The US construction industry is no stranger to risk. From dangerous machinery and hazardous heights to unpredictable working environments, site safety remains one of the sector’s most pressing challenges. But one invisible threat often goes overlooked: Legionella, the waterborne bacteria responsible for Legionnaires’ disease: a potentially fatal pneumonia.

Legionella is already a global public health concern and infection rates in the United States continue to climb at an alarming pace. Over the past two decades, reported Legionellosis cases have increased by nearly 1,000%.¹ While climate change, warmer temperatures and the growing complexity of water systems are widely cited as contributing factors, the exact causes of this rapid uplift remain largely unknown. What is clear, however, is that construction and renovation projects create ideal conditions for Legionella to thrive.

Why Construction is Highly Vulnerable

Construction projects inevitably disrupt water systems, creating multiple opportunities for Legionella contamination. Unlike occupied buildings with regular water usage, construction sites often involve long phases where plumbing networks sit idle or partially completed - conditions that make water systems especially prone to bacterial growth.

One of the biggest concerns is stagnation. When water sits motionless in pipes or tanks, it provides the perfect setting for biofilm to develop - an environment in which Legionella thrives. On top of this, dirt, dust and building materials can easily make their way into exposed pipework or storage systems during construction and renovation, adding further risk of contamination.

Temperature fluctuations also play a role. Legionella bacteria thrive and multiply in water temperatures between 68°F and 113°F (20°C to 45°C). Idle or incomplete systems often allow water to remain at ambient temperatures within this temperature range. Together, these factors create a dangerous cocktail of conditions for bacterial survival and proliferation.

Compounding this issue is the demographic profile of the construction workforce itself. One in five construction workers in the United States is now over the age of 55², and research shows that individuals over 45 are significantly more susceptible to Legionnaires’ disease. This combination of environmental and health factors makes the construction industry more exposed to Legionella risk than many other sectors. In fact, one prominent investigation into the occupations at increased risk of acquiring Legionnaires’ disease found construction workers had 1.82 times the rate compared to non-construction occupations.³

At the same time, high-profile Legionella outbreaks continue to demonstrate the devastating consequences when prevention fails. Most recently, of course, this was seen in New York City, where a cluster linked to contaminated cooling towers caused more than 100 infections and, tragically, several deaths. Incidents like these underscore the importance of proactive measures — particularly for the construction sector, where workers face elevated risk.

Current Protections and Where They Fall Short

To address this, the widely-adopted ASHRAE Standard 188 developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), provides a framework for building operators - including those working in construction - to implement comprehensive water management programs that proactively control risks related to the growth and transmission of Legionella in building water systems, including regular monitoring and maintenance. Many states and cities also stipulate their own specific standards, especially in jurisdictions with recent outbreaks or stricter health requirements.

From our experience though, there is scope to raise the bar on safety through a more robust and routine Legionella testing regime.

Of course, most construction site duty holders will already be well acquainted with the standard lab-culture method whereby water samples are collected from water systems on site and sent to an accredited laboratory which will identify the presence or absence of Legionella. However, this approach is timely, cumbersome and has limitations.

Foremost, most lab culture tests take 7-10 days to return results. Yet Legionella can double in a day. This large time lag means increased exposure and risk for businesses, employees, and the public. Water samples can also get damaged in the transportation process, potentially killing the Legionella inside and increasing the risk of a false negative result. Lab culture testing is also unable to detect Viable but Non-Culturable (VBNC)  Legionella — which though dormant can still be incredibly dangerous due to their ability to resuscitate and cause an infection — even being able to do so directly in human lung cells. 

The Role of Rapid Testing

Designed to break this cycle, construction duty holders are increasingly turning to rapid testing solutions. Modern kits can detect Legionella in as little as 25 minutes, allowing site managers to identify risks in near real time. Independent studies have shown these methods provide accuracy on par with traditional laboratory culture testing, but with speed that enables immediate preventive action.

Detecting Legionella so quickly empowers duty holders to react promptly to contamination and take appropriate action, thereby significantly minimizing the risk of exposure and human infection. Not only does using this method for routine testing during a construction project help reduce risk and minimize potential exposure to workers, but it also offers additional information during necessary reviews of the risk assessment, and provides peace of mind for the contractor, building owner and their responsible person.

Importantly too, construction sites are dynamic environments where evolving activities such as demolition, excavation, re-pressurization and such can all contribute to the Legionella risk. Rapid testing allows for frequent monitoring and adaptation to changing conditions.

Prevention must take priority

For an industry already managing one of the world’s most hazardous professions, Legionella may seem like a secondary concern. Yet with infection rates climbing, an aging workforce at higher risk and the precedent of fatal outbreaks, the US construction sector can no longer afford to underestimate this hidden danger.

By adopting rapid testing and reinforcing existing water management programs, the industry has a chance to stay ahead of the curve. Protecting workers, safeguarding communities and ensuring compliance all hinge on recognizing that when it comes to Legionella, prevention is always better — and safer — than cure.

For further information, please visit: https://hydrosense-legionella.com/

Sources

¹ https://pmc.ncbi.nlm.nih.gov/articles/PMC10540183/ 

² https://www.constructiondive.com/news/construction-labor-retirement-recruiting-dei/651184/

³ https://pmc.ncbi.nlm.nih.gov/articles/PMC11167715/