NYC congestion pricing study estimates 13% particulate pollution drop in toll zone

New York City’s congestion pricing program was associated with roughly 13% less fine-particle pollution inside its Manhattan toll zone during its first year, according to a Columbia-led study reported on October 7. The finding gives residents and other cities a new estimate of the program’s possible air-quality effect, but an earlier city evaluation found no statistically significant pollution change attributable to tolling. The two assessments used different measurements and methods.

The new analysis, described by Columbia Climate School and published in Environmental Science & Technology Letters, estimates pollution inside the zone relative to what trends outside it would predict. That distinction matters because fine-particle pollution, known as PM2.5, was already falling across the region. The study does not establish that every measured decline inside the zone resulted from the toll.

How the Columbia study estimated the air-quality change

New York began charging most vehicles entering Manhattan south of 60th Street on January 5, 2025. The Central Business District Tolling Program was designed to reduce traffic and raise money for public transit. Columbia’s researchers examined its first year using real-time pollution readings from 15 New York City Community Air Survey sites, hourly vehicle counts at two Manhattan tunnel crossings and satellite observations of nitrogen dioxide.

The researchers compared monitoring sites inside and outside the toll zone while accounting for weather and seasonal effects. They estimated that PM2.5 within the zone was about 1.3 to 1.4 micrograms per cubic meter lower than expected from outside-zone trends, equivalent to roughly 13%. This is a modeled estimate of the change attributed to tolling, not a claim that pollution fell by 13% at every location.

Study co-author Daniel M. Westervelt, of Columbia’s Lamont-Doherty Earth Observatory, described the estimated reduction within the zone as modest. At two sites outside the zone, near the Brooklyn-Queens Expressway and Mott Haven, the researchers estimated an increase of about 0.5 micrograms per cubic meter. Those estimates were not statistically significant, and Westervelt cautioned against treating them as definite effects of tolling.

Why the city’s earlier assessment was more cautious

New York City’s Health Department published a separate first-year evaluation in August. It examined PM2.5, nitrogen dioxide, nitric oxide and black carbon, including readings from 12 sites inside the zone and sites in environmental-justice neighborhoods near major highways. Using a Van Wyck Expressway monitoring site as a control, the department applied a time-series model that accounted for weather and longer-term pollution trends.

The department concluded that pollution inside the zone decreased slightly or stayed the same in 2025 compared with 2024, but that measured levels were not significantly different because of congestion pricing. It found no tolling-attributable pollution increase at the environmental-justice sites it monitored. At one Brooklyn-Queens Expressway location, one pollutant improved less than at the control site. Those findings concern the department’s monitored locations and statistical approach; they do not directly retest Columbia’s estimate.

Separating a toll’s effect from other changes is difficult. The Health Department says weather, wildfire smoke, heating, cooking and construction can affect readings, while air quality in the city has generally improved over nearly two decades. Its report estimates that traffic accounts for roughly 14% of New York City’s PM2.5 emissions and 20% of its nitrogen-oxide emissions. A change in vehicle volumes therefore need not produce an equally large change in measured pollution.

What residents outside the toll zone still need to know

The possibility of pollution shifting to neighborhoods outside the zone remains a local concern. Reporting on the city study in August, The New York Times quoted South Bronx Unite’s environmental-justice and research director, Micaela Martinez, saying some South Bronx communities had experienced an increased burden, even as the group welcomed positive borough-level news. The city’s finding of no attributable increase at its monitored sites and Columbia’s statistically inconclusive estimates near two outside-zone locations do not settle every neighborhood-level question.

Columbia also reported that satellite-observed nitrogen dioxide fell more than 20% across the metropolitan area in 2025 against a 2018–2024 baseline, but said it could not attribute that regional drop to congestion pricing. Neither first-year evaluation demonstrates a health benefit or establishes that the observed air-quality patterns will persist. Westervelt has called for longer-term analysis, additional pollutants and improved satellite observations; the Times reported that the Health Department planned continued monitoring through the end of 2026 and beyond.