IOWA CITY - When the weather heats up, like this weekend, many people buy bottled water to stay hydrated. Sure, it's costly, but it's convenient. But is it really better for you than tap water? Local researchers say one of the biggest differences between the two has to do with plastic.

Chrissie McGaffigan plays tennis practically every day. This college athlete always brings bottled water to practice.

"Just cause it's in the fridge, and it's ready. It's easy to just grab and go," says McGaffigan.

Ahmed Akhter chooses a cheaper way to stay hydrated when he's working out.

"Usually I just drink from the the fountain. It saves money cause I don't have to buy a 24 pack," says Akhter.

Researchers at the University of Iowa Hygienic Laboratory say McGaffigan's bottled water and Akhter's tap water are pretty much the same in terms of overall quality. That comes after testing 10 popular bottled water brands.

"For the most part, the level of contaminants, there does not seem to be a major significant difference in the quality of one water type verse the other," says Dr. John Vargo of the University of Iowa Hygienic Laboratory.

So, people who prefer bottled water might want to focus more on the type of plastic used.

"When water is put in the bottle, it has the ability to slowly leach chemicals out of the plastic," says Dr. Vargo.

One of those chemicals is phthalate. In high doses, the chemical can disrupt a person's endocrine system, which helps regulate things like metabolism and growth. The Environmental Protection Agency tracks the phthalate levels in tap water, but the Food and Drug Administration does not do the same for bottled water.

"Even though they are supposed to follow the same regulations the EPA requires for water testing, for some reason, it has not made a decision on whether there should be mandatory testing for this particular phthalate," says Dr. Vargo.

In the meantime, you can do your own research to make sure the plastic is safe. Find the little triangle on the bottle and look at the number inside it. A number one is okay to use once. A number two and a number five are safe to use more than once.

While Akhter doesn't have to worry about such numbers with tap water, McGaffigan will need to make sure she uses her number one water bottle one time.

---

Here is a list of useful links:

Bottled Water Basics - http://www.epa.gov/safewater/faq/pdfs/fs_healthseries_bottlewater.pdf

Water on tap: What you need to know - http://www.epa.gov/safewater/wot/pdfs/book_waterontap_full.pdf

FDA Regulates the Safety of Bottled Water - http://www.fda.gov/Food/ResourcesForYou/Consumers/ucm046894.htm

Bottled Water - FDA Safety and Consumer Protections Are Often Less Stringent Than Comparable EPA Protections for Tap Water - http://www.gao.gov/new.items/d09610.pdf

Recycling: A look at plastics - http://www.recyclenow.org/r_plastics.html

UI Hygienic Lab research is cited in Natural News - http://www.naturalnews.com/026513_clay_bentonite_clay_calcium.html