New York City
An overview of the city, the people, and its air quality
About New York City...
Location
New York City (NYC) is situated on the northeastern coast of the United States, at the confluence of the Hudson River and the Atlantic Ocean. It consists of five boroughs: Manhattan, Brooklyn, Queens, The Bronx, and Staten Island.
History
NYC, originally New Amsterdam, was founded by the Dutch in 1624 and renamed by the English in 1664. It was pivotal in the American Revolution and grew rapidly in the 19th century due to immigration and industrialization. In the 20th century, it became a global center for finance, media, and arts, despite challenges like the Great Depression. Revitalization in the 1990s led to its current status as a diverse, cultural, and economic powerhouse.
Population density map of New York City and surrounding areas.
Population
In 2023, with an estimated population of 8,258,035 people across 300.46 square miles (778.2 km²), NYC ranks as the most densely populated city in the United States.
'Smaze' around the Empire State Building in 1952 (John Duprey/NY Daily News Archive/Getty Images).
Air Pollution in NYC
In the 1950s, a toxic cloud of pollution, termed 'smaze' (smoke and haze), settled over NYC for six days due to trapped emissions from coal power plants, factories, and cars. Similar events occurred in 1963 and 1966, causing dozens of deaths. At the time, the city had only one air quality monitoring station and a crude version of an air quality index. These severe pollution incidents helped lead to the creation of the Clean Air Act, the U.S. Environmental Protection Agency (EPA), and the modern EPA’s Air Quality Index (AQI), which guides public health warnings and responses.
Due to these initiatives, air quality in NYC has improved over the past decades. Reductions in sulfur dioxide (SO 2 ), carbon monoxide (CO), and lead levels resulted from actions such as phasing out leaded gasoline, enhancing vehicle emission standards, and regulating industrial emissions.
Throughout the 1990s and early 2000s, further improvements were achieved with advancements in technology and stricter enforcement of air quality standards. The introduction of cleaner fuels and the adoption of cleaner energy sources significantly reduced particulate matter (PM) and nitrogen dioxide (NO 2 ) levels.
However, ozone (O 3 ) pollution remains challenging, often exceeding National Ambient Air Quality Standards (NAAQS), particularly in summer. NYC is still classified as a nonattainment area for this pollutant under the 2015 8-hour O 3 standard.
Time series of SO 2 , PM 2.5, NO 2 , and O 3 concentrations from 2009 to 2022 (NYC Environment and Health Data Portal).
U.S. EPA Emissions Data for NYC
The U.S. EPA releases the National Emissions Inventory (NEI) every three years, providing a comprehensive estimate of air emissions for criteria pollutants, their precursors, and hazardous air pollutants from various sources. The NEI primarily relies on data provided by State, Local, and Tribal air agencies for sources within their jurisdictions, which is then supplemented and refined by the U.S. EPA for thorough coverage and accuracy. For PM 2.5 and CO, emissions mainly originate from the city due to traffic and residential sources.
U.S. EPA emissions data for PM 2.5 and CO in 2017.
Criteria Air Pollutants in NYC
Due to the Clean Air Act, the U.S. EPA regulates six 'criteria pollutants' nationwide: particulate matter, ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide, and lead. All of these pollutants have been shown to pose a threat to both public health and the environment. To regulate these pollutants, there are nationwide standards and monitoring efforts. Several U.S. EPA monitors are distributed across New York State, with most of the sites concentrated within the most populated areas of NYC. These sites monitor five out of the six criteria air pollutants (except lead).
Criteria air pollutants throughout 2023
Nitrogen Dioxide (NO 2 )
The U.S. EPA conducts daily in-situ measurements of NO 2 throughout the State of New York. This pollutant has both natural and anthropogenic sources. Anthropogenic sources include industry and transportation, while natural sources include plant emissions, lightning, and biomass burning.
The following map shows the daily maximum values for each of these sites throughout 2023.
Sulfur Dioxide (SO 2 )
The main sources of SO 2 emissions are fossil fuel combustion and natural volcanic activity. This pollutant is an irritant, affecting the respiratory system, eyes, and skin. SO 2 is also a precursor to particulate matter.
Carbon Monoxide (CO)
It is a colorless, odorless, and tasteless gas produced by combustion processes. It is emitted from space heaters, car exhausts, stoves, fireplaces, and any other devices powered by fossil fuels. This criteria air pollutant can cause chest pain in vulnerable individuals as well as fatigue in healthy people.
