Ozone Exposure in the Electricity Industry

Introduction
Ozone is a highly reactive naturally occurring gas that can cause a variety of symptoms including eye, nasal and respiratory tract irritation as well as nausea and headache. Occupational exposure is rare. This case report details an unusual case of ozone exposure in electrical substation workers.

Methods
Employees (5) working in an enclosed electrical substation next to a nuclear power station in the UK were examined following concerns of possible ozone exposure. Medical histories and spirometry were taken. The 2 substations (400 KV and 250KV) on the site which were located by the sea and where symptoms were reported were visited and spot sampling for ozone was undertaken by Dräger tube sampling.

Results
A variety of symptoms were reported by workers including cough, headache, sore throat, nausea and chest tightness. None had asthma and spirometry was normal. Symptoms were not present every day and were noted when a chlorine type smell was prevalent in one of the substations. Symptoms were reported only when working in one of the substations. Dräger sampling showed no evidence of ozone in one substation but readings between 0.1 ppm and 0.4 ppm were found in the 250 KV substation.

Discussion
Our investigation concluded that occupational ozone exposure was the likely cause of worker symptoms. Ozone levels were on occasions likely to be above occupational exposure standards. It was unclear why this was restricted to one of the substations. Improved ventilation was introduced which improved symptoms. Ozone is known to be produced by electrical discharge. Cases of occupational exposure are relatively rare and exposure is not normally seen as a problem for substation workers. The location of the substation building immediately next to the sea could be relevant. Our findings resulted in a detailed survey of ozone exposures in other enclosed electrical substations.