light pollution is one of the effected types which increases the health problems .
also the light intensity in the big city at the night effects plant by increasing photosynthesis which raises substantially chemical substances to plant.
A key factor in regulating sleep and your biological clocks is exposure to light or to darkness so falling asleep with light on may not be the best thing for a good night sleep. Before sleeping turn off the lights because when lights are on serotonin is secreted, this will be delayed if you leave the lights on and that affect sleep..
Yes, It is very bad, apart from creating or resulting in sleeping disorder, it can also cause other health problems like Depression, Cancer, reproductive health problem, obesity. Thank you.