Low Birth Weights in New Jersey Correlated to Coal Power Plant Emissions in Pennsylvania

Alana Cook
November 24, 2017

Submitted as coursework for PH240, Stanford University, Fall 2017


Fig. 1: Coal burning power plant pollution. (Source: Wikimedia Commons)

Opened in 1958, the Portland Generating Station (PGS) power plant, located in Northampton County, Pennsylvania, operated as a coal burning power facility until 2014. While operating at its peak, the PGS coal plant was ranked as the fifth dirtiest U.S. power plant as measured by sulfur dioxide emission rate. [1] In 2007, neighboring states Connecticut and New Jersey filed suit against the plant and then owner, RRI Energy alleging violations of the Clean Air Act. [2] The multi-state lawsuit sought to have RRI both quantify and eradicate the dispersal of air pollutants, namely sulfur and nitrogen dioxides. After a seven year legal battle, PGS agreed to shut down its coal-fired boilers and convert to diesel power. While this brought resolution to the lawsuits, ongoing studies indicate long lasting health effects may still linger. [1] One study, conducted by researchers from Lehigh University and the University of Pennsylvania, points to a correlation between the air contaminants emitted from the power plant and low weight births within an area proximate to the facility. [2]


The study drew its causal inferences from two separately filed petitions - one from the New Jersey Department of Environmental Protections (NJDEP) and the other from the Environmental Protection Agency (EPA) - in which it is stated that sulfur dioxide emissions from PGS crossed state lines into New Jersey, spreading the polluted air as far as 20 to 30 miles away. The EPA's investigation also concluded that PGS was the sole pollution source causing the downwind state to violate air quality standards set by the EPA, emitting 30,465 tons of sulfur dioxide in 2009 alone. [1] These findings provided a creditable basis of information from which to conduct their study.

Fig. 1: Map of New Jersey counties, with Portland Generating Station marked by solid dot. (Source: A. Cook. After Yang et al. [2] Map template source: Wikimedia Commons)

From there, the study first identified New Jersey counties (and individual zip codes within them) most affected by the air pollution, then measured the effects of the pollution with a focus on birth weights of babies in these counties. The NJDEP's petition had already identified four counties in New Jersey that were most at risk of being contaminated by the dangerous air pollutants from the plant: Hunterdon, Warren, Sussex, and Morris county. Using a formula to calculate weather and human-related variables, the researchers created a list of zip codes on which they would focus their study.

The researchers intentionally ignored zip codes directly next to the plant, as residents in those counties were likely to be more aware of the negative impact of the plants and have implemented protection behaviors and countermeasures. These behaviors would confound the data if not explicitly controlled for. This study was also unique and warranted given that it was a pioneer in studying these effects in wealthier areas. [1] Previous studies were mainly focused on lower income areas directly surrounding the power plants, covering areas in which people were aware of being exposed to the harmful pollutants but often unable to afford other housing. [2]


Basing their study on live singleton births in New Jersey between 1990 and 2006, the study encompassed about 96.58% of all live births in New Jersey during that time. Multiple-birth cases were not considered in this data due to confounding factors of those pregnancies that could not be controlled for (such as low birth weight due to carrying multiple fetuses). The study then classified the birth weights into three categories: normal, low birth weight (weighing less than 2,500 grams at birth), and very low birth weight (weighing less than 1,500 grams at birth). The study ultimately concluded that babies born in those four counties affected by PGS's pollution were more likely to be born with a low birth weight by about 0.4 percentage points or 6.50 percent (0.004/0.0615), and about 0.19 percentage points or 17.12 percent (0.0019/0.0111) more likely to be born with a very low birth weight. Both of these figures are statistically significant at the 1 percent level and the result of 147,382 observed births. [1]


This study serves to broaden public understanding of the environmental and human health risks associated with emissions released from coal-burning power plants. The researchers were able to conclude, based on "suggestive evidence that an increase of 1,000 tons of sulfur dioxide emissions ... that come from upwind directions during during the final stage of pregnancy could increase the likelihood of [low birth weight] by about 0.15 percentage points or 2.44 percent." [1]

Power plant emissions that are carried downwind are difficult to regulate and can be dangerous if they go unchecked. The effect of this was revealed in a way not previously documented by focusing on the health effects of fetuses in wealthy areas. This provided a situation with few other confounding variables for the health and birth weight of the fetuses, given the heightened access to healthcare and general higher quality of life and health for the expecting mothers. The study ultimately proved that the unchecked spread of these harmful pollutants can affect anyone, no matter one's wealth, place of residence, distance from the pollutant's source, or age.

© Alana Cook. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] M. Yang et al., "The Impact of Prenatal Exposure to Power Plant Emissions on Birth Weight: Evidence from a Pennsylvania Power Plant Located Upwind of New Jersey," J. Policy Anal. Manage. 36, 557 (2017).

[2] D. Fears, "Wealth Didn't Matter. Pollution from a Coal-Fired Plant, Carried Miles by Wind, Still Hurt Their Babies," Washington Post, 3 Apr 17.