As reported by ScienceDaily (8/11) Exposure to Magnetic Fields in Pregnancy Increases Asthma Risk, Study Suggests
Women with high exposure to magnetic fields during pregnancy may have a higher
risk of asthma in their children, according to a Kaiser Permanente study
appearing online in the Archives of Pediatrics & Adolescent Medicine.
In this prospective study, researchers compared the daily magnetic field
exposure of 801 pregnant women in Kaiser Permanente Northern California and
used electronic medical records to follow their children for 13 years to see
which children developed asthma. The study found that women with high EMF
exposure in pregnancy had a more than threefold risk of asthma in their
offspring compared with mothers whose exposure level was low.
This is the first study to demonstrate a link between maternal magnetic field
exposure in pregnancy and the risk of asthma in offspring. Previous research
has found that EMF -- generated typically by power lines and appliances such as
microwave ovens, hair dryers and vacuum cleaners -- could lead to miscarriage,
poor semen quality, immune disorders, and certain type of cancers. Recently,
the International Agency for Research on Cancer, a WHO agency, classified radio
frequency EMF as a possible carcinogen. "While the replication of the finding
is needed, the message here is exposure to electromagnetic fields is not good,
and we need to pay attention to its adverse effect on health," said study lead
author De-Kun Li, MD, PhD, a reproductive and perinatal epidemiologist at the
Kaiser Permanente Division of Research in Oakland, Calif. Dr. Li published the
original study in 2002 that found high EMF exposure can lead to miscarriage.
The prevalence of asthma has been steadily rising since the 1980s, making it the
most common chronic condition among children. Thirteen percent of children
under 18 have asthma, which is caused by malfunction of the respiratory organs
and the immune system. "EMF exposure is ubiquitous. Because of the widespread
exposure, any adverse health effect of EMF could impact many people and cause a
serious public health problem," said Dr. Li.
Studying the EMF health effect has been difficult because everyone is exposed to
EMF at some level, so there is no truly "unexposed control group" for easy
comparison, researchers said. Health researchers must rely on comparing those
with high EMF exposure levels to those with low EMF exposure levels to detect
potential adverse EMF effects, Li said.
Women in this study wore a small meter during their pregnancy that measured
their daily exposure to low frequency magnetic fields from electricity-related
sources such as microwave ovens, hair dryers, vacuum cleaners, fans, coffee
grinders and fluorescent light bulbs, power lines, and transformer stations.
This study did not measure high frequency (radio frequency) EMFs from wireless
networks, wireless towers and wireless devices such as cell phones and smart
meters. The researchers adjusted for study participants who lived near freeways
but it did not change the results of the EMF-asthma association. "In this
study, we observed a dose-response relationship between mother's MF level in
pregnancy and the asthma risk in her offspring. In other words, a higher
maternal EMF exposure during pregnancy led to a higher asthma risk in
offspring," Dr. Li said.
In this new study, the researchers also found that two known risk factors for
asthma, maternal history of asthma and being the first-born child, exacerbated
the EMF effect on the asthma risk. "This finding further supports the
EMF-asthma association," says Dr. Li. "The best way to reduce your magnetic
field exposure is distance. Magnetic field strength drops dramatically with
increasing distance from the source," said Li. "So pregnant women should try to
limit their exposure to known EMF sources and keep distance from them when they
are in use."
The study was funded in part by the California Public Health Foundation.
Co-authors on the study include Hong Chen, MPH, and Roxana Odouli, MSPH, both
of the Kaiser Permanente Division of Research.