LEGIONELLA ASSESSMENT & PREVENTION

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1 LEGIONELLA ASSESSMENT & PREVENTION CRE Applications BuildingsOne August 19, 2016 Legionella is a pathogenic group of bacteria comprising the series pneumophilia, which can cause legionellosis, including a pneumonia-type illness called Legionnaires disease and a mild flu-like illness called Pontiac fever. Legionella can be transmitted by the operation of water-based systems that generate air-borne mists capable of conveying the Legionella cells to humans in proximity to these aerosol mists. Legionnaires disease is a serious type of lung infection (pneumonia) that people can get by breathing in small droplets of water contaminated with Legionella. When Legionella is aerosolized from a water system, and breathed in by a person, the bacteria can enter the lungs. Once in the lungs, the Legionella bacteria can multiply and spread. Incubation is generally from 2 to 10 days and can take up to two weeks. The bacterium is not transmissible from person to person and most people exposed to the bacteria do not become ill. U.S. Occupational Safety and Health Administration (OSHA) has indicated Legionnaires Disease is becoming more common and serious in the United States. The World Health Organization says that the incidence of legionellosis is increasing and is currently at a rate close to 70 cases per million people.

2 LEGIONELLA ASSESSMENT & PREVENTION Sporadic incidents of Legionnaires disease continue to occur across the globe. Legionellosis remains a significant concern to public health officials, facilities managers, and building owner-operators. This concern is particularly true of buildings having domestic water systems, cooling towers, other HVAC evaporative condensers, and decorative water fountains, all of which can generate warm waterborne mist pathogens that can be inhaled into human lungs. In 2015, about 5,000 people were diagnosed with Legionnaires disease and more than 20 outbreaks were reported to the CDC. According to CDC Director Tom Frieden, M.D., M.P.H., many of the Legionnaires disease outbreaks over the past 15 years could have been prevented. FEDERAL HEALTH AGENCIES & INDUSTRY ORGANIZATONS Guidance and Expertise in Assessing Risk & Implementing Control Measures There are several federal health agencies that provide recommended guidance in assessing the potential for Legionella and control guidelines to manage the risk. Center for Disease Control and Prevention (CDC) World Health Organization (WHO) Occupational Safety & Health Administration (OSHA) Building service-related industry associations that provide recommended guidance in assessing Legionella risk and control guidelines to manage the risk include: American Society of Heating, Ventilation and Air Conditioning Engineers (AHRAE) Cooling Technology Institute Association of Water Technologies The owner-operator s utilization of federal and industry resources, complemented by services provided by the building s water treatment service provider, HVAC and plumbing contractors, MEP engineering firm, on-site engineers, and maintenance staff comprise the resources necessary to evaluate potential risks and mitigate the production and airborne transmission of Legionella bacteria. 2

3 ENVIRONMENTAL / PHYSICAL CRITERIA In order for Legionella bacteria to produce in water-based systems it must have certain pre-conditions in place. The temperature of the water is a key determinant as it relates to the formation and growth of Legionella. The graphic below illustrates the general temperature ranges that will kill / control Legionella or allow it to potentially produce and grow. Legionella Growth Temperature Range The temperature ranges above are not precise, are variable dependent upon a number of factors including source expertise and experience. In any case, the temperature ranges provide a reliable indicator of the potential for the development and growth of Legionella. 3

4 COMMON SOURCES OF LEGIONELLA The most common encountered building system sources of Legionella include the following: RISK ASSESSMENT - FORMATION & PROLIFERATION AEROSOL EXPOSURE FACILITY POPULATION The first phase in approaching Legionella prevention and mitigation is Risk Assessment. How owneroperators, e.g., facility/property managers, senior engineers, etc., approach risk assessment will vary based on a number of broad factors starting with the types and locations of water-based systems operating at the facility. The owner-operator will also consider the occupancy at the building and the potential human proximity and exposure to airborne mists associated with water-based systems. Assessing the potential for development, growth, and human airborne transmission of the Legionella pathogen can be complex. However, it s an essential responsibility for building owneroperators in ensuring a safe working environment for their building population - occupancy, customers, and visitors. Each system type, e.g., domestic water system, cooling tower, evaporative condenser, water feature, etc., will require an assessment specific to the risks associated with each system. Broadly speaking, the assessment will consider the following aspects of each system: 1. Legionella Formation and Proliferation, 2. Aerosol Exposure, and 3. Population Susceptibility. 4

