I first moved to NYC in the summer of "˜91. The only thing anyone recycled in my neighborhood at the time were jokes about the Mets starting rotation.
But that all changed quite quickly, thanks to the Mobro 4000, that famous barge that hauled trash from New York to Belize and back in 1987 before some genius in Brooklyn figured out how to incinerate it.
The event captured the nation's attention and garbage became a hot issue in the late "˜80s and early "˜90s. In 1988, Resin Identification Codes started to appear on the bottom of plastic bottles classifying each by polymer type, which made it easier for them to be sorted for recycling.
But did you know the same number can help you determine which bottles are safe for drinking and which aren't? Lately, plastics numbered 3, 6, and 7 have come under scrutiny because of suspicions that they may leach harmful chemicals into whatever it is you happen to be drinking. So if you want to be extra cautious, aluminum or stainless steel might be a better choice at the gym. Otherwise, check the number on the bottom and make sure you've got the non-leaching 1, 2, 4, or 5 type.
For those curious about the polymers behind the number, Wiki has a handy chart that, excuse the pun "“ breaks them all down.