If the effect of RF doesn't go beyond thermal, then you probably shouldn't be concerned about sitting next to an antenna dish any more than about sitting next to light bulb of the equal power. At the same time, even if the effect is purely thermal, it may be different from the light bulb since RF penetrates deeper in tissues, and the organism may or may not react differently to the heat that comes from inside rather than from outside. Or it may not matter - I don't know.

And apparently, there is a noticeable body of research, in which I can poke some holes, but which at least adheres to basic standards of peer-reviewed journals, that suggests the existence of non-thermal effects, and links to various medical conditions. However, my background in medicine and biology is not enough to thoroughly evaluate this research, beyond noticing that there are some apparent problems with that, but it doesn't appear to be obviously false either.