By Lou Goldstein

Throughout the United States and beyond, improper HVAC system maintenance may pose a health risk not only to immediate workers, but the surrounding community as a whole.

Legionella bacteria (Legionella) were first discovered by public health officials in 1976, with their name stemming from a pneumonia-like outbreak following a large gathering of American Legion members in the city of Philadelphia. The illness caused by Legionella bacteria was officially named Legionnaires’ Disease. This discovery led health officials to make the connection that Pontiac Fever, which had been the subject of a mysterious illness less than ten years prior in Michigan, was also caused by Legionella.

Another significant Legionella outbreak occurred within The Bronx in New York City during the summer of 2015 where well over one hundred individuals were sickened, leading to twelve deaths.  This outbreak was bookended by two separate, however much smaller outbreaks occurring in 2015.

The 2015 outbreak heightened awareness of the dangers Legionella poses to public health, and highlighted how densely populated communities are at high risk.  According to a 2003 study titled A Community-Wide Outbreak of Legionnaires Disease Linked to Industrial Cooling Towers—How Far Can Contaminated Aerosols Spread? by Nguyen et al., Legionella bacteria can be transferred via aerosol particles at up to six kilometers (about 3.7 miles) from the source.  The bacteria thrive in warm to hot environments, multiplying quickly in stagnant water.

“What legislation protects the public from Legionella risks?”

The 2015 New York City outbreak prompted New York State to develop legislation requiring action to prevent Legionella risks.  Prior to this point, the only provision for general worker protection was set forth by Section 5(a)(1) of the Occupational Safety and Health Act of 1970 (OSHA), which mandates that employers provide their workers an “employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm.” However, the lack of a specific reference to Legionella and its related diseases in OSHA made it difficult to enforce compliance with the issue. In addition, despite historic Legionella outbreaks dating back over 40 years, no federal or state laws directly addressed Legionella risks.  As a result, Legionella protection measures were a low priority for lawmakers and consequently many facility managers, as well.

Specific legislation on preventing transmission of Legionella within building systems was rather slow to develop. No formal regulations were initiated until pressure was brought on by the Bronx outbreaks.  In August 2015, Governor Andrew Cuomo of New York announced the immediate adoption of emergency regulations intended to prevent future Legionella outbreaks and to promote better hygiene with respect to maintenance of building water systems. These emergency regulations developed into the first-of-their-kind New York State Department of Health (NYSDOH) Protection Against Legionella regulations in early 2016, which described steps to prevent bacterial transmission in building water systems, referencing ANSI/ASHRAE Standard 188–2015, Legionellosis: Risk Management for Building Water Systems, which was published at a similar time. Both items have been updated since, and New York City has additionally adopted their own set of rules.

The Centers for Disease Control and Prevention (CDC) and similar organizations currently have guidelines directly and indirectly related to Legionella prevention, but there are no additional further regulations on the federal level or in the other 49 states.

How did the 2016 Protection Against Legionella Regulations immediately affect building owners and property managers within New York State?

The New York State regulations came with a collection of preventative and monitoring-based requirements for building owners whose facility contains one or more on-site cooling towers, evaporative condensers, or other wet cooling devices. The following items were immediately required:

  • Registration of all wet cooling devices that are being actively operated, including equipment/system specifications
    – Active updates to the NYSDOH registry with testing results, startup/shutdown date, etc.
  • Preparation of a Maintenance Program and Plan which describes all building water systems as they relate to the wet cooling devices, and how disinfection is being performed. This required Plan is not submitted to the NYSDOH, but must be kept on-site at all times.
  • Requirement for devices to be cleaned yearly using an approved biocide prior to seasonal operation
  • Bacterial culture sampling of each device’s water basin for Legionella, paired with an inspection
  • Notification of the local health department in case of elevated Legionella concentrations
    – Depending on the severity of the bacteria concentration, an increase in biocide dose and/or an emergency cleaning may be required

What evolved from the original New York State Regulations?

Typical cooling tower, located on a building roof.

Five months after the 2016 Protection Against Legionella Regulations came into effect, an updated version was published which made some minor changes (most notably adding monthly bacteriological “dip slide” testing) to the requirements for facilities with cooling towers. The changes were put into effect in Subpart 4-1 – Cooling Towers, which remains current.

At the same time, Subpart 4-2 – Health Care Facilities was issued by the NYSDOH (which also remains current). This Subpart mandated the following for all health care facilities, which was to be followed in addition to the existing cooling tower requirements:

  • Health care facility owners must perform an Environmental Assessment of their facility, which includes information on historical construction details, window configurations, number of beds, etc.
  • Formulation of a Sampling and Management Plan for the health care facility, where sampling locations are chosen based on the Environmental Assessment. This is in addition to the required Maintenance Program and Plan.
  • Sampling is required at intervals not to exceed 90 days for the entire first year after the Plan is adopted, and annually from that point on. There is an exception for water systems which serve solid organ transplant or hematopoietic stem cell transport patients, which must continue to be sampled at intervals not to exceed 90 days.

What type of disinfectants are effective and commonly used to destroy Legionella?

Disinfectants used to combat Legionella should be effective at removing the bacteria while not posing a significant risk to human health.  Chlorine and bromine-based solutions (both oxidizing and non-oxidizing types) are a preferred choice for building owners and facility managers. These biocidal chemicals can be used for pre-use/after-season cleanings and daily, continuous dosing of building water. Dose strength, location and timing will vary from facility to facility and should be evaluated based on sampling results.

Does this relate to the current COVID-19 pandemic?

Somewhat. Although Legionnaires Disease, the disease caused by Legionella, is a bacterial infection rather than viral, it causes essentially the same symptoms as have been reported so far with COVID-19. It also affects immunocompromised and elderly individuals disproportionately.  About 10,000 cases of Legionnaires Disease were reported in the United States last year, and this is thought to be an underreported figure. Although Legionnaires Disease is not known to be communicable, the CDC reports that approximately 1 in 10 patients diagnosed with the disease will die from complications.

What obstacles factor into Legionella compliance and adoption of hygienic practices?

Often times, maintenance of cooling tower systems and/or building water resources is handled by an internal, full-time employee.  In this specific case of Legionella-prevention where the initial New York State regulations were recently passed, there will naturally be pushback from those who are used to operating in a manner now inconsistent with the regulations. Expenses that were previously considered unnecessary such as costs for testing materials, biocides, and hiring of a professional consultant and/or cleaning company now factor into decision-making and compliance. The known potential for Legionella bacteria to spread (up to two miles as mentioned above) and underreporting of infections due to its resemblance to pneumonia are effectively placing an increased responsibility (and liability) on building owners to comply with regulations.

Another major obstacle is enforcement of the regulations.  There are over 11,000 cooling towers registered in New York State alone, and likely many more than this number have not self-registered.  Enforcement by the NYSDOH was sparse at the outset of the regulations; but, in the past few years, enforcement responsibilities have been granted to several local health departments throughout the state to promote compliance. It is likely that this pattern will continue and enforcement will eventually become more consistent and routine.

A commitment to proper water system maintenance and a regular sampling and inspection schedule is the most effective way to ensure that Legionella will not spread.  Small changes to existing maintenance and disinfection practices can immediately make a big difference.


Lou Goldstein is an Engineer at Walden Environmental Engineering, PLLC in Oyster Bay, NY who helps manage Walden’s Legionella compliance services. He can be reached at 516-624-7200 or through www.WaldenEnvironmentalEngineering.com.

Comments