A richer conceptualization of ?exposure? for epidemiological studies of the ?EMF mixture?

Neutra, Raymond; Pizzo, V. Del

doi:10.1002/1521-186x(2001)22:5+<::aid-bem1023>3.0.co;2-c

Cited by 6 publications

(3 citation statements)

References 19 publications

(17 reference statements)

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“…The most innovative proposal was to calculate the area under the curve of each of the 31 recordings. The underlying idea was to take into account the intensity of exposure and the time spent at these exposure levels [Neutra and Del Pizzo, 2001]. We also calculated the moving average for 1 h periods to smooth the data and thus attenuate the influence of the extreme values.…”

Section: Metricsmentioning

confidence: 99%

“…The RCM expresses the variability of exposure, while the RCMS reflects its temporal stability. Both are calculated from measurements taken every 15 or 30 s. Despite the absence of knowledge about the possible pathophysiologic and biological mechanisms of magnetic field exposure, numerous research teams are studying its measure with the goal of defining one or several metrics that would better estimate exposure [Sahl et al, 1994;Zhang et al, 1997;Villeuneuve et al, 1998;Ahlbom et al, 2001;Kaune et al, 2001;Neutra and Del Pizzo, 2001;WHO/IARC, 2002].…”

Section: Introductionmentioning

confidence: 99%

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Characterization of exposure to extremely low frequency magnetic fields using multidimensional analysis techniques

Verrier¹,

Souques

Wallet

2005

Bioelectromagnetics

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Our lack of knowledge about the biological mechanisms of 50 Hz magnetic fields makes it hard to improve exposure assessment. To provide better information about these exposure measures, we use multidimensional analysis techniques to examine the relations between different exposure metrics for a group of subjects. We used a combination of a two stage Principal Component Analysis (PCA) followed by an ascending hierarchical classification (AHC) to identify a set of measures that would capture the characteristics of the total exposure. This analysis gives an indication of the aspects of the exposure that are important to capture to get a complete picture of the magnetic field environment. We calculated 44 metrics of exposure measures from 16 exposed EDF employees and 15 control subjects, containing approximately 20,000 recordings of magnetic field measurements, taken every 30 s for 7 days with an EMDEX II dosimeter. These metrics included parameters used routinely or occasionally and some that were new. To eliminate those that expressed the least variability and that were most highly correlated to one another, we began with an initial Principal Component Analysis (PCA). A second PCA of the remaining 12 metrics enabled us to identify from the foreground 82.7% of the variance: the first component (62.0%) was characterized by central tendency metrics, and the second (20.7%) by dispersion characteristics. We were able to use AHC to divide the entire sample (of individuals) into four groups according to the axes that emerged from the PCA. Finally, discriminant analysis tested the discriminant power of the variables in the exposed/control classification as well as those from the AHC classification. The first showed that two subjects had been incorrectly classified, while no classification error was observed in the second. This exploratory study underscores the need to improve exposure measures by using at least two dimensions: intensity and dispersion. It also indicates the usefulness of constructing a typology of magnetic field exposures.

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Section: Metricsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characterization of exposure to extremely low frequency magnetic fields using multidimensional analysis techniques

Verrier¹,

Souques

Wallet

2005

Bioelectromagnetics

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“…Exposure assessment of studies on the health effects of extremely low-frequency (ELF) magnetic fields (MFs) is further complicated by the fact that it is not known as to which exposure metric is the most pertinent for the possible biological effects (Neutra and Delpizzo, 2001). Time-average MF (or alternatively, the product of MF strength and time) has been used in most epidemiological studies.…”

Section: Introductionmentioning

confidence: 99%

Use of short-term measurements for assessing temporal variability of residential ELF magnetic field exposure

Eskelinen

Niiranen

Juutilainen

2003

J Expo Sci Environ Epidemiol

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In this study, we introduced and tested a new approach to characterize residential magnetic field (MF) exposure. Short-term 20-min MF measurements were obtained by a person who carried out instantaneous spot measurements in residences. Compared to spot measurements, the 20-min measurement could potentially improve exposure assessment, because it contains information of temporal variations of MF, which have been suggested as biologically important characteristics of MF exposure. We have used this new exposure assessment method on a study of maternal MF exposure and reproductive outcomes. To validate the new method, the exposure of 30 subjects was measured with a more accurate ''gold standard'' method (24 h personal exposure measurements). The measures of validity used were the Spearman correlation coefficient (r), sensitivity, and specificity. We evaluated the validity of the 20-min measurements for estimating several different exposure metrics for the entire 24 h measurement period or for the hours spent at home: arithmetic mean, median, percentage of time above 0.15 mT, standard deviation, rate of change metric, standardized rate of change metric, constant field metric, and three metrics for the occurrence of high-peak exposures. The 20-min measurement was modestly associated with standard deviation and the rate of change metric, but gave very little information of other metrics of temporal variation. The 20-min measurement can also be used for assessing exposure metrics such as arithmetic mean and median, but it does not seem to offer any advantages compared to traditional 'spot' measurements. The 20-min measurement was not useful for assessing occurrence of high-peak exposures. We conclude that the 20-min measurement is useful for estimating some aspects of MF temporal variability.

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Use of spot measurements for assessing residential ELF magnetic field exposure: A validity study

Eskelinen

Keinänen

Salonen

et al. 2002

Bioelectromagnetics

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The purpose of this study was to evaluate residential short term "spot" measurements as surrogates for long term personal magnetic field (MF) exposure. In an epidemiological study on birth weight and pregnancy delay, MF exposure was assessed by taking five spot measurements in each room. For a subsample of 30 subjects 24 h personal MF measurements were made, and the following exposure metrics were calculated: 24 h arithmetic mean, 24 h median, percentage of time above 0.15 microT, and percentage of time above 0.29 microT. The 24 h exposure metrics were used as gold standards, when evaluating the validity of various summary measures calculated from spot measurements for assessing personal exposure. Based on Spearman correlation coefficient (r), specificity and sensitivity, the average of the spot measurements of a residence resulted in least exposure measurement error (misclassification). Also the above bed spot value correlated better with the 24 h metrics than any room average. Spot measurements performed about equally well in predicting different types of exposure metrics.

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A richer conceptualization of ?exposure? for epidemiological studies of the ?EMF mixture?

Cited by 6 publications

References 19 publications

Characterization of exposure to extremely low frequency magnetic fields using multidimensional analysis techniques

Characterization of exposure to extremely low frequency magnetic fields using multidimensional analysis techniques

Use of short-term measurements for assessing temporal variability of residential ELF magnetic field exposure

Use of spot measurements for assessing residential ELF magnetic field exposure: A validity study

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