Tacogirl, to be on the safe side, be sure that any reusable plastic water bottles, such as Nalgene, are marked with recycling #4 and not #7. #7 plastic contains bisphenol A, a chemical which has recently come under scrutiny for it's negative health effects.

Canada has banned baby bottles and toys made from #7 plastic.

http://www.sciencedaily.com/releases/2008/04/080422114734.htm

Do any bottles designed for single use contain the bad chemical?

Look at the number inside the recycling symbol. If it's a 7 then it contains BPA.

I see that article also advises "reduce use of canned foods" but I couldn't find a reason quoted. Does this chemical BPA also affect cans? If so, all cans or just aluminum or tin-plated steel?

Have you seen the plastic lined cans in Belize? We have them here in Canada and they are the ones in question. In regular cans you only have to worry about lead leaching out of the solder

Hadn't noticed them, till now.

As you say, with traditional tin-plated steel cans the main concern is lead. But of course aluminum is increasingly associated with Alzheimers, so maybe the new cans aren't actually an improvement.

Unfortunately it is still unclear whether excess aluminum in the brain is a cause of Alzheimers or an effect of contracting the disease. ...but I still gave up all of my aluminum cookware and utensils many, many years ago.

Many deoderants contain Aluminum also which is directly absorbed into your body. This may explain why I am getting so forgetful lately!
Seems nothing is safe anymore.

Usually only anti-perspirants contain aluminum so if you have concerns about this, use a simple deodorant instead. ...and bathe and change your clothes often since fresh sweat doesn't stink anyway

I'm more worried about the harmful effects of the stress caused by all the worrying about the harmful effects of everything else!!