California power lines study

Following the findings of the CCRG epidemiological studies into childhood cancer and proximity to power lines in the UK, various studies were set up to see if the same unexpected effects - elevated leukaemia rates at distances out to 600 m, and, subsequently, the finding that the risk declined from the 1960s to the present - could be replicated in other countries.  One of these was the French Geocap study.  The largest, however, was in California.  That has now (2016) published its results for distance (the results from calculated magnetic field are coming in a separate paper).  A summary of the results is given in the following graph from the paper:

graph of results of california study

There is a raised risk for leukaemia in the 0-50 m band but not statistically significant, and, looking at the whole of the results, it would be hard to claim that much weight should attach to it.  The CCRG finding of consistently increased risks out to 600 m is clearly not replicated.  The paper concludes:

Our findings did not clearly support an increased childhood leukaemia risk associated with close proximity (<50 m) to higher voltage lines, but could be consistent with a small increased risk. Reports of increased risk for distances beyond 50 m were not replicated.

These are the results for power lines >200 kV.  Results for 100 kV and 60 kV show even less suggestion of any risks.

Does this contradict the CCRG findings?

Well, it certainly doesn't support the CCRG findings, and neither did the French Geocap study.  But this study covers 1986-2008, and Geocap covered the even later period 2002-2007.  These are periods when CCRG results (see graph below) also found no, or much reduced, risks in the UK:

graph of CCRG follow on results

So neither Geocap nor this California study lend direct support to the CCRG findings - but neither do they actually contradict the CCRG.

 

The Abstract

Br J Cancer. 2016 May 24. doi: 10.1038/bjc.2016.142. [Epub ahead of print]

Childhood leukaemia and distance from power lines in California: a population-based case-control study.

Crespi CM, Vergara XP, Hooper C, Oksuzyan S, Wu S, Cockburn M, Kheifets L.

BACKGROUND:

Studies have reported an increased risk of childhood leukaemia associated with living near high-voltage electric power transmission lines that extend to distances at which magnetic fields from lines are negligible. We conducted a large records-based case-control study of childhood leukaemia risk in the population living near power lines in California.

METHODS:

The study included 5788 childhood leukaemia and 3308 central nervous system (CNS) cancer cases (for comparison) born in and diagnosed in California (1986-2008), and matched to population-based controls by age and sex. We geocoded birth address and estimated the distance from residence to transmission lines using geographic information systems, aerial imagery, and, for some residences, site visits.

RESULTS:

For leukaemia, there was a slight excess of cases within 50 m of a transmission line over 200 kV (odds ratio 1.4, 95% confidence interval 0.7-2.7). There was no evidence of increased risk for distances beyond 50 m, for lower-voltage lines, or for CNS cancers.

CONCLUSIONS:

Our findings did not clearly support an increased childhood leukaemia risk associated with close proximity (<50 m) to higher voltage lines, but could be consistent with a small increased risk. Reports of increased risk for distances beyond 50 m were not replicated.

See also:

Other epidemiological studies of childhood cancer and power lines: