PBTs have a high environmental mobility relative to other contaminants mainly due to their resistance to degradation (persistence). This allows PBTs to travel far and wide in both the atmosphere and in aqueous environments.nother factor that makes PBTs especially dangerous are the degradation products which are often relatively as toxic as the parent compound. These factors have resulted in global contamination most notable in remote areas such as the arctic and high elevation areas which are far from any source of PBTs.
They have been claimed as the oldest free-standing structures on Earth, although the largely buried GÃ¶bekli Tepe complex is far older. Archaeologists believe that these megalithic complexes are the result of local innovations in a process of cultural evolution.
Several cities listed here, which are over 5000 years old, popularly claim to be the oldest city in the world. 1  Argos, Greece (6thâ5th millennium BC) 2  Athens, Greece (5thâ4th millennium BC) 3  Byblos, Lebanon (3000 BC)  Damascus, Syria (3rd millennium 1  BC) Luxor, Egypt (3200 2  BC) Jericho, West Bank (3000 BC or earlier)  Beirut, Lebanon (3000 BC)