Cities like Washington often experience high levels of light pollution, largely because concentrated outdoor lights shine upward. A new study by the nonprofit organization Darksky International found that residents in Wards 7 and 8 are disproportionately exposed to potentially harmful light pollution compared with other neighborhoods in the city.
Guidelines from the American Association of State Highway and Transportation Officials (AASHTO) recommend minimum average illuminance levels for roadways to start between 0.3 and 0.6 foot-candles, the unit that measures the intensity of light on a surface per a one-square-foot surface. In the two wards east of the Anacostia River, the light levels combined across both areas exceeded AASHTO’s minimums by 238% as compared to 181% across the city’s other six wards.
“All outdoor light at night, regardless of source or intensity, is a pollutant with potential impacts on human health,” Darksky wrote in the study. “Even small amounts of nighttime light are enough to suppress melatonin production, and scientists have long recognized that disrupting circadian rhythms harms human health.”
Sky glow pollution also affects wildlife behavior, especially nocturnal animals, and can block the visibility of solar system objects. The movement trying to fight this pollution and preserve the nighttime environment is called the dark-sky movement, first and most widely advanced by Darksky International. The nonprofit strongly advocates for outdoor lighting that will effectively reduce sky glow.
The District Department of Transportation (DDOT) has also been trying to mitigate this form of pollution in the city through its D.C. Smart Street Lighting Project, which upgraded the city’s streetlight network of more than 75,000 lights to LED, advancing energy efficiency.
“Our ability to modernize our infrastructure is directly related to our ability to increase the quality of life for Washingtonians in all eight wards,” D.C. Mayor Muriel Bowser said when the initiative was approved. “With this project, we’re doing so much more than just replacing lights – we’re making our streets safer, our communities more connected, and our city more resilient.”
While the project, which was completed in May 2024, is helping the city’s energy efficiency, the issue of light pollution still remains a large issue at hand, as shown in Darksky’s study. The nonprofit is pushing for DDOT to launch a pilot project of light curfews, recommends that the government agency address any remaining street light “hot spots,” and urges the Department of Health to warn residents of the negative effects nighttime artificial light exposure can have on their health.
“We commend DDOT for taking advantage of LED technology that allows dimming, but carefully timed dimming in overnight hours should be considered more broadly across the city,” said Wayne Savage, vice president of the Darksky International D.C. Chapter. “Artificial light at night is a pollutant that threatens the health of all District residents when used in excess.”
