Weak radio frequency fields seem to affect the body clocks of cockroaches. If the finding is confirmed, it could mean that weak radio waves – which are already known to disorient birds – are capable of affecting a wide range of animals.
However, Martin Vacha of Masaryk University in the Czech Republic, who conducted the study, says he is “very cautious” about his team’s results. In normal conditions, there might not be any effect on insects, he says, and the team isn’t making any claims about possible effects on people.
Many claims have been made about possible effects of electromagnetic fields on humans and other animals. In particular, it is been claimed that the radio waves from mobile phones could cause cancer. But radio waves are much less energetic than, say, X-rays and don’t cause the damage to DNA that leads to cancer. Nonetheless, some researchers think they could have more subtle effects on living tissue.
A couple of recent studies, for instance, have suggested that static magnetic fields affect the body clock of fruit flies. Vacha and his colleagues decided to look at whether they affect cockroaches too.
Slowing down the clock
His team kept cockroaches in constant dim UV light, with no clues as to whether it was night or day, and measured the animals’ activity using image analysis software. From that they worked out what time their body clocks were keeping.
When they exposed the animals to either static magnetic fields or weak radio frequency broadband noise, the cockroaches’ periods of activity became an hour or two longer. In other words, their body clocks were running more slowly.
Vacha says the team tested frequencies much lower than those from mobile phones. But many electric devices, such as computers, produce this kind of broadband noise.
However, had the cockroaches been exposed to natural light cycles, the radio frequencies would probably have had little impact, says Vacha. “My guess is that in real life it does not have such a big effect.”
While many studies have suggested that magnetic or electric fields affect animals in various ways, these results often fail to stand up when others repeat the tests, says Peter Hore at the University of Oxford. “Replication is crucial in this field.”
Hore says his own team has failed to replicate two studies that found that magnetic fields affect the behaviour of fruit flies in a maze, and their climbing speed in tubes.
However, one finding has stood up. Several studies have now shown that very weak radio frequency noise can disorient small migratory songbirds held in cages, says Hore. That is intriguing because the leading theory for how birds detect magnetic fields is via proteins called cryptochromes – and cryptochromes also play a key role in maintaining circadian rhythms in animals.
Vacha thinks radio waves may interfere with animal body clocks via cryptochromes. His team has previously shown that disabling a cryptochrome gene in cockroaches prevents them detecting magnetic fields.
But the radio waves that disrupt the orientation of caged birds are in theory a thousand times too weak to affect cryptochromes, says Hore, so the mechanism still isn’t clear. “It’s a bit of a puzzle.”
There is also no evidence that wild birds are affected by electromagnetic fields. They may fly high enough to avoid interference, Hore says.
Some people believe they are “hypersensitive” to electromagnetic fields and suffer adverse effects such as headaches. But tests have found that such people are unable to tell whether or not they have been exposed to fields.
Other scientists are sceptical, and say the study needs to be independently confirmed.