Legionnaires' disease exposure from contaminated water vapour

What is the potential risk?

Workers exposed to water vapour, mist, or sprays containing Legionella bacteria may be at risk of developing Legionnaires’ disease. Legionella bacteria multiply in warm water and may be found in any water system in residential, commercial, or industrial buildings, including:

  • Cooling towers
  • Air conditioners and dehumidifiers
  • Potable water piping and fixtures
  • Swimming pools, hot tubs, and spas
  • Water tanks
  • Decorative water features (fountains, waterfalls, water walls, etc.)

If water containing the bacteria becomes airborne, through vapour, mist, or sprays, it may be inhaled by workers or members of the public.

Legionnaires’ disease cannot be transmitted from human to human. People with the disease have symptoms similar to pneumonia and can be effectively treated with antibiotics.

Scientific literature shows that the incidence of Legionnaires’ disease in North America is increasing. People with decreased immune function or chronic lung problems are at a greater risk of developing Legionnaires’ disease if they are exposed to the bacteria.

Workers at risk of developing Legionnaires’ disease may include those who work in recreational (swimming pool) facilities, in buildings using water tanks or cooling towers, or around water mist or spray systems.

What industries may be at risk?

  • All industries where there is water system maintenance (e.g., potable water piping, ice machines, cooling towers, air conditioners, humidifiers, rainwater reclamation systems, water walls, fountains, etc.)
  • Municipalities (swimming pools, spas, hot tubs, etc.)
  • Construction (water tankers and dust control systems, etc.)
  • Health care (medical and dental irrigation systems, etc.)
  • Agriculture (sprinkler and irrigation systems, etc.)

How can I reduce the risk in my workplace?

As an employer, you need to know if there is the potential for the risk identified in this advisory to be present in your workplace. It’s your responsibility to regularly inspect your workplace, and to ensure that your safety procedures and practices control the risk.

The following information highlights some of the sections of the Occupational Health and Safety (OHS) Regulation and Guidelines that are most relevant to this risk. Section 4.78 of the OHS Regulation requires employers to maintain acceptable air quality. This includes inspecting for conditions that would promote the growth of micro-organisms, such as water leaks or stagnant water pools, and ensuring there is adequate treatment of open-water systems associated with ventilation equipment, such as cooling towers and humidifiers, to control biological growth.

Under section 4.79 of the Regulation, the employer must ensure that the indoor air quality is investigated when complaints are reported. The investigation may include sampling for airborne contaminants (e.g., Legionella) suspected to be present in concentrations associated with the reported complaints.

Section 5.2 requires that if a worker is or may be exposed to a biological agent, which could cause adverse health effects, the employer must prepare and implement written procedures to eliminate or minimize the risk of exposure to the biological agent.

Section 6.34 of the Regulation deals with exposure to biological agents and states that if a worker has or may have occupational exposure, the employer must develop and implement an exposure control plan (ECP), based on the precautionary principle, that meets the requirements of section 5.54.

Where can I find resources?

You can access the following resources:

Publication Date: Mar 2021 Asset type: Risk Advisory Reference: RA 2015-26