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Study: 2020 Local Ambient Air Pollution Concentrations Fell Sharply as Vehicle Traffic Shrank & Clairton Plant Operations Held Steady

PITTSBURGH--(BUSINESS WIRE)-- A study analyzing area traffic and ambient air quality data from an air quality monitoring station near U. S. Steel’s Mon Valley Works found that there was a 40% decrease in particulate matter (PM2.5) ambient air concentrations when comparing readings from before and after the COVID-19 stay-at-home order in Spring 2020.

In the study, environmental consulting firm Trinity Consultants verified U. S. Steel’s finding that included an analysis of data collected from the Liberty Monitor, along with Pennsylvania Department of Transportation (PennDOT) traffic data taken from within a 40-mile radius of that site. Over the period reviewed, there was no change in production at the Clairton Plant, while the number of total vehicles on southwestern Pennsylvania roadways in the area examined fell by 50%.

The data review opportunity afforded by these unique circumstances, suggests a direct, significant correlation between the amount of vehicle traffic and Liberty Monitor PM2.5 concentrations. Both U. S. Steel and Trinity intend to further examine these findings and share them with the appropriate state and local authorities, including the Allegheny County Health Department. These findings are consistent with several other reports of substantial improvements in PM 2.5 concentrations in other cities during similar reductions in vehicle traffic as a consequence of COVID-19 shelter in place orders.

“Trinity confirmed that there was a significant correlation between vehicle traffic volumes and monitored PM2.5 concentrations at Liberty around the time of the COVID-19 stay-at-home orders. Further evaluation of this dataset, as well as traffic and monitor concentrations from other timeframes, could prove useful to more fully understand PM2.5 contributions,” said Ian Donaldson, managing consultant, Trinity Consultants.

“These findings shed light on the impact that mobile sources, such as vehicle emissions have on our community, including during weather conditions such as inversions, and indicate the importance of multifaceted strategies to address the impact of inversions. We look forward to exploring this further and support and encourage similar efforts by other members of our community,” said Brett Tunno, DrPH, environmental engineer, U. S. Steel.

U. S. Steel is targeting a 20% reduction in greenhouse gas emission (GHG) intensity by 2030, using 2018 as the baseline year for measurement. The company views its ‘Best of Both’ strategy as a companywide investment in sustainability, by incorporating electric arc furnace (EAF) steelmaking to reduce GHG emissions and improve the scrap recycling rate within U. S. Steel.

Founded in 1901, the United States Steel Corporation is a Fortune 250 company and leading integrated steel producer. With extensive iron ore production and an annual raw steelmaking capability of 23.2 million net tons, U. S. Steel produces high value-added steel products for the automotive, infrastructure, appliance, container, and energy industries. The company’s “Best of Both” integrated and mini-mill technology strategy is advancing a more secure, sustainable future for U. S. Steel and its stakeholders. With renewed emphasis on innovation and customer focus, the company produces cutting-edge products such as U. S. Steel’s proprietary XG3™ advanced high-strength steel. U. S. Steel is headquartered in Pittsburgh, Pennsylvania, with world-class operations across the United States and in Central Europe. For more information, please visit

Amanda Malkowski
External Lead
Corporate Communications
T – (412) 433-2512
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Source: United States Steel Corporation