Street lighting has been blamed for up to 50% of the urban sky glow due to 95% of the light directed down toward the pavement being reflected upward at reflectance rates ranging from 6% for asphalt to 25% for concrete (Ref 1). Urban sky glow has been reported to be increasing around 30% annually in some American cities (Ref 5).

LIGHT POLLUTION ENVIRONMENTAL EFFECTS OF ROADWAY LIGHTING, Carl Shaflik, BASc, PEng

In March 2013, a study found that Hong Kong is one of the worst offenders in the world for light pollution. Parts of the territory have been registered as 1,200 times brighter than a normal dark sky. Researchers say light pollution can affect health.

BBC News, Reported by Jennifer Pak.

These days, there are light-dimming technologies other than low-pressure sodium that are very safe. Depending on the method employed, dimming can also reduce energy demand by 40% and maintenance costs by 50%.68 Although centralised management systems can be more expensive to install, the payback time can be as little as 4-5 years.

Source: Artificial Light in the Environment Report, UK, Page 26 ISBN: 9780108508547)

Our understanding of the adverse effects of light pollution is vague and based mostly on purely observational case studies. Nonetheless, there is clear evidence that artificial lighting can alter physiology, including hormonal balance, as well as behavior, orientation, organism fitness, food web interactions, and biotope connectivity. The artificial disturbance of the natural day/night cycle may, as a result, have serious psycho-physiological and even medical consequences for humans, along with ecological and evolutionary implications for animals, plants, and even entire terrestrial, freshwater, and marine ecosystems

(Rich and Longcore 2006, Navara and Nelson 2007)