For the first time, new citywide regulations issued by the NYC Health Department are in effect requiring building owners to test cooling towers for Legionella bacteria more frequently than anywhere else in the country. The amendments mandate building owners test for Legionella bacteria every 31 days when the cooling tower is operating — 3 times more frequently than was previously required — further strengthening one of the nation’s most rigorous and protective laws. The NYC Health Department has As the new rules take effect, NYC Health Commissioner Dr. Alister Martin has issued a commissioner’s advisory to notifiy building owners of actions required to meet the new cooling tower mandates and remind them of the critical role these owners play in keeping New Yorkers safe.
“The Mamdani Administration is enacting commonsense policies that prioritize New Yorkers’ health and safety,” said Deputy Mayor for Health and Human Services Dr. Helen Arteaga. “Today, we are announcing new amendments that will strengthen safety standards for cooling towers and help us respond to the existence of harmful bacteria more quickly and efficiently. As the temperatures rise, it is increasingly important that we monitor for and protect every New Yorker against Legionella, and that’s exactly what these regulations aim to do.”
On August 29, 2025, the NYC Health Department announced the end of the Central Harlem community cluster of Legionnaires’ disease. By the end of the cluster, there had been 118 cases of Legionnaires’ disease; 92 people had been hospitalized; and sadly, seven people had died in connection with this cluster. In collaboration with the NYC Health Department, the New York City Council enacted amendments to New York City’s landmark cooling tower law, authorizing the more rigorous testing schedule to require buildings to demonstrate effective Legionella control and increase fines for property owners who fail to comply with the law. The new requirements guide building owners in improving management practices and technical capacity for even safer cooling tower operation.
The NYC Mayor’s Office proposed a package of resources and policy changes to implement these changes. The NYC Health Department was allocated an additional $13 million in the fiscal year 2027 budget to support the agency’s routine cooling tower inspections and any future response to Legionnaires’ disease clusters. This includes:
- Hiring 23 new water ecologists, increasing staff to 56 cooling tower inspectors. These new staff are currently in the onboarding process and will help the city meet its goal of annually inspecting all NYC cooling towers.
- Establishing a community engagement team staffed by community health workers based in the Health Department’s Neighborhood Health Action Centers to be rapidly deployed to provide information and education to neighborhood residents during a community cluster investigation and to focus on improving the health of New Yorkers year-round.
- Identifying and developing partnerships with local organizations that can help reach community members and strengthen messaging.
The NYC Health Department notified all cooling tower operators that the final rule is in effect and is conducting outreach and education about the new requirements to help owners comply. There are approximately 4,000 buildings with registered cooling towers across the five boroughs.
The Health Department is also working with other city agencies, including DCAS and DOB, to identify new ways to improve cooling tower monitoring and maintenance at City-owned buildings, including increasing awareness of a citywide contract available for maintenance, testing, and remediation services, and to strengthen the registration of cooling towers at buildings under construction.
The NYC Health Department has an extensive investigation and notification system for Legionnaires’ disease and response, investigating every case of Legionnaires’ disease and monitoring daily for patterns in cases.
Legionnaires’ disease is a type of pneumonia that is caused by the bacterium Legionella, which grows in warm, stagnant water. People — especially those at higher risk — can get sick by breathing in water vapor if it has Legionella bacteria. Symptoms resemble other types of pneumonia and can include fever, chills, muscle aches, and cough. It is not transmitted from person to person and can be treated with antibiotics when caught early. Individuals at higher risk for Legionnaires’ disease include those ages 50 and above, cigarette smokers, and people with chronic lung disease or weakened immune systems.
If there is a pattern of multiple cases reported across a community in a short span of time, the NYC Health Department investigates cooling towers as a potential source. Cooling towers present a risk of spreading Legionnaires’ disease at a community level because they operate with warm water and their fans generate water vapor that may contain Legionella that’s traveling outside in the environment.
The NYC Health Department also evaluates a building’s internal water system when two or more cases of Legionnaires’ disease are detected at a single address in a 12-month period. Building evaluations are sporadic and the exposure is only to residents of the building. These pose no risk to the surrounding community.
