Radiant heat from a fireplace is infrared - also an EM field.

We know that UV light, which starts around 400 nm, causes damage beyond its heating effects, so yes, EM fields in general can be a problem.

But 835 MHz is about 30 cm wavelength - far larger than the size of the cells, much less the molecules in the cell.

With 25+ years of research, including epidemiological studies of people working with or living near high-power transmitters, there's very little evidence that RF causes problems beyond simple heating.