Legionella and Legionnaire s Disease Basics for Long-Term Care Facilities

Transcription

1 Legionella and Legionnaire s Disease Basics for Long-Term Care Facilities John H Murphy BSc MHSc MBA PhD(C) ROH CIH Resource Environmental Associates Limited 11 Allstate Parkway, Suite 110, Markham, ON L3R 9T8 1

2 Agenda 1. Natural Ecology, Diseases, and Building System Colonization 2. Risk Factors for Colonization and Illness 3. Risk Assessment: What to Measure, and What Not to Measure 4. Relevant Workplace Guidelines / Regulations 5. Water System Bacterial Remediation Methods 6. Water System Bacterial Prophylatic Methods 2

3 1. Natural Ecology, Diseases and Building System Colonization 1.1 Natural Ecology of Legionella 1.2 Diseases 1.3 Mechanisms of Human Exposure to Legionella 1.4 Perspective on Legionella: 1976 to Mid-2000s 3

4 1.1 Natural Ecology of Legionella gram-negative, aerobic, rod-shaped bacterium, common in natural aquatic environments (lakes, streams, ponds) and damp soil over 50 species, 70 serotypes (serotype = sub-species having a distinguishing type of blood agglutinating protein) temperature range for survival: F optimal temperature range for proliferation: F (typical DHW temperature range for rooms in hospitals, long-term care centres, many hotels) Legionella micrograph 4

5 1.1 Natural Ecology of Legionella Parasite of amoebae and paramecium (Legionella hard to kill because of protection afforded by host organisms) Lives as part of an ecosystem with other microbes in fresh water It is likely that Legionella requires the nutrient conditions inside of a host cell in order to reproduce itself Legionella may only be free swimming ( planktonic ) outside the host an interim stage between host rupture and invasion of a new host Legionella micrograph 5

6 Suspected Life Cycle of Legionella 2007 Resource Environmental Associates Limited 6

7 1.2 Diseases Legionellosis is an infectious disease caused by bacteria belonging to the genus Legionella. Over 90% of legionellosis cases are caused by Legionella pneumophila Legionellosis is clinically expressed in two forms: Legionnaires' Disease Pontiac fever 7

8 1.2.1 Legionnaires' Disease Disease etiology: bacteria enters mouth or sinus passages inhaled or aspirated into bronchioles bacteria amplify Symptoms: Early flu-like symptoms: slight fever, headache, aching joints and muscles, lack of energy, tiredness, loss of appetite Common pneumonia-like symptoms: high fever (102 F to 105 F, or 39 C to 41 C), cough (dry at first, later producing phlegm), difficulty in breathing or shortness of breath, chills, chest pains 8

9 1.2.1 Legionnaires' Disease Diagnosis: diagnosis of pneumonia + appearance of chest X-ray + positive Legionella antibody results thought to be often mis-diagnosed because symptoms are indistinguishable from other pneumonias (est cases annually in Canada) Prognosis: 15% mortality rate (similar to other types of pneumonia) Treatment: Macrolide or fluoroquinolone antibiotics 9

10 1.2.2 Pontiac Fever Essentially a very mild form of Legionnaires' disease that is self-remedying in 3 to 5 days after onset of symptoms 10

11 1.2.3 Disease Comparison Characteristic Legionnaires disease Pontiac fever Incubation period 2-10 days, rarely up to 20 days 5 hrs-3 days (most commonly hrs) Duration Weeks 2-5 days Case-fatality rate Variable, can reach 40-80% in hospital patients No deaths Attack rate 0.1-5% of the general population % in hospitals Up to 95% Source: World Health Organization (WHO) (2007). Legionella and the prevention of legionellosis. Geneva, WHO. 11

