Leszczynski: Brief Opinion on the NTP Rat Study – “The more you know, the more you know you don’t know.”

Publication of the full results of the NTP study, yet again, re-confirms what Aristotle said “The more you know, the more you know you don’t know”. No matter how disappointed some might be, this is the reality of the scientific research.

The study is a classic toxicology. Namely: rats were long-term exposed to various doses of cell phone radiation and their health was followed over the long period of time.

NTP study demonstrates that exposures to cell phone radiation cause biological and health effects in animals. This confirms that the biological and health effects in humans are possible.

Toxicology Approach and Radiation Exposure

Animal toxicology studies are standard procedure in assessing carcinogenicity of chemical and physical agents. Genetic and physiological similarities between humans and e.g. rats or mice are the reason why these animals are commonly used in biomedical and pharmaceutical research. Animal toxicology studies are especially useful/required when the data from human studies (epidemiology or volunteer) is insufficient or inadequate and where ethical considerations preclude certain experimentation on humans.

According to the US EPA “…the default option is that positive effects in animal cancer studies indicate that the agent under study can have carcinogenic potential in humans. Thus, if no adequate human or mode of action data are present, positive effects in animal cancer studies are a basis for assessing the carcinogenic hazard to humans…” (US EPA 2005. Guidelines for Carcinogen Risk Assessment. EPA/630/P-03/001F).

In general, toxicology studies can be performed either by life-time exposing animals to doses of chemical/radiation that humans are exposed to or by exposing animals to high over-doses of chemical/radiation, over-doses so high that humans will not experience them in normal life situations.

If the animals, exposed to dose similar to dose humans are in everyday life, experience any health effects this means that it is possible that humans may experience health effects (not necessarily the same health effects as animals are experiencing). However, if animals do not experience any health effects when exposed to doses humans are in everyday life, such study does not provide information as to the possibility of the effect of exposure on humans. Such no-effect outcome does not mean that humans are safe and will not have any health effects because animals do not have them.

If the animals are exposed to high overdose of the studied agent and they do experience health effects this means that humans may experience health effects (not necessarily the same health effects as animals are experiencing). However, if the animals exposed to high overdose of the examined agent do not experience health effects, it is likely that humans are safe and will not experience health effects.

In case of the NTP study, the two toxicological approaches were somewhat combined and animals were exposed for the life-time to both, low doses of radiation that humans may experience in their daily lives and to high doses of radiation that humans will not be exposed in normal circumstances. Because of the heating properties of the microwave radiation, the highest used dose of exposure in NTP study was defined and determined as the highest tolerated dose.

The 28-day study of the NTP study was used to find out what is the highest tolerated dose of radiation (power) exposure. Such highest tolerated dose was defined to be the dose that does not increase body temperature more than 1oC. In the 28-day study it was determined that at power levels of up to 6 W/kg, the body temperature does not increase more than 1oC. The 2-year study was performed using this highest tolerated dose where the maximal power level was set at the 6 W/kg.

Exposures to radiation were whole body exposures. Dosimetry estimates indicated that the exposure intensities in the brain of rats that were similar to human exposures from cell phones held next to the head. However, this does not mean that effects observed the rat brains were caused solely by the radiation absorbed by the brain itself. The exposure of the rest of the rat’s body to radiation likely caused generation and release of various biologically active mediators that likely affected also the brain. Thus, in case of the whole body irradiation it is difficult to distinguish what brain effects were caused by the radiation absorbed by the brain and what was caused by the mediators generated in the rest of the rat’s body. The same applies to all tissues and organs analyzed in rats. The observed effects are likely sum of the effects caused by radiation absorbed by the organ/tissue and by the mediators released in the rest of the rat’s body.

The whole body exposures, causing plethora of biological effects in various organs of the body, might be giving us indications of what is ahead in human setting. Thee smart phones, connected continuously to internet and synchronizing apps are emitting similar levels of radiation as during talking. Such operating phones are commonly placed in various locations on the body while stored in pockets. Potential effects of the radiation on brain were examined extensively. However, effects of the similar levels of radiation penetrating other vital organs of the human body were not studied. Introduction of smart phones has changed the situation and generated new research needs.

Perinatal and Adult Rat Body Weight Findings

Statistically significant and non-significant effects such on body weight, while these effects are not immediately life threatening, their occurrence clearly demonstrates that the normal metabolism of animals was altered by the RF exposures, leading to the variability in the weight of newborn and adult animals. We do not know what mechanisms underlie these effects and we need urgent research to find out. Summa summarum, these non-lethal effects show destabilization of normal metabolism in exposed animals by the radiation exposures at all used power levels.

