The only way to fully waterproof a mattress is to use plastic. Some plastics are very toxic (vinyl) and some are safe and non-toxic. It all depends on how the plastic is manufactured and what chemicals are used. The thin film or membrane that Naturepedic uses in their organic cotton waterproof pad is a polyurethane plastic. Polyethylene could not be used because that material would break down during hot water washing. So they use a polyurethane film that is manufactured without the use of toxic chemicals. It's very different from polyurethane foam since toxic chemicals are added in order to make foam.

We are confident that this is the safest waterproof pad available and it is the only one that is GreenGuard certified so we know for sure there is no off-gassing.
 
We also have wool puddle pads, but unfortunately wool is not waterproof, it is water resistant. Wetness may go through a wool puddle pad so we always recommend getting 2 wool puddle pads or adding a thick cotton pad to your puddle pad if you will have