The National Toxicology Program (NTP) study was a huge (potentially definitive) animal study carried out in the USA over many years, and costing in excess of $25M. It's controversial, to say the least, with antiphone activists citing it as solid evidence and the bulk of the scientific community being quite disappointed at its quality, to put it politely. It claimed to have found increased cancer in heart tissue of rats and possibly in some other locations. They examined rats and mice, and found nothing in the mouse studies and nothing when they looked at female rats. Only males. Which should ring alarm bells right away.
The fundamental problem was that they overexposed the animals hugely. The
mice, for example, had absorbed powers of up to 12 watts per kg (W/kg) of
their whole body. weight. For context, the corresponding human exposure
limit (based on avoidance of thermal effects) is 0.08 W/kg. So they were
exposing at up to 150 times the human exposure limit. For the rats it's
abut 75 times. Those are very significantly thermal levels of exposure.
They attempted to control for this by showing that the animals' core
temperatures did not rise by more than one degree, but they will have been
thermoregulating strongly to maintain that. We know that heat is
bioactive, and that heat and thermoregulation cause a raft of biophysical
and biochemical effects. At these levels the study was not really looking
at RF: it was looking at the effect of cooking the animals gently. This
was a huge error in experimental design which renders the study entirely
Experimental design 101 is that you treat control and exposed animal exactly the same but for the agent you are investigating. We go to great lengths to control for heat, noise, vibration etc. Heating the exposed but not the controls violates that fundamental rule. The analogy sometimes used for this is that it's like testing the toxicology of a liquid by throwing it at an animal still in the bottle, and then claiming it causes brain damage.
This was not only a waste of $25M, it was also a wasted opportunity. This study could have been done with appropriate exposure levels and provided useful and valuable information. It's not likely ever to be repeated, so that window of opportunity has been squandered by a simple and obvious error in experimental design. And it involved the pointless death of a lot of animals. In UK at least, ethical committees would have demanded that such large-scale animal experimentation be justified by a cast-iron experimental protocol.
This article addresses only the gross errors in exposure level. Other scientific review bodies have identified potentially serious issues with other parts of the experimental design analysis (opens in a new window).
It's notable that attempts to publish the study in the peer-reviewed literature were not successful, and it eventually had to be self-published.