when you have a COMMA + -ING type modifier, the following two rules hold:
* the modifier modifiers the <i>entire preceding clause</i> (i.e., the ACTION in that clause)
* the SUBJECT of the preceding clause is taken to be the SUBJECT of the -ing participle.so, in this case, "having gone unregulated since they were developed..." refers to the industrial methods.
this is an actual ERROR - an incorrect pronoun - since the chemicals were developed 50 years ago.