WASHINGTON — The big trucks roar out of Port Newark, N.J., like a beastly herd, snorting, grinding gears and belching exhaust as they rush through the predominantly black South Ward neighborhood.
‘‘In one hour, no matter when we count, we have about 400 trucks come through,’’ Kim Gaddy said.
The diesel trucks help move $1 billion worth of cargo annually in and out of Port Newark, a cornerstone of the nation’s third-largest port system — the Port of New York and New Jersey — and the source of tens of thousands of jobs. But the pollution exacts a heavy toll on residents, advocates say.
And they fear it could get much worse.
The widening of the century-old Panama Canal will allow a new generation of gigantic cargo ships to slip between the Atlantic and Pacific oceans within two years. Bigger ships mean more trucks hauling goods in and out of port communities — areas that studies have shown are disproportionately poor, have higher minority populations, and a greater incidence of asthma and other respiratory illnesses.
Gaddy and her three children, ages 8 to 24, have asthma, as do thousands of other adults and children in Newark, where the asthma-related death rate is nearly twice that of the suburbs. Environmentalists and residents say that particulate-matter pollution from trucks contributes to poor health in areas that have the fewest resources to fight it.
Nationwide, African Americans and Latinos who live around ports are far more likely to breathe dirty air, according to a 2011 study by a global research firm, ICF International, published in the Journal of Public Health.
‘‘You hear about the killings in Newark, but the heart attacks we die of in higher numbers are never talked about,’’ said Gaddy, an organizer for the New Jersey Environmental Federation. ‘‘The pollution is killing us. We’re fighting for our lives.’’
In Newark’s Ironbound community near the port, Miguel Duran, 33, has asthma, as do his children. His 13-year-old son said he sees the shimmering fumes of idling trucks. He watched the trucks go by Hawkins Elementary School in Ironbound when he was a student there, playing on the recreation field, inhaler in his pocket.
The $5.25 billion project to widen the canal — started in 2007 and expected to be finished in 2015 — has touched off a race among ports along the Atlantic Ocean and Gulf of Mexico eager to attract the world’s largest container ships and their enormous cargo. They are investing billions of dollars to deepen their harbors and expand their operations.
Only a handful of the 360 ports in the United States can handle the biggest cargo ships, and only two, Baltimore and Norfolk, Va., are in the east. Many of the superships carry cargo from Asia and use West Coast ports.
Residents and environmentalists in the South Ward and Ironbound are fighting a proposal to make way for the big ships and increase truck traffic at Port Newark: raising the nearby Bayonne Bridge from 150 feet to 215 feet so towering stacks of cargo can pass beneath it.
The bridge-raising plan is supported by Newark’s mayor, Cory Booker, who called the port system an economic engine that drives the region.
Booker, a Democrat, argues that pollution will probably decrease because the new ships will be more fuel efficient and that a program will help truck drivers buy more fuel-efficient rigs and get rid of older models.
That same argument is echoed by other officials. A spokesman for the Port Authority of New York and New Jersey, Christopher Valens, said raising the Bayonne Bridge will lead to only ‘‘a nominal change’’ in the number of trucks that load at the port every year.
But the Environmental Protection Agency has its doubts. ‘‘We believe that changes in cargo movement associated with the project could result in some change in community impacts, particularly related to port traffic and air quality,’’ John Filippelli, director of the clean air and sustainability division for EPA’s Region 2, wrote in a March letter to the Coast Guard commander.
The port authority recently entered into an agreement with the New Jersey Department of Environmental Protection that could pave the way to raising the bridge. The department said it would monitor the port to determine if there is an increase in trucks and a decrease in air quality.
But advocates say the department should not have entered into an agreement without requiring an environmental impact study of air quality, and they said they are considering legal action.