Consistent perinatal effects were observed between modulations, and in both the 28-day and 2-year studies,

  • lower dam body weights in late gestation and lactation
  • lower pup body weights and
  • lower pup survival rates
  • no effect on survival of dams during gestation or lactation and
  • no effect on littering, litter size or live litter pup numbers
  • lower body weight gains during gestation in dams exposed to GSM during the 28-day and 2-year studies
  • lower body weight gains during gestation in dams exposed to CDMA in 28-day studies
  • lower pup survival for GSM at 9 W/kg in early lactation
  • lower pup survival for CDMA at 6 and 9 W/kg in early and late lactation
  • lower male and female pup body weights in early lactation in GSM and CDMA at ≥ 6 W/kg
  • body weight decreases resolved and were not observed at later time points in the 2-year studies

Effect of radiation exposures on body weight is well seen in graphs on page 93 of the NTP report. In male rats the effect on weight of animals was more pronounced than in female rats. It looks like young male rats (red oval) had lower weight than controls and older rats (green oval) had higher weight than controls. In female rats this effect was seen only in older rats (green oval). This might suggest that:

  • Radiation exposure affects metabolism what causes changes in the weight of animals
  • Radiation might cause different metabolism-related effects in young and old animals.

An oddity: male rats’ survival data were unexpectedly affected by the higher severity of chronic progressive nephropathy in the male control group.

“…In the 2-year studies, there was significantly lower survival in the shared male sham control group compared to almost all exposed groups, for both modulations. Survival began to decline at a faster rate than in exposed groups after week 75. In the sham control group, 28% of animals survived to study termination, compared to 48% to 68% for exposed groups across both modulations…”

This oddity in survival of the control male rats is a “warning” that the too small groups of animals may, in spite of being inbred strains, be affected by a random chance occurrences of various ailments. This may have significant impact on the final results of the study.

It is unclear whether this “odd” lower survival of the male rats had any connection with the lack of glioma in control group.

Male Fertility

There is some evidence suggesting that cell phone radiation might affect male fertility by affecting sperm. Such effects were not observed in rats:

“…At 14 weeks, sperm motility and counts were evaluated in male rats exposed to GSM or CDMA. Exposure to whole-body GSM- or CDMA-modulated cell phone RFR, up to 6 W/kg, did not result in significant changes/differences in reproductive organ histopathology or sperm parameters in male rats compared to the sham controls…”

However, this does not mean, and should not be automatically interpreted, that human fertility will not be affected because rats’ was not.

When considering the frequent storage of the phone by the men in the trousers’ front pocket, an interesting observation, though not statistically significant and that might be just a chance event, was the detection of effects on prostate gland:

“…There were increased incidences (not statistically significant) of prostate gland adenoma in 3 W/kg rats, and a single incidence of prostate gland carcinoma in the same group. The incidence and severity of prostate epithelial hyperplasia was slightly higher in all exposed groups of GSM male rats. An exposure-related increase in the incidence of prostate gland epithelial hyperplasia was also observed in CDMA male rats…”

Schwannomas and Gliomas

The most significant findings of the NTP study were the observation of development of Schwannomas (statistically significant) and gliomas (statistically non-significant) in the exposed animals. Increased risk for developing of the same tumors was shown in epidemiological studies. This is a very important finding. NTP study strengthens the evidence obtained from epidemiological studies showing increases in acoustic neuroma (similar to Schwannoma) and glioma. Now, mechanism for the development of Schwannoma and glioma should be determined.

Is it possible that nerve-cells “caretakers” – Schwann cells and glial cells – are sensitive to cell phone radiation?

It needs to be determined whether radiation induces Schwannoma/glioma by itself or whether RF radiation only assists in development of tumors caused by other factor(s).

The first option is more dangerous but less likely. Dangerous because many users could be at risk of developing Schwannoma/glioma but it is less likely because RF has low energy. The second option is less dangerous and more likely. Less dangerous because RF would only assist in developing of the Schwannoma/glioma caused by other factors. Both cancers are rare diseases so, there would be not so many persons that would develop them with the assistance of RF co-exposure. This option seems more likely because RF has been shown to activate various cellular signaling pathways, able to assist in development of cancer.

Schwannomas of the heart (similar to acoustic neuroma observed in epidemiological studies) were detected in rats exposed to both modulations, GSM and CDMA and were statistically significant:

“…At 2 years, there were similarities in neoplastic and non-neoplastic responses between modulations. Following exposure to GSM- or CDMA-modulated cell phone RFR, there were increases in the incidences of malignant schwannoma in the heart of male rats, with a significant positive trend in the incidences in GSM- and CDMA-exposed males and a significant pairwise increased incidence in CDMA 6 W/kg males. Also observed in the heart were significantly increased incidences of right ventricular cardiomyopathy in 3 and 6 W/kg GSM male and female rats and 6 W/kg CDMA male rats…”

As seen from the Table 20 (fragment), numbers of the observed Schwannoma cases among the male rats were relatively small, with the exception of the highest exposure at 6 W/kg.

