Bad Plastic in Water Bottles

I heard an interview with some health expert on CBC Radio yesterday talking about the dangers of ingesting chemicals transferred from plastic containers such as water bottles. Most plastic containers are labeled on the bottom with a number from 1 to 7. The good numbers are 1, 2, 4 and 5. The bad numbers are 3, 6 and 7, which are apparently full of all kinds of nasty chemicals that