12 1.2.3 Disease Comparison Characteristic Legionnaires disease Pontiac fever Symptoms Often non-specific Loss of strength High fever Headache Blood-streaked sputum Non-productive, dry cough Chills Muscle pain Difficulty in breathing, chest pain Diarrhoea (25-50% of cases) Vomiting, nausea (10-30% of cases) CNS effects such as confusion and delirium (50% of cases) Renal failure Influenza-like illness (moderate to severe) Loss of strength High fever and chills Muscle pain Headache Joint pain Diarrhoea Nausea, vomiting (in a small proportion of cases) Difficult breathing and dry cough Source: World Health Organization (WHO) (2007). Legionella and the prevention of legionellosis. Geneva, WHO. 12

13 1.3 Mechanisms of Human Exposure to Legionella Commonly found in treated municipal water supplies (resistant to chlorine and bromine at levels used in municipal water treatment), and private well systems Commonly found in domestic and cooling / process water systems -- especially biofilm and scale, but can also be isolated from bulk water 13

14 1.3.1 What is a Biofilm? Biofilm is a slimy film lining the inside walls of water pipes, that consists of an agglomeration of living and dead microorganisms. Biofilms are often adhered to mineral scales comprised mostly of precipitated calcium, magnesium and iron oxides, that line the inside walls of water pipes. Scale formation is more common where the water is hard (i.e. has high concentrations of calcium, magnesium and / or iron). Commensurate microorganisms for Legionella include algae, Flavobacteria, and Pseudomonas, which supply essential nutrients for growth of Legionella, and hosts such as amoebae and protozoa. 14

15 1.3.1 What is a Biofilm? 15

16 1.3.2 Legionella in Building Water Systems Where present in municipal water supplies and/or private well systems, some Legionella will enter the domestic water lines of every building served by the system Once in the building s main domestic water feed, the fate of Legionella is determined by the characteristics of the individual systems to which the water is distributed 16

17 Typical Three-Temperature Water System (Hospitals, Hotels, Long-Term Care Facilities) DOM HOT (> 50 C) DOM WARM (< 50 C) DOM COLD (< 20 C) Portable Mist- Emitting Devices Stationary Mist-Emitting Devices MUNICIPAL WATER OUTDOORS INDOORS Process Water Mist-Emitting Devices 17

18 Fate of Legionella in the Domestic Hot Water System DOM HOT (> 50 C) The DHW system typically supplies kitchens, laundries, and tub rooms in hospitals, LTC facilities, and hotels > 50 C suppresses and kills Legionella MUNICIPAL WATER Legionella should not be present in significant concentrations in the DHW tank nor the supply lines to faucets so long as the delivery temp. is at least 50 C Legionella may colonize biofilm in the recirculation lines if temps. are <50 C (which is typical) 18

19 Fate of Legionella in the Domestic Warm Water System DOM WARM (< 50 C) The DWW system typically supplies patient / resident rooms, and public washrooms in hospitals, LTC facilities, and hotels MUNICIPAL WATER 35 C to 45 C is the ideal temperature range for Legionella proliferation If other habitat factors are present, there is potential for Legionella colonization of the DWW system (tank, supply lines, recirculation lines) 19

20 Fate of Legionella in the Domestic Cold Water System DOM COLD (< 20 C) The DCW system typically supplies all potable and utility faucets (e.g. outdoor faucets, dishwashers, washing machines, janitor s sinks, etc.) Typically no recirculation MUNICIPAL WATER Legionella is dormant < 20 C Colonization of the cold system is not likely to occur unless there are dead legs or other stagnant areas with more moderate temperatures 20

21 Fate of Legionella in the Domestic Cold Water System with Dead Legs or Stagnant Zones Rarely used faucet MUNICIPAL WATER Stagnant line DOM COLD (< 20 C) A dead leg is a section of pipe that has no flow due to it being capped off at the terminus Water temperatures in dead legs and stagnant lines can be at room temperature or higher (e.g. if beside a DHW line or air duct) Dead leg Former faucet location Colonization can occur in dead legs and stagnant lines 21

