I usually recommend you places I saw and found also worth for your visit. The following places I did not see, and you don’t need to see them. These are the Earth most polluted regions. Believe, you may not go there, but there are living people! Being subject to such strong pollution, they are more often ill, live less etc.
If you think to megacities as New York, Tokyo, Mexico City you are wrong! These megacities became environmental friendly and aware, it is not so bad living there. Keep in mind the following places and avoid them:
1. Chernobyl,Russia. It was the center of the worse accident in a nuclear plant up to now, which affected large areas in Ukraina, Belarus, and Russia. Radioactivity caused many genetic disasters.
2.La Oroya, Peru, the centre of peruvian mining since 1930. Peru gets there lead, copper,silver etc.