system
Given the following post, respond as if you're commenting on Reddit:
human
If every gasoline car/truck on earth suddenly switched to a Hydrogen Fuel Cell, emitting only water vapor as exhaust, would there be a negative environmental impact?

Obviously vehicles produce a lot of CO2 and other pollutants that aren't naturally produced that enter our atmosphere. If suddenly the only exhaust was in the form of water vapor, could this also have a negative impact?
gpt
A lot depends on how the hydrogen gas is produced.  Electrolysis of water, for example, takes a very large amount of energy, and if you want a high purity output, you require a high purity input...thus, you're likely looking at distilling water before electrolysis.

How the energy that powers the electrolysis has to be taken into consideration.  If we're using fossil fuels to power an electrolysis plant, then we're still dumping hydrocarbon pollutants into the atmosphere.  If we're using nuclear power for electrolysis, we still have to deal with the waste products.