Ozone (O 3 )
There are two types of ozone: good ozone and bad ozone. Good ozone is found high in the stratosphere, while bad ozone exists in the lower layer, known as the troposphere. At ground level, ozone is a potent oxidant, damaging the cardiovascular system and causing symptoms such as coughing, chest tightness, and shortness of breath. The U.S. EPA monitors O 3 levels closely and sets standards that cities must meet.
Particulate Matter (PM 2.5 )
Particulate matter is categorized by its size (the diameter of the particle in μm) rather than its composition. The two categories regulated by U.S. EPA are PM 2.5 and PM 10 . On the right, the concentration of particulate matter in μm/m 3 across NYC is displayed.
Particulate Matter (PM 10 )
Coarser particulates, categorized as PM 10 , are also regulated in NYC. However, there are not nearly as many sites for PM 10 as there are for PM 2.5 .
U.S. EPA averages of gas and particulate pollution, excluding CO.
A wrap up for U.S. EPA monitoring in 2023
As shown in the averages on the left, NO 2 constitutes a significant portion of trace gas pollution. However, CO leads with a yearly average of 375.3 ppb. NO 2 presents an average of 27.21 ppb, while O 3 and SO 2 have yearly averages of 37.1 ppb and 0.992 ppb, respectively.
Exploring the Distribution of Emissions in 2022 Report by the NYC Mayor's Office of Climate and Environmental Justice, we can examine greenhouse gas emissions not reported by the U.S. EPA, such as carbon dioxide (CO 2 ).
Distribution of CO 2 emissions by sector in 2022 (NYC Mayor's Office of Climate and Environmental Justice).
Do you want to learn more about the regulations, monitoring, and effects of air pollution in NYC? Check the website below!
Monitoring Surface Ozone using CAMS
CAMS global reanalysis provides surface O 3 concentrations at a resolution of about 80 km. Using deep learning and incorporating fine-scale meteorology features, CAMS can be downscaled to 1 km resolution.
Left: CAMS 8-hr ozone overlaid with U.S. EPA measurements; Right: Downscaled CAMS 8-hr ozone using deep learning from January to September 2023 (Atmospheric and Environmental Research Lab, University of Iowa).
CAMS reanalysis has a good agreement with U.S. EPA measurements. The downscaled and bias-corrected product can further increase the R square by 84% and reduce the bias by 10 ppb.
Left: Comparison between CAMS 8-hr ozone and U.S. EPA measurements; Right: Similar but for the downscaled CAMS 8-hr ozone (Atmospheric and Environmental Research Lab, University of Iowa).
Impacts of Canadian Wildfires on NYC
In June 2023, NYC was heavily impacted by smoke from wildfires raging in Quebec. These wildfires were part of an unprecedented wildfire season in Canada, exacerbated by climate change, which created warmer and drier conditions. As a result, smoke from over 150 wildfires drifted into the northeastern United States, leading to severe air quality issues in NYC and other regions.
Evolution of the Canadian wildfires in June 2023 (NASA Earth Observatory animation by Michala Garrison).
The air quality in NYC plummeted to hazardous levels, with the city recording the worst air quality in the world on June 7, 2023. The AQI reached over 400 in some areas, far surpassing the level considered hazardous for health. This event led to health advisories, especially for vulnerable populations such as children, the elderly, and individuals with preexisting respiratory and heart conditions. Residents were advised to stay indoors, and the city distributed masks to help mitigate the inhalation of harmful particulates.
Plume of Canadian wildfires affecting New York City in June 2023 (National Weather Service New York NY).
In addition, the thick smoke reduced visibility across the city, affecting daily activities and transportation. Flights were delayed, and outdoor events were canceled or postponed due to the unsafe air conditions.
Hourly PM 2.5 concentrations in NYC surpassed 400 µg/m³ on June 7, 2023, with daily concentrations reaching up to 180 µg/m³ on the same day.
Hourly and daily PM 2.5 concentrations in June 2023.
The maps below, generated from HYSPLIT backward trajectories, trace the origin and path of the smoke, illustrating how air parcels transported pollutants from Quebec wildfires to NYC. This example shows the significant impact of long-range pollution transport on distant locations and highlights the importance of addressing transboundary air quality challenges through international cooperation.
HYSPLIT backward trajectory maps showing air parcel movements leading to wildfire smoke arrival in New York City in June 2023.
