B

　　We all have a fair idea about the common types of environmental issues.However，light pollution may be a new term to many of us.But，the fact is，artificial light does affect the natural light levels in the same way as other man­made sources.Similar to other pollution types，it affects mankind，other living forms and the environment as a whole.

　　What is light pollution？It is an umbrella term for representing all forms of misused artificial light.In the broad sense，light pollution is defined as the unwanted change of natural light levels in the environment due to effects of man­made light sources.Human activities are directly or indirectly responsible for this form of pollution.

　　The obvious cause of light pollution is to use external lighting products inappropriately.It can be apartment light，office lighting，car headlights，station lights，streetlights and many more.With reference to these many contributing sources，it won’t be wrong to say that is an outcome of industrial civilization.

　　Light pollution is harmful to both plants and animals.Upon studies，it is found that obvious effects are observed in the behavior of nocturnal animals.Needless to mention，bright light at night makes it difficult for these animals to hunt，wander and perform their regular activities.

　　Light pollution is directly or indirectly responsible for causing several diseases.Its effects are related to disturbance in the physical rhythm.It contributes to risks of developing cancerous cells.Light pollution is nothing less than a threat to human health.

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