Recall that the impact of major health crises are not usually apparent right away, and certainly not at the early stages of the adoption cycle of the underlying technology/product.
We're in the midst of an experiment, with all of us as subjects; devices we take for granted were introduced to the general populace without longitudinal studies evaluating their safety. The early, convenient thesis was that only ionising radiation could have biologically significant effects, but there's no reason at all to conclude that (Adey, 1993). Still, many stakeholders continue to trot out the idea that only the area of the body that is measurably heated by radiation exposure is affected by it. At this level of analysis, exploration of the issue tends to be superficial.
There have been some epidemiological studies looking into correlation between exposure to EMF radiation resulting from mobile phone use, as well as from other sources, and the development of brain tumours, with some finding an apparent correlation (Baldi, Coureau, Jaffré, Gruber, Ducamp, Provost, Lebailly, Vital, Loiseau, and Salamon, 2011; Cridland, 1993) and others not (Aydin, Feychting, Schuz et al., 2011; Repacholi, Lerchl, Röösli, Sienkiewicz, Auvinen , et al., 2010; Frei, Poulsen, Johansen, Olsen, Steding-Jessen and Schuz, 2011)
However, as Saracci and Samet (2010) note,
" In high-income countries, mobile phone use began in the 1980s but was not widely prevalent until the mid-1990s. The cancer cases in the study were diagnosed between 2000 and 2004. As a consequence, <5% (110/2409) of the meningioma cases and <9% (252/2972) of the glioma cases occurred >10 years since start of mobile phone use. None of the today's established carcinogens, including tobacco, could have been firmly identified as increasing risk in the first 10 years or so since first exposure. Ionizing radiation is a recognized cause of brain tumours but except for rare instances the radiation induced cases occur on average after 10–20 years since the time of first exposure. INTERPHONE shares with all studies previously carried out on mobile phones and cancer the inherent limitation that it can investigate only a short period of observation since first exposure; the distribution of exposure is brief and truncated leaving limited incubation time for an exposure-related cancer to develop."
The conclusion of most studies is that we don't know; it's too early to tell.
What has been shown is that mobile phone radiation is sufficient to alter the permeability of the blood brain barrier.
"We have demonstrated that microwave exposure produces an unequivocal effect on the BBB in our rats. The clinical importance of this finding, however, is disputable. Our method for detection of albumin is extremely sensitive and reveals even minute amounts of albumin leaking through the BBB, so small that they may be harmless to the brain. However, the potential health hazards of the opening the BBB during exposure to wireless communication demands further investigation."
(Persson, Salford and Brun 1997 pp.458-459).
The effect on the blood brain barriers of rats from 2 hours' exposure to the radiation from a regular mobile phone can be observed both immediately and two weeks after exposure (Nittby, Brun, Eberhardt, and Malmgren 2009)
There are some complex theories as to the mechanisms by which this could be caused (Leszcynski, Joenväärä, Reivinen and Kuokka, 2002), potentially leading to brain injury (d’Avella, Cicciarello, Angileri, Lucerna and Tomasello, 1998), as well as evidence for similar observations with ionising radiation (Yuan, Gaber, Boyd, Wilson, Kiani, and Merchant, 2006).
This being the case, it would not be unreasonable to suggest that increased permeability of the blood-brain barrier could be a contributory factor in neurological and partially-neurological conditions, with at least one study finding exceedingly high levels of aluminium found in children with autism (Mold, Umar, King and Exley, 2018).
If I use a mobile phone for even a few minutes the way most people do, I experience debilitating headaches, dizziness and fatigue that can last for hours. But of course because that's not a very common reaction, people dismiss it.
But given that we're dealing with an untested technology perhaps a bit of caution would be warranted; maybe we shouldn't just assume that exposing children to "microwaves at a level up to 10^20 times the original background radiation since the birth of universe." (Nittby at al., 20009 p.103) is likely to do no harm.
Or we can ignore the problem til research proves it's too late to fix it.
References
Adey (1993) Biological Effects of Electromagnetic Fields. Journal of Cellular Biochemistry, Volume 51, pp.410-416.
Aydin, Feychting, Schuz et al. (2011) Mobile phone use and brain tumors in children and adolescents: a multicenter case-control study. Journal of the National Cancer Institute, Volume 103, Issue 16, 17 August 2011, Pages 1264–1276.
Baldi, Coureau, Jaffré, Gruber, Ducamp, Provost, Lebailly, Vital, Loiseau, and Salamon (2011) Occupational and residential exposure to electromagnetic fields and risk of brain tumors in adults: a case-control study in Gironde, France. International Journal of Cancer, Volume 129, Issue 6, pp.1477-1484.
Cridland (1993) Electromagnetic fields and cancer: a review of relevant cellular studies. NRPBR256. Chilton, UK: National Radiological Protection Board.
d’Avella, Cicciarello, Angileri, Lucerna and Tomasello (1998) Radiation-Induced Blood-Brain Barrier Changes: Pathophysiological Mechanisms and Clinical Implications. In: Marmarou A. et al. (eds) Intracranial Pressure and Neuromonitoring in Brain Injury. Acta Neurochirurgica Supplements, Volume 71. Springer, Vienna.
Frei, Poulsen, Johansen, Olsen, Steding-Jessen and Schuz (2011) Use of mobile phones and risk of brain tumours: update of Danish cohort study. British Medical Journal, Volume 343, No.7830 p. 946.
Johansson, Nordin, Heidin and Sandström (2010) Symptoms, personality traits, and stress in people with mobile phone-related symptoms and electromagnetic hypersensitivity, Journal of Psychosomatic Research, Volume 68, Issue 1, pp. 37-45.
INTERPHONE Study Group (2010) Brain tumour risk in relation to mobile telephone use: results of the INTERPHONE international case–control study. International Journal of Epidemiology, Volume 39, Issue 3, 1 June 2010, Pages 675–694.
Leszcynski, Joenväärä, Reivinen and Kuokka (2002) Non-thermal activation of the hsp27/p38MAPK stress pathway by mobile phone radiation in human endothelial cells: Molecular mechanism for cancer- and blood-brain barrier-related effects. Differentiation, Volume 70, Issue 2-3, pp.120-129.
Mold, Umar, King and Exley (2018) Aluminium in brain tissue in autism. Journal of Trace Elements in Medicine and Biology, Volume 46 pp.76-82.
Nittby, Brun, Eberhardt, and Malmgren (2009) Increased blood–brain barrier permeability in mammalian brain 7 days after exposure to the radiation from a GSM-900 mobile phone, Pathophysiology, Volume 16, Issues 2-3, pp.103-112.
Persson, Salford and Brun (1997) Blood‐brain barrier permeability in rats exposed to electromagnetic fields used in wireless communication. Wireless Networks, Volume 3, Issue 6, pp.455-461.
Repacholi, Lerchl, Röösli, Sienkiewicz, Auvinen , et al. (2010) Systematic review of wireless phone use and brain cancer and other head tumors. Bioelectromagnetics, Volume 33 pp.187–206.
Saracci and Samet (2010) Commentary: Call me on my mobile phone…or better not?—a look at the INTERPHONE study results. International Journal of Epidemiology, Volume 39, Issue 3, 1 June 2010, Pages 695–698.
Yuan, Gaber, Boyd, Wilson, Kiani, and Merchant (2006) Effects of fractionated radiation on the brain vasculature in a murine model: Blood–brain barrier permeability, astrocyte proliferation, and ultrastructural changes. Radiation Oncology, Volume 66, Issue 3, pp. 860-866.