CO2 levels now aren't great, but I'm not sure Roman-era lead emissions were an improvement: https://phys.org/news/2019-05-roman-polluted-european-air-heavily.ht

CO2 levels now aren't great, but I'm not sure Roman-era lead emissions were an improvement: https://phys.org/news/2019-05-roman-polluted-european-air-heavily.html https://phys.org/news/2019-05-roman-polluted-european-air-he...