That's really hard for me to answer, because while I can address the physics side pretty well the physiology side is not really my forte. More importantly, you have to have someone who knows the studies
holistically rather than piecemeal, because of the numbers.
What I mean is -- and I'm not necessarily accusing bioinitiative.org; I'm just stating that it's something we have to watch out for -- it's possible for a lot of reports from credible institutions that have good, correct studies warning about X, even if X is totally harmless.
One of the easiest ways for this to happen is the simple fact that at least one in twenty journal results should be wrong, because that's how 95% confidence intervals work. If a thousand 95% studies are done on a safe thing then you should ideally have 50 studies which can't make that conclusion.
Let me speak about a case which is related which I do know a little about; the Interphone study. This was a massive international case-control study on the effect of mobile phone radiation (also microwaves) on various forms of brain cancer. You can see one of the full articles reporting the data here:
http://ije.oxfordjournals.org/content/39/3/675.long
In this case, bioinitiative.org released a press release stating "Today’s release of the final results of the ten-year long World Health Organization INTERPHONE Study confirms previous reports showing what many experts have warned – that regular use of a cell phone by adults can significantly increase the risk of glioma by 40% with 1640 hours or more of use (this is about one-half hour per day over ten years). Tumors were more likely to occur on the side of the head most used for calling."
I will state that that press release -- not necessarily the whole bioinitiative.org project; I don't know enough to say that, but that press release in particular -- is cherry-picking the data significantly. Lots of bloggers picked up this headline too, but I don't think they read the scientific study that they were blogging about (as a rule).
If you actually look at that study you'll see -- to take table 2 as my example -- that there is a table of 50 results presented with 95% confidence intervals. Of those 50 results, a shocking twenty of them result a statistically-siginificant observed preventative effect of cell phone radiation on meningioma and glioma while only one of them (the glioma case that they cite) showed a statistically observed damaging effect. The authors' actual conclusion was much more meek, "Overall, no increase in risk of glioma or meningioma was observed with use of mobile phones. There were suggestions of an increased risk of glioma at the highest exposure levels, but biases and error prevent a causal interpretation. The possible effects of long-term heavy use of mobile phones require further investigation." (There may even be simple correlations which would cause cell-phone users to have less cancer -- maybe strong social bonds protect against cancer and cause cell phone use; or maybe people who use their brains more find the distraction of cell phones harder to resist and also have a higher turnover in brain cells, making it harder for cancer cells to find purchase, or something.)
As far as I know, that is the largest study that has ever been done on cancer, but there may be other "detrimental impacts" (as you call them) which are not cancer, of course. You would need to consult someone who has a holistic view of the info, not a physicist who happened to read that one study when it came out in 2010.