203B2/en

There is work being done all over in many little areas that will cumulatively change fireworks. My personal opinion is that as more research is conducted on the long term impacts of repeated fireworks displays (especially from theme parks, outdoor public event spaces), the more likely it is fireworks companies will be forced to adapt, and soon the industry standard will not include perchlorates or heavy metals in any substantial quantity.