Before I go into the details, to put this all into perspective, if you're this worried about your health, don't eat out. Questionable plastics are widely used in the food service industry (to package commercial food-service- quality ingredients in the first place).
The seven most common types of plastic used in food containers are:
#1 PET or PETE, polyethylene terephthalate
#2 HDPE, high density polyethylene
#3 PVC, polyvinyl chloride (vinyl)
#4 LDPE, low density polyethylene
#5 PP, polypropylene
#6 PS, polystyrene (Styrofoam)
#7 polycarbonate (Lexan)
Most "disposable" water bottles are made from #1, PET:
Some preliminary research suggests that [repeated use and washing] can release potentially harmful chemicals. But the studies have had inconsistent results, and researchers disagree about whether these compounds pose a significant risk.1
Dr. Mercola recommends only containers of #2, #5, or #4 plastic, "none of which are known to leach harmful substances."2 Another source recommends #2 and #5, but instead of #4 it recommends #7, polycarbonate.3 However, Mercola cites a recent study which found problems with polycarbonate.4 This is what plastic carboys are made of, as well as the newer Nalgene bottles.
Why Mercola recommends #4, low density polyethylene, I don't know, but another source also recommends #2, 4, and 5 as well as #1.5
Overall, judging from these and other sites I visited,6 it seems that almost everyone agrees that #2, HDPE, when it's food grade, is best. And this is what most five gallon food buckets as well as the interior of most ice chests are made of.7 Igloo coolers, however, are an exception. They are actually #5, polypropylene,8 which I guess is OK, except that right now mine is moldy.
So it looks I'll be making three gallons of melon vinegar in my five-gallon bucket tonight, courtesy of the local supermarket bakery. Maybe it will smell like icing.
1 "Ask the Experts," UC Berkeley Wellness Letter, May 2005, http://wellnessletter.com/html/wl/2005/wlAskExperts0505.html
2 "Nalgene water bottles appear to be unsafe," http://www.mercola.com/2004/apr/7/nalgene_water.htm. See also "Study: Nalgene plastic may be harmful," http://www.datelinealabama.com/article/2004/02/18/5340_news_art.php3. Nalgene responds at http://www.nalgene-outdoor.com/technical/bpaInfo.html. More discussion and links at "Are Nalgene water bottles really unsafe?" discussion board, late February, 2006, http://ask.metafilter.com/mefi/33382. See also Our Stolen Future, http://www.amazon.com/exec/obidos/ASIN/0452274141/metafilter-20/ref=nosim/.
3 "Any food grade HDPE, PP, or polycarbonate container is appropriate for brining." See "Food Grade Plastic Containers For Brining," 12/3/06, http://www.virtualweberbullet.com/plastics.html.
4 see note 2
5 "Smart Plastics Guide: Healthier Food Uses of Plastics," The Institute for Agriculture and Trade Policy (IATP), http://www.environmentalobservatory.org/library.cfm?refid=77083
6 Another seemingly hokey article on the subject: http://www.omeganutrition.com/articles-other-finalsay.php
7 see note 3