Cool.

How much is a megagram of carbon? or of CO2? How many trees is that?

What do you picture when you think of that? Is it something you have an intuitive reference for? Almost assuredly you don't. Very few people do could tell you about how many hectares of a typical temperate first would be required to be set aside annually to store or sequester that 500k megagrams of carbon (hint: alot).

Hand wringing because they didn't use a unit even, likely, that you would likely have no clue how to understand it's interpretation, is misguided at best.

It's appropriate to communicate through units people understand; the real problem is their use of a number which is also practically incomprehensible. Using cars is fine, using 500k is problematic, because few if any human has a context for what 500k cars looks like.

A more appropriate units conversion might have been that the inhalers have emissions equivalent to all the vehicle emissions of states A, B and C