Researchers in China may have found a link between EMF produced by EHV lines and transformers and leukemia. For years it's been thought that the EMF produced by low frequency (50-60Hz) power lines and transformers caused childhood leukemia by breaking down bonds in DNA structures. Further it was shown that in certain regions, clusters of childhood leukemia cases were found around transmission lines and substations. However in laboratory tests none of this could ever be replicated and no DNA structure dissolution could be seen.
However Xiaoming Shen and coworkers at the Jiao Tong University School of Medicine in Shanghai have discovered that only children with a genetic variant, known as polymorphism (aka “snp” pronounced snip) are more predisposed to this condition. The found that children with this condition, who lived within 300 feet of transmission lines or substations had over four times the incidence of leukemia than similar children in similar environments without snp variants in their genes.
Children with these snp variations have difficulty repairing DNA structures after they have been broken. Shen and Tong theorize that these children near EMF sources aren’t experiencing increased DNA restructuring, they are just predisposed to have problems rebuilding DNA, and then the EMF further hampers their reconstruction and cause increased incidences of leukemia.
An abundance of further information about the details of the research and technical causation of can be obtained by reading the article in this link:
http://www.informaworld.com/smpp/content~content=a906347140
My question, as an engineer, is how EHV lines contribute to this more than household wiring. A transmission line in the system I’m working on currently is typically around 138kV and carries around 250A. While these transmission lines carry much more power than your typical household wiring, the amperage is not a whole lot more (in this case it’s carrying about 10,000 more power, while only carrying 10x more current). The reasoning behind this is due to voltage transformation, the higher the voltage the lower the current.
So the current is not significantly higher, and we know from fundamental physics that the EMF from this line of charge (I say that the model for a transmission line in this case is best suited to an infinite line) drops as a function of 1/r2 where r is the distance to the source. Further we know from amperes law that the electromagnetic flux (B-field) is equal to μ0 times the enclosed current. Therefore, using the numbers already used here a child 150ft (half the 300ft distance stated by Shen et al) away from a EHV line carrying 250A, will be exposed to roughly 4.58*10^-8 Tesla. However, the same child in a house with a wire carrying enough current to power an average stove, will experience 9.162*10^-6T, which is about 100 times GREATER exposure of EMF than the child sitting 150ft from a transmission line.
I use these numbers because I had a customer complain once about EMF from a line, and after going out to her house with an EMF meter and proving to her that the field was greater in her house from the EMF than it was outside near the line, she was assuaged of the transmission line’s danger to her.
