led by Dr. De-Kun Li, a
reproductive and perinatal epidemiologist at
the Kaiser Permanente in Oakland, California USA, claims that children of pregnant women who have been exposed to magnetic energy emnating
from electrical items such as hair dryers, microwaves and vacuum cleaners have
a greater risk of developing asthma.
The study has
been published in the online Journal - Archives
of Pediatrics & Adolescent Medicine.
It is the first to link maternal
exposure to magnetic energy and asthma
Previous Studies - There have been earlier studies that have linked exposure
to magnetic energy (generated by common sources such as power lines and
electrical appliances) to miscarriage, poor semen quality, immune disorders
studies pointed fingers at
microwaves ovens, hair dryers and vacuum cleaners. However, these studies lacked consistency, as they required
to be carried out over a long period of time.
For the recent prospective study,
De-Kun Li and his group of researchers examined the daily magnetic field exposure
of 801 pregnant women who resided in Northern California.
The scientists then analyzed the medical
records (for 13 years) of the children born to these women, to check for
During their pregnancy the subjects wore on their person a small
monitor for 24 hours to record their magnetic field exposure from daily
household items such as microwaves,
fans, coffee grinders, hair dryers, vacuum cleaners, and fluorescent light
bulbs, transformer stations and power lines.
"In this study we observed a dose-response
relationship between mother's MF (Magnetic Field) level in pregnancy and
the asthma risk in her offspring.In other words, a higher maternal MF exposure
during pregnancy led to a higher risk in offspring." Dr De-Kun Li said.
According to Li, for the average
population, children of women whose level of exposure was in the range of the
bottom 10 percent would have approx. 13.6 percent absolute risk of developing
asthma while women whose exposure was in the highest range carry a 33 percent
risk of producing children who developed asthma during the 13-year study period.
Li said it is not very clear about the connection between exposure to power
lines and asthma, he mentioned that prior studies by his team established a
link between high exposure to
electromagnetic fields and risk of miscarriages.
also said that some animal studies indicated that electromagnetic field
exposure can affect immune response, which could in turn predispose a person to
Dr Li suggested that daily, wide- spread
exposure to magnetic fields (such as
through home appliances) caused a serious public health concern.
He recommended that pregnant women minimize
their exposure to known magnetic field sources .
Comments and Controversies
"That's a striking figure. That magnitude of
association we don't see very often. If it was correct, and that's a big 'if,'
that would be really startling" says David Savitz, PhD, a professor of
community health and obstetrics and gynecology at Brown University in
Savitz, said that unlike cigarette smoke or
lead, there's little evidence that low-frequency EMFs (such as those measured
in the study) are harmful.Therefore
there is no need to give up using appliances such as air dryer just yet.
But Savitz and others recognize the
importance of this research. "There are a lot of important topics that started
out looking pretty flaky and pretty unlikely. There was a time when it made no
sense that smoking could be bad for
you," he remarks as other experts agree.
"The study appears to be well executed and
the finding is surprising," says Jonathan M. Samet, MD, a pulmonologist and
epidemiologist of the Keck School of Medicine at the University of Southern
California in Los Angeles.
It must be remembered that Samet recently led
a World Health Organization panel that came to the conclusion that EMFs from
cell phones and other wireless devices could be carcinogenic.
Li's study did not monitor exposure to higher frequency
electromagnetic fields that are generated by mobile phones or mobile
The study has drawn plenty of criticism too.
Professor of Paediatric Epidemiology at the
University of Leeds, Patricia McKinney, said the study had several flaws.
"The investigation lacks a biological
basis or hypothesis to test; papers cited in support of possible adverse effects
of EMF (electromagnetic fields) on reproductive outcomes and the immune system
are selective and ignore the major reviews which have concluded that the
findings fail to provide a sufficiently strong case for any further
investigation of this topic," McKinney
"Crucially, we cannot determine how
representative the sample was - an important factor in epidemiological studies
as this selection bias may have been linked to mothers who were more heavily
exposed to EMF or likely to have children with asthma," McKinney added.
Visiting professor at University of
Southampton, professor William Stewart observed that the study had several weaknesses in the way it
measured magnetic fields and believed that the findings could be categorized as pure "chance".
The above topic has always been controversial
and Li's study has suggested that there could be some connect between magnetic
fields and human health.
Li understands the need for more research to confirm his
findings. This, he believes, would help in bringing out new strategies in
dealing with the chronic disease, Asthma.