It’s been a constant point of tension for many of the residents in the areas affected by this summer’s outbreak of Legionnaires’ disease, which has killed three people so far.
While the city’s Department of Health and Mental Hygiene said it’s pinpointed 11 buildings with active Legionella bacteria, officials have not been willing to release their locations — only identifying five ZIP codes where they said people are most at risk.
Health Commissioner Michelle Morse said she doesn’t want to give New Yorkers a false sense of security if they aren’t anywhere near the affected buildings. Legionella bacteria can form in the cooling towers atop buildings and spread through the air, potentially infecting people whether they live in a building or not.
But some residents said that’s left them wanting more information.
Gothamist analyzed nearly a decade of publicly available inspection and violation data from the five ZIP codes to give a clearer picture of how the city has enforced safety rules meant to prevent Legionnaires’ outbreaks. We found that while the number of inspections citywide has dropped dramatically since Mayor Eric Adams took office, they dropped more precipitously in the five affected ZIP codes identified by the health department.
The health department did not respond to questions about whether increased testing could have helped prevent the current outbreak.
Here’s what else we discovered:
How many cooling towers are in the affected ZIP codes?
Thousands of the city’s buildings have rooftop cooling towers, which circulate water through air conditioning systems. But the warm water that pools in their tanks can become an incubator for potentially deadly Legionella bacteria, which can grow to dangerous levels within two weeks if left unchecked, according to public health experts.
Once that bacteria becomes vaporized into the air, breathing it can result in Legionnaires’ disease, a type of pneumonia. The outbreak in Harlem that started in late July has so far hospitalized more than 20 people.
As of Aug. 13, there were 97 cooling towers in the 10027, 10030, 10035, 10037 and 10039 ZIP codes. The 10027 ZIP code, which contains Morningside Heights, Manhattanville and Central Harlem, accounts for more than half of those, with a total of 50 cooling towers.
It’s a fraction of the 4,929 towers spread across all of New York City. But Manhattan has the most by far, with 3,635, about three-quarters of the total.
How much have inspection numbers declined in those ZIP codes?
First, a little background: A 2015 city law passed in the aftermath of a historic outbreak that killed 16 allows the city to inspect cooling towers for compliance. Those inspections got off to an aggressive start in 2017, with 5,095 conducted that first year. The number plummeted during the COVID-19 pandemic.
By 2022, they were back to 4,443, but have dropped again to a near-pandemic low since Adams entered office. This year, the city is set to inspect less than half of the towers it did at the start of his administration.
That decline has been even more pronounced in the ZIP codes where the outbreak is concentrated. A record number of towers, exactly 100, were inspected in 2021. In the first four months of 2025, however, the city was on track to inspect only about a quarter of that number, although the current outbreak likely led to an increase in inspections in those neighborhoods. More recent data is not yet available.
Health department spokesperson Chantal Gomez said the agency aims to inspect all towers once a year, but 40% of all the city’s towers — including within the five affected ZIP codes — have not been inspected since 2023. Gomez said staffing shortages are to blame for the decline.
“We take a risk-based approach when prioritizing inspections — including based on compliance history,” Gomez wrote in an emailed statement.
Juan Genao, a building operations associate who helps oversee water testing for LaGuardia Community College, said city inspections are critical for making sure cooling towers are safe.
“We’re talking about the health and safety of people,” he said. “If you don’t have the city overseeing them, it’s very easy for people to cut corners, and all of a sudden you have an outbreak.”
William Fowler, a spokesperson for the Adams administration, told Gothamist that the health department has the staff it needs to address the current outbreak.
What have building owners been doing to comply with the law and ensure safety?
City inspections are just one part of the city’s regulatory framework. Regular testing conducted by building owners is the first line of defense. The 2015 law requires owners to test their cooling towers weekly for all bacterial growth and every three months for Legionella bacteria. Owners have to report their Legionella test results to the city.
Our analysis found that slightly more building owners in the five ZIP codes were in good standing when compared to the rest of the city. About 75% of towers in the affected areas have up-to-date reporting on their Legionella testing as of early August. Whereas the citywide average is 73%.
Slightly more than half of the towers in the five ZIP codes that are in good standing have not been inspected by the city since 2023.
What about the towers that were behind on testing? Were they inspected?
It’s unclear whether a building that fails to report Legionella test results is more likely to be flagged by the health department for inspection. The agency did not answer questions about whether prioritizing these cooling towers is part of its risk-based approach.
While 75% of towers in the five outbreak ZIP codes were up-to-date on their testing, 17 had no reported test results at all. The health department said some of those towers could be inactive and would therefore not be required to test. But the agency would not confirm which towers were no longer operational.
To get around this limitation, Gothamist identified cooling towers that did have test results at some point in the past year, but not in the past three months.
By that definition, 5% of the towers in the affected ZIP codes that were behind on their reported test results had also not been inspected by the city since 2023 — a total of five towers. That figure is slightly higher than a citywide average of 3%.
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