Summary of HSL report on legionella outbreaks and HSE formal enforcement action over recent years

In September 2011, HSE’s legionella committee requested an analysis of outbreaks over a 10-year period and a review of enforcement data over the last 5 years, to identify any trends and failures to meet the standards described in the Approved Code of Practice L8.

Here are the key findings:

Evaporative cooling systems including cooling towers and evaporative condensers

The total numbers of cases and fatalities related to evaporative cooling systems (ECS) over the 10-year period (229 infections (Of which 193 were Legionnaires’ Disease and 36 were Pontiac fever) and 10 fatalities) may not be large compared with other hazards across GB. However, experience has shown that, when ECS are not properly managed, the resulting outbreaks often affect a considerable number of members of the public due to the range over which plumes of infected aerosols may travel. These events can therefore be categorised as low frequency, high impact, events.

Analysis of previous outbreaks has shown that:

  • 16% were due to poorly managed ECS, but this must be set in the context that, in a significant proportion of outbreaks, the source of the outbreak remained unknown and so the figure is likely to be higher;
  • in those outbreaks where ECS were identified as the source, failures could largely be traced to inadequacies in the risk assessment process and implementation of a suitable scheme of control.

Analyses of formal enforcement data shows that:

  • ECS accounted for 35% of notices, with approximately 70% of these falling within the manufacturing sector;
  • similar failings (risk assessment and control measures) led to formal enforcement action being taken;
  • since May 2006, a total of 11 cases have been successfully prosecuted with the majority of these relating to combined failings in risk assessment and management systems.

Hot and cold water systems (H&CWS)

Reported figures for infections and fatalities arising from hot and cold water systems are not well classified.

Analyses of formal enforcement data reveal that:

  • over 60% of notices served on legionella since January 2007 were as a result of failures to control legionella risks in H&CWS;
  • 93% of these notices were served on premises in the public services sector;
  • the number of prosecutions relating to H&CWS since May 2006 accounted for 43% of the total (14).

Spa Pools

  • Some 14% outbreaks have been traced to poorly managed spa pools, resulting in 29 cases of LD with 3 deaths, as well as 226 cases of Pontiac fever.