22 Legionella in Portable Mist-Emitting Devices Portable Mist- Emitting Devices WATER (> 20 C) The temperature of water in portable mist-emitting devices (e.g. humidifiers) will be room temperature or higher If fed with cold water, the initial Legionella concentration should be low MUNICIPAL WATER DOM COLD (< 20 C) The concern with these devices is the potential for biofilm formation from constant use and inadequate cleaning, Legionella proliferation in the biofilm, followed by emission in mists 22

23 Legionella in Stationary Mist-Emitting Devices DOM COLD (< 20 C) MUNICIPAL WATER WATER (> 20 C) Stationary Mist-Emitting Devices The temperature of water in stationary mist-emitting devices (e.g. ventilation system mist humidifiers) will be room temperature or higher If fed with cold water, the initial Legionella concentration should be low The concern is the potential for biofilm formation in lines and drip pans from inadequate cleaning, Legionella proliferation in the biofilm, and mist emission 23

24 Legionella in Process Water Mist-Emitting Devices Cooling towers are the most common process water mistemitting devices The water temperatures in these systems are usually optimal for Legionella proliferation MUNICIPAL WATER Process Water Mist-Emitting Devices These systems are also prone to scale and sediment build-up, which promotes biofilm formation Proper programs of cleaning, disinfection and testing are essential to control Legionella 24

25 1.3.2 Legionella in Building Water Systems Examples of reservoirs for Legionella bacteria in buildings: Process water systems and equipment: cooling towers and associated lines and chiller evaporative condensers heating, ventilation and air conditioning equipment components (humidifiers, drip pans, wet insulation) Domestic water systems and equipment: potable water lines water storage tanks portable humidifiers 25

26 1.3.2 Legionella in Building Water Systems cooling towers and associated lines and chiller Photo source: Baltimore Air Coil web site Photo source: Photo source: 26

27 1.3.2 Legionella in Building Water Systems evaporative condensers Photo source: 27

28 1.3.2 Legionella in Building Water Systems commercial heating, ventilation and air conditioning equipment components UNHYGIENIC CONDENSATE DRIP PANS COMMERCIAL HVAC EVAPORATIVE HUMIDIFIERS Photo source: Ace Industrial Air Treatment web site Photo source: 28

29 1.3.2 Legionella in Building Water Systems Domestic humidification devices TYPICAL COOL MIST PORTABLE HUMIDIFIER RESIDENTIAL FURNACE PAD HUMIDIFIER 29

30 1.3.2 Legionella in Building Water Systems potable water lines INDOOR DOMESTIC PIPING OLD MUNICIPAL WATER SUPPLY LINE 30

31 1.3.2 Legionella in Building Water Systems water storage tanks 31

32 1.3.2 Legionella in Building Water Systems Some of these Reservoirs can release Legionella contaminated water on an ongoing basis, e.g. mist emitting cooling / condensing towers evaporative humidifiers drip pans heavily colonized domestic water systems Implications for occurrence of bacterial exposure and illness: some exposure, no cases some exposure, some cases 32

33 1.3.2 Legionella in Building Water Systems Heavily colonized domestic water systems are believed to have potential for more significant Legionella releases on a timelimited basis (yet be non-problematic most of the time). Legionnaires disease outbreaks are very often correlated with construction and renovation projects. It is suspected that these types of activities cause significant de-scaling and biofilm liberation from domestic water systems, which in turn leads to Legionella exposure and illness. 33

34 Scenario: Stagnant Water Dispersal Following System Shut-Down Stagnant water 2007 Resource Environmental Associates Limited 34

35 Scenario: Biofilm Disturbance in Domestic Water System Biofilm Microbial contents released into water flow 35

36 So don t forget to flush! These scenarios illustrate why it is important to thoroughly flush domestic water systems following repairs and shut-downs; and it may be prudent to flush domestic systems on a regular basis over the course of prolonged construction or renovation projects. Plumbing system shut-downs, construction and maintenance and activities are commonly associated with discolouration, rust or sediments in the domestic water, and it would be prudent to assume that when these conditions appear, biofilm dispersal may also have occurred. 36

