Residential Noise Exposure and Health: Evidence from Airport Runways

Noise pollution is a threat to public health. In the United States the Day-Night Average Sound Level (DNL) is required not to exceed 65 decibels (dB). This threshold, aimed at preventing hearing loss, is significantly higher than the 55 DNL threshold used by the World Health Organization, since an increase of 10 dB means 10 times as much sound energy. We conduct the first empirical study on the causal effect of lowering the threshold to 55 DNL on infant health, using two unique datasets: one is the National Transportation Noise data, first released in 2017 and providing measured noise levels (in dB) at exact locations for the year 2014; the other is birth data from the New Jersey Department of Health, including the exact home address of each pregnant woman.

The National Transportation Noise data provide a map that reveals sharp changes in noise exposure in areas near airports, where air pollution can be evenly distributed but noise exposure differs significantly, with the pattern of noise levels closely following the airport runway layout. Because our birth data are from New Jersey, we focus on the noise exposure of mothers living close to Newark Liberty International Airport (EWR), one of the largest airports in the country. One important characteristic of EWR is that the north-south runway is frequently used, whereas the east-west runway is only occasionally used, which allows us to exploit exogenous variation in noise exposure among those living equally close to the airport: those living north-south of the runway are exposed to much greater noise pollution than those living east-west of the runway.

Note that the noise data are only available for 2014, which means the examination of infant birth outcomes by using birth data beyond years 2014 and 2015 requires the assumption of noise exposure being time invariant. To relax this assumption, we alternatively use as our measure of noise exposure the directionof mother’s home relative to the EWR’s north-south runway, controlling for the distance between the two locations. The direction is measured by azimuth (going from zero to 360 degrees). An azimuth of zero (or 180) means living due North (or due South) of the runway. We compare each azimuth with the north-south runway to create an indicator equal to one for living along the runway. While living close to the airport may not be exogenous, living along the runway could be exogenous unless the mother chooses where to live taking into account the airport’s runway layout.

Our study focuses on low birth weight (LBW), an important birth outcome associated with a variety of adverse outcomes during adulthood. We find a significant increase of LBW risk due to noise exposure. Our study has important implications for the U.S. Federal Aviation Administration’s NextGen program by highlighting its unintended health impact. The NextGen program aims to improve aircraft fuel efficiency by using narrower paths for airplane landings and takeoffs, which however has significantly increased the noise exposure in areas along airport runways.