You're right again, maybe they should write "not as harmful as others"?

Cooling towers emit water vapor rather than smoke or harmful fumes, and thus do not directly contribute to climate change, their operation is associated with indirect environmental impacts and local atmospheric effects that warrant consideration.

https://www.rsc.org/news-events/articles/2007/02-february/cooling-towers/

https://www.starcoolingtowers.com/sustainable-cooling-how-cooling-towers-contribute-to-environmental-preservation/