37 1.3.2 Legionella in Building Water Systems EXTERIOR / ADJACENT TO BUILDING: WORK ON WATER SUPPLY SYSTEMS RESULTING IN ENTRY OF SOILS INTO SYSTEM Seeding INSIDE OF BUILDING: DOMESTIC WATER SYSTEM (PIPING, WATER TANKS, FAUCETS, DRAINS) Seeding OUTSIDE OF BUILDING: WATER SUPPLY Seeding INSIDE OF BUILDING COOLING TOWERS, EVAPORATIVE CONDENSERS, CONDENSING TOWERS Bioamplification, discharge of mists to air, discharge during maintenance Bioamplification and liberation of scale and biofilm containing Legionella (maintenance, pressure shock, stagnation) Drinking, Washing Mists Aspiration Inhalation Lungs Mists Ingestion to Mouth Other organs 37

38 Types of Water Systems Where Legionella Has Been Found cooling towers condensing towers evaporative condensers fluid coolers that use water evaporation to reject heat domestic hot-water systems with water heaters that operate below 60 C (140 F) and deliver water to taps below 50 C (122 F) poorly maintained humidifiers and decorative fountains that create a water spray and use water at temperatures favorable to growth spas and whirlpools with aeration dental water lines, which are frequently maintained at temperature above 20 C (68 F) and sometimes as warm as 37 C (98.6 F) for patient comfort stagnant water in fire sprinkler systems warm water for eye washes or safety showers 38

39 1.4 Perspective on Legionella: 1976 to Present 1977: Legionella pneumophila first identified at an American Legion convention in Philadelphia in 1976, causing 34 deaths out of 182 patients Late 1970s: first nosocomial legionellosis cases identified Early 1980s: introduction of urinary antigen testing over traditional culture / direct fluorescence assay (DFA) detection methods led to earlier recognition of LD outbreaks 1990s: macrolide and fluoroquinolone antibiotics prescribed more for treatment of pneumonia (more effective than traditional betalactam types), leading to a decline in LD-related deaths 2000s: series of regulations / guidance documents established worldwide in response to global outbreaks 39

40 1.4.1 Notable Outbreaks Legionnaires Disease OUTBREAK DATE LD CASES DEATHS CASE- FATALITY RATE SUSPECTED SOURCE OF OUTBREAK American Legion Convention, Philadelphia, USA Flower exhibition, Bovenkarspel, Netherlands Melbourne Aquarium, Melbourne, Australia % % % Unknown (cooling tower suspect); L. pneumophila first identified Whirlpool spa at adjoining consumer product fair Start-up of new cooling tower Murcia, Spain % Barrow-in-Furness, UK % Seven Oaks LTC Home, Toronto, Canada % Cooling tower at local hospital, largest LD outbreak on record AC unit at local arts centre, worst outbreak in UK history Rooftop cooling tower (?), domestic water system (?) 40

41 1.4.2 WHO: Mortality Rates and Survival 19% of cases died in the LD outbreak in Philadelphia (1976) Subsequently, average mortality confirmed to be 15-20% for hospitalized cases In 1997, the CDC reported a US case-fatality rate of 40% in nosocomial cases, compared to 20% among people with community-acquired legionellosis More recently, data from the US and Australia indicated casefatality rates of 14% for nosocomial and 5-10% for communityacquired infections In Europe, the overall case-fatality rate is about 12% Source: World Health Organization (WHO) (2007). Legionella and the prevention of legionellosis. Geneva, WHO. 41

42 1.4.3 Canada The results of a 2003 multicentre Canadian study on LD revealed mortality rates of 10-25% for community-acquired Legionella infection requiring hospitalization A seasonal predominance of cases 40% for L. pneumophila serogroup 1 (LP1) infection was noted during the months of July to September Only 2.1% of patients were infected with LP1, which is specific to urine antigen detection Another review paper also suggested that total dependence on urine antigen testing may miss up to 40% of legionellosis cases Sources: (1) Fields et al (2002). Legionella and Legionnaires Disease: 25 years of investigation. Clinical Microbiology Reviews, 15(3): (2) Marrie et al (2003). Legionnaires disease results of a multicentre Canadian study. Can J Infect Dis, 14(3):

