Children whose mothers had high exposure to electromagnetic fields while pregnant may have an increased risk of developing asthma, US researchers said in a study that adds to an ongoing debate.
Many prior studies have failed to show convincingly that chronic exposure to electromagnetic fields – from power lines and appliances such as microwave ovens, hair dryers and vacuum cleaners – are harmful to human health.
But many of these studies required people to estimate their exposure levels over several years, says Dr De-Kun Li, a scientist at the Kaiser Permanente in Oakland, California.
To get a more conclusive answer, Li designed a study in which 801 pregnant women wore monitors that measured their exposure to magnetic fields for 24 hours.
Measurements were taken from microwaves, hair dryers, fans, coffee grinders and fluorescent light bulbs, power lines, and transformer stations.
It did not monitor exposure to higher frequency electromagnetic fields generated by cellphones or cellphone towers.
The team used medical records to follow the women's children for 13 years. During the follow-up, 130 children, or 20.8 percent of study participants, developed asthma.
Most of these cases were diagnosed before age five.
They then compared exposure levels during pregnancy to rates of asthma and found that children whose mothers had the highest exposure levels were 3.5 times more likely to develop asthma than those who were in the bottom 10 percent.
沒有留言:
張貼留言