Hydration is a key factor for health. We need to drink plenty of water every day to keep our bodies and minds running smoothly. And with the questionable safety and quality of some municipal water sources, bottled water can seem like a tempting way to satisfy our thirst.

But water in plastic bottles comes with its own potential dangers. Here are a few reasons you may want to think twice before cracking open another bottle.

Danger 1: Bisphenol A (BPA)

Used to soften plastic to make it more malleable, bisphenol A (BPA) is found in canning lids, water bottles, and childrens toys. Animal studies have shown that BPA is an endocrine inhibitor and can interfere with the proper functioning of the reproductive system. BPA leaches into any liquid it touches, and heat increases the transference. BPA accumulates over time in the body with repeated exposure, and is especially dangerous for children and pregnant and nursing women.

Even the FDA, notorious for its negligence when it comes to toxic health hazards, admits that BPA may pose considerable health risks. The FDA recommends that people reduce their exposure to BPA as much as possible.

Danger 2: Lying Labels

In the U.S. bottled water can be up to 30 percent straight tap water and still be labeled as spring water. Purified or drinking water is usually completely tap water. The testing procedures for the safety of bottled waters are not rigorous, and even in bottles that are tested a surprisingly high amount of dangerous chemicals are still considered acceptable by regulatory agencies.

Danger 3: The Number Game

The numbers on the bottom of plastic bottles refer to the type of plastic from which they are made. Bottles that are labeled with a number 1 are often made of PET (polyethylene terephthalate), which has the potential to leach carcinogenic DEHA into liquids. Plastics labeled number 3, 6, and 7 usually contain the BPA mentioned above (though BPA may be present in any type of plastic).

The least dangerous types of plastic are numbers 2, 4, and 5, which tend to be made of harder plastic. If you must use a plastic bottle, go with one of those numbers. But if you can taste plastic in your water than it is leaching, whatever the number.

Danger 4: Bacteria

Plastic bottles are breeding grounds for dangerous bacteria. Putting your mouth on the spout of a reused bottle exposes you to a wide range of viruses and germs. If you must use plastic, do not reuse disposable bottles. There is no safe way to kill the bacteria without causing degradation of the plastic. And do not touch your lips to even reusable plastic bottles if you can help it.

Danger 5: More Plastic than the Planet Can Handle

The next three sections are more about the dangers of plastic to the environment. While these are not as personal, part of being healthy is recognizing our place and responsibility within the larger eco-system.

Plastic does not biodegrade. There is no way to safely and completely dispose of plastic. Plastic often ends up in landfills or as litter, and makes it way into water sources. This poisons soil and groundwater with toxic additives and byproducts. Scientists estimate that it will take over a thousand years for plastic to disintegrate completely.

Small plastic particles make their way into marine life, slowly poisoning birds and fish (and creatures further up the food chain, like humans). Burning plastic produces toxic fumes and ash, so bottles cannot be safely incinerated. And only about 10 percent of plastic bottles are recycled.

Danger 6: An Unsustainable Resource

It takes a lot of water and oil to produce plastic water bottles. In case you did not know, plastic is usually made of crude oil that has been manipulated into a semi-solid shape. This is why it is so toxic. More oil is required to produce and transport the bottles. And as much (or more) water is used in the bottle manufacturing process as the bottles will eventually contain.

On the other side, plastic recycling is a loosing battle. Each time plastic is recycled it degrades in quality, until eventually it must be disposed of permanently, where it will sit in a landfill, or the ocean, for hundreds of years.

Danger 7: The True Cost of Cheap Water

Some bottled water is shipped around the country or around the world. As mentioned above, this uses insane amounts of water and oil, just to move water from one place to another. If the water in your bottle is actually from a spring or tropical preserve, this means it has been taken from the water supply of the people local to the area. In many cases, this means those people now have to deal with depleted or poisoned water resources.

As you can probably tell, I think plastic water bottles are more trouble than they are worth. For the cost of a months supply of plastic bottles, you can get a stainless steel or glass reusable bottle that will not poison you, and a high-quality water filter that will make your tap water safe to drink. Consider your health and the health of the planet before you buy another plastic bottle.