Water safety plans can mitigate Legionella risk

Legionella is a serious threat to marine vessels, but an effective water safety plan can help to mitigate the risk, according to John Chillingworth, senior marine principal at Lucion Marine, reports Marine Link, a former chief engineer on Cunard Line’s QE2 liner and a marine technical manager with more than 27 years’ experience in dealing with marine asbestos and hazardous materials.

He noted that the initial symptoms of Legionella usually included flu-like symptoms such as headaches, muscle pain and fever, with symptoms of pneumonia once the bacteria begins to infect the lungs. Although the worst degree of Legionella can cause death, there is also a lesser-known form called Pontiac, which can often be misdiagnosed as flu and which can only be accurately identified with a urine test. The Pontiac strain is like a severe five-day flu for fit people, but it can be worse for older people or those with breathing difficulties.

The disease is not contagious and is usually caught by breathing in small droplets of contaminated water, usually in the shower. It is transmitted by an airborne mist and can develop in still water between 20°C and 50°C. It can also lie dormant in otherwise ‘safe’ water systems for years, protecting itself in other matter available in the water system biofilm.

Chillingworth said that it was therefore important that water supplies be kept below 20°C for cold water and above 50°C for the hot supply.

Although there have been a number of high-profile cases among cruise ship passengers, there have also been cases of shipyard fitters dying from Legionella after stripping down equipment such as pumps and being exposed to contaminated water. All types of ships are at risk, including offshore accommodation vessels, which are known to have had several cases of the disease after being laid up and re-commissioned without the proper attention to potable water safety. Container vessels have large potable storage tanks that are used infrequently, while skin tanks may prevent a ship’s water system from maintaining the cold-water temperature below 25°C.

Chillingworth wrote that, although there was far more awareness today of the risks of onboard Legionella and its effects, there was a perceived lack of knowledge at both vessel management and crew level. There was also a significant corporate risk with the potential damage to reputation, and operator integrity on the line, for anyone whose vessel becomes affected by the disease.

Chillingworth said that this reinforced the need for a thorough Legionella risk assessment to be included as part of a preventative ship repair and maintenance program, with yards alerted to any potential risks before a vessel arrives in dock. “A proper Water Safety Plan (WSP), as recommended by WHO Water Safety Guidelines, should be implemented and based on an individual vessel risk assessment, and not, as is usually the case, a generic set of broad guidelines. This must also be ‘owned’ by the vessel’s management”, wrote Chillingworth

He said that it was also important that the WSP included elements proposed by the WHO Guide to Ship Sanitation. This covers system assessments which describe the water supply system up to the point of consumption and operational monitoring (including identification and monitoring of the control measures applied onboard). Verification and programmes to manage people and processes should also be covered under the management and communication elements.