UMHIVTDC

個人認為
從一個句子的順序性來看
chemical pollutants that have gone virtually unregulated    since they were developed more than 50 years ago

->they 就近形容 前面的主詞


Industrialization and modern methods of insect control have improved the standard of living around the globe while at the same time introducing some 100,000 dangerous chemical pollutants that have gone virtually unregulated    since they were developed more than 50 years ago

=>they 若要形容最遠的 metods



以上比較, 我想就進形容 會比較恰當


但, 如果就您所說的符合邏輯與異的部份, 我想 如果把since they... 搬到前面:
Industrialization and modern methods of insect control, since they were developed more than 50 years ago, have improved the standard of living around the globe while at the same time introducing some 100,000 dangerous chemical pollutants that have gone virtually unregulated.


這是不是 可以符合您要的語意邏輯 同時又滿足就進指代的文章順序性?


單純個人看法~