Comparison of statistic methods for censored personal exposure to RF-EMF data
- PDF / 636,277 Bytes
- 11 Pages / 547.087 x 737.008 pts Page_size
- 12 Downloads / 135 Views
Comparison of statistic methods for censored personal exposure to RF-EMF data Alberto Najera & Raquel Ramirez-Vazquez & Enrique Arribas & Jesus Gonzalez-Rubio
Received: 24 May 2019 / Accepted: 9 December 2019 # Springer Nature Switzerland AG 2020
Abstract Several studies have characterized personal exposure to RF-EMF, which allows possible effects on health to be studied. All equipment has a detection limit, below which we obtain nondetects or censored data. This problem is a challenge for researchers as it makes the analysis of such data complex. We suggest reconsidering the statistical protocols of the nondetects analysis by comparing four different methods. Three of them substitute censored data using different approaches: regression on order of statistics (ROS) to simulate data below the detection limit (Method 1), substituting nondetect values by the detection limit divided by 2 (Method 2), a naïve calculation (Method 3) using the detection limit as a valid measurement. The fourth method consists of considering censored data to be missing values (Method 4). This article examines how these methods affect the quantification of personal exposure. We considered data from 14 frequency bands from FM to WiMax measured in Albacete (Spain) for 76 days every 10 s by a personal exposimeter (PEM) Satimo EME Spy 140.
A. Najera : J. Gonzalez-Rubio (*) Faculty of Medicine, University of Castilla-La Mancha, Albacete, Spain e-mail: [email protected] R. Ramirez-Vazquez : E. Arribas Department of Applied Physics, University of Castilla-La Mancha, Albacete, Spain
Methods 3 and 2 gave similar mean and median values to Method 1, but both underestimated the mean values when high nondetects records occurred, which conditioned the physical description of the real situation. The mean values calculated by Method 4 differed from those obtained by Method 1 but were similar when the percentage of nondetects was below 20%. Our comparison suggests that nondetects can be neglected when the percentage of censored data is low to provide a more realistic physical situation. Keywords Exposimeter . Personal exposure . Radiofrequency electromagnetic fields . Detection limit . Censored data
Introduction In the last few decades, several studies that describe and characterize personal exposure to radiofrequency electromagnetic fields (RF-EMF) using portable personal exposimeters (PEMs) have been published generally in Europe; see Sagar et al. (2018) for a review. This relatively small equipment takes measurements at a very high resolution, over long times and in real environments. The most widely previously used equipment is Satimo EME SPY 120 (Satimo, Brest, France), whose accuracy or detection limit (DL) is 0.05 V/m. The latest models 140 and 200 have improved DL that drops to 0.005 V/m (0.06631 μW/m2), with up to 20 frequency bands (model 200) from FM (88 MHz) to WiFi 5G (5.8
77
Page 2 of 11
GHz). Other commonly used exposimeters are the ESM 140 (Maschek Electronik, Bad Wörishofen, Germany), different models from Narda (Narda Safety T
Data Loading...
