Michel Plante

Seasonal mercury exposure and oxidant-antioxidant status of James Bay sport fishermen

The effects of a moderate seasonal exposure to methylmercury on plasma low-density lipoprotein (LDL) oxidation and cardiovascular risk indices are not known. The objective of the study was to assess the effects of a seasonal exposure to mercury at similar dose reported to increase cardiovascular risk through fish consumption. Effects on lipoprotein cholesterol and fatty acid profiles, LDL oxidation, and blood oxidant-antioxidant balance were to be assessed in sport fishermen presenting normal blood selenium and omega-3 fatty acid contents. Thirty-one healthy James Bay sport fishermen were assessed for within-subject longitudinal seasonal variations in hair and blood mercury, plasma oxidized LDL, lipophilic antioxidants, homocysteine, blood selenium, and glutathione peroxidase and reductase activities determined before and after the fishing season and compared by matched-pair tests. Hair mercury doubled during the fishing season (2.8+/-0.4 microg/g, P<.0001). Baseline blood selenium, homocysteine, and erythrocyte fatty acid profiles did not change. Plasma high-density lipoprotein cholesterol increased (+5%, P=.05), whereas very low-density lipoprotein cholesterol and oxidized LDL decreased (-8%, P=.05; -18%, P=.008). Blood glutathione peroxidase (+9.7%, P=.001), glutathione reductase (+7.2%, P<.0001), and total glutathione (+45% P<.0001) increased during the fishing season. Plasma total coenzyme Q10 (+13%, P=.02), ubiquinone-10 (+67%, P=.03), and beta-carotene (+46%, P=.01) also increased, whereas vitamin E status was unaffected. Pairwise correlations revealed no association between mercury exposure and any of the biomarkers investigated. In contrast, strong predictors of cardiovascular risk such as high-density lipoprotein cholesterol, oxidized LDL, and glutathione peroxidase improved during the fishing season despite elevated methylmercury exposure. The beneficial effects of seasonal fishing activity and fish consumption on cardiovascular health may suppress detrimental effects of concomitant moderate methylmercury exposure.

Human perception of electric fields and ion currents associated with high-voltage DC transmission lines

The objective of this study was to assess the ability of humans to detect the presence of DC electric field and ion currents. An exposure chamber simulating conditions present in the vicinity of high-voltage DC (HVDC) lines was designed and built for this purpose. In these experiments, the facility was used to expose observers to DC electric fields up to 50 kV/m and ion current densities up to 120 nA/m2. Forty-eight volunteers (25 women and 23 men) between the ages of 18 and 57 years served as observers. Perception of DC fields was examined by using two psychophysical methods: an adaptive staircase procedure and a rating method derived from signal-detection theory. Subjects completed three different series of observations by using each of these methods; one was conducted without ion currents, and the other two involved various combinations of electric fields and ion currents. Overall, subjects were significantly more likely to detect DC fields as the intensity increased. Observers were able to detect the presence of DC fields alone, but only at high intensities; the average threshold was 45 kV/m. Except in the most sensitive individuals, ion current densities up to 60 nA/m2 did not significantly facilitate the detection of DC fields. However, higher ion current densities were associated with a substantial lowering of sensory thresholds in a large majority of observers. Data analysis also revealed large variations in perceptual thresholds among observers. Normative data indicating DC field and ion current intensities that can be detected by 50% of all observers are provided. In addition, for the most sensitive observers, several other detection proportions were derived from the distribution of individual detection capabilities. These data can form the basis for environmental guidelines relating to the design of HVDC lines.

Evaluation of a Questionnaire-Based Method for the Estimation of Methylmercury Exposure of Recreational Anglers in the James Bay Territory (Québec, Canada)

