Abstract
Data from the Centers for Disease Control and Prevention (CDC) shows improper maintenance of public spas increases risk for Legionnaires’ disease. Legionnaires’ disease affects thousands of individuals each year and represents a signifcant public health burden, with a 10% case fatality rate and an estimated annual hospitalization cost burden of $433 million.1,2 CDC’s Model Aquatic Health Code (MAHC) offers critical guidance for reducing the risk of Legionnaires’ disease in public aquatic facilities.
For example, the MAHC contains construction, operation and procedural requirements to facilitate appropriate water pH and disinfectant concentrations levels in public spas. Additionally, the MAHC outlines policies and certifications for training documentation among aquatic facility staff. Facility owners, operators, managers and other stakeholders involved in design, construction, maintenance and repair of building water systems can use the MAHC provisions to develop a water management program in aquatic facilities that is compliant with ASHRAE Standard 188–2015, Legionellosis: Risk Management for Building Water Systems. These elements will support program elements such as control limits, corrective actions and record keeping, which are important components of an ASHRAE Standard 188–2015-compliant water management program. Incorporating the MAHC principles of proper spa operations and maintenance, trained operators and monitoring can help reduce risk of Legionnaires’ disease.
Legionnaires’ Disease
Legionnaires’ disease is caused by inhalation of water droplets contaminated with the bacteria Legionella, which is the leading cause of illness among reported drinking water outbreaks in the United States.3 Factors associated with Legionella growth are biofilm, scale and sediment, water temperature and pH fluctuations, inadequate disinfectant levels, water pressure changes, water stagnation and warm temperatures.4 Since Legionella thrives in warm freshwater environments, improperly maintained spas can allow Legionella to grow to high numbers and infect people that use or come close enough to spas to inhale the contaminated mist.
CDC’s MAHC defines a spa as “a structure intended for either warm or cold water where prolonged exposure is not intended.” Spa structures are intended to be used for bathing or other recreational uses and are not usually drained and refilled after each use. Spa types include, but are not limited to, hydrotherapy, air induction bubbles and recirculation.4 The MAHC is voluntary guidance based on science and best practices that can help local and state authorities and the aquatics sector (e.g., public health, operators, industries and other aquatic facility stakeholders) make swimming and other water activities healthier and safer. States, localities and the aquatics sector can use the MAHC to reduce the risk for outbreaks, drowning and pool-chemical injuries. The MAHC guidelines are all-inclusive and address the design, construction, operation, maintenance, policies and management of public aquatic facilities.5
Public Health Data to Support MAHC Use
Frequent health and safety violations of local aquatic facility codes (e.g., pH, temperature and disinfectant concentration) have often been reported at public pools and spas, and continue to challenge proper pool and spa maintenance. In 2016, CDC’s Network for Aquatic Facility Inspection Surveillance (NAFIS) reported that 11% of routine pool inspections (5,139 out of 43,636) resulted in immediate closure.6 An even higher percentage of routine hot tub/spa inspections reported to NAFIS resulted in closure: 15.1% (2,217 of 14,637).
The NAFIS data shows that the most frequent hot tub/spa violations from inspections were problems with:
Disinfectant concentration (19.2%);
pH (27.5%);
Pool chemical safety (9.9%); and
Excess water temperature (7.5%).
In 2016, CDC further reported that hot tubs (when improperly maintained) was the third most common water source implicated among Legionnaires’ disease outbreaks investigated by CDC. More specifcally, human errors were implicated in at least half of all investigated outbreaks and included:7
Improper flter maintenance;
Defcient disinfection levels;
Inadequate monitoring; and
Poor temperature control and ventilation.
The CDC data highlights that improper operation and maintenance of public spas is common, and that missed prevention opportunities can lead to outbreaks of Legionnaires’ disease.
