Electromagnetic exposure 'increases asthma risk'
Source: Agencies |
August 3, 2011, Wednesday
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Print Edition
Print Edition
Children whose mothers had high exposure to electromagnetic fields while pregnant may have an increased risk of developing asthma, according to US researchers.
Many previous studies have failed to prove chronic exposure to electromagnetic fields - such as those from power lines and appliances such as microwaves ovens, hair dryers and vacuum cleaners - are harmful to health.
But many of these studies required people to estimate their exposure levels over several years, according to De-Kun Li, senior research scientist at the Kaiser Permanente in Oakland, California, whose study appears in Archives of Pediatrics & Adolescent Medicine.
In pursuit of a more conclusive result, Li designed a study in which 801 pregnant women wore monitors that for 24 hours measured their exposure to low-frequency magnetic fields from electronic and electrical sources such as microwaves, hair dryers, fans, coffee grinders, fluorescent light bulbs, power lines and transformer stations.
It did not monitor exposure to the higher frequency electromagnetic fields generated by mobile phones or mobile phone towers.
The team used medical records to follow the progress of the women's children for 13 years. During the follow-up, 130 children, or 20.8 percent of study participants, developed asthma. Most of cases were diagnosed before the age of five.
They then compared exposure levels during pregnancy to rates of asthma development and found that children whose mothers had the highest exposure levels - within the top 10 percent of women in the study - were 3.5 times more likely to develop asthma than those who were in the bottom 10 percent.
The risk for children whose exposure was somewhere in the middle - between 10 percent and 90 percent - was 75 percent higher than for those in the lowest exposure group.
For the average population, Li said, children of women whose exposure levels were in the range of the bottom 10 percent in the study would have about a 13.6 percent risk of developing asthma. Women whose exposure was in the highest range would have about a 33 percent risk.
Some 13 percent of children under 18 have asthma, which is caused by malfunction of the respiratory organs and the immune system.
Many previous studies have failed to prove chronic exposure to electromagnetic fields - such as those from power lines and appliances such as microwaves ovens, hair dryers and vacuum cleaners - are harmful to health.
But many of these studies required people to estimate their exposure levels over several years, according to De-Kun Li, senior research scientist at the Kaiser Permanente in Oakland, California, whose study appears in Archives of Pediatrics & Adolescent Medicine.
In pursuit of a more conclusive result, Li designed a study in which 801 pregnant women wore monitors that for 24 hours measured their exposure to low-frequency magnetic fields from electronic and electrical sources such as microwaves, hair dryers, fans, coffee grinders, fluorescent light bulbs, power lines and transformer stations.
It did not monitor exposure to the higher frequency electromagnetic fields generated by mobile phones or mobile phone towers.
The team used medical records to follow the progress of the women's children for 13 years. During the follow-up, 130 children, or 20.8 percent of study participants, developed asthma. Most of cases were diagnosed before the age of five.
They then compared exposure levels during pregnancy to rates of asthma development and found that children whose mothers had the highest exposure levels - within the top 10 percent of women in the study - were 3.5 times more likely to develop asthma than those who were in the bottom 10 percent.
The risk for children whose exposure was somewhere in the middle - between 10 percent and 90 percent - was 75 percent higher than for those in the lowest exposure group.
For the average population, Li said, children of women whose exposure levels were in the range of the bottom 10 percent in the study would have about a 13.6 percent risk of developing asthma. Women whose exposure was in the highest range would have about a 33 percent risk.
Some 13 percent of children under 18 have asthma, which is caused by malfunction of the respiratory organs and the immune system.
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