The New York City Community Air Survey

NYCCAS Report: 2008-2021

In 2007, the New York City Department of Health and Mental Hygiene (Health Department) established the New York City Community Air Survey (NYCCAS), the largest ongoing urban air monitoring program of any U.S. city. NYCCAS, which began collecting data in December 2008, is a collaboration between the Health Department and Queens College of the City University of New York and provides data to:

This report:

  • Provides a summary of key findings, the air monitoring program, monitoring site selection, and descriptions of the pollutants measured
  • Describes the trends in air pollutant levels from more than a decade of data from winter 2008-2009 through fall 2021 for fine particulate matter, nitrogen dioxide, nitric oxide, black carbon, wintertime sulfur dioxide and summertime ozone
  • Presents maps of neighborhood air pollution levels by year
  • Identifies the local sources that contribute to high levels of these pollutants in New York City neighborhoods

Key Findings

Citywide, annual average levels of four key pollutants have gone down between the first year of monitoring, 2009, and the most recent year of data, 2021.

  • Fine particles (PM2.5)         -40%
  • Nitrogen Dioxide (NO2)    -38%
  • Nitric Oxide (NO)              -58%
  • Sulfur Dioxide (SO2)          -97%

Air quality improved significantly after local regulations required building owners to convert to cleaner heating oils by 2015. These heating oils were a major source of SO2 in New York City. In 2021, only eight of our 90 sites detected any SO2, and the levels at those sites were similar to SO2 levels measured on Whiteface Mountain in the Adirondack Mountains, demonstrating the success of the clean heating oil requirements.

Air quality changes with location.

PM2.5, NO2, NO, and BC are highest in:

  • Areas with higher density of commercial cooking grills and charbroilers
  • Industrial areas, specifically areas with higher density of warehouses
  • Areas of higher traffic density
  • Areas with higher building density

Ozone (O3) levels are highest in:

  • Areas with lower vehicle emissions

Methods

The Health Department designed NYCCAS to understand how average air pollution levels vary from place to place within New York City. NYCCAS staff mount samplers on street light poles 10 to 12 feet off the ground along residential and commercial streets and in parks. The monitors use a small battery-powered pump and filters to collect air samples. Our air samplers are deployed at each NYCCAS site once each season and collect data for a two-week period. Samples are collected in all seasons for NO, NO2, PM2.5 and BC; in the summer for O3; and in the winter for SO2. For more details on sample collection methods, see Appendix 1 (PDF).

The New York State Department of Environmental Conservation also has a network of 19 air quality monitors in New York City that are required by the Federal government, but they are mounted on building roofs. We placed our air samplers at street level to measure pollution where people spend time, and where traffic-related pollution levels are usually higher.

NYCCAS has also deployed a limited number of monitors that can measure PM2.5 levels in real time. These monitors allow us to monitor air pollution as it changes based on the time of day, weather or due to local pollution sources, such as heavy-duty trucks. The data from these monitors is available here: Real-Time Air Quality.

Pollutants Measured

Fine particles (PM2.5) are tiny airborne solid and liquid particles less than 2.5 microns in diameter. PM2.5 is the most harmful urban air pollutant. It is small enough to penetrate deep into the lungs and enter the bloodstream, which can worsen lung and heart disease and lead to hospital admissions and premature deaths. PM2.5 can either be directly emitted or formed in the atmosphere from other pollutants. Fuel combustion in vehicles, boilers in buildings, power plants, construction equipment, marine vessels and commercial cooking are all common sources of PM2.5. Between 20% and 30% of the PM2.5 in New York City's air comes from sources in areas upwind from the city, such as coal-burning power plants in the Midwest.

Black carbon (BC) is one type of PM2.5 and is the sooty black material emitted from gas and diesel engines, coal-fired power plants and other sources that burn fossil fuels. It comprises up to 20% of fine particulate matter in New York City. Unlike other fine particles, BC is primarily from local sources. Inhalation of BC is associated with health problems, including respiratory and cardiovascular disease, cancer and birth defects. BC also contributes to climate change by altering the patterns of rain and clouds.

