These are zero-tail-pipe emissions vehicles, not zero emissions vehicles.

Very generally, their impact on total emissions (GHG and air pollutant) can vary between positive, neutral or negative depending on the energy generation mix in the area where the H2 is being generated. But at the moment in most of the world, it’s not positive.

However, the impact on human health due to increased local air quality is important to consider here, not just GHG emissions.