The MAHC
The MAHC, updated every two years, is comprised of six chapters that contain guidelines to improve health and safety in aquatic facilities. Chapters that are pertinent to the risk reduction of Legionnaires’ Disease in public spas are: Design and Construction (Chapter 4), Operation and Maintenance (Chapter 5) and Polices and Management (Chapter 6). The MAHC outlines specifc guidance that can be incorporated into water management programs to reduce Legionella growth and spread in spas.
MAHC Design and Construction (Chapter 4)
Chapter 4 incorporates specifc design and construction language that can be used to reduce the risk of Legionnaires’ disease in new aquatic facilities or substantial alteration of an aquatic facility or venue.
For example, the MAHC includes requirements for automated disinfection and pH control, defnes fow rates and turnover times, outlines inlet spacing to ensure adequate mixing and requires a means to easily drain and clean the spa.
MAHC design and construction requirements also specify that spas have proper ventilation with an air-handling system that complies with ASHRAE Standard 62.1- 2013, Ventilation for Acceptable Indoor Air Quality.
MAHC Operation and Maintenance (Chapter 5)
Chapter 5 addresses specifc operational and maintenance recommendations for spas, including requiring aquatic facilities to have a preventative maintenance program, continuous operation of the recirculation system, flters and flter media listed and labeled to conform with NSF/ANSI 50, Equipment for Swimming Pools, Spas, Hot Tubs and Other Recreational Water Facilities, and fltration and backwashing rates.
MAHC operational and maintenance standards also require the establishment of minimum and maximum disinfectant concentrations, minimum and maximum pH levels, water quality chemical testing frequency, water clarity specifcations, prohibition of cyanuric acid use in spas and regular draining and cleaning of spas.
It also recommends routine, compliant and follow-up assessments of public aquatic facilities conducted by trained supervisors and aquatic facility operators.
MAHC Policies and Management (Chapter 6)
Spa-specifc policies and procedures include recommendations that all spa operators have appropriate state or local certifed pool and spa operator and chemical handling training. The MAHC outlines essential topics in qualifed operator training courses and staff training requirements. Additionally, these trained staff should be available during peak hours and seasons that spas are used most frequently.
Pool and spa operators play a critical role in Legionnaires’ disease risk reduction. These professionals should have a working knowledge of the key areas of MAHC and ASHRAE guidance and their relationship to waterborne disease mitigation.
Keeping the MAHC updated is an ongoing task.3 CDC works with the Council for the Model Aquatic Health Code (CMAHC) to help ensure the Model Aquatic Health Code is regularly updated and stays current with the latest science and best practices. CMAHC members from public health, aquatics sector, business, universities and the general public work across the country to ensure the latest scientifc and technological improvements are addressed by the MAHC. Recommendations to improve the MAHC are sent to CDC every two years to ensure the guidance is adequately updated.
Conclusion
Incorporating the MAHC, in conjunction with A SHRAE guidance, can be a powerful tool to develop and implement a water management program to reduce the risk of Legionnaires’ disease associated with public spas.
Legionella Prevention Resources.
Legionnaires’ Disease General Information
Disinfection of Hot Tubs Contaminated with Legionella
Preventing Illness and Injury at the Pool and Hot Tub
www.cdc.gov/healthywater/pdf/swimming/resources/legionella-factsheet.pdf
How to Sample Spas and Fountains During Legionellosis Outbreaks
Water Management to Prevent Legionella
Model Aquatic Health Code Tools
www.cdc.gov/mahc/pdf/2016-mahc-code-fnal.pdf
www.cdc.gov/mahc/pdf/2016-mahc-annex-fnal.pdf
www.cdc.gov/mahc/fact-sheets.html
www.cdc.gov/mahc/infographic-decoding-lg.html
www.cdc.gov/mahc/pdf/mahc-aquatic-facility-inspection-report.pdf
www.cdc.gov/mahc/pdf/mahc-aquatic-facility-inspection-report-cheat-sheet.pdf
References
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