Nitrogen dioxide (NO2) and nitric oxide (NO) are part of a group of pollutants called "oxides of nitrogen" (NOX). Exposures to NOX are linked to increased emergency department visits and hospitalizations for respiratory conditions, particularly asthma. NOX also reacts with other compounds in the atmosphere to form PM2.5 and ozone. A variety of combustion sources produce NOX in New York City, including motor vehicles, buildings, marine vessels and construction equipment.

Ozone (O3) forms at ground level when NOX emissions combine with sunlight and other airborne pollutants. Measured O3 concentrations are often highest in the summer and downwind from areas with high NOX emissions, such as places with high traffic density. In areas with heavy traffic, NOX reacts with any ground-level O3 to reduce O3 concentrations. As a result, NYCCAS has measured lower O3 levels near roadways, in city centers and in other areas of high NOX emissions density. Higher levels of O3 are seen in areas away from dense traffic and building emissions.

Sulfur dioxide (SO2) is produced mainly by burning oils with high sulfur content, such as No. 4 and No. 6 oil (also known as residual fuel oil), or high-sulfur No. 2 oil. The primary use of fuel oil in NYC is to heat buildings and water, which is why we only monitor it in the winter. Some high-sulfur oil is also used to generate electricity and power marine vessels. SO2 exposures can worsen lung diseases, causing hospitalizations and emergency department visits for asthma and other respiratory conditions. SO2 also contributes to the formation of PM2.5 in the atmosphere, resulting in PM2.5 exposures downwind of SO2 emissions.

NYCCAS Sites

The monitoring locations represent a wide variety of New York City environments – sidewalks, busy streets, parks and quiet neighborhood roads. Most of the sites (80%) were chosen by the Health Department to ensure representation in all types of neighborhoods, including residential, commercial and industrial areas. The locations vary in how many trees they have and in the density of traffic and buildings. The remaining sites were selected because they are near potentially high-emission locations that were not captured in the initial assignment. These include Times Square, the Port Authority Bus Terminal and the entrance to the Holland Tunnel. The number of sites has changed over the years as we have learned about air quality in our city. In 2021, we monitored 78 routine locations and an additional 15 sites in low-income neighborhoods that would benefit from additional monitoring to understand potential sources of emissions. We refer to these as Environmental Justice Sites, in green on the map.

Pollutant Maps

NYCCAS installation

Since it is impossible to sample the air in every location in New York City, we monitor representative sites to determine how pollution levels vary in relation to traffic, buildings, trees and other neighborhood factors. We use NYCCAS monitoring data along with data on land use, traffic, building emissions and other neighborhood factors around the monitors to build a land-use regression (LUR) model. We then use the associations from these models to estimate the seasonal average air pollution levels at locations across the city, including places where no NYCCAS measurements were collected. For more details on emission source data, see Appendix 1 (PDF). For more details on the analysis methods, see NYCCAS Scientific Publications.

In the maps below, you can select a pollutant to see how air pollution is distributed throughout the city and how it has changed over time. The city’s air quality has changed significantly since NYCCAS began monitoring, as can be seen in the maps below. The levels of BC, NO2, NO, SO2 and PM2.5 have been significantly reduced citywide. The areas where we see the highest levels of these pollutants has also shifted.

Over time, there are better data available for us to understand the relationships between land use and pollution, and the air pollution patterns have shifted as the city changes. Although industrial land use has been a primary indicator of BC, NO, NO2 and PM2.5 pollution in the past, in the most recent years of data we see evidence that the density of warehouses with loading docks better explains the difference in pollution levels between neighborhoods. Areas with a higher density of warehouses, such as Newtown Creek area in Queens and Brooklyn, near JFK airport, Sunset Park in Brooklyn and Hunts Point in the Bronx, have higher levels of pollution.

