There is a lot of existing research on harmful effects of radiation on human tissue. For example there are higher rates of cataract in the eyes of radar technicians. 

With 5G radiation rates will increase vary greatly. We may be starting to see the radiation intensity approaching what radar technicians have seen in the past. 

This research should continue because not all technicians have been affected the same way. Moreover, we should have more surveys of people in high-radiation environments. Other sensitivities such as cancer may be possible at higher radiation intensities. 

In particular low-frequency radiation of people who live near power lines has been controversial for many years. Power lines which carry over hundred thousand volts can have strong fields at ground level. Hardly enough to kill you but there are many complaints to power companies.