1. WHAT IS LEGIONELLA (WHERE DOES THE BACTERIA COME FROM)?
Legionella bacteria occur naturally in moist environments, colonizing in artificial or natural reservoirs of fresh water and moist soils.
2. WHAT IS LEGIONNAIRES’ DISEASE, OR LEGIONELLOSIS?
It is an infection caused by Legionella pneumophila bacteria, which is a serious form of pneumonia (lung infection). In 15-20% of cases, the infection is fatal.
3. WHAT IS PONTIAC FEVER?
It is a non-pulmonary infection like the flu, caused by Legionella bacteria. The infection usually clears up quickly. Approximately 95% of exposed individuals will develop this infection.
4. HOW IS THE INFECTION TRANSMITTED?
The infection comes from inhaling contaminated aerosols (microdroplets). Contamination sources are facilities that favor the growth of bacteria, which is spread in the environment through mist formed.
5. CAN IT BE CONTAGIOUS?
No, it is not contagious.
6. WHO IS MOST AT RISK?
Mainly those with a weak immune system (e.g., elderly, immunosuppressed transplant patients, etc.). Smokers and alcoholics are also at a higher risk.
7. WHY ARE COOLING TOWERS FAVOURABLE PLACES FOR THE GROWTH OF LEGIONELLA?
The temperature of the water in cooling towers is ideal for the growth of Legionella. Moreover, the water often contains nutrients (scaling, corrosion, organic matter) and provides shelter (mud, dirt and amoebae). Water droplets can travel up to one mile from the airflow and lead to infection over a wide area.
8. WHY DOES ONE TOWER BECOME INFECTED AND NOT ANOTHER? WHAT ARE THE CONTRIBUTING FACTORS?
Corrosion, scaling, fouling and the presence of silt are aggravating factors, providing nutrients and ideal locations for the development of Legionella bacteria. A facility that allows stagnant water is another contributing factor.
9. ARE SOME TOWER DESIGNS MORE SUSCEPTIBLE TO BACTERIA GROWTH THAN OTHERS?
In theory, no. However, a tower with a basin that drains poorly, or with stagnant areas, can cause an accumulation of mud, which worsens the problem.
10. HOW DO THE BACTERIA TRAVEL FROM COOLING TOWERS TO THE PEOPLE?
The bacteria are carried by the wind. Water droplets can travel several miles and become the source of infection over a large area.
11. HOW DO THE BACTERIA GET INTO THE COOLING TOWER?
Usually via potable water systems.
12. WHY DOES THE TREATMENT OF DRINKING WATER NOT ELIMINATE THE BACTERIA?
Legionella bacteria is not particularly strong but the amoeba (a larger microorganism) present in drinking water is highly resistant to regular disinfection methods. The amoeba becomes a “Trojan horse,” harboring the parasite bacteria.
13. CAN A TOWER CONTAMINATE ANOTHER TOWER THROUGH THE AIR?
There is a possibility of seeding, as the water is sprayed out and can reach another tower. However, the bacteria will only multiply to a critical level if the conditions are favorable in the seeded tower.
14. ARE THERE OTHER SYSTEMS THAT CAN INFECT PEOPLE WITH THIS BACTERIA?
Decorative fountains, spas, humidifiers and air washers, dental equipment, foggers, domestic hot water (showerheads) and metalworking equipment (cutting oils) are all possible vectors of infection.
15. DOES THE ADDITION OF BIOCIDES TO COOLING TOWERS ENSURE THE ABSENCE OF LEGIONELLA?
No, biocides do not guarantee the absence of the bacteria, which can withstand certain conditions and may also be protected by the environment (deposits, biofilm, amoeba).
16. IS THERE ANY SPECIFIC BIOCIDE FOR LEGIONELLA?
Halogens such as bromine, chlorine and chlorine dioxide are all effective with the proper dosage. Among the non-oxidizing biocides, many of which are tested for Legionella, are isothiazolin, DBNPA, and glutaraldehyde. Again, proper dosage is required.
17. AT WHAT CONCENTRATION DOES THE PRESENCE OF LEGIONELLA PNEUMOPHILA BECOME DANGEROUS?
A concentration above 100 pneumophila bacteria per milliliter has been shown to be hazardous to human health.
18. IN CANADA, IS THERE A MAXIMUM STANDARD IN TERMS OF LEGIONELLA PNEUMOPHILA POPULATION IN WATER?
There are two levels of intervention:
Over 10,000 CFU/L (colony forming units per liter of water), corrective measures must be made to the maintenance program.
At 1,000,000 CFU/L, an emergency disinfection must be carried out and the maintenance program must be corrected and re-certified.
