Realistic models are needed to evaluate induced electric currents and fields at the cellular and subcellular levels. An intermediate step could involve the development of better models of the body, such as the incorporation of anisotropies; the complexity of today's models is generally limited to inhomogeneities in tissues.
Studies are needed to better understand the correlation between wire codes and magnetic fields for different utility-service areas; this work is needed before multi-city epidemiologic studies (using wire codes) can be undertaken and to better interpret the studies already completed. Such data might also be useful for extending meta-analyses to more meaningful exposure estimates.
Grounding system current is one of the three major sources of residential magnetic fields. It seems reasonable to assume that ground currents will be greater in areas with higher wire codes or near substations (the ultimate destinations of ground return currents). How grounding system currents vary as a function of distance from substations and how these might correlate with wire-code categories are questions that could be studied.
Studies of the correlation between personal-exposure measurements (or time-weighted-average measurements) taken days, months, and years apart might contribute to an understanding of the relationship between contemporary magnetic-field strengths and magnetic fields measured at the time of disease etiology.
The stability of wire codes (they change little with time over reasonably long periods) suggests that wire codes should correlate as well with contemporary spot (or time-weighted-average) measurements as they would with historical (prediagnosis) measurements. However, several trends complicate that hypothesis, and studies could examine the relationships. For example, many regions tend to increase the current demand over time, causing power lines to become more heavily loaded. Eventually, the power lines in a particular area might have to be upgraded to handle the load; thus, the wire configuration is changed, and the