5 RISK ASSESSMENT - FORMATION & PROLIFERATION AEROSOL EXPOSURE FACILITY POPULATION Regarding formation and proliferation, preventing biofilm growth is a critical control measure against the spread of Legionella. Once developed, biofilm is difficult to remove from certain water-based systems. Maintaining water temperature within a prescribed range is the first step in directly minimizing biofilm and reducing the potential for Legionella formation and growth. However, with certain systems, including cooling towers, evaporative condensers, and domestic hot water systems, water temperatures within or near the Legionella formation and growth range is required in the practical, effective, and efficient operation of these systems. A comprehensive water treatment program will consider the control methods of biofilm accumulation, through biocide use, proper ph range, supplemented w i t h c l e a n i n g a n d disinfection. Cooling towers are often considered the most recognized source of Legionnaires disease outbreaks. The potential for Legionella proliferation in cooling towers, evaporative condensers, and decorative water features is primarily impacted by water temperature, source water quality, and water stagnation. When water temperature cannot be reasonably maintained outside of the Legionella production and growth range, effective biocide chemical treatment and maintaining the appropriate water ph will help reduce or eliminate biofilm growth. 5

6 RISK ASSESSMENT - FORMATION & PROLIFERATION AEROSOL EXPOSURE FACILITY POPULATION For ornamental water features (water fountains), system design has a major influence on the potential for Legionella growth and the amount of aerosol produced. Size and Location: The potential for spreading Legionella to humans is, to a certain extent, proportional to the size of a water feature (amount of aerosol produced) and its location (aerosol circulation path and proximity to humans). Submerged components and drainage: Legionella can grow in submerged components including plastic tubing. The ability to readily access a drain, located at the lowest point in the system, can facilitate basin draining, maintenance and cleaning of water feature system equipment. Flow Type: Water features that spray or mist water create the breathable aerosol water droplets associated with the potential for Legionella transmission to humans. Cascade type waterfalls or enclosed water features reduce the risk of aerosol production and transmission. Lighting: Water features incorporating submerged lighting significantly increase the risk of Legionnaires disease. Heat produced by light fixtures can increase water temperatures to >68 F; a more dangerous Legionella production range. Owner-operators weighing the pros and cons associated with having a decorative water feature should consider utilization of (low heat) Light Emitting Diode (LED) lighting or fiber optic lighting in lieu of heat generating lighting systems, including halogen and incandescent light fixtures. 6

7 LEGIONELLA TESTING The process of periodic Legionella testing can prove instrumental in verifying the effectiveness of a building s water treatment and internal surfaces cleaning program. Periodic Legionella testing can be considered the final phase and confirmation of the building s Legionella control and monitoring program. Legionella testing can substantiate the overall effectiveness of the property owner-operator s Legionella prevention program and safe environment for occupants and visitors conducting business at the facility. Legionella testing can be formally incorporated within the water treatment service provider s expertise, responsibility, and scope of work. The testing for Legionella (L. pneumophilia), and other waterborne pathogens, is typically performed in a controlled environment (laboratory setting) accredited to conduct this specialized work. If the presence of Legionella is detected in a test sample, the effected system should undergo emergency disinfection, cleaning, and corrective actions as a matter of priority. A proactive and systematic water-based systems operations & maintenance (O & M) program including legionella risk assessment, cleaning, disinfection, chemical treatment, water temperature control, inspection, and Legionella testing will have a direct impact in ensuring the health and well-being of people at our facilities. A v a i l a b l e i n B u i l d i n g s O n e l i b r a r y o f d o c u m e n t s Legionella Assessment and Prevention Program offers additional insight into best practice Legionella mitigation applications and procedures 7