19. IS A BACTERIA ANALYSIS BY CULTURE ON A STICK AN ADEQUATE LEGIONELLA CONTROL MEASUREMENT?
No, there is no correlation between the total population of bacteria and the presence of Legionella pneumophila.
20. IS THE ATP ANALYSIS AN ADEQUATE LEGIONELLA CONTROL MEASUREMENT?
No, there is no correlation between ATP and pathogenic bacteria in cooling towers.
21. WHAT DOES DISINFECTING COOLING TOWERS INVOLVE?
Disinfection normally involves using an oxidizing biocide, a biodispersant and mechanical cleaning. The steps are usually:
Disinfect with an oxidant
Physically empty and clean the tower
Do another test 48 hours later
22. WHAT ARE THE BEST PRODUCTS FOR DISINFECTION?
Bromine gel, primarily, along with other halogen-based biocides. Biodispersants play an integral part in removing biofilms.
23. WHY IS DISINFECTING WITH CHLORINE NOT AS EFFECTIVE AS BROMINE?
Bromine is a better disinfectant than chlorine if the pH is alkaline, which typically occurs in cooling towers.
24. IS IT POSSIBLE THAT EVEN AFTER DISINFECTION, THE BACTERIA ARE STILL PRESENT?
Yes. There may be areas that are still contaminated with bacteria, especially in dead leg areas.
25. CAN A CLIENT BE PRESENT DURING THE DISINFECTION OF A TOWER?
Yes, they can be present if they take the proper safety precautions, which means wearing an appropriate mask and personal protective equipment.
26. HOW CAN WE ELIMINATE THE RISK ASSOCIATED WITH LEGIONELLA?
We cannot eliminate the risk, but rather minimize it by applying best practices.
27. HOW CAN WE REDUCE THE RISK?
Risk management is based on good maintenance practices, including a water treatment program and effective performance assessments. A quick, reliable sampling and detection program must be in place to ensure an effective response to contamination. With modern analytical technologies, such as DNA detection, results are available within 48 hours after collection.
28. WHAT DO RISK MINIMIZATION PACKAGES FROM MAGNUS INCLUDE?
Packages include a range of services for the detection and minimization of Legionella such as:
Water analysis by culture
Monitoring Legionella levels in water by DNA analysis
Monitoring Legionella levels in biofilm by DNA analysis
Inspections and audits of optimization systems
Preventive maintenance programs for chemical equipment and mechanical treatment
Disinfection during start-up
Monitoring of microbiological indicators
29. ARE THERE ANY GUIDES THAT EXPLAIN BEST PRACTICES? WHO PUBLISHES THEM?
Explanatory guides are published by the RBQ, ASHRAE, CTI and AWT. AWT provides guidelines on bacterial populations, so it is a more complete reference. Certain European guides are also very detailed: HSE (Health & Safety Executive), ACOP 18 (Approved Code of Practice and Guidance), EWGLINET (European Legionnaires Disease Surveillance Network), and EWGLI (European Working Group for Legionella Infections).
30. DO OTHER JURISDICTIONS HAVE LEGISLATION ON THIS SUBJECT?
The City of Hamilton in Ontario maintains a register that records everything related to Legionella. Several European countries and Australia have legislation in place.
31. WHAT ANALYTICAL TECHNIQUES ARE AVAILABLE FOR LEGIONELLA PNEUMOPHILA?
The methods used are culture analysis and DNA analysis.
32. WHAT IS THE DIFFERENCE BETWEEN DNA DETECTION AND CULTURE DETECTION?
DNA detection is based on the detection and quantification of the DNA of the bacteria. This technique allows for quick, accurate measurement of the bacterial population (less than 48 hours), while it takes about 14 days to get the results of detection by culture. This method is more specific and identifies the complete profile of the bacteria, but it only detects culturable bacteria.
33. IS IT POSSIBLE TO IDENTIFY THE COOLING TOWER RESPONSIBLE FOR AN INFECTION?
Yes, if we compare the complete profiles of the bacteria collected from patients with those in the cooling tower.
34. THE RESULTS OBTAINED BY DNA DETECTION ARE EXPRESSED IN GU. WHAT DOES GU MEAN?
GU stands for “genomic unit.”
35. DOES THE PCR UNIT CORRESPOND TO THE UFC UNIT?
Statistically, there is no direct correspondence. They are similar but not equal.
36. SOME COMPANIES OFFER A SITE TEST WITH IMMEDIATE RESULTS. IS THIS EFFECTIVE?
No. In general, the detection thresholds are too high for water from a cooling tower (100 CFU/mL), which makes these tests qualitative only.
37. DOES EVERY WATER TREATMENT COMPANY OFFER A DETECTION PROGRAM?
No. Few companies offer the service, and even fewer do it using their own resources.
La Régie du bâtiment du Québec