The Bronx Ranks the Moldiest Borough in NYC

New Yorkers call 311 for all kinds of reasons, from illegal dumping to living standard violations like insufficient heating or rats. In a rainy city like New York, landlords maintain a responsibility to keep residences free of moisture. However, many renters find themselves having to call 311 to report unsafe conditions due to mold.

Mold raises health concerns like headaches and itchy eyes, but in more serious cases, it can cause fungal infections that require diagnosis and treatment. Mold also affects landlords, as repeat issues could indicate excessive moisture that could turn into more serious property damage. To find out how much New Yorkers struggle with mold issues, RentHop looked into reports for mold from 2017 through July 6, 2023, and discovered that more renters have filed complaints about mold in recent years. Read on to see if mold is becoming an issue in your neighborhood.

Key Findings


  • The Bronx is New York City’s moldiest borough, with 112.3 complaints per 10,000 residents. Four of the five neighborhoods with the most complaints reside in the Bronx.
  • Fordham Heights receives the most mold complaints, averaging 656.3 complaints per year.
  • September 2021 received the most mold complaints on record since 2017, coinciding with when Hurricane Ida flooded residences and increased moisture levels.
  • Month-over-month, renters complain most about mold in the fall and winter months.
  • 2023 complaints exceed past month records for March, May, and June, indicating that this year may receive the highest volume of complaints on record.

Mold Complaints by NYC Borough

The chart above breaks down the number of mold complaints by year by borough. As you can see, since 2019, the Bronx has received the most complaints each year. As of July 6, the borough has received 4,775 complaints this year, or 112.3 reports per 10,000 renter-occupied units, making it the moldiest among the five boroughs.

From 2017 to 2018, mold complaints increased in every borough. However, complaints decreased in 2019 and 2020. Renters left the city during COVID-19, limiting the instances where they would notice mold in their apartments. As renters returned to the city and began working from home, complaints quickly increased to pre-2019 levels, remaining high through 2023.

Mold Complaints, Mapped Out By NYC Neighborhoods

The interactive map below breaks down mold complaints to NYC 311 by neighborhood and highlights the top reported addresses. To fairly rank each neighborhood, we divided the average yearly complaints from 2017 to 2022 by the total number of renter-occupied units. The darker the shade, the more complaints per 10,000 renter-occupied units. We also included median one-bedroom rents by neighborhood as a reference point for renters.

As you can see on the map, mold complaints are largely concentrated in the Bronx and parts of Brooklyn. Upper Manhattan, past Central Park, has also received more mold complaints from renters.

The Moldiest Neighborhoods in New York


  • Fordham Heights, Bronx: 166 complaints in 2023, average 656.3/year
  • Flatbush, Brooklyn: 315 complaints in 2023, average 499.7/year
  • University Heights, Bronx: 196 complaints in 2023, average 468/year
  • Tremont, Bronx: 170 complaints in 2023, average 437.5/year
  • Belmont, Bronx: 219 complaints in 2023, average 426.8/year

The Mold Problem Is Getting Worse In These Neighborhoods


  • Westerleigh-Castleton Corners, Staten Island: 16 complaints in 2023 (+300%)
  • Middle Village, Queens: 19 complaints in 2023 (+280%)
  • Stuyvesant Town – Peter Cooper Village, Manhattan: 6 complaints in 2023 (+200%)
  • Great Kills-Eltingville, Staten Island: 29 complaints in 2023 (+163.64%)
  • Arden Heights-Rossville, Staten Island: 5 complaints in 2023 (+150%)

New York City Has Gotten Moldier In Recent Years

When breaking down mold complaints month-over-month, we observe that renters complain more about mold in the fall and winter. During the spring and summer months, complaints decrease. While mold is more likely to grow under warm and humid conditions, it is more likely that renters spend less time in their apartments during the warmer months and that they will use air conditioning units and dehumidifiers to improve air quality. During the winter, when they spend more time at home and do not open the windows for fresh air, complaints increase.

Hurricane Ida’s Impact


Mold complaints reached their highest level on record in September 2021, when renters flocked back to the city post-pandemic for work and school. However, increased moisture and humidity compounded complaints. On September 1st, Hurricane Ida swept through the city, severely flooding many neighborhoods. In a historic natural disaster, unparalleled amounts of rain fell to displace cars, flood basements, and create opportunities for mold growth. Renters felt the effects of the storm and discovered more mold that month, lasting through the rest of 2021.

Hotter Spring and Wetter Summer


Renters have complained more about mold this year than in the past. 2023 mold complaints in March, May, and June exceed complaints from the same period since 2017. Complaints continue to increase year-over-year since 2020, with 2023 expected to exceed 2022 complaints.

While there is no significant event that directly increased mold complaints in recent years, there are several potential circumstances leading to current conditions. New York City is warmer than past years on record, and with temperatures and humidity levels increasing, mold has more opportunities to grow. 2022 became the sixth hottest summer on record, and if the environment continues growing warmer, mold may increase as well.

Additionally, renter attitudes may be changing to demand more from their building owners and to hold them responsible for negligence. Rental prices in New York City are at their highest, and many renters paying a large sum of their earnings may no longer justify poor living conditions that they wrote off when paying cheaper rents. Modern technology also connects renters, potentially increasing mold complaints. For example, one renter’s viral Tiktok video about mold in her NYC apartment influenced other renters to purchase mold kits and check conditions in their homes. With more renters easily learning about mold and increasing their expectations of landlords, more cases may escalate to 311 complaints.

Why Is It Important to Me as a Renter?

Exposure to mold can cause various symptoms, and living in a mold-infested apartment will prolong and intensify the effects. Renters with mold allergies or asthma can suffer more intense reactions to mold. Overall, those living in mold-infested apartments are more likely to suffer from wheezing, red or itchy eyes, a stuffy nose, and skin irritation, according to the Center for Disease Control (CDC). In severe cases, renters can develop fungal infections that require diagnosis and treatment by a medical professional.

To limit the risk of symptoms and infections, renters should avoid living in apartments with mold and promptly report any appearances to their property manager.

How to Spot Mold During a Showing?

Since mold can be bad for your health, it’s important that you recognize signs of mold during apartment showings. Some common signs of mold include:

  • Gray, green, yellow, black, or orange patches
  • Furry, slimy, or powdery areas
  • Musty, earthy, or stale smells

Mold grows more easily in wet and damp places. If the bathroom does not have a window or if the apartment does not have strong ventilation, it is easier for mold to grow. Mold may appear on fabric, wallpaper glue, wood, and other surfaces. Warm temperatures and high humidity increase the likelihood of mold.

If you’re touring an apartment and believe you see mold, ask the agent or person showing the unit for further information. Should they identify mold in the unit, the owner should take proper steps to remove the mold before your move-in date.

What to Do When You Find Mold in Your Apartment?

If you discover mold while living in your apartment, you should contact your landlord or property manager to address the issue. Some mold spots may be safe and easy to clean on your own, but documenting the incident to building owners can establish a timeline if the problem continues or grows worse. Landlords are responsible for properly cleaning mold and improving any situations that continue to increase the presence of mold in the apartment Your building manager may send someone to come and clean the mold and address the root of the problem, like a leaky pipe.

If your landlord or property manager does not address the mold, call 311 to report the issue or file a complaint online to the Department of Housing Preservation and Development (HPD). HPD will attempt to contact your building manager and potentially send a uniformed Code Enforcement inspector to review the situation and check for any additional violations. They will ticket the building owner for violations.

Should the situation not improve, you may reserve the right to withhold your rent. However, renters in this position should seek legal counsel before proceeding with this option.

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