New Jersey babies born across the river from a Pennsylvania power plant emitting sulfur dioxide had a nearly 7 percent higher risk of arriving with a low birth weight, according to new research.

A spokesman for the firm that operates the plant said Tuesday that the risk no longer exists, since the plant is rarely online, and doesn't use coal now.

But the researchers say theirs is the first such look at a single, verified source of cross-state pollution and its impact on pregnancy and live births. They hope the study, released this week, can help guide public policy.

"The EPA confirmed the pollution was from one single source," said the study's lead author, Muzhe Yang, a Lehigh University economics professor.

Yang believes the study has important implications given the strong association between low birth weight and later implications for the child's health and development.

Yang's team looked at 153,801 live, single births in Warren, Sussex, Hunterdon and Morris counties from 1990 through 2006. The counties are across the Delaware River from the Portland Generating Station, just south of the Water Gap. The study excluded multiple births.

They found that babies born 20 to 30 miles within wind patterns from the plant had a 6.5 percent higher likelihood than usual of being born at a low weight, defined as 5.5 pounds or less.

The risk of a very low birth weight -- 3.3 pounds or less --  increased by 17 percent over babies born outside of the plant's wind patterns, the study found.

The team pulled from multiple state and federal databases that included detailed patient, healthcare, climate and pollution information.

It also purchased wind data recorded at Allentown Lehigh Valley International Airport – a weather station close to the power plant.  In general, the wind near the power plant blows east into New Jersey.

The study has its roots in a 2010 New Jersey Department of Environmental Protection finding that the Portland plant was responsible for sulfur dioxide pollution over the four counties and the polluted communities were downwind.

The DEP showed that the four counties often suffered sulfur dioxide levels above the National Ambient Air Quality Standards.

In 2011, the EPA ruled that the plant had to reduce emissions within three years.

At the time, Portland was a coal-fired plant. NRG Energy bought the plant in December 2012 when the case was still making its way through the courts. NRG shut the coal units down in 2014 and paid $1 million to fund environmental improvements. David Gaier, a spokesman for NRG, said three turbines on site barely run, but when they do they use natural gas or heating oil.

The most recent EPA data available show the plant reduced sulfur dioxide emissions by 86 percent between 2010 and 2014, when it was phasing out coal.  It reported zero sulfur dioxide emissions in 2015 – the last year data are available.

Yang said the study could help craft policy in pollution cases that cross state lines. He said state regulations and timetables are often different from each other.  So, it's possible federal coordination would help.

Yang was joined in the study by Rhea A. Bhatta, a data analyst at the University of Pennsylvania's department of pathology and laboratory medicine; Cheng-I Hsieh, a professor at National Taiwan University's department of bioenvironmental systems engineering; and, Shih-Yi Chou, an economics professor at Lehigh.

The peer-reviewed study was published in the Journal of Policy Analysis and Management.