而prep1-97:Industrialization and modern methods of insect control have improved the standard of living around the globe while at the same time they have introduced some 100,000 dangerous chemical pollutants, having gone virtually unregulated since they were developed more than 50 years ago.这里面having可能修饰pollutants,也可能修饰they have introduced some 100,000 dangerous chemical pollutants整个分句,所以having产生了修饰歧义