Rapporteur Report: Sources and Exposure Metrics for ELF Epidemiology (Part 1)

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High quality epidemiological studies on the possible link between exposure to non-ionising radiation and its effects on human health are of great importance for radiation protection. The main sources of ELF fields are domestic appliances, different electrical energy distribution systems, and all types of electrical machinery and devices in the workplace. In general, the ELF fields present in the environment show complex temporal patterns and spatial distributions, depending on the generating source. The complete characterisation of the different field sources often requires highly sophisticated instrumentation, and this is therefore not feasible within the scope of epidemiological studies. On average, indvidual exposure from ELF fields is low in both the working environment and in residential areas. People are subject to significant ELF exposure, with regard to biological effects, only in certain workplaces. Different methods have been developed to determine levels of exposure received by study subjects, with the aim to rank exposed and non-exposed groups in epidemiological studies. These include spot measurements. calculations or modelling. The different methods used to estimate total exposure in epidemiological studies may result, to a differing extent, in a misclassification of the study subjects. Equally important for future studies is the selection of the appropriate exposure metric. The most widely used metric so far is the time-weighted average, which thus represents a quasi standard metric for use in epidemiological studies. In addition, wire codes have been used for a long time in residential studies, and job titles are often used in occuptional studies. On the basis of the experience gained in previous studies, it would be desirable to develop standardised, state-of-the-art protocols to improve exposure assessment. New surrogates and metrics were proposed as the basis for further studies. But only few of these have recently undergone preliminary testing. A favourite candidate is the dB/dt metric. because it is closely related to known biological interactions.