Drinking water from a plastic bottle, once considered the "gold standard" of hydration and thirst quenching on the run, has recently come under attack from health and environmental experts. The good news is that not all plastic bottles are created equal. Some may be better than others.

In 1988, The Society of the Plastics Industry (SPI) developed an identification system for recycling purposes that divides plastic into 7 distinct types, each with a numerical code. The number is generally found on the bottom of the container, however, the numbering by manufacturers is voluntary.

If present, you can use this number as a starting point, in addition to information on the product label itself, to determine if it is right for you.

Here's a guide to what these numbers mean, some uses of different types of plastic and the potential concerns that have been raised.

1. Polyethylene Terephthalate (PET, PETE):

   • single-use water bottles, soft drink bottles
   • environmental concern: unnecessary use of energy and resources for recycling purposes
   • health concern: potential leaching of antimony trioxide, a chemical used to make PET, into contents after prolonged storage time; possible bacterial contamination if bottle is reused (cannot withstand high temperatures for sanitizing)

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2. High Density Polyethylene (HDPE):

   • opaque milk, juice and large water containers
   • concerns: minimal to date

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3. Polyvinyl Chloride (V or PVC):

   • juice bottles, cling wrap, plastic toys
   • health: chemicals present in toys may be potential health hazard, especially for children under the age of three

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4. Low Density Polyethylene (LDPE):

   • squeezable food bottles, flexible lid containers
   • concerns: minimal to date

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5. Polypropylene (PP):

   • reusable, microwaveable, dishwasher safe, opaque kitchenware; disposable take-out containers, yogurt and margarine tubs, ENVIROCLEAR® plastic water bottles
   • concerns: minimal to date
   • concerns: minimal to date

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6. Polystyrene (PS):

   • egg cartons, disposable cups, take-out containers, grocery meat and vegetable trays
   • health: potential to leach the chemical styrene, especially when oily foods are heated in these containers

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7. Other (often polycarbonate (PCB), used to harden plastic, to be differentiated from biodegradable plastics made from corn, potato starch or sugar cane; multilayer ethyl vinyl alcohol (EVOH)):

   • baby bottles, sippy cups, sports bottles
   • environmental: multilayer EVOH not recyclable
   • health (PCB): leaching of Bisphenol A (BPA), an endocrine disrupter, into contents, especially when subjected to heat; possible hazard for infants, possible increased risk of diabetes, heart disease in adults

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What does this all mean? You may want to limit your use of containers bearing #1, 3, 6 and 7 (PCB) and (EVOH), when possible. Those with #2, 4 and 5 may be a better choice at the present time. Those without numbers may be questionable.

alternative to plastic are stainless steel and aluminum refillable water bottles. These can be pricey and somewhat heavy to carry when filled. The newest alternative, ENVIROCLEAR® , (#5), a clear, reusable, refillable, dishwasher safe, lightweight, cost effective, BPA-free plastic water bottle may be your best bet to date.