title: Statistical analysis of personal radiofrequency electromagnetic field measurements with nondetects.
abstract: Exposimeters are increasingly applied in bioelectromagnetic research to determine personal radiofrequency electromagnetic field (RF-EMF) exposure. The main advantages of exposimeter measurements are their convenient handling for study participants and the large amount of personal exposure data, which can be obtained for several RF-EMF sources. However, the large proportion of measurements below the detection limit is a challenge for data analysis. With the robust ROS (regression on order statistics) method, summary statistics can be calculated by fitting an assumed distribution to the observed data. We used a preliminary sample of 109 weekly exposimeter measurements from the QUALIFEX study to compare summary statistics computed by robust ROS with a naïve approach, where values below the detection limit were replaced by the value of the detection limit. For the total RF-EMF exposure, differences between the naïve approach and the robust ROS were moderate for the 90th percentile and the arithmetic mean. However, exposure contributions from minor RF-EMF sources were considerably overestimated with the naïve approach. This results in an underestimation of the exposure range in the population, which may bias the evaluation of potential exposure-response associations. We conclude from our analyses that summary statistics of exposimeter data calculated by robust ROS are more reliable and more informative than estimates based on a naïve approach. Nevertheless, estimates of source-specific medians or even lower percentiles depend on the assumed data distribution and should be considered with caution.
authors.affiliation: Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland. roeoesli@ispm.unibe.ch
authors.forename: Martin
authors.initials: M
authors.lastname: Röösli
authors.forename: Patrizia
authors.initials: P
authors.lastname: Frei
authors.forename: Evelyn
authors.initials: E
authors.lastname: Mohler
authors.forename: Charlotte
authors.initials: C
authors.lastname: Braun-Fahrländer
authors.forename: Alfred
authors.initials: A
authors.lastname: Bürgi
authors.forename: Jürg
authors.initials: J
authors.lastname: Fröhlich
authors.forename: Georg
authors.initials: G
authors.lastname: Neubauer
authors.forename: Gaston
authors.initials: G
authors.lastname: Theis
authors.forename: Matthias
authors.initials: M
authors.lastname: Egger
mesh_terms: D000328:Adult; D000465:Algorithms; D001822:Body Burden; D040421:Cell Phone / Q000706:statistics & numerical data*; D003430:Cross-Sectional Studies; D003627:Data Interpretation, Statistical; D004781:Environmental Exposure / Q000032:analysis*; D006801:Humans; D011829:Radiation Dosage; D011834:Radiation Monitoring / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013557:Switzerland / Q000453:epidemiology