Mobile phone use and temporal skin heat sensation

International audienceEpidemiological investigation of mobile phone (MP) users reported symptoms of discomfort feeling, warmth behind/around or on the ear and heat sensation of the cheek. These symptoms may be due to thermal insulation, conduction of the heat produced in the phone by the battery currents and running of the radiofrequency (RF) electronic circuits, and electromagnetic field (EMF) energy absorbed by the user's head. Using a Luxtron 790 fiberoptic thermometer we measured the temperature of the temporal skin due to GSM 1800 MHz MP radiated power (125 mW). We suppressed the EMF exposure by switching the RF signal from the antenna to a 50 O load. The ambient air temperature was 23°C and the MP was held in the normal position of use for 30 minutes to reach the thermal steady state. With a switched off MP, the increase in skin temperature was statistically significant 1.88°C. When MP was switched on, the increase was 2.93°C in reception mode, 3.29°C in emission mode without load and 3.31°C in emission mode with load. The temperature difference with or without load was not significant (tl7 = 0.707; p = 0.489), which means that the contribution of EMF absorption to skin heating is negligible. The result suggests that the heat sensations reported by the MP users are exclusively caused by thermal insulation and heat conduction from MP associated with long calling time

Thermal skin damage and mobile phone use

International audienceMobile phone "cell phone" use has dramatically increased over th last decade, but doubts remain over its safety. Epidemiological investigation of mobile phone (MP) users reported symptoms of discomfort feeling, warmth behind/around or on the ear and heat sensation of the cheek. These symptoms may be due to thermal insulation, conduction of the heat produced in the phone by the battery currents and running of the radiofrequency (RF) electronic circuits, and electromagnetic field (EMF) energy absorbed by the user's head. Using a Luxtron 790 fiberoptic thermometer we measured the temperature of the temporal skin due to GSM 1800 MHz MP radiated power (125 mW). To perform a sham exposure, we suppressed the EMF exposure by switching the RF signal from the antenna to a 50 Ohms load. The ambient air temperature was 23°C, the relative humidity was 50 +- 10 %, the air flow rate in the room was 0.01 m.s-1 (natural convection) and the MP was held in the normal position of use "cheek position" (CENELEC Standard 50361) for 30 minutes to reach the thermal steady state. With a switched off MP, the increase in skin temperature was statistically significant 1.88°C. When MP was switched on, the increase was 2.93°C in reception mode, 3.29°C in emission mode without load and 3.31 °C in emission mode with load. The temperature difference with or without load was not significant (t = 0.707; p = 0.489), which means that the contribution of EMF absorption to skin heating is negligible. The highest temperature increases detected during these experiments (TSkin = 37.1°C ~ core temperature) are in the environmental range and are lower than those physiologically experienced by the surface skin during hot summer days. No skin damage by thermal insuit is experienced for Tskin < 44°C, whereby a pain sensation replaces the feeling of temperature elevation in humans. This local skin temperature increase will cause thermoregulation responses. The skin blood vessels will be dilated and skin will be wet. The result suggests that the heat sensations reported by the MP users are exclusively caused by thermal insulation and heat conduction from MP associated with long calling time. No thermal skin damage can be suspected using MP in normal use

Dosimétrie avec un fantôme en gel de tête humaine

National audienc

Échauffement et champs radiofréquences des téléphones mobiles

L’objectif principal de ce projet était de déterminer si une exposition chronique aux champs radiofréquences (RF) émis par un téléphone mobile (TM) peut constituer un risque pour la santé des utilisateurs. Ceux-ci sont plus de quarante millions en France. Même si, au niveau individuel, les conséquences paraissent aujourd’hui négligeables, au niveau collectif, du fait du grand nombre d’utilisateurs, elles doivent être considérées comme un problème potentiel de santé publique. Le rayonnement radiofréquence émis par les téléphones mobiles numériques (GSM) constitue, par sa proximité avec la tête de l’utilisateur, une des sources de champs électromagnétiques les plus importantes auxquelles l’Homme ait jamais été exposé. L’absorption du rayonnement électromagnétique peut entraîner un échauffement de la peau et des tissus sous-jacents. Le réchauffement local peut modifier la régulation thermique à trois niveaux : - en augmentant le stockage local de chaleur dans l’organisme, - en modifiant la température cérébrale ou la température du sang irriguant le cerveau, - en modifiant les influx nerveux issus des thermorécepteurs cutanés de la tête et ainsi en agissant sur les fonctions de régulation végétative ou sur le confort thermique

Modélisation par un mannequin thermique des échanges de chaleur sèche d'un nouveau-né dans un incubateur fermé (validation et applications biomédicales)

