How does further reducing lead in the fuel compare to all the other emissions' impact?

I would imagine that lead is dangerous for a long as it's being used, whereas CO2 has an annoyingly long half life that we need to actively remove in (currently) time- or energy-intensive processes, while it's reducing healthy years of life for millions of people —speaking of air pollution from combustion in general here, I don't have specific numbers for airplanes but as an airplane company you are surely better aware of this than me