Ahmedabad: In a collective study by IIT-Kharagpur, School of Planning and Achitecture, Bhopal, and ITM University, Gwalior have revealed the impact of night-time light pollution on individuals, trees, birds, and insects in cities. In their findings, they have discovered that too much of the night-time lights suppress melatonin, a sleep hormone, causing insomnia.
“An hour-long exposure to midnight lighting ranging from 3,000 lux to 200 lux can suppress melatonin by 71% and 16% respectively,” the study says. A 39-minute exposure to light from a normal incandescent bulb at home causes human melatonin levels to dip by 50%. Fluorescent light takes 15 minutes and white LED takes 13 minutes to suppress melatonin to that level, the study says.
Coming back to light pollution in Indian cities, the study developed a brightness index ranging from 0 to 100 nano-watts/cm2/steradian. The study found that Delhi had the maximum area under light pollution.
The second was Hyderabad, followed by Bengaluru, Mumbai, Ahmedabad, Chennai, Pune, Jaipur, and Surat.
The study posits that the area under the “white range”, very high light pollution, scores 100 or more. Hyderabad showed considerable light pollution. The area beneath the orange range, or falling in the 25-50 band, has Delhi again on the top, followed by Hyderabad, Bengaluru, Mumbai, Chennai, Kolkata, Jaipur, Ahmedabad, Pune, and Surat.
The light pollution maps for Indian cities were prepared using hight-resolution satellite imagery.
The study also suggests measures to control light pollution. “New buildings should not include the use of glass that produces horizontally-polarized light,” the study says. “Furthermore, asphalt road surfaces near environmentally sensitive zones can be converted to a non-polarizing substance by incorporating a comparatively rough surface on the top or by the usage of granules to scatter light.”
The study says that trees with large canopies can be considered in landscaping to help reduce glare and to reflect light towards the sky.