43 1.4.3 Canada Average cases of Legionellosis per 100,000 persons, British Columbia 0.08 Alberta 0.15 Saskatchewan 0.07 Manitoba 0.06 Ontario 0.29 Quebec 0.26 New Brunswick 0.13 Nova Scotia 0.19 P.E.I Newfoundland 0 CANADA 0.20 Source: Public Health Agency of Canada, Notifiable Diseases On-Line. 43

44 1.4.3 Canada Legionellosis incidence rates in Canada, 2002 Rate per 100,000 population Source: Public Health Agency of Canada, Notifiable Diseases On-Line. 44

45 1.4.3 Canada Source: Ng et al (2009). Laboratorybased evaluation of legionellosis epidemiology in Ontario, Canada, 1978 to BMC Infectious Diseases 2009, 9:68. 45

46 Questions? 46

47 2. Risk Factors for Colonization and Illness 47

48 2. Risk Factors for Colonization and Illness Legionnaires Disease Risk = [ p Introduction ] [ p Proliferation ] [ p Dispersal ] [ p Discharge ] [ p Exposure ] [ p Susceptibility ] 48

49 2. Risk Factors for Colonization and Illness Legionnaires' Disease Risk = [ p Introduction ] [ p Proliferation ] [ p Dispersal ] [ p Discharge ] [ p Exposure ] [ p Susceptibility ] 49

50 p Introduction MICROBE INTRODUCTION water treatment systems microbial load of water supply season distribution system contamination faucet opening contamination nutrient introduction backflow contamination pipe repairs, removals 50

51 2. Risk Factors for Colonization and Illness Legionnaires' Disease Risk = [ p Introduction ] [ p Proliferation ] [ p Dispersal ] [ p Discharge ] [ p Exposure ] [ p Susceptibility ] 51

52 p Proliferation LEGIONELLA PROLIFERATION system sterilizatio n THERMAL CHEMICAL host proliferation warm water temperature biofilm formation f f 52

53 f Biofilm Formation recirculation / agitation microbes and nutrients water storage tank design stagnant flow BIOFILM FORMATION SCALE ACCUMULATIO N anti-fouling treatment system sterilization anti-scale treatment THERMAL CHEMICAL FLUSHING CHEMICAL piping system "dead legs" old piping hard water building age 53

54 f Warm Water Temperature recirculation / agitation WARM WATER TEMPERATURE piping insulation H-C cross connections intentionally warm heat loss in pipe runs pipe routing 54

55 2. Risk Factors for Colonization and Illness Legionnaires' Disease Risk = [ p Introduction ] [ p Proliferation ] [ p Dispersal ] [ p Discharge ] [ p Exposure ] [ p Susceptibility ] 55

56 p Dispersal water pressure surges LEGIONELLA AND HOST DISPERSAL IN WATER SYSTEM FLOWS air hammering of pipes dislodging of biofilm / sediments water system shut-downs water main construction construction, maintenance, demolition pipe repairs, removals transmitted vibration 56

57 2. Risk Factors for Colonization and Illness Legionnaires' Disease Risk = [ p Introduction ] [ p Proliferation ] [ p Dispersal ] [ p Discharge ] [ p Exposure ] [ p Susceptibility ] 57

58 p Discharge, p Exposure INHALATION OF CONTAMINATED AEROSOLS aspiration INGESTION OF CONTAMINATED LIQUIDS faucet aerators shower heads therapeuti c tubs respirator y therapy devices decorative fountains humidifier s cooling towers dental water lines personal hygiene drinking tap water dilution of concentrate s 58

59 2. Risk Factors for Colonization and Illness Legionnaires' Disease Risk = [ p Introduction ] [ p Proliferation ] [ p Dispersal ] [ p Discharge ] [ p Exposure ] [ p Susceptibility ] 59

