MONACA, Pa. — The massive ethane cracker plant in Beaver County is bringing thousands of jobs to Western Pennsylvania. But Action News Investigates has learned it may also bring thousands of tons of air pollutants to a region that already has some of the nation's dirtiest air.

At the cracker plant site, dozens of cranes soar into the sky as thousands of construction workers assemble the petrochemical facility that will convert natural gas liquids into plastics.

The project has breathed new life into what was an industrial wasteland. But some medical experts who are also environmental advocates said breathing will be much harder once the plant is up and running.

“To me it's about breathing. It's about health,” said Dr. Ned Ketyer, a retired pediatrician affiliated with Pitt's Climate and Global Change Center. He said the plant's toxic fumes will affect health as far south as Pittsburgh. “Allegheny County is already dealing with higher risks of cancer because of air pollution and I believe this is going to make things much worse,” Ketyer said.

Volatile organic compounds, or VOCs, are a major industrial pollutant. Environmental Protection Agency records show the industrial plant with the largest VOC emissions in Western Pennsylvania is the Clairton Coke Works, with 291 tons of VOCs in 2014, the most recent year available.

But the cracker plant's state permit says it is allowed up to 522 tons of VOCs per year.

Ammonia is another air toxin. “That can have immediate effects on the brain and the liver,” Ketyer said. EPA records show the Coke Works and U.S. Steel's Edgar Thomson Works in Braddock combined emitted 139 tons of ammonia in 2014. But the cracker plant's permit allows for even more -- 152 tons.

The cracker plant is also allowed to emit 2.2 million tons of carbon dioxide per year. That is equivalent to 488,000 cars.

Shell and the state Department of Environmental Protection said there is no need to worry. “Those numbers seem large but they are absolutely the lowest numbers that can be achieved using the technology that's currently available,” said Ron Schwartz, regional director for the DEP.

He said the DEP did two studies of the cracker plant's potential health impacts and they showed “that there would be no detrimental effect on human health through the environment, and the Department of Health also reviewed those results and concurred with our findings.”

Shell spokesman Joseph Minnitte said the company "takes the health of the community and our staff very seriously." Further, “Inhalation risk assessments performed by Shell and PA DEP concluded that chronic cancer and non-cancer risks as well as acute non-cancer risks do not exceed PA DEP's benchmarks," Minnitte said.

But chemist and environmental advocate Wilma Subra, of Louisiana, disagrees. “The air emissions are going to be so severe, they're going to notice it immediately,” she said. Subra has studied the impact of cracker plants in Louisiana, where an industrial area between New Orleans and Baton Rouge has been called "cancer alley."

She said that, as in Louisiana, the Beaver cracker will lead to more petrochemical plants in the area, and that will have a dramatic impact on public health. “It's going to be as bad or worse than any of the plants in Louisiana and then suddenly, you're going to have a Pennsylvania cancer alley like we have here in Louisiana,” she said.

Asked if the cracker plant could lead to a cancer alley in Pennsylvania, Schwartz said, “That's not something I can comment on.”

In Beaver, where the business district is just a couple of miles from the cracker plant, shoppers said they were excited about the number of jobs being created. But some of them said they had no idea how much pollution may be coming out of the plant. “It's not a big conversation that I hear in town,” said Gayle Latulippe, of Beaver.

But some area residents were alarmed to hear the cracker plant is allowed more VOC emissions than the Clairton Coke Works.

“Oh, it's a big concern. I mean, how are we supposed to breathe?” said Liz Zagorski, of Beaver. She lives a mile from the plant. She said she is especially worried for her great-nephew: “What's it going to be like when he gets to be old enough to be running around?” she said.

Subra said local residents are right to be worried. “The politicians are going to be looking back and their children are going to be looking at them saying, 'Why did you do this? Why did you sell us out?'" she said.

A second cracker plant, in eastern Ohio, is in the planning stages. And West Virginia officials are discussing the possibility of another cracker plant.

A consent agreement between Shell and several environmental groups will require continuous air monitoring at the fence line of the cracker plant. The DEP said it will also monitor the air near the plant starting early next year.