It has been recently announced that scientists from Japan and South Korea are planning a partial replication of the NTP study. According to what is known now, not all parameters of the NTP study will be used in this Japan/South Korea replication study. It is logical approach. Technological progress, since the time when NTP study was planned and set up, has been swift and exact replication of radiation exposures from some 5 years ago might be of little use for the currently used exposures.
The document of the planned experiments, released by Japanese scientists is in Japanese, but it has a very informative English summary. It appears that not all experimental parameters were already agreed upon and that negotiations are still ongoing.
First, here are the replication parameters presented in the document published by the Japanese scientists. Several parameters are already confirmed but several are still open for discussion:
- Exposure level: Whole body averaged SAR at 4 W/kg (confirmed)
- Frequency/waveform: 900 MHz/CDMA (confirmed)
- Exposure protocol: 10 min on/10 min off, 18hours/day, initiated in utero on gestation day 5 for 2 years (104 weeks) after delivery (confirmed)
- Exposure apparatus: Custom-made reverberation chamber, identical in both countries (adopting RC proposed by Korean ETRI: details to be discussed)
- Arrangement of cages, stirrers and antennae in the RC (details to be discussed)
- Measurement of core body temperature during exposure: Pilot study needed (details to be discussed)
- Material of cage: Polycarbonate (confirmed)
- Animal species: Harlan SD rat, male only (confirmed, how to obtain needed number (75) with the same birthday for each group: details to be discussed)
- Groups: Exposure, sham exposure, cage control, thermal control (how to provide thermal load (equivalent to induce core body temperature rise > 1 oC: Exposure to infrared? High ambient temperature? Continuous exposure at 4 W/kg?) (details to be discussed)
- Number of animals per group: 70 for 2-year + 5 for 14-week interim evaluation (genetic toxicology, by Comet assay and micronuclei assay) (confirmed)
- Measurement of feed/water intake (confirmed: what kind of feed to be provided (dedicated feed for Harlan SD imported from USA?): details to be discussed)
- Target organs for pathological evaluation: Based on OECD Guidelines (confirmed)
- Selection of contracted research institute: Compliance to GLP necessary (confirmed)
Japanese and South Korean teams agreed to establish an International Steering Committee consisting of researchers from South Korea/Japan and from the international scientific community of EMF researchers. Composition of the ISC was to be discussed and several candidates were proposed:
- Alexander Lerchl (Jacobs University Bremen, Germany)
- M. H. Repacholi (Visiting professor, University of Roma La Sapienza; former coordinator, WHO International EMF Project)
- Emilie van Deventer (Leader, WHO International EMF Project)
- Dr Eric van Rongen (Chair, ICNIRP)
- Vijayalaxmi (University of Texas Health Science Center, USA)
- Joe Wiart (Telecom Paristech, France)
- Michael Wyde (National Institute of Environment and Health Sciences, USA: Principal Investigator of the NTP study)
The proposed composition of the International Steering Committee is clearly focused on ICNIRP and WHO EMF Project scientists. This might be considered as pitfall and may hamper the credibility of the research project. To increase the credibility of the International Steering Committee, it would be advisable to include also scientists with opinions differing from the opinions expressed by ICNIRP and WHO EMF Project.
During my visit to Seoul in August 2018, besides having a keynote lecture at the annual South Korean EMF conference and another lecture for the South Korean team that will be executing replication of the NTP study, I was asked to provide advice on the parameters of the NTP replication study.
During discussions with the South Korean scientists I was informed that the Korean replication of the NTP study will expose animals to currently used 4G LTE radiation. That is why the apparently decided exposure to 900 MHz/CDMA is surprising. It would of course replicate NTP study but it would be fairly useless for the evaluation of the carcinogenicity of the currently used 4G LTE.
My advice on SAR and number of animals, with justification, was as follows [because, while in Seoul, we discussed exposures to 4G LTE, my advice used term ‘Korean LTE study’]:
- NTP study used as highest SAR 6W/kg. This led to heating of the animal by 1 oC.
- DL suggestion: use SAR of 4 W/kg. It will not warm up animals as much as the SAR of 6 W/kg. However, lower exposure will require increased sensitivity of the assay for biological effects = more animals per group than in the original NTP study. As length of exposure, I suggest to follow the NTP study protocol and use: 10 minutes ON / 10 minutes OFF for total of 18 hours and 20 minutes per day (this makes total of 9 hours 10 minutes of ‘ON’ exposure and 9 hours 10 minutes of ‘OFF’ exposure). Making simultaneously lower SAR than in the NTP study and changing the exposure protocol (as you suggested 2 hours/day only) might cause that the effects will disappear, and not because there will not be effects but because the design will cause “lack of effects”.
Number of animals
- NTP study used 90 animals / group.
- Korean LTE study plans to use only 70 animals / group
- DL suggestion: it is strongly advisable to use more animals than 70 per group, even up to 150 animals / group. The reason is twofold. First, you will be looking for rare effects. In case of glioma, NTP study found, at the most, 2 cases per 90 animals. In case of schwannoma NTP study found 5 cases per 90 animals. Reducing number of animals to 70 per group will diminish chances of finding effect. Secondly, results in the NTP study were obtained at exposures of SAR 6 W/kg. Korean LTE study will use SAR of 4 W/kg. This means the effect of exposure is to be expected to be lower than in NTP study. Therefore, to detect any glioma or schwannoma cases, Korean LTE study needs more animals to increase sensitivity of the assay. Increasing number of animals per group to 150 will increase sensitivity. Preliminarily planned use of 70 animals per group in the Korean LTE study will cause that you will not be able to detect effects of exposure because of a priori made flaw in study design – too few animals = too low sensitivity of the assay.