MAGNETIC fields from power lines [...].
High levels of exposure have effects in the womb that more than triple asthma risk, a study suggests. However, the controversial American research was criticised by British experts who questioned the way it was carried out.
Around 800 pregnant women from the San Francisco region of California were recruited for the study, originally designed to look at the effect of magnetic fields on miscarriage.
Each participant was asked to wear a small magnetic field recording device for 24 hours during the first or second threemonth period, or trimester, of their pregnancy.
The meters measured exposure to magnetic fields from electrical sources such as power lines, microwave ovens, vacuum cleaners, hair dryers and fluorescent lights. They did not measure radio frequency magnetic fields from wireless networks and mobile phones.
After the children were born, data on the numbers developing asthma were collected over 13 years. Each one milligaus (mG) increase in magnetic field level during pregnancy was associated with a 15% increased rate of asthma in offspring.
Children whose mothers were exposed to a high magnetic field level of more than two mG had a more than 3.5-fold increased risk of asthma compared with those whose mothers had low levels of exposure.