Light pollution could be said to pose a little problem to others. But in reality, they cause a real problem, indirectly. http://mind42.com/pub/mindmap?mid=b45d4348-100b-4913-aee4-1e2e020e8b9e the following link is a mindmap about Light pollution. Hope you will learn more about Light pollution.
There are serveral causes of light pollution. If you had looked at the mindmap above, you would know that poor built artificial light cause the problem too. As there are lots of artificial-light, we need to find a specific place to focus on. There are a lot of types of lights built. Example: Street light, Traffic light, housing lights.
In common sense,(cause i could not find any proof) there are more street light than any kind of other lights outdoor. Furthermore, the light indoor are mostly pointed downwards so they do not pose such a big problem. But look at the picture of the street light:
Only the top part is covered and the sides are not.
Through all this, My team decided to focus on streetlight of Light pollution.