TABLE 2-10 Typical Exposure Specifications to be Defined, Evaluated, and Reported in Any Experimenta

Critical Specifications

Desirable Specifications

Frequency of the field

Transients (when turning on/off); the time or frequency characteristic

Waveform type: sinusoidal, pulsed

Waveform: exact time or frequency domain characterization

Magnitude of the field in the exposure and sham apparatus

Magnitude of the other field (magnetic for exposure to the electric field and vice versa)

 

A record of the amplitudes of the exposure and sham-exposure fields throughout the experiment

Direction of the field in exposure apparatus

Direction of the background field (undesired) in the sham-exposure apparatus

Type of control (e.g., true sham, unexposed treated identically) and their location

Identical exposure of control except the field magnitude

Duration of exposure

Time of day of exposure (animal studies only)

Estimated uniformity of the field

Measured uniformity of the exposure and sham-exposure fields

Dimensions of exposure apparatus

Design sketches or photos of exposure apparatus

Location and type of cages

Size and material of cages; number of animals per cage

Number of animals or cell culture dishes per exposure apparatus

Rotation of cages (schedule and details)

Temperature

Illumination and noise level in exposure and sham apparatus (only for animal studies)

a Applies to in vivo and in vitro exposures to electric and magnetic fields.

Common potential artifacts associated with magnetic-field-exposure systems are heating, vibrations, and audible or high-frequency (nonaudible for humans) noise. These factors can be minimized but not entirely eliminated with careful design and construction, which can be costly. The most economic and reliable way of addressing and solving these problems is through essentially identical design and construction of the field-and sham-exposure systems except for the current direction in bifilarly wound coils (Kirschvink 1992; Caputa and Stuchly 1996). This solution provides for the same heating in both systems. Vibration and noise are usually not exactly the same but are similar. To limit the vibration and noise, the coil windings should be restricted mechanically in their motion.



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