Microshocks are the phenomenon where people and conducting objects acquire charges in an electric field, and the charge can equalise by means of a small spark from the object to a point on the person's skin.
The various exposure limits that control exposures to EMFs sometimes mention indirect effects such as microshocks, but usually only in a fairly general way.
More detailed guidance for the UK is contained in a Code of Practice adopted in 2013 by Government (DECC, DH, and the Devolved Adminstrations) and industry (the Energy Networks Association). This Code of Practice is available as a download or from DECC.
Two of the key statements are:
"This Code of Practice recognises that there is no reasonable way to avoid microshocks in all circumstances, even in circumstances when they are at a frequency and severity that is clearly undesirable, and therefore that not all situations producing microshocks are expected to be remedied."
"This Code of Practice also recognises that control of microshocks is not based on a simple quantitative limit. Rather, there is a suite of measures that may be called upon in particular situations."
It then outlines the "suite of measures" that should be called on, in summary, and in rough order of preference:
- Electricity companies will, where reasonably practicable, avoid designing new power lines that would create fields of 5 kVm-1 or greater in homes, other land in residential use, their curtilage, and schools
- Electricity companies will continue to make information available to the public about microshocks. They will seek appropriate ways to communicate to specific communities affected (e.g. cyclists and horse-riders)
- When an electricity company becomes aware that a particular situation is giving rise to microshocks in a persistent and annoying manner:
- The company will offer focussed advice and information specific to the situation;
- Where earthing is an easy solution, this is encouraged, and will be explained to the landowner or occupier by the electricity company;
- Where microshocks occur in someone’s garden, or in other circumstances where one individual could be exposed to multiple shocks over a prolonged period, every reasonable effort will be made by the electricity company to develop solutions by earthing, by changing a conducting object to an insulating one, by use of appropriate clothing, or by screening structures or trees and vegetation; and
- Where a site-specific risk analysis indicates a significant risk of injury (assessed using normal health and safety practice) from startle reactions to a microshock, mitigation measures, potentially including screening structures, will be developed by the electricity company, and, to the extent that it lies within the company’s control, deployed, if this can be done without becoming unreasonable.
Note that these are edited summaries, see the Code of Practice for the full wording and for extra explanatory material.