This executive summary describes the final report for this project.
Martin-Marietta Energy Systems Contract No. 62X-ST72V
This project developed recommended guidelines for electric and magnetic field (EMF) personal exposure measurement (PEM) studies. The recommendations are flexible and intend to provide guidance for investigators with varied research objectives, rather than dictate specific methodologies. The guidelines fall into two categories: general guidelines for planning a study, and specific guidelines for developing a detailed study design and protocols. Supporting discussions, and suggested implementation procedures are also included.
The purpose of establishing general guidelines for exposure studies is to ensure that valid data are collected and that the data meet the study objectives including, if appropriate, any risk assessment requirements. To accomplish these goals, investigators should employ the following steps when planning an EMF PEM study :
By succinctly stating the purpose of the study at the outset, and referring to it frequently, questions regarding the overall study design and the written study plan can be addressed without ambiguity. The purpose statement may evolve as the study design develops and resource constraints are addressed but any changes or compromises in the purpose will be clearly known. Before beginning measurements there must be a purpose statement that is understood and accepted by the investigators, their managers, and all sponsors of the study.
The written study plan is a general descriptive document and should address the following elements of the EMF PEM study:
The recommended specific guidelines for developing detailed plans and protocols for a PEM study apply to six elements of a study: study design, subject issues, quality assurance, uncertainty evaluation, archival plans and pilot studies. The topics and issues addressed in the specific guidelines are:
Study Design. Specific recommendations are provided for: selecting the field characteristics to be measured, selecting appropriate PEM instrumentation, developing a sampling strategy, establishing time-activity record-keeping protocols, and developing plans for data management, data analysis, and documentation of the study's methods and results. It is recommended that, at a minimum, a time-weighted average exposure of the resultant magnetic field should be measured and reported. Sample size, sampling parameters, and resource considerations are discussed along with a presentation of the sampling strategies: simple random sample, systematic sample, stratified sample, cluster sample and multistage sample. The following methodologies for time-activity record-keeping are presented: diary, self-administered or interview questionnaire employing retrospective, prospective or concurrent record-keeping.
Subject Issues. Guidance is provided for managing subject-related issues such as: obtaining organizational approvals for the participation of subjects; developing the forms to obtain a subjects informed consent; developing the procedures to maintain the confidentiality of subjects; developing clear, unambiguous PEM protocol instructions for the subjects; developing a plan to provide subjects with their PEM data; and developing PEM procedures that minimize the possibility of protocol violations.
Quality Assurance. Recommendations to ensure the quality and integrity of the data from a PEM study include: the implementation of appropriate and generally accepted procedures for the sampling process, data collection, data management, and data analysis; the implementation of a plan for verifying the calibration and confirming the functionality of PEM meters on a regular basis; the development of methods for assessing the consistency of the PEM and its associated data and the completeness of all data soon after each observation; and the introduction of automated and/or manual procedures for verifying the accuracy of the data entered into data bases.
Uncertainty Evaluation. An uncertainty evaluation of a PEM EMF study should be performed to determine the magnitude and acceptability of factors likely to contribute to uncertainty; and to plan for an estimate of both the observed uncertainty introduced by various factors and overall observed uncertainty. The evaluation will assist in planning and implementing data validation procedures.
Archival Plan. Guidance is provided to develop specific plans for the archiving of raw data, processed data, study documents, and other study materials such as forms; written protocols; instructions to subjects and data collectors; and software tools.
Pilot Studies. The specific recommendations include pilot studies of all aspects of the study design. This includes testing protocols for: sampling, instrumentation, PEM, time-activity record-keeping, subject participation, and quality assurance.
The document contains a literature review of PEM studies that provides background information and reference to works presenting PEM protocols and related issues. Selected references have been summarized in a standard format and included as an appendix.
To illustrate the effects of subject characteristics on activities possibly related to EMF exposure, existing time-activity survey data for children and adults in California were examined. The largest and most consistent differences in locations and activities observed in these data were related to age and gender. The differences suggest that these should be important subject attributes in an EMF PEM study.
The guidelines were tested in two pilot studies by an independent investigator. One pilot study measured EMF PE for 50 high school students who kept concurrent time-activity diaries and completed questionnaires regarding their activities. The subjects for the second pilot study were employees at an electronics manufacturing plant. They either kept a time-activity diary or their activities were recorded by an observer during work hours. PEM results from both pilot studies are presented in an appendix. Modifications and enhancements were made to the guidelines in response to feedback from the pilot studies investigator.
The combination of the general guidelines, specific guidelines, and background materials provides a prospective investigator of electric and magnetic field personal exposure with a foundation for developing, implementing and reporting a scientifically sound, valid PEM study.