A whistleblower who revealed to RTÉ Investigates that up to one million litres of oil had leaked from ESB underground cables over the past 20 years has appeared before an Oireachtas Committee.

Seamus O'Loughlin told members of the Joint Committee on Communications, Climate Action and Environment that he took some succor from the fact that the ESB is now a more compliant and safer utility for its workers.

The Environmental Protection Agency (EPA) began an investigation into the leaks following the RTÉ Investigates programme which revealed the leaks occurred mainly in the Dublin area, including along cable lines close to the Grand and Royal Canals.

However, Mr O'Loughlin said the events have taken "a very heavy toll on his personal and professional life".

He also said it was his understanding that further improvements have happened since he submitted a protected disclosure to the Minister earlier this year.

Mr O'Loughlin, who worked for the company for more than 25 years, made a number of Protected Disclosures to the Department of Communications, Climate Action and Environment.

However, he said it was with "a profound sense of regret that I find myself in front of you today washing the dirty linen of a company that I have worked for all my adult life and that I owe an awful lot to".

Mr O'Loughlin said he remains off on stress related leave.

In a later session, senior executives from the ESB told the committee that the issues highlighted by the programme had been identified as part of their safety and environmental reporting systems and many had already been the subject of internal review, investigation and action.  

Managing Director of ESB Networks Paddy Hayes said the company has invested in an open culture which encourages employees to identify and report any safety issues or potential safety issues.

On the leakage of fluid from ESB underground cables, Mr Hayes said that the current rate of fluid leakage was in line with international comparators, but that he acknowledged that bringing forward these steps would have reduced the historical volumes of fluid used.

Mr Hayes acknowledged that there were a number of areas where they could and should have done more.

Paul Mulvaney, Executive Director, ESB Networks told members that the fluid that leaked was biodegradable and did not enter the canal.