Exposure to magnetic fields that are produced by power lines, electronics, and cell phone towers has been suggested to be linked to several health problems. Researchers from the Kaiser Foundation Research Institute, lead by Dr. De-Kun Li, have found that in utero exposure to magnetic fields increases the risk of developing asthma in the unborn child. The results of the research were published online in the journal Archives of Pediatric and Adolescent Medicine. The researchers used data from a prospective cohort study using mother child pairs performed at Kaiser Permanente Northern California. In the study, the mothers carried a meter that was designed to measure magnetic field exposure during a 24 hour period during the first or second trimester of pregnancy. The researchers adjusted for confounding factors such as age, race, education, smoking during pregnancy, and maternal history of asthma. The children were followed up for as long as a 13 year period and about 20% developed asthma (130 of 626 children). The researchers found a statistically significant linear dose response relationship between maternal magnetic field exposure and the risk of developing asthma in their offspring. For every 1 milligaus increase in magnetic field exposure to the mother during pregnancy there was an associated 15% increased risk of developing asthma in their offspring. Children of mothers with the highest magnetic field exposure had more than 3.5 fold increased rate of childhood asthma compared to children of mothers with the lowest exposure to magnetic fields. In addition, there was also a statistically significant association observed for birth order and maternal history of asthma. Firstborn children had higher risk, and children of mothers with a history of asthma had higher risk of developing asthma when mothers were exposed to magnetic fields during pregnancy. The authors wrote, “Our findings provide new epidemiological evidencethat high maternal [magnetic field] levels in pregnancy may increase the riskof asthma in offspring… the findings of the present study open up a new area in understanding the risk factors for asthma and the health effects of ubiquitous [magnetic field] exposure, especially during pregnancy”. The findings of the study need to be replicated, but will undoubted cause increased controversy in the debate about the placement of power lines and cell phone towers.
De-Kun Li et al. “Maternal Exposure to Magnetic Fields During Pregnancy in Relation to the Risk of Asthma in Offspring” published online August 1, 2011 Arch Pediatr Adolesc Med doi:10.1001/archpediatrics.2011.135