Proper utility scale gas generators come with proper utility scale pollution controls to make sure nasties like fine particulate and NO is filtered or properly reduced into some much less harmful to human health.

CO2 is bad for us long term. But there are plenty of other nasty combustion products that are extremely bad for humans in the short term. Which is why we have pollution and air quality regulations.

Portable generators don’t meet any of the stronger requirements that utility scale systems have to meet, because it’s assumed they’re only operated in small numbers for short periods of time. They’re not designed to safe to operate in large numbers over long periods of time in the same place. For that you need proper pollution controls