U.K. linesmen's experience of microshocks on HV overhead lines

Possible Influences of Spark Discharges on Cardiac Pacemakers

Exposure to spark discharges may occur beneath high voltage transmission lines when contact is initiated with a conductive object (such as a motor vehicle) with the spark discharge mediated by the ambient electric field from the line. The objective of this study was to assess whether such exposures could interfere with the normal functioning of implanted cardiac pacemakers (PMs). The experiment consisted of PMs implanted in a human-sized phantom and then exposed to spark discharge through an upper extremity. A circuit was designed that produced spark discharges between two spherical electrodes fed to the phantom's left hand. The circuit was set to deliver a single discharge per half cycle (every 10 ms) about 10 μs in duration with a peak current of 1.2-1.3 A, thus simulating conditions under a 400-kV power line operating at 50 Hz. Of 29 PMs acquired, all were tested in unipolar configuration and 20 in bipolar configuration with exposure consisting of 2 min of continuous exposure (one unit was exposed for 1 min). No interference was observed in bipolar configuration. One unit in unipolar configuration incorrectly identified ventricular extra systoles (more than 400 beats min(-1)) for 2 s. The use of unipolar configuration in new implants is extremely rare, thus further minimizing the risk of interference with the passage of time. Replication of this study and, if safety for human subjects can be assured, future testing of human subjects is also advisable.

New electric-shock job exposure matrix

BACKGROUND

To evaluate a consistent association between jobs in "electric" occupations and amyotrophic lateral sclerosis (ALS), a comprehensive job exposure matrix (JEM) that includes electric shocks and magnetic fields (MF) is needed.

METHODS

We used incident electric shocks and electrocutions from two available data sources along with expert judgment to create a JEM that was integrated into an existing MF JEM. The final JEM contained ordinal electric-shock exposure assignments for 501 job titles.

RESULTS

Main occupational groups experiencing the electric shocks were precision production, craft, and repair occupations. Specific jobs with the highest proportion of shocks per 100,000 workers were: electrical apprentices (99.7), mechanic and repairer helpers (74.0), hoist and winch operators (63.3), and electrical power installers (52.4). Examples of job titles with low electric-shock exposures were administrative support occupations, data-key entry operators, and waiters and waitresses.

CONCLUSIONS

Combining publicly available data with an expert panel is a viable method to construct an electric-shock MF JEM. This JEM will allow an evaluation of association between electric shocks and neurodegenerative diseases.