In the project described here, exposure arising during tasks involving hand-held spot-welding guns with separate 50 Hz AC power supplies was assessed for the first time with reference not only to results of workplace measurements, but also to calculated current densities in the human body. Current densities were analysed, visualized and finally evaluated in a three-dimensional field simulation in multiple layers of the human body for frequently occurring work situations.
Before persons who have been fitted with active implants can return to their workplaces, it must be determined whether the function of the implants could be disrupted by electric, magnetic or electromagnetic fields in the working environment. For many tasks, this is not considered an issue. It is however critical for work involving manually guided electric tools such as power drills, circular saws, jig saws and manual routers. Observance of a safety distance of up to 40 cm from the tools is therefore recommended in such cases. Experience has shown observance of such a great distance to be unrealistic in practice.
The project was to examine systematically the levels of the fields emitted by manually guided electric tools as a function of the power supply (mains, battery) and the potential influence of these levels upon implants in the human body. A mathematical model was to be used to calculate the disruptive voltages induced on the input of an implant. This model employs a body model in which the arrangement of the tissue structures corresponds to the human anatomy. The objective was to use the results to formulate practical measures for the protection of persons fitted with implants during work involving manually guided electric tools.
In the project concerning electromagnetic fields on manually guided medium-frequency/inverter-based spot-welding machines, the distribution of the magnetic field and the effects of this field were analysed and visualized in a body model on welding tongs of varying electrode interval and geometry. The results were visualized for selected levels of the body (trunk, neck, head), compared with the values in the guidelines of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) for low-frequency magnetic fields, and evaluated.
IFA Project 4211 concerning the assessment of possible interference with cardiac pacemakers and CRTs (devices for cardiac resynchronization therapy) caused by high-frequency electromagnetic fields
The project studied the exposure of persons fitted with cardiac pacemakers or defibrillators in the close field of a high-frequency electromagnetic field (f > 16.9 MHz). The electric voltages induced on the input to the implant were determined for a range of exposure scenarios by field simulation calculations with the use of a digital body model including implant. From this, a procedure was then developed for estimation of the voltage generated on the input to the implant based upon the power density measured in the near field of the antenna. The action limits for the mean power density were included in the analyses in accordance with the German Ordinance on protection of workers against hazards presented by electromagnetic fields (EMFV), Table A3.4.
Interference with cardiac implants caused by electromagnetic fields generated by electronic article surveillance systems
The possible interference with active implants (specifically cardiac pacemakers and implantable cardioverter-defibrillators, ICDs) caused by electronic article surveillance systems used in the retail trade (radio-frequency identification systems, RFIDs) was studied at the request of the German Social Accident Insurance Institution for the trade and distribution industry (BGHW). Several measurements were conducted on site in order to record the workers' exposure. RFID systems with operating frequencies in both the low-frequency and high-frequency ranges were studied. Besides evaluation of the exposure for all workers in accordance with DGUV Regulation 15, the fields arising were evaluated for possible interference for workers fitted with an active cardiac implant.
Division 4: Ergonomics, Physical environmental factorsTel: +4930 13001-3480
Division 4: Ergonomics, Physical environmental factorsTel: +49 30 13001-3481
Division 4: Ergonomics, Physical environmental factorsTel: +49 30 13001-3482