The impoundment of reservoirs temporarily increases the methylation of mercury bound to flooded soils and vegetation and the transfer of methylmercury (MeHg) to fish. MeHg levels in various fish species of hydroelectric reservoirs located in the James Bay territory increased by factors of 3 to 7, then gradually declined toward initial concentrations 10 to 20 years after flooding, depending on reservoir characteristics. The potential risk of increased MeHg exposure for recreational anglers who consume fish from these reservoirs had not been assessed previously. A less invasive method than systematic measurement of Hg levels in hair was developed to determine MeHg exposure of recreational anglers. A fish consumption questionnaire-based approach was combined with a toxicokinetic model to estimate the corresponding hair MeHg concentrations. The results were compared with actual analytical determinations of hair Hg levels for the 94 recreational anglers recruited for the study. The values predicted by the model based on self-reporting consumption overestimated actual hair Hg levels by an average factor greater than 6. The mean hair level predicted for the most recent period (September-October) was 23.3 µg.g−1 compared to 3.6  µg.g−1 for the measured value. Although the questionnaire protocol may certainly be improved to increase the precision of estimations, direct hair Hg measurement remains the more effective means to assess Hg exposure.

Smart meters and routers radiofrequency disturbances study with pacemakers and implantable cardiac defibrillators.

There is no scientific literature that examines radiofrequency (RF) interference from Smart Meters with cardiac implantable electronic devices (CIEDs). The objective of this in vitro study was to assess any potential interference with Medtronic CIEDs (Medtronic Inc., Minneapolis, MN, USA).

Magnetophospenes in humans exposed to ELF MF up to 50 mT, a threshold study

Although magnetophosphene perception is the most reliable reported effect on acute human neurophysiological responses to extremely low frequency (ELF) magnetic field (MF) exposure, current knowledge is based on small sample size, non-replicated experiments. In this study, we established MF levels triggering magnetophosphenes at 20, 50, 60 and 100 Hz in humans. Magnetophosphene perception and EEG were collected in 55 magnetic flux density conditions randomly delivered in each frequency group (2 experiments, total n=145). Results indicate that threshold values 1) need to be reported as a function of dB/dt instead of flux density, and 2) are frequency-dependent (higher sensitivity to lower frequencies). No clear trend was found in EEG data.

Impact of electromagnetic fields on human vestibular system and standing balance: pilot results and future developments

Although studies have found that extremely low-frequency (ELF, < 300 Hz) magnetic fields (MF) can modulate human standing balance, the acute effects of electromagnetic fields on standing balance have not been systematically investigated. This work aims to establish the threshold for acute standing balance modulation during ELFMF exposure. One hundred volunteers will be exposed to transcranial electric stimulations (Direct Current - DC and Alternating Current - AC, 1 mA) and ELFMF (0 to 160 Hz, 0 to 100 mT). The displacement of their center of pressure will be collected and analyzed as an indicator of vestibular performance. During pilot testing (n=6), we found increased lateral sway with DC, and to a lesser extent, AC exposure. The ELFMF exposure system still needs to be adapted to allow meaningful results. Future protocol design will test for possible effects due to exposures in the radiofrequency range (i.e. above 3 kHz). These results will contribute to the literature documenting exposure guidelines aiming to protect workers and the general public.

Impact of electromagnetic fields on human vestibular system and standing balance: Pilot results and future developments

Although a few studies have found that extremely low-frequency (ELF, <; 300 Hz) magnetic fields (MF) can modulate human standing balance, the acute effects of electromagnetic fields (EMF) on standing balance have not been systematically investigated. This work aims to establish the threshold for standing balance modulation during ELF MF exposure. One hundred volunteers will be exposed to an ELF MF (0 to 160 Hz, 0 to 100 mT) and stimulated using transcranial electric stimulation (DC and AC, 1 mA). The displacement of their center of pressure will be collected and analyzed using validated sway characteristics to detect modulations of vestibular function. Future protocols will be designed to test for possible effects due to exposures in the radiofrequency range (i.e. above 3 kHz). These results will contribute to the literature documenting exposure guidelines aiming to protect workers and the general public.

Champs électriques et magnétiques de très basse fréquence : il est temps d’être raisonnable

« Le hasard ne favorise que les esprits prepares ». Louis PasteurL’amiante, l’encephalite spongiforme bovine,le diethylstilbestrol chez les femmes enceintes,l’hormone de croissance humaine : autant de crises de sante publique qui ont contribue a l’emergence du principe de precaution. A cette liste faut-ilajouter les champs electriques et magnetiques (CEM)produits par le courant electrique de frequence 50-60 Hz ?Lespremieres interrogations datent des annees soixante [...]