Power lines: what the wires outside actually produce
The innocuous-looking pole line can out-radiate the transmission tower - and the reasons are the same net-current physics that governs everything else on this site.
Not all lines are alike
People rank power lines by how alarming they look: transmission towers worst, wooden distribution poles next, the little service drop to the house least. The gaussmeter frequently reverses that ranking. What matters is current, geometry, and balance - not voltage or visual drama.
| Source | Typical situation at house distance |
|---|---|
| High-voltage transmission lines | Large currents, but conductors hang far away and are reasonably balanced; fields at the edge of a right-of-way commonly measure a few milligauss and fall steadily with distance. High readings are confined to homes essentially adjacent to the corridor. |
| Neighborhood distribution lines | Closer to bedrooms than any tower, and their balance depends on the neutral. A primary line whose return current partly flows through the earth and water mains - instead of its own neutral - behaves as a net-current source, and its field reaches surprisingly far. |
| Service drops and pad transformers | Intense but extremely local; a pad transformer's field typically vanishes into background within several meters. Distance solves these by itself. |
Why an "innocuous" line can read high
A perfectly balanced line - every ampere going out matched by an ampere coming back alongside it - largely cancels its own field. Utility distribution systems, however, are multi-grounded by design: the primary neutral is bonded to earth at pole after pole, and to every house grounding system (and through them, the metal water network) along the way. Some return current therefore abandons the neutral and comes home through the ground and the plumbing. The line's outgoing and returning currents no longer match; the difference is net current, and the whole line radiates accordingly. This is why a modest wooden-pole line with a neutral problem can produce higher bedroom readings than a transmission corridor two blocks away - and why the same house often shows water-pipe current indoors: it is one interconnected circuit, and your plumbing is part of it.
Diagnosing an outside source
The signature is straightforward with a meter: readings that are highest on the side of the house facing the line, that fall as you move away from it, and that persist with the house's main breaker off. Readings that also track time of day - rising with evening load - point at distribution current rather than any fixed installation. Map carefully before concluding; indoor net currents mimic outside sources more often than people expect, and they are far easier to fix.
What can actually be done
Use distance you already own. Field strength falls off continuously; in many homes, moving a bed to the far wall, or a child's room across the hall, cuts exposure by half or more at zero cost. Measure first - the gradient tells you exactly what a few feet buys.
Call the utility about suspected neutral problems. A distribution line radiating heavily because of a deteriorated or undersized neutral is a power-quality defect the utility has its own reasons to correct - bad neutrals cause stray voltage complaints, equipment trouble, and losses. Utilities routinely investigate; a polite report of measured milligauss levels and their time-of-day pattern gets a better response than a health argument.
Fix the indoor half. Where neighborhood return current enters via the water service, the electrician-plumber correction described on the net-currents page removes the indoor contribution even though the line outside is untouched. In practice this is often where most of the bedroom reading was coming from anyway.
Skip the shielding. For reasons covered on the shielding page, materials that meaningfully attenuate 60 Hz magnetic fields are engineering products for enclosed volumes, not something applied to a bedroom wall facing a pole line.
Perspective
The research picture on power-frequency fields has not fundamentally moved since IARC's 2002 "possibly carcinogenic" (Group 2B) classification: an unresolved statistical association in childhood-leukemia epidemiology, no established mechanism, and decades of further study that neither cleared nor convicted. Summaries from the NIEHS and the World Health Organization lay out that evidence honestly. The stance this site inherits from its namesake book fits the facts as well now as in 2001: panic is unwarranted, cheap and permanent reductions are frequently available, and the sensible response to uncertainty is to take the cheap reductions and get on with life.