60 p Susceptibility LEGIONNAIRES DISEASE / PONTIAC FEVER lung health immune deficiency advanced age critical care status chemotherapy 60

61 Questions? 61

62 3. Risk Assessment: What to Measure, and Not to Measure 62

63 3. Risk Assessment: What to Measure, and Not to Measure To assess the risk of a building s water systems becoming colonized by Legionella, it is necessary to: a. Develop an understanding of the features and operation of the building s various water systems. b. Characterize each system in terms of the six confluent risk factors (which in turn means considering a host of subordinate risk factors). c. Apply professional judgment and experience to gauge the apparent magnitude of the risk, and the specific actions necessary to reduce the level of risk. 63

64 3. Risk Assessment: What to Measure, and Not to Measure Measure water temperatures All water systems Starting points and terminus points Count numbers of faucets The more there are, the larger and more complex the system is likely to be, and the more likely it is to have dead legs, stagnant flow zones, recirculation problems, etc. 64

65 3. Risk Assessment: What to Measure, and Not to Measure Collect bulk water and piping system swab samples (OPTIONAL): If there is heavy Legionella colonization of the water system, it is highly likely to show up by bulk water sampling and culturing, and will almost certainly show up by bulk and swab sampling with Polymerase Chain Reaction (PCR) analysis. If there is minor Legionella colonization, it may or may not turn into a future problem, and it may or may not be detected by bulk or swab sampling with culturing. It will likely be detected by PCR, but so what? If there are non-viable Legionella cells in the system, they may still be detected by PCR but non-viable cells won t cause infection. False negatives / positives limit the usefulness of sampling in a situation where there is no outbreak. 65

66 3. Risk Assessment: What to Measure, and Not to Measure In general, routine culturing of samples from water systems MAY NOT be predictive of exposure risk for the following reasons: Presence of Legionella cannot be equated to the risk of infection: the bacterium is frequently present in water systems without being associated with disease cases Varying interpretation of lab results due to different methods Risk of illness following exposure is influenced by several factors other than the concentration of organisms in a sample Test results only represent counts at the time of sample collection; a negative result may lead to a false sense of security because rapid colonization can occur if the water systems suffer neglect Testing is not a substitute for sound maintenance practices and water treatment. 66

67 REA Water System Risk Assessment Form DOMESTIC WATER SYSTEM Risk Factors Risk Sub-Factors Risk Rating Low Med High Biofilm formation potential Scale accumulation potential Microbial contamination potential Microbial proliferation potential Water hardness Hot water tank horizontal v vertical position Hot water cold bottom feed / hot top out opposite Hot water tank agitator Water tank dumping and cleaning practices Expected microbial load of source water supply Potential degree of water supply line contamination On-site water treatment system microbial prevention Extent of potential backflow contamination Extent of system openings subject to contamination Domestic HW tank temperature Domestic HW line temperature Domestic HW tap delivery temperature Adequacy of pipe insulation Presence of HW recirculation system HW recirculation system feed back to HW tank Reverse osmosis treatment 67

68 REA Water System Risk Assessment Form DOMESTIC WATER SYSTEM Risk Factors Risk Sub-Factors Risk Rating Low Med High Biofilm formation potential Microbial proliferation potential Extent of dead legs Extent of inactive / stagnant lines Piping system sterilization practices Potential for dislodging biofilm Water pressure surges Exposure potential Potential for inhalation of aerosols Air hammering Construction Demolition Maintenance Water system shutdown Water main construction Pipe repair / removal Faucet aerators Indoor decorative fountains Outdoor decorative fountains Central mist humidifiers Portable mist humidifiers Showering 68

