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Environmental Health Investigations Branch

General

Background

In many parts of the country electric and magnetic fields (EMF) in schools have become a matter of discussion and debate. The question being debated is "Are EMFs harmful to human health?" and if so, "At what level?" Unfortunately, there is no scientific consensus on these topics at this time. This checklist focuses on the magnetic field components of EMF, the major concern of scientists and health officials. An overview of the full nature of EMF and associated health issues can be found in Questions and Answers about Electric and Magnetic Fields Associated with the Use of Electric Power.

It is clear from reviewing the scientific literature that there is controversy as to whether there is an EMF hazard, as well about what aspect or what level of the EMF mixture would carry any such hazard. It follows that using a simple gaussmeter (a device for measuring magnetic fields) to measure one aspect of the EMF mixture and selecting a particular level as "safe" or "dangerous" is also controversial.

Checklist Purpose

This checklist deals with conventional "no and low cost" techniques. It provides practical ways to minimize exposure to magnetic fields in the building of new schools. It proceeds step-by-step from initial planning and site selection through construction, furnishing and occupancy. It considers the entire school campus as well as individual areas and rooms. It is intended as a practical document for school facility planners, school building advisory committees, project managers, school architects, engineers and inspectors. It will enable them to evaluate, in a systematic way, the many decisions they can make in order to reduce exposures to EMF.

While some of the information in the annotated checklist below can be applied to existing school facilities, it is most relevant to new construction, where there are numerous opportunities to minimize EMF at no or very low cost. The expense and time required to retrofit all existing schools in a district to reduce magnetic fields would generally be high. The uncertain benefits of these more expensive actions should be weighed against other educational priorities.

California Public Utility Commission Policy

In California, where this checklist was developed, the Public Utility Commission advised the state's utilities that at this time it is reasonable to carry out no and low cost measures to reduce magnetic fields when constructing new electric utility facilities. In these instances in California "no and low cost" is defined as up to four per cent of the project cost if it achieves at least a fifteen percent field reduction.1 For school projects this may be defined differently. The use of no and low cost techniques outlined in this checklist versus using "EMF standards" may significantly minimize EMF exposures without getting bogged down in controversy which could come from using fixed standards.

EMF Levels

One way of looking at schools is to apply what we have learned from our experiences with houses, which have been the main subject of studies to date. Gaussmeter surveys of large numbers of California houses2 indicate that half of them have spot readings in the middle of the living room above 0.7 milligauss (mG, a unit measuring magnetic field flux density), while only ten per cent have a reading above 1.5 mG. In a rough qualitative way one may aim to have the EMF levels of high-occupancy areas in the new schools resemble the typical home exposure.

Checklist Philosophy

This checklist is composed of a number of "no and low cost" techniques which if followed will tend to minimize magnetic fields in the schools. This approach is suggested rather than purchasing gaussmeters or hiring magnetic field surveyors (whose practitioners have a wide variability in expertise and backgrounds and whose practice is currently unregulated and uncertified).

Local school districts may choose, however, to use a gaussmeter as a tool for checking that electrical wiring design and specifications have been followed, and others may choose even more extensive uses. This checklist, however, restricts itself to no and low cost techniques which do not require a gaussmeter or major change in the way school districts, architects, and contractors conduct their work. People wanting to perform magnetic field measurements or modeling should consult with appropriate professionals.

Because a school campus uses much more electricity than a typical home, there are bound to be some areas on a campus with fields much higher than found in a typical home. Simple forethought in planning and design can place such areas in low-occupancy locations. However, expending resources to lower very high anticipated magnetic fields in a new school to somewhat high fields (far above those of the typical residence) probably is not a no and low cost technique.

"No and Low Cost" Techniques

The four basic no and low cost techniques for EMF avoidance are:
  • maximize distance between EMF sources and high-occupancy areas
  • maximize cancellation of magnetic fields by minimizing the distance between conductors in the circuit and by strict adherence to the National Electric Code (NEC)
  • avoid "net current" conditions by adhering to established electric codes and using sound engineering practices to keep circuits balanced
  • reduce electrical current
This checklist is provided to help review options for utilizing these four field reduction techniques. Options are considered below in the various stages of school construction: program development, site selection, site planning, building design, construction documents, construction, and occupancy.


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