Glioma has been suggested to be linked with cell phone radiation exposures in four epidemiology case-control studies. It was also shown that the gliomas occur in the most radiation-exposed areas of the brain. The increased incidence of glioma was observed in the male rats exposed to GSM and CDMA, but the result was not statistically significant.

“…In the brain, there were incidences (not statistically significant) of malignant glioma in all groups of GSM male rats, in 6 W/kg CDMA male rats, and in 1.5 W/kg CDMA females, compared to no incidences in either the male or female sham control groups. There were also occurrences of glial cell hyperplasia in the brain of GSM and CDMA male rats and CDMA female rats that were not observed in sham control animals…”

In fact, that authors of the NTP study concluded that:

“…Several other, weaker, responses were observed in both modulations including malignant glioma in the brain, […] The relationship between these responses and exposure to GSM or CDMA RFR was uncertain…”

As seen from the Table 22 (fragment), numbers of the observed glioma cases among the male rats were small and no dose dependent increase/decline was observed.

DNA Damage

The important issue is observation of an increased levels of damaged DNA in some tissues and organs of the exposed rats. Is RF responsible for the damage or is RF inhibiting DNA repair mechanisms? What happens with the damaged DNA – will it be repaired or will it persist in next cell generations? Is similar increase in damaged DNA happening in people exposed to cell phones? We need answers to these questions too.

Temperature of the Animals

In some exposure conditions temperature of the animals was increasing but by no more than 1oC. This is toxicology study and this is understandable side-effect of the over-exposure to RF.  This over-exposure-associated temperature increase might have impact on some of the observed biological effects but, at the same time, such small temperature increase is not known to cause glioma or other cancers.

Some other Ailments and Effects

These were observed but these were not possible to determine whether occurrence was in any way related to GSM and CDMA exposures:

“…adenomas in the pituitary gland (pars distalis), and pheochromocytomas of the adrenal medulla. Additionally, in GSM male rats there were marginal responses in the prostate gland, granular cell tumors of the brain, and in pancreatic islets that were not observed in CDMA-exposed rats, and in CDMA-exposed male rats, there was a response in the liver. The relationship between these responses and exposure to GSM or CDMA RFR was uncertain…”

Variety of the ailments and biological effects observed in exposed rats might be either chance findings or might be related to the overall effect of exposures on animals’ metabolism.

The Problem of the NTP Study

The major problem of the NTP study is sensitivity of the assays that are determined by the number of animals used in experiments. While the total number of the animals might be high, the numbers of animals in each experimental group are relatively small – limited to 90 animals. This is the problem when considering effects of radiation on the occurrence of rare diseases. Schwannomas and gliomas are such rare diseases. Spontaneous “appearance” or “disappearance” of a single case of disease from the small 90-animals experimental group has significant consequences. Thus, it is very surprising that research project where it was at least potentially expected that rare diseases such as Schwannoma or glioma may show up, was designed to use so small numbers of animals in each experimental group. As a consequence, the biological and health effects observed in the NTP study are most commonly not significant statistically. Not enough sensitivity in the assays precludes making far reaching conclusions.


  • Detection of Schwannoma in the heart and glioma in the brain, when combined with the observed DNA damage and with the previously demonstrated increased risk of developing acoustic neuroma and glioma among the avid users of cell phones, strengthens the scientific evidence that the cancer is not only possibly but it is even probably developing in users of the cell phones. This does not automatically mean that cell phone radiation itself causes cancer. Cell phone radiation might be a co-factor in the development of cancer. This does not automatically mean that all cell phone users are at risk of developing cancer.
  • Induction of a plethora of effects, both statistically significant and not, suggests that cell phone radiation might cause biological and health effects. Distinguishing between temperature- and radiation-induced effects was not possible in this study
  • The age-dependent differences in the impact of exposures on weight of the animals may suggest that some of the cell phone radiation effects might be age related: young and old respond differently.
  • Whole-body exposure-induced effects may suggest that not only brain but also other tissues and organs might be affected. It is important to consider in the era of smart phones, exposing not only brain but also other tissues and organs in the proximity of the pockets used for storing phone on the body.
  • Avoidance and/or minimizing of exposures from cell phones is a good precautionary measure.

5 thoughts on “Leszczynski: Brief Opinion on the NTP Rat Study – “The more you know, the more you know you don’t know.”

  1. Pingback: Leszczynski: Brief Opinion on the NTP Rat Study – “The more you know, the more you know you don’t know.” | Smart Meter News

  2. Every animal model has advantages and disadvantages. Animals are not humans even if the genomes look similar…

  3. Yes we need more research. The US government is unlikely to pay for it.

  4. Has anyone considered that rats – unlike humans – synthesize vitamin-C in their bodies, as to possibly offset some oxidative stress effects from RF-exposure? I’m thinking Guinea-pigs might be a better model organism for such studies, as they can’t produce vitamin-C and might match humans better in that regard.

  5. Pingback: NTP Study – my first impressions… | BRHP – Between a Rock and a Hard Place

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