There have been too few sites with SO2 values above the detection limit for us to include data after winter 2017-2018 in these maps and charts. SO2 levels have gone down dramatically since Local Law 43 of 2010 prohibited the burning of heavy fuel oil (No. 6) in New York City buildings (PDF). Historical maps for SO2 and other pollutants are available by clicking on the “All years” button below.

Winter and summer average maps for BC, NO2, NO and PM2.5 are available in Appendix 2 (PDF).

Citywide, annual average levels of Black Carbon declined by 45% between 2009 and 2021, an average of 0.05 micrograms per cubic meter per year.

Across the 13-year period, higher levels were consistently seen near warehouses within industrial areas (reflecting increased truck traffic density) and in areas with higher nearby commercial cooking grills/charbroilers.

In 2021, seasonal average BC concentrations across NYCCAS monitoring sites ranged from 0.23 to 1.9 micrograms per cubic meter.

Citywide, annual average levels of Nitric Oxide declined by 58% between 2009 and 2021, an average of 1.7 parts per billion per year.

Across the 13-year period, higher levels were consistently seen at sites with higher nearby building density, emissions from overall traffic and from truck traffic related to warehouses.

In 2021, seasonal average NO concentrations across NYCCAS monitoring sites ranged from 2.6 to 59.9 ppb.

Citywide, annual average levels of Nitrogen Dioxide declined by 38% between 2009 and 2021, an average of 0.86 parts per billion per year.

Across the 13-year period, higher levels were consistently seen at sites with higher nearby building and traffic emissions. The persistence of building density as the most important indicator of NO2 reflects the continued use of fossil fuel combustion for heat and hot water, even as fuels become cleaner and equipment more efficient.

In 2021, seasonal average NO2 concentrations across NYCCAS monitoring sites ranged from 3.7 to 37.1 ppb.

Since the first summer (2009) when relatively cool temperatures contributed to lower levels of Ozone, citywide summertime average levels varied slightly year to year (ranging from 27.8 ppb to 31.4 ppb between 2010 and 2021), without a consistent trend.

Higher levels were consistently measured at sites with lower traffic density and lower NO2 concentrations such as areas of outer Queens, Brooklyn, and Staten Island, reflecting less removal of ozone from the atmosphere by fresh combustion NOX emissions.

In summer 2021, seasonal average O3 varied from 24.3 to 38 ppb across the monitoring sites.

Citywide, annual average levels of fine particulate matter declined by 40% between 2009 and 2021, an average of 0.4 micrograms per cubic meter per year.

Recently, higher levels of PM2.5 have been seen at sites with nearby commercial cooking grills/charbroilers and traffic emissions. This is largely due to buildings using cleaner fuels for heating and therefore emitting less PM2.5 than when NYCCAS began monitoring.

In 2021, seasonal average PM2.5 concentrations across NYCCAS monitoring sites ranged from 2.4 to 15.1 micrograms per cubic meter.

Pollutant Trends

Since monitoring began in winter 2008-2009 in New York City, we have seen a decrease in most of the air pollutants we measure. However, the concentrations of NO2, NO and PM2.5 continue to be higher in industrial zones with more diesel truck traffic, neighborhoods with large numbers of restaurants, and areas of higher traffic and building density.

Air pollution changes not only by neighborhood, but also by season. Some pollutants are highest in certain seasons of the year because of either weather patterns or emissions sources. For example, O3 is produced when NO and NO2 and other airborne pollutants react in the presence of heat and sunlight. Therefore, we only monitor O3 in the summer when direct sunlight is highest and days are longer.

The figure below illustrates how the levels of each air pollutant change by season from winter 2008-2009 to fall 2021. We compare trends among locations with high, medium and low densities of the most common sources of each pollutant.

Pollutant by Source

Pollutant Predictors

NYCCAS data were analyzed using a land-use regression (LUR) model. LUR models estimate associations among pollution levels, average traffic, building emissions, land use and other neighborhood factors around the monitoring sites. The pollution sources that contribute most to differences in concentrations of NO, NO2, BC, and PM2.5 across NYC are listed in the table below. SO2 is now so low in NYC that it is not possible to build a LUR model for the most recent years of data.

