[ RadSafe ] Proximity to Power Lines at Birth May Increase Leukemia Risk

[Susan Gawarecki]

This may be of interest in the ongoing debate about health effects of 
electromagnetic fields.  It also occurs to me that families living near 
power lines are more likely to be exposed to herbicide sprays used along 
the right-of-way.

Susan Gawarecki

Proximity to Power Lines at Birth May Increase Leukemia Risk
By Tom Ewing , MedPage Today Staff Writer
http://www.medpagetoday.com/tbindex1.cfm?tbid=1141

OXFORD, England, June 2-Children's risk for leukemia is slightly higher 
for those who lived in homes near high-voltage overhead electrical lines 
at birth, according to a large case-control study published in BMJ.

The authors of the study were quick to point out that although the 
evidence suggests a causal relationship between overhead power lines and 
childhood leukemia that the phenomenon may be due to chance.

"The most obvious explanation of the association of leukemia with 
distance from a power line is that it is a consequence of exposure to 
magnetic fields," wrote Gerald Draper, M.D., and colleagues at Oxford's 
Childhood Cancer Research Group.

"However, we have no satisfactory explanation for our results in terms 
of causation by magnetic fields, and the findings are not supported by 
convincing laboratory data or any accepted biological mechanisms."

In the largest case-control study on the subject, the researchers found 
that compared with those who lived more than 600 meters from a line at 
birth, children who lived within 200 meters had a relative risk of 
leukemia of 1.69 (95% CI 1.13-2.53). And compared with those who lived 
between 200 and 600 meters away from a power line, they had a relative 
leukemia risk of 1.23 (95% CI 1.02 -1.49).

While there was a significant (P <0.01) trend in leukemia risk in 
relation to the reciprocal of distance from a line, no excess risk in 
relation to proximity to lines was found for other childhood cancers.

The researchers used birth registry records to identify 29,081 children 
under age 15 who had been born in England or Wales between 1962 and 1995 
and had been diagnosed with cancer (9,700 with leukemia). For each case, 
the researchers selected from birth registration records a control 
matched for sex, birth date, and birth-registration district.

Using postal codes, the researchers identified those who had, at birth, 
been living within 1 km of a 132-kV, 275-kV, or 400-kV overhead power 
lines. For 93% of the addresses, the researchers obtained a 0.1-meter 
grid reference, with which they calculated the shortest distance to any 
of the transmission lines that had existed in the subjects' year of 
birth. This enabled the researchers to develop a complete set of 
accurate distances for all subjects within 600 meters of a line.

On the basis of their investigation, the researchers concluded that 
there is an association between childhood leukemia and proximity of home 
address at birth to high-voltage power lines. The apparent risk extends 
to a greater distance than would have been expected from previous 
studies, they reported.

Although few children in England and Wales live close to high-voltage 
power lines at birth, the researchers noted, "there is a slight 
tendency" for the birth addresses of children with leukemia to be close 
to these lines than those of matched controls.

To put the risk in perspective, the researchers wrote that assuming that 
the higher risk of high-voltage lines is indeed a consequence of 
proximity to the lines, then of the 400 to 420 cases of childhood 
leukemia occurring annually in England and Wales, about five would be 
associated with power lines.

This study returns to the long-held (1979) concern that the 
low-frequency magnetic fields produced by power lines may be associated 
with cancer, especially childhood cancer.

In 2001, the International Agency for Research on Cancer classified 
extremely low-frequency magnetic fields as "possibly carcinogenic" on 
the basis of limited epidemiological evidence and "inadequate" evidence 
from animals.

Expressing skepticism in a commentary accompanying the BMJ study, 
Heather Dickinson, Ph.D., a researcher at the University of Newcastle 
upon Tyne, wrote:

"Magnetic fields from power lines are very weak, so it would be 
surprising if they caused leukemia. The increased risk closer to power 
lines may reflect some other factor that varies geographically.

"However, this study did not include estimates or measures of the 
magnetic field from either the power lines or other sources.

"We don't yet fully understand the etiology of childhood leukemia. 
Nevertheless, we are now reasonably sure that it often involves damage 
to DNA before birth, probably in response to infection, chemicals, 
ionizing radiation, or other environmental exposures. "