We have previously studied the occurrence of pacemaker EMI from

We have previously studied the occurrence of pacemaker EMI from an electronic article surveillance gate, an induction cook top, and a welding machine [10]. However, there are several other common EMF sources that could potentially interfere with pacemakers.
Mobile phones have been shown to cause interference in older pacemaker models, particularly with unipolar sensing settings, but also with bipolar sensing feature commonly used in modern pacemakers [11–14]. We found no previous data on EMI with pacemakers from mobile phone semagacestat stations. However, because EMFs emitted by base stations are similar to those emitted by mobile phones, they may also be possible sources of EMI in specific situations [15,16]. This may happen for instance if a maintenance worker with a pacemaker installs or maintains base station antennae with his chest close to an active transmitter.
Only one study related to trains and pacemakers was found and it is about possible EMI in a magnetically levitated linear motor car [17]. We found no reports on EMI with pacemakers from EMFs in electric trains. However, our previous measurements indicated that the EMFs in certain sites inside old models of electric commuter trains are rather high, and may pose a danger to pacemaker patients. The areas with the highest magnetic fields were found to be close to the thyristor cabinets in the hallways of the trains. In Finland, electric trains use a 25 kV/50 Hz voltage, and the engines of the trains use electric current varying from 300 A to 600 A, depending on the driving speed. During acceleration the current can reach almost 1000 A [18].
Overhead high voltage transmission lines emit electric and magnetic fields that have been suspected to cause EMI with pacemakers [7,8,19,20].

Materials and methods

Results
The study population consisted of six women and five men. The mean age was 52 years with a range 34–64 years. One of the pacemakers was programmed to AAI(R) mode, two to VVI(R) mode, six to DDD(R) mode, and two to DDI(R) mode [21,22]. The mean time in use of the pacemakers was 2.5 years (range, 0.3–7.0 years). Indication of pacing was sick sinus syndrome in four patients, disturbed atrioventricular conduction in five patients, and atrial fibrillation with bradycardia in two patients.

Discussion
High voltage transmission lines can produce considerably high electric and magnetic fields in the surrounding area and below. These fields are reported as possibly affecting the operation of pacemakers [7,8,19,20]. This can cause problems for any pacemaker patient moving near transmission lines, but especially to workers who maintain the lines. Although we found no EMI between the transmission lines and the pacemakers in this study, high voltage transmission lines still remain a potential source of EMI.
A thorough individual risk assessment is required prior to when a worker can safely return to work after a pacemaker implantation [23]. At most workplaces, such as offices, schools, and shops where EMFs are generally weak, only a general risk assessment is needed. First, the employer has to identify the need for a risk assessment. This involves a survey to determine general details about pacemakers, as well as basic operational methods about the pacemaker of the worker. Also the special instructions concerning EMI that may have been given to the employee need to be determined. Next, the level of the risk assessment must be evaluated. It is important to recognize possible sources of EMI in the workplace. When it is not clear whether or not strong EMFs exist in the work environment, a special risk assessment is to be carried out, including the measurement of EMFs. The findings, and possible actions they require, must be estimated so that the areas the employee needs to avoid can be defined, and his/her working methods can be rearranged. All the findings should be documented for possible further use. The assessment shall be maintained, and updated every time fundamental changes are made at the workplace or to the pacemaker\’s programmable settings.