Fuel used to provide heat and hot water in buildings has become significantly cleaner under state and local regulations requiring use of cleaner burning fuels. As a result, commercial charbroiling and grilling operations have become a more important source of PM2.5 emissions over the past several years. The number of commercial cooking charbroilers and grills in an area now explains PM2.5 and Black Carbon differences among neighborhoods better than building emissions. For more information on these changes, see Tracking changes in New York City's sources of air pollution.

Indicator Description Associated sources and interpretation
Loading docks Number of warehouse loading docks within 600 m Emissions from trucks idling and traveling to and from warehouses
Commercial cooking Number of permitted commercial cooking grills and charbroilers within 100 m Emissions from commercial cooking
Truck and bus traffic density PM2.5 emissions from truck and bus traffic within 900 m PM2.5 emissions from trucks and buses estimated from emissions rates and vehicle miles traveled
Road density Area of impervious road surface within 100 m Emissions of motor vehicles on paved roadways
Indicator Description Associated sources and interpretation
Loading docks Number of warehouse loading docks within 600 m Emissions from trucks idling and traveling to and from warehouses
Bus traffic Location on a bus route (compared to non-bus route locations) Emissions from buses and other vehicles on busy roadways - indicator of traffic congestion
Traffic density Traffic density, weighted by relative NOX emissions rates and vehicle type (car, truck, bus) within 400 m NOX emissions from all on-road motor vehicles based on vehicle miles and the relative emission rates of different vehicle types
Impervious surfaces Percent impervious surface within 100 m Emissions of motor vehicles on paved roadways
Indicator Description Associated sources and interpretation
Building density Area of interior building space within 1,000 meters Combustion of heating oil and natural gas
Loading docks Number of warehouse loading docks within 900 m Emissions from trucks idling and traveling to and from warehouses
Traffic density Traffic density, weighted by relative NOX emissions rates and vehicle type (car, truck, bus) within 1000 m NOX emissions from all on-road motor vehicles based on vehicle miles and the relative emission rates of different vehicle types
Impervious surfaces Percent impervious surface within 100 m Emissions of motor vehicles on paved roadways
Bus traffic Location on a bus route (compared to non-bus route locations) Emissions from buses and other vehicles on busy roadways - indicator of traffic congestion
Indicator Description Associated sources and interpretation
NO2 Level of NO2 measured at the same location Nitric oxides (NOx) at elevated concentrations react with ground-level ozone (O3) to create NO2 and O3, also called "quenching ozone."
Tree cover Tree cover within 50 m Reduced levels thorugh reactions of ozone with leaf surfaces.
Indicator Description Associated sources and interpretation
Commercial cooking Number of permitted commercial cooking grills and charbroilers within 1,000 meters Emissions from commercial cooking.
Loading docks Number of warehouse loading docks within 600 m Emissions from trucks idling and traveling to and from warehouses
Traffic density Weighted by relative PM2.5 emissions rates by vehicle type (car, truck, bus) within 250 meters PM2.5 emissions from all on-road motor vehicle based on vehicle miles and the relative emissions rates of different vehicle types

Conclusion

This report underscores the importance of emissions reduction efforts over the past decade and highlights the continued need to reduce emissions citywide. The City’s sustainability plan, PlaNYC, and its roadmap to reduce greenhouse gas emissions, 80x50, have already and will continue to improve air quality, providing important public health benefits to all New Yorkers. These strategies and measures include:

  • Reducing emissions from commercial charbroiling through regulations and technical support to restaurants
  • Creating low or zero emission freight networks and reducing reliance on trucks
  • Improving and expanding public transit
  • Getting the most polluting trucks off New York City streets
  • Accelerating the phase-out of fossil fuel combustion in buildings focusing on the communities most impacted by air pollution related health impacts

Air quality in New York City has greatly improved over the past decade and will continue to improve with efforts to control emissions from the most important sources.

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