Environmental Justice
The Fight for Cleaner Air: Environmental Justice and NO x in NYC
In the 19th century, NYC evolved from a modest port into a major metropolis, driven by massive migration and uncontrolled industrialization. To address these challenges, the city invested heavily in infrastructure such as sewers and parks. However, the benefits were not evenly distributed, often favoring wealthier populations at the expense of marginalized communities. For instance, Seneca Village, a thriving predominantly Black community, was demolished to make way for Central Park, exemplifying a stark environmental injustice. Towards the end of the century, public health improvements emerged with the establishment of health and sanitation departments and the construction of sewer systems.
The U.S. EPA employs the Environmental Justice Index (EJI) to measure the cumulative impacts of environmental burdens on human health and health equity. The EJI integrates environmental and demographic indicators at the Census block group level to highlight areas with higher environmental burdens and vulnerable populations.
EJ Index = (The Environmental Indicator Percentile for Block Group) x (Demographic Index for Block Group)
The proximity of individuals of color to Superfund sites has been linked to various adverse outcomes. Superfund sites are locations contaminated by hazardous materials and are considered candidates for cleanup by the U.S. EPA. In neighborhoods like the South Bronx and parts of Brooklyn, where highways cut through densely populated areas, the air reveals a story of disparity. Here, the effects of NO x pollution are evident in increased asthma rates, higher hospital admissions, and heightened community tensions as residents fight for their right to clean air. While affluent areas benefit from stricter zoning laws and greener urban planning, these frontline communities continue to suffer from the legacy of historical industrial zoning and traffic congestion.
Environmental Justice Indexes for demographic indicators (low-income and people of color), NO 2 , superfund proximity, and asthma in New York City (EPA EJScreen Data).
Today, NYC’s industrial landscape continues to contribute to environmental inequities. The map on the right shows power plants across New York State, illustrating how ongoing industrial activities, including energy production, perpetuate the pollution issues that disproportionately affect marginalized neighborhoods. Even though these industries bring economic benefits to the region, they also maintain and exacerbate environmental disparities, impacting communities already burdened by historical and systemic disadvantages.
PM 2.5 and O 3 concentrations in NYC
Pollutant concentrations in NYC vary due to several factors, including traffic and emission sources, ozone formation and transport, the urban heat island effect, and the presence of vegetation and green spaces. Environmental justice adds another important dimension, as lower-income and marginalized communities often face higher pollution levels—such as elevated PM 2.5 concentrations, as shown in the map below—and cumulative environmental burdens. These neighborhoods, typically located near highways and industrial areas, are subject to greater health risks.
Ozone behaves differently than PM 2.5 because it is a secondary pollutant, formed through chemical reactions involving emissions when exposed to sunlight, rather than being directly released from sources. As a result, O 3 levels are typically higher in areas downwind from sources of combustion emissions, such as the Rockaways and Lower Staten Island.
PM 2.5 and O 3 concentrations in New York City in 2022 (NYC Environment and Health Data Portal). Use the slide tool to compare variations between the two images.
EPA Air Now
The Air Now Interactive Map allows us to look at the Air Quality Index (AQI), a a color-coded index designed to communicate whether air quality is healthy or unhealthy. It also showcases information about monitoring sites, concentrations, information about the criteria pollutants, announcements about air quality and more!
But not everything is negative...
NYC has been implementing policies and actions to ensure the safety of its inhabitants. The State of New York is phasing out high-sulfur 'dirty fuels,' which improves air quality, reduces emissions, and saves lives. These efforts have had the greatest impact in neighborhoods with poor air quality and high rates of premature deaths, as shown in the maps below. To protect the most vulnerable populations, NYC has been increasing efforts to monitor emissions and model air quality. Over the past decade, additional monitors have been installed at 15 environmental justice sites.
Reduction in PM 2.5 concentrations and associated health outcomes under a cleaner fuel rules scenario in New York City (NYC Environment and Health Data Portal).
There are also community efforts that seek to inform, support, and inspire change for all residents of NYC. One of these organizations is the New York City Environmental Justice Alliance.
Extreme Heat & Air Quality information.
Looking for a place to volunteer your time and inform your neighbors about air quality? Look no further!
Be a Buddy information.
NYC is diverse and full of life. Improving air quality comes from collaborative efforts between all communities and sectors cohabiting together. Change and progress is in community.
Meet the Team!
From left to right: Odanibe Maghogho, Abril Lunar, Weizhi Deng, Salem Ibrahim, Caroline H. Wikuats.