At least environment-wise hydrogen leaks aren't an issue:

Hydrogen is a strong indirect greenhouse gas.

The climate impact of hydrogen is about 34 times higher than CO2 when measured over a 20-year period. Looking at the impact over 100 years, the global warming potential reduces to between eight and 13 times.

Hydrogen causes this by stabilising methane in the atmosphere and creating tropospheric ozone and stratospheric water vapour.

https://www.euractiv.com/section/energy-environment/news/scientists-reiterate-concerns-about-climate-warming-hydrogen-leaks/

Burning hydrogen is 10x cleaner but not pollution free.

Using a fuel cell creates electricity and heat without pollution, but is a source of heat enough to call something a BBQ?

What is so special about this lens?

Why can't other manufacturers create something similar?

Tailgate parties

Landing on the moon was such a huge PR event. Everything that could be controlled was controlled.

What if a backup TV broadcast was created in case of broadcast equipment failure?

i am quite certain that people do not emit particles or NOx like this.

Car tyres, naked flames, trash, waste disposal.

In particular nobody is just exhaling heavy metals.

Yeah. I can't shoehorn heavy metals into this scenario. Soda cans?

Again, probably more particles, NOx, Plastic debris etc. from the audience.

Any football game with a flyover is multiple times more polluting.

I heard somewhere it was to save ink.

Maybe they were pulling my leg.

A local, professional display uses about 80lb of gunpowder (NEQ). When combusted this will produce about 40lb of CO2. To put this in context, most new internal combustion engines will produce about 190gm of CO2 per mile.

Therefore a single car would need to travel 88 miles to emit the equivalent amount of CO2 of your typical fireworks display. If you consider the a round trip distance for the entire audience to watch a single fireworks display, gunpowder is a fraction of the CO2 footprint.

Uncle Ribbit.

What sort of permit is needed for a sword cane?

Because he has money and no morals.

A better question is, at what immoral act would a trump supporter draw the line?