With the phenomenal growth in the number of users of mobile phones worldwide, there is public concern that cell phone radiation may cause adverse health effects such as brain cancer. Recently, the US National Technology Program (NTP) and the Ramazzini Institute published their animal studies on the cancer-inducing potential of cell phone radiation. Though the former is yet to publish its conclusions, interested parties interpreted the studies wrongly. On September 4, 2018, the International Commission on Non Ionizing Radiation Protection (ICNIRP), the agency whose recommendations most nations and agencies, such as the WHO, accept published an eight-page report questioning the usefulness of these reports and asserting that both these studies have inconsistencies and limitations. The very expensive, $25 million NTP study did not provide any input for revising the currently recommended radiofrequency guidelines.
Weight of evidence
The NTP researchers used weight of evidence approach, whereby potential effects were described as being supported by ‘clear’, ‘some’, ‘equivocal’ or ‘no’ evidence (where a study was not adequate for comment on potential effects, it is described as an ‘inadequate study’).
The researchers did not find any ‘clear’ evidence in their studies; the strongest evidence of carcinogenicity reported was (‘some evidence’) for male Hsd: Sprague Dawley SD rats exposed at different specific absorption rates (SAR) of (electromagnetic radiation) energy. They found that the exposure-response relation to be statistically significant.
Falcioni et al reported a significant increased incidence of schwannomas (a type of tumour) in the hearts of male rats exposed at the highest SAR (0.1 W/kg) of mobile phone radiation, which according to them is consistent with one of the NTP studies. They also reported increased incidence of heart Schwann cell hyperplasia — proliferation of apparently normal cells — (male and female) and malignant glial tumours (female only), but these were not statistically significant.
Limitations
The ICNIRP noted that both studies followed good laboratory practice (GLP); both used much larger numbers of animals than previous research, and both exposed animals over the whole of their lives. However, the Commission noted that “in determining the relevance of the results for human exposure guidelines, potential limitations need to be carefully considered, and whether any of the evidence regarding health effects in rodents is sufficiently strong and relevant to humans to serve as a basis for exposure guidelines”.
ICNIRP criticised the studies on many grounds, including methodological deficiencies.
“For cancers which have benign tumour precursors, progression to cancer often involves a sequence from hyperplasias (proliferation of apparently normal cells), to dysplasia (cell abnormalities present), to cancer (a small percentage of these cells undergo malignant transformation)” ICNIRP explained.
Quoting appropriate literature, ICNIRP observed that for schwannomas, less than 30% of hyperplasias progress to malignancy..., thus many more benign hyperplasias should be observed than malignant schwannomas.
“The NTP study found approximately equal numbers of hyperplasias and malignant schwannomas, which is a large departure from the expected ratio of many hyperplasias to very few malignancies. These results suggest that for radiofrequency fields to be carcinogenic, they would need to affect the conversion rate from hyperplasias to malignancies in addition to potentially inducing hyperplasias. However, with very few cases with cardiac Schwann cell hyperplasia and schwannomas (for example, none in the control group), it is difficult to interpret and accept this finding without further clarification,” ICNIRP argued. The Commission noted that Falcioni et al also did not report the expected conversion rate.
The Commission asserted that it saw two mutually inconsistent sets of results, and no similar literature for comparison.
The agency found that the distribution of malignant cardiac schwannomas across the experimental groups in the two studies also reduces confidence in the data.
“ICNIRP considers that the NTP (2018a, b) and Falcioni et al (2018) studies do not provide a consistent, reliable and generalizable body of evidence that can be used as a basis for revising current human exposure guidelines,” the Commission concluded. It may not amuse many activists and scaremongers!
ksparth@yahoo.co.uk
(The writer is a former secretary of the Atomic Energy Regulatory Board)
