Humans have been upsetting the balance of nature and creating mass pollution for how long now? 50 years? 75 years?
I think its related to the heavy production of plastic... which actually fits your time line...
rubber, paper and glass were once used are three products that have been replaced with plastic....they complained about forests being cut down so plastic saw a surgence when milk bottles were replaced with waxed cardboard and then later, plastic.... You need oil to produce plastic.