La quantification et la partition des différents types d'échanges de chaleur du nouveau-né permettent de mieux connaître et d'améliorer le contrôle de l'environnement thermique dans l'incubateur afin d'assurer à l'enfant un développement optimal. L'approche actuelle de ces transferts thermiques est purement théorique et repose sur de nombreuses approximations mathématiques et physiques. La conception d'un mannequin thermique ayant les dimensions anthropométriques exactes d'un nourrisson de 1400 g a été réalise e dans le but d'estimer les différents paramètres thermiques caractérisant les équations d'échanges de chaleur dans les incubateurs. Ces paramètres dépendent en effet des formes et courbures des différents segments corporels. L'utilisation du mannequin permet de simuler rapidement, de manière précise et reproductible les échanges de chaleur entre le corps et l'environnement. Il permet aussi d'éviter la variabilité interindividuelle qui est particulièrement importante chez les enfants prématurés ainsi que les contraintes éthiques. Le modèle mannequin a permis de calculer différents paramètres indispensables à la gestion de l'environnement thermique dans les incubateurs en particulier ceux liés aux échanges de chaleur sèche par rayonnement. Ceci a permis d'évaluer la température de rayonnement dont la mesure est complexe et qui n'est actuellement pas prise en compte pour réguler l'ambiance thermique dans les incubateurs malgré l'importance des échanges thermiques radiatifs. Le modèle a également permis de répondre à des préoccupations médicales consistant à vérifier certaines hypothèses sur la Mort Subite Inexpliquée du Nourrisson (MSIN) avec une analyse de l'effet position de couchage dorsale ou ventrale sur les échanges de chaleur. D'autres études ont confirmé l'importance de la tête dans la régulation thermique du nouveau-né et le choix de laisser la tête non couverte afin d'éviter une hyperthermie cérébrale lorsque le nouveau-né est trop habillé. Enfin, une étude a montré que la chaleur sèche perdue par la tête est influencée de manière significative par la position de la face sur le matelas lorsque le nouveau-né trop habillé porte un bonnet. Cet aspect met en évidence l'importance de la régulation thermique comportementale chez l'enfant nouveau-néAssessment and knowledge of the partition of the various heat exchanges by newborn is necessary to improve performances and thermal comfort in incubators. A thermal mannequin representing the real shape of a premature newborn weighting 1400 g has been made. Using the present thermal mannequin is more accurate to assess heat exchanges than existing mathematical or others measurements approaches. The model takes in account the complexity of the different segment which greatly influences the heat exchanges with the environment. The thermal mannequin is the most successful device ye for assessing heat transfer. The model solves the problem of the repeatability and the safety of the measurements near the heat tolerance limits of the newborns. The model assess dry heat loss exchanges in incubator in particularly radiant heat exchange that is a predominate way of heat exchanges making possible the calculation of radiant temperature into incubator that is difficult to do in practice. The thermal mannequin is a good tool to test medical hypothesis about the relation between body position and the risk of thermal stress induced by increased body heat storage and the Sudden Infant Death Syndrome (SIDS). Others results confirm the importance of the head in thermoregulation when the newborn is heavily clothed. Finally, a study show that heat loss from the head is modified significantly by head position when the mannequin heavily clothed has the head covered by a bonnet. The thermoregulatory component is important for newbornsAMIENS-BU Santé (800212102) / SudocSudocFranceF

Influence of neonate's body position with and without a plastic blanket on body heat loss assessed from a thermal mannequin

International audienceThe present study aimed at assessing the net gain of body heat storage induced by a transparent plastic blanket draped over small premature neonates in the prone and the supine positions. Thermal stress is particularly important in premature and small-for-gestational-age infants characterized by high values of the ratio between skin surface area and body mass, the greater this ratio, the greater the body heat exchanges. The large skin permeability enhances body water loss. The risk of hypothermia is particularly increased at birth and during operations on naked neonates implying opening of the canopy (surgical operation, blood sampling and gastric aspiration). In the first day of life, the rate of evaporation can reach 100 g.h-1.m-2 in very preterm infants. To prevent the large amount of water loss it is sometimes recommended to cover the neonate with a plastic blanket. In closed incubator Fanaroff et al.(3) pointed out that a transparent plastic heat shield reduces the insensible water loss of 44 % in low birth weight neonates lower than 1250 g and postnatal age less than 10 days. For postnatal age greater than 10 days, the magnitude of this reduction was only 19 %. Bell et al.(2) also reported that the addition of a heat shield in an incubator decreased the water loss by 10 % in infants with mean birth weight of 1570 g. However the efficiency of this solution which depends on the physical environment but also on the inter individual difference in the ability to exchange heat with the environment remains questionable and the use of a plastic blanket is still a controversial topic. The total heat loss of premature infants depends on various factors such as gestational age, nutritional state, mean skin temperature, body hydromineral balance, vigilance state, metabolic rate and of the postnatal age which modifies the skin keratinisation. Thus, it is difficult to obtain homogeneous data base that takes into account all these factors and there are conflicting data on the effectiveness of plastic blanket. To rule out these confounding factors we use a sweating mannequin the advantage of which is that it measures directly the total heat loss with the environment without interference with these factors

Assessment of whole body and regional evaporative heat loss coefficients in very premature infants using a thermal mannequin : influence of air velocity

International audienceIn human adults, experimental assessment of the evaporative heat loss coefficient (he) requires a fully wetted skin surface area implying exposure to severe heat stress. For ethical reasons, this type of experimental situation is impossible to perform on neonates. The aim of the present study was to assess he values in clinical situations for the body as a whole and for the different body segments, in particular, in natural and forced convection and using an anthropomorphic, sweating, thermal mannequin to represent a very small premature neonate (body mass 900 g). Skin hydration (i.e., simulated sweating) was performed by two electronic pumping systems, providing a steady adjustable flow of water to the mannequin surface. Experiments were carried out in a closed-incubator heated to air temperatures of 33 degrees C and 36 degrees C, with air velocities (V,) ranging from 0.01 to 0.7 m s(-1), and with four levels of air relative humidity (40, 50, 60, and 80%). For the body as a whole, h(e) = 7 W m(-2) mb(-1) in natural convection, whereas in forced convection h(e) was 11.7, 12.4, and 14.1 W m(-2) mb(-1) for air velocities of 0.2, 0.4, and 0.7 m s(-1), respectively. As far as local he is concerned, our results showed that the relative values of regional water loss in forced convection differ greatly from those observed under still air conditions. Thus, increasing air velocity enhances the heterogeneity in regional skin cooling, which may contribute to the neonate's thermal discomfort