69 REA Water System Risk Assessment Form DOMESTIC WATER SYSTEM Risk Factors Risk Sub-Factors Risk Rating Low Med High Exposure potential Potential for inhalation of aerosols Potential ingestion of bulk water Therapeutic whirlpool / jacuzzi tubs Use of tap water to clean respiratory therapy devices Use for beverages / drinking water Face washing Bathing / Showering Occupant risk factors Advanced age Lung health Chemotherapy Critical care Transplant Immune deficiency 69

70 REA Water System Risk Assessment Form COOLING TOWER AND CHILLER Risk Factors Aspect Risk-Sub Factor Risk Rating Low Med High Biofilm fouling Design / Construction There are dead legs, stagnant lines, and loops that are difficult to drain. Constructed of corrosion resistant materials Construction of smooth and non-porous materials Multiple-cell cooling tower basins can be individually isolated Distance of piping between the cooling tower and the chiller (total wetted surface) Operating Practices Chiller barrel inspection, cleaning, disinfection practices. Cooling tower inspection, cleaning, disinfection practices. Cooling towers maintained according to manufacturer s recommendations. Proper dosing with biocides Rotation of biocides Proper dosing with biodispersants Free halogen in the cooling tower / chiller circuit kept in the range of 0.5 to 1.0 mg/l free halogen (as per Cooling Tower Institute recommendations) Proper water testing regime Make-up water filtered and treated with trace (or greater) halogen residual. Are the tower, lines and chiller barrel drained, cleaned and disinfected before start-up, and after any long shutdown period (greater than 1 week)? 70

71 REA Water System Risk Assessment Form COOLING TOWER AND CHILLER Risk Factors Aspect Risk-Sub Factor Risk Rating Low Med High Biofilm fouling Operating Practices Cleaning, flushing and disinfection at (a) start-up; (b) post lay-up; and (c) on a regularly scheduled basis. Tower, lines and chiller barrel drained and kept dry when the tower is taken out of service Non-removable dead legs in the piping system - blown down regularly? (particularly after biocide treatments and cleanings) Direct free cooling (chilled water) risers - blown down weekly? Is the basin inspected with regular frequency to determine need for cleaning? All valves in the system are exercised periodically by opening and closing them fully Proper dosing with anti-corrosion chemicals Siting Potential for entry of plant life and nutrients. Prevailing winds can introduce bacterial nutrient sources into the cooling tower (e.g. kitchen exhausts, industrial emissions having nutrient value, forests or fields that generate appreciable airborne organic dusts, etc.) 71

72 REA Water System Risk Assessment Form COOLING TOWER AND CHILLER Risk Factors Aspect Risk-Sub Factor Risk Rating Low Med High Mist dispersal Design / Construction Siting High efficiency mist drift eliminators present and maintained Potential for mist drift to nearby air intakes Potential for exposure Protective Equipment Entry to building Prevailing winds blow mists to target receptors Tower drift proximity to the facility's air intake system. Workers exposed to cooling tower mist drift provided with appropriate respiratory protection. Openable windows / doors in downstream proximity to mist emissions points. Filtration in air handling systems 72

73 REA Water System Risk Assessment Form AIR HANDLING AND COOLING SYSTEMS Component Risk Sub-Factors Risk Rating Low Med High N / A Outdoor Air Handling Units Protected from rain infiltration Adequate air filters Humidifiers - Mist Discharge Humidifiers - Pressurized Steam Discharge Not recommended for use. If present, Risk Rating is "High" Discharge line self-draining when non-operational Drip pan designed to minimize water accumulation Drip pan drain lines clear and functioning Humidifiers - Evaporative Steam Discharge Water temperature achieved in heating pan Water pan discharge / dumping frequency Water pan descaling / cleaning practices Cooling Coils Drip pans designed to minimize water accumulation Drip pan drain lines clear and functioning Acoustic Lining Air plenum free of moisture-absorbing acoustic lining Duct work free of moisture-absorbing acoustic lining 73

74 REA Water System Risk Assessment Form RISK FACTOR PROFILES Low Med High Biofilm formation potential (i.e. introduction, proliferation) Potential for dislodging biofilm (i.e. dispersal) Exposure potential (i.e. discharge, exposure) Occupant risk factors (i.e. susceptibility) Overall risk ratings As % of possible rating 48% 14% 35% 74

75 Questions? 75

76 4. Relevant Workplace Guidelines / Regulations Many countries (Canada, US, UK, Australia) have developed guidelines and/or regulations for the prevention of legionellosis and the control of Legionella in water systems Guidelines are advisory Regulations and codes of practice have a more formal standing and are supported by legislative enforcement Existing guidelines and regulations vary in scope and design, but typically have consensus on certain features, such as general support for a risk management approach 76

77 4. Relevant Workplace Guidelines / Regulations US OSHA Technical Manual, Chapter 7 ASHRAE Guideline Cooling Tower Institute Guideline US CDC Guideline 77

78 US OSHA Outbreak Response Measures Shut-down ventilation systems pending inspection and remediation Isolate or evacuate at risk individuals Prohibit washing with hot / warm tap water Prohibit consumption of cold water - switch to bottled water Inspect air handling systems for standing water eliminate and sterilize Remove porous linings of air handling units if wet or damp Perform water system sterilization (domestic and at risk process water systems) as soon as possible Do pre- and post-sterilization water testing primarily to assess adequacy of sterilization 78

79 ASHRAE Guideline American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Guideline : Minimizing the risk of legionellosis associated with building water systems Intended for use with non-residential building systems and centralized systems in multi-family residential buildings Coverage: describes Legionella ecology, modes of transmission and monitoring methods discusses contamination risk in various building water systems: potable and emergency water systems heated spas architectural fountains and waterfall systems cooling towers, including fluid coolers and evaporative condensers evaporative air coolers, misters, air washers, and humidifiers 79

80 US CDC Guideline US Centers for Disease Control and Prevention (CDC), 2003: Guidelines for Environmental Infection Control in Health-Care Facilities Divided into two Parts with moderate focus on legionellosis and other waterborne bacterial infections in healthcare settings Part I: Background and literature review Highlights issues around construction, renovation and repair work Detailed sections on cooling towers, dialysis equipment, ice machines, hydrotherapy tanks and pools, and misc. medical / dental equipment Part II: Recommendations for environmental infection control Rated based on scientific evidence and regulatory requirements Outline strategies for engineering and infection control, epidemiologic investigation and risk assessment Address control of disease transmission, maintenance practices, remediation, and infection control strategies for general and protective (e.g. transplant units) environments 80

81 Other Recommended Reading UK Health and Safety Executive (2004), Legionnaires Disease A Guide for Employers: concise six-page guide to help employers understand Legionella health risks. Available on-line: 81

82 Questions? 82

83 5. Water System Bacterial Remediation Methods ADVANTAGES Chlorination and Flushing (chlorine, chlorine dioxide, etc.) METHOD Superheating and Flushing Portable silver-copper ionization system (no flushing) Silver nitrate treatment (no flushing) Effective Fast implementation Immediate / quick effect Easy to do Relatively inexpensive Water system available Some residual suppression In the peer reviewed literature 83

84 5. Water System Bacterial Remediation Methods METHOD DISADVANTAGES Chlorination and Flushing (chlorine, chlorine dioxide, etc.) Superheating and Flushing Portable silver-copper ionization system (no flushing) Silver nitrate treatment (no flushing) Dosing system required Plumbing mod ns required Water system unavailable Risks to residents / patients Risk of damage to plumbing Need strong DHW system Requires math Requires conc trn monitoring Delayed / slower effect No residual suppression 84

85 Questions? 85

86 6. Water System Bacterial Prophylactic Methods FEATURES Chemical Treatment Systems (Ozone, Chlorine) UV Lamp Reverse Osmosis Water Softening Permanent silvercopper ionization system (no flushing) Periodic Superheating and Flushing Biofilm suppression Reduction in scale formation Bacteria suppression Legionella suppression ( ) 86

87 Questions? 87

88 End of Slide Series 88