Increase in atmospheric CO2 concentration beyond which level can become damaging over longer periods?

Carbon dioxide is the major limiting factor for photosynthesis.  The concentration of CO2 is very low in the atmosphere (between 0.03 and 0.04 per cent). Increase in concentration upto 0.05 per cent can cause an increase in CO2 fixation rates; beyond this the levels can become damaging over longer periods.