But some scientists have started to question whether plastic bottles that hold water and other drinks might actually be harmful to consumers' health.
In a few weeks, the government will release a large-scale study about certain plastic bottles after animal tests showed that Bisphenol A affects hormones. Until then, some say they will switch over to good old-fashioned glass.
A lot of reusable plastic bottles people take to gym or work on a daily basis contain a chemical called Bisphenol A, which concerns a growing number of some scientists.
"The effects are primary reproductive and fertility effects in both male and female organisms," said Dan Tessier, toxicologist at the University of Illinois at Chicago's School of Public Health.
To check if your bottle contains Bisphenol A, just flip it over and check the number inside the little triangle.
Any bottle with the number 3, 6 or 7 has the potential to release the chemical.
The Federal Food and Drug Administration and the plastics industry agree with scientists, who say the chemical leaches out at such low levels that it is safe.
"The toxic effects on rats were done at levels that are thousands of times higher than we are exposed to in the environment," said Dr. Gilbert Ross, medical direction of the American Council on Science and Health.
Still, a federal panel of experts said there is concern that even low levels can cause neural and behavioral effects in children and fetuses.
NBC News video reports on water bottles Click Here to Watch Video
A TV report about the harmful Bisphenol-A chemical to be found in baby feeding bottles and other plastic products....baby feeding bottles bisphenol plastic health Click below triangle to play video
Chemical Threat in Plastics? Click below triangle to play video
What Each Number Means
#1 - Polyethylene Terephthalate (PETE) or (PET). Polyester is its nickname.
Used for: soft drink and water bottles, beer bottles, mouthwash bottles, peanut butter and salad dressing containers, ovenable film, ovenable pre-prepared food trays.
Recycled into: Polar fleece clothing, fiber, tote bags, bottles, clothing, furniture, carpet.
#2 - High Density Polyethylene (HDPE).
Used for: milk, water and juice containers, trash and retail bags, liquid detergent bottles, yogurt and margarine tubs, cereal box liners.
Recycled into: liquid laundry detergent containers, drainage pipe, oil bottles, recycling bins, benches, pens, doghouses, vitamin bottles, floor tile, picnic tables, lumber, mailbox posts, fencing.
#3 - Vinyl (Polyvinyl Chloride or PVC)
Used for: Clear food packaging, shampoo bottles, medical tubing, wire and cable insulation. There has been increasing concern over the potential toxicity of PVC, watch the media for developments.
#4 - Low Density Polyethylene (LDPE)
Used for: Bread bags, frozen food bags, squeezable bottles (e.g. honey, mustard).
#5 - Polypropylene (PP)
Used for: Ketchup bottles, yogurt containers and margarine tubs, medicine bottles
#6 - Polystyrene (PS)
Used for: Compact disc jackets, food service applications, grocery store meat trays, egg cartons, aspirin bottles, cups, plates.
#7 - Other: Use of this code indicates that the package in question is made with a resin other than the six listed above, or is made of more than one resin used in combination.
Used for: Three and five gallon reusable water bottles, some citrus juice and ketchup bottles
