Prof. Susan Averett's latest research links artificial light with increased risk of preterm birth
By Bryan Hay
Light pollution does more than deprive us of the pleasures to ponder the night sky. Unnatural light also adversely affects fetal health, according to new research by Susan Averett, Charles A. Dana Professor of Economics, and two of her colleagues.
By examining New Jersey Department of Health birth records from 2004 to 2016, the trio found that light pollution, or more specifically skyglow, the artificial light that reflects off particles in the air and accumulates in urban areas, increases the chances of preterm births by nearly 13%.
The study, the first of its kind and recently published in Southern Economic Journal, revealed that increased nighttime brightness, characterized by being able to see only one-fourth to one-third of the stars that are visible in the natural unpolluted night sky, is associated with an increase in the likelihood of a preterm birth.
While we tend to think of light as a sign of economic prosperity and wellness, humans still need darkness to maintain their health.
Averett said she and her colleagues, Laura Argys, professor of economics at University of Colorado at Denver, and Muzhe Yang, professor of economics at Lehigh University, discussed at a conference a few years ago how light pollution is largely overlooked in economics research. Their collaboration and conversations also inspired a study, published last year in the Journal of Environmental Economics and Management, about how airport noise may increase the likelihood of low birth weight babies.
“We found out that the light pollution was a neglected area for infant health and read the literature about how light pollution disrupts circadian rhythms in humans and other animals,” Averett says. “So that was where we started.”
“This is an important gap to fill given the fact that in the United States as of 2016, 18 states, the District of Columbia, and Puerto Rico had adopted laws aimed at reducing light pollution,” the study says. “The most common feature of these laws requires the installation of shielded light fixtures that emit light only downward.”
Additionally, the study notes that outdoor lighting is designed to improve visibility, but its installation does not often take into account the impact on human circadian rhythm. As a result, greater usage of artificial light at night, which increases skyglow, can disrupt a human body’s biological clock, for example, by suppressing the production of melatonin, a hormone that regulates the sleep-wake cycle, and leading to low birth weights.
“It’s amazing to me how much light pollution there is,” Averett says. “One of the things that we mentioned toward the end of the paper is that this doesn’t have to be this way. Germany, for example, has much more conservative lighting, so they don’t have nearly as much light pollution.
“There are streetlights being installed in some cities to reduce the amount of light pollution while still maintaining safety for people,” she adds. “So it doesn’t have to be this way. It doesn’t have to be a byproduct of the way we live.”
An innovative part of the study involved the use of an empirical regularity discovered in physics, called Walker’s Law. It uses a nonlinear transformation of a city’s population and the distance to the city’s center to predict exposure to artificial light at night.
The use of Walker’s Law requires information on a mother’s residence at a level more detailed than the city in which she lives. The research team’s access to New Jersey Department of Health data made this detailed information accessible.
“By using Walker’s Law, we got the part of skyglow that wasn’t related to where people live,” Averett says. “One of the big issues is, of course, that people might locate in areas that are lighter or darker in ways that would influence their health, and therefore we wouldn’t be finding the effect of skyglow. So I think the way we’re measuring skyglow is the innovative part of the study.”
With the study published, urban planners and medical professionals might make use of its findings, she says.
Urban planners might examine the tradeoff of safety and too much light when considering installing municipal lighting systems, and medical professionals might advise avoiding sources of skyglow during a pregnancy.
“Light is associated with greater economic prosperity. When you have well-lit streets, you might have commercial shopping centers, which are going to be more likely located in more affluent areas,” Averett says. “Now we have this idea that a sign of affluence can be bad for your health. But a little natural darkness can be a good thing.”