They are mammoth warehouses large enough to fit football fields inside them, handling many of the more than 20 billion packages Americans send and receive each year.

But for people who live around them, the round-the-clock semitrailer traffic at these giant hubs significantly worsens air pollution, according to a new NASA-funded study that tracked pollutants from space.

The research, led by scientists at George Washington University, is the first of its kind; it used satellite technology to measure a harmful traffic-related pollutant called nitrogen dioxide, zooming in on nearly 150,000 large warehouses across the United States. They found that nitrogen dioxide, which can lead to asthma and other health problems, jumped 20 percent on average near the warehouses. At the busiest facilities the increase was higher.

“The average warehouse built since about 2010 looks a lot different than the warehouses that were built prior to that, with lot more loading docks, a lot more parking spaces,” said Gaige Kerr, the lead author of the study and an assistant research professor of environmental and occupational health at the Milken Institute School of Public Health of George Washington University.

“They’re also increasingly being built in dense clusters next to other warehouses, and attract a lot more traffic, specially heavy-duty vehicles. And that’s very bad when it comes to pollution.”

The research underscores how logistics hubs have fast become a significant contributor to pollution as American heavy industry, a traditional source of pollution, has receded over the past decades and as the power sector has cleaned up its power plants.