Posted on octobre 07 2019
There’s emerging evidence that exposure to one type of radiation from cellphones and other devices might be linked to a major adverse health outcome in women: miscarriages.
A new study published in the journal Scientific Reports found a strong link between higher levels of exposure to a type of radiation called magnetic field non-ionizing radiation and higher risk of miscarriage in a group of nearly 1,000 women living in the Bay Area of California.
Specifically, the researchers, from Kaiser Permanente in Northern California, found that a woman’s miscarriage risk rose from 10 percent to 24 percent as she was exposed to higher levels of magnetic field non-ionizing radiation.
This research is still in the early stages. The study did not show that the non-ionizing radiation — which is given off by cellphones, cordless phones, smart meters, wireless networks, power lines, and microwaves — caused the miscarriages. But it suggests there’s a possible link.
And it’s worth paying attention to because it comes in the context of many other studies that show how environmental factors — such as pollution and toxic chemicals — can affect fertility and reproduction.
“[This study] exposes a known concern — these environmental contributors to adverse reproductive health outcomes, including miscarriages — without yet having a precise cause and effect established,” said Nathaniel DeNicola, an assistant professor of obstetrics and gynecology at George Washington University, who was not involved in the study.
That means this is an area of research to keep an eye on. It doesn’t mean that people’s cellphones are directly damaging fetuses.
Non-ionizing radiation explained
To understand the study, we need a brief primer on radiation. As the National Institutes of Health explains, radiation is invisible energy that can come in the form of electric and magnetic fields.
These energy fields power the various devices we rely on and are generally split into two radioactive categories: non-ionizing radiation and ionizing radiation. The big difference between these two types of radiation is that higher-frequency ionizing — emitted by X-rays, gamma rays — is known to cause direct cellular and DNA damage that can lead to cancer. Lower frequency non-ionizing radiation, meanwhile, has generally been thought to be less dangerous, because, researchers have long believed, it can’t interfere with cells in the same way.
But increasingly, we’re learning that even this more benign type of radiation could be affecting our bodies in subtle and harmful ways. And that’s where the new Scientific Reports study comes in.
“Electromagnetic field radiation has a biological effect”
The researchers behind the paper, epidemiologists at Kaiser Permanente, wanted to look into miscarriage specifically because, unlike cancer, it doesn’t take years to develop, and they thought it would be easier to draw correlations between exposure and health outcome.
Based in Oakland, California, they recruited 913 Bay Area women at the start of their pregnancies and then tracked them for up to 20 weeks (the period during which miscarriages happen).
The vast majority of miscarriages are caused by genetic factors — but environmental factors are also believed to play a significant role. The researchers wanted to see if there was a link between magnetic field non-ionizing radiation, which is all around us — again, emitted from everything from power lines to wireless networks, cell towers, and cellphones — and miscarriages.
To gauge radiation exposure, the women wore a radiation-measuring meter for 24 hours. They were then asked whether the day they wore the device was representative of a typical day during their pregnancies to make sure that the reading was accurate.
The researchers grouped the women into four categories based on their exposure levels: The lowest quartile got less than 2.5 milligauss (the measure for magnetic field non-ionizing radiation) in the 24-hour period, and the top three quartiles, more than that.
What they found was quite striking: Women in the top three quartiles — with the higher levels of non-ionizing radiation exposure — were at a nearly three times greater risk of miscarriage compared to women at the lowest quartile of radiation exposure. This finding held even after the researchers controlled for factors that might explain the differences between the groups, like smoking status, history of miscarriages, age, and race.
In absolute terms, a woman’s miscarriage risk rose from 10 percent (at the lowest levels of radiation exposure) to 24 percent (among the higher levels of exposure).
“There’s an association here,” lead author De-Kun Li, a senior research scientist at Kaiser Permanente Northern California, told Vox. But again, since this was an observational study and not an experimental study, Li could not establish causation between the low-level radiation and miscarriages. Not all women with higher radiation exposure levels miscarried, and there were miscarriages in the lowest quartile.
Instead, Li said, the study shows that “electromagnetic field radiation has a biological effect.”
How relevant is this finding for women living in other parts of the country? In terms of exposure to radiation, Li said, there’s no reason to believe women living in the Bay Area are any different from women living in cities anywhere in the US. And their risk of miscarriage is also no higher than the national average (10 percent). “It’s a very generalizable [finding],” he said.
What the study could not say
Still, there were a few issues with the paper that are worth pointing out. As always, this is a single study and would need to be replicated among other groups of women.
Joel Moskowitz, a UC Berkeley public health researcher who has studied cellphone radiation, told Vox he thought the study was well designed and compelling. But he noted that because the researchers only measured magnetic field non-ionizing radiation, it’s possible the women who miscarried were exposed to radio-frequency radiation that was a risk factor for them too.
DeNicola noted that it’s possible the women in the highest-exposure group who miscarried had other traits or exposures that made them more prone to miscarrying. Perhaps they lived in environments with higher levels of air pollution, for example.
“It’s too soon to draw a strong conclusion about this study and what patients should do with their cellphone — but reproductive health is an environmental health issue,” said DeNicola. “And whether it’s pollution or other endocrine-disrupting chemicals that are in [the] environment, they need to be explored in research and policy.”
Researchers also don’t yet fully understand the mechanisms by which magnetic field non-ionizing radiation may interfere with human health. Again, ionizing radiation is known to interfere with cells and cause genetic mutations — which is why, for example, you shouldn’t get too many X-rays or sunburns throughout your life. But the biological mechanisms by which non-ionizing radiation interfere with health is less clear.
Li just hopes that his study spurs more research on this question. “Right now, the prevailing assumption is that electromagnetic fields are something that doesn’t have a biological effect. But our study will hopefully make people rethink that assumption.”
What about cellphones and cancer?
The scientific jury is still out on whether cellphones cause cancer, in part because the studies that would equivocally answer that question are really hard to do and the research we have is marred by methodological flaws. For example, many of the studies we have are based on people’s recall about their radiation exposure, instead of careful measurement.
But recent, much-anticipated reports from the NIH’s National Toxicology Program — which looked at the effects of cellphone radiation in rats and mice — also concluded that non-ionizing radiation may have biological effects. “They go against the notion that non-ionizing radiation is completely harmless,” said Dr. John Bucher, a senior scientist and author on the reports. He and others point to the heating effects of non-ionizing radiation — which heat up your cellphone and your food in the microwave — and may damage tissue in harmful ways.
For now, though, “human data is very mixed,” he said. If you’re concerned about your exposure, Li suggested, avoid or keep a distance from sources of non-ionizing radiation — and be sure not to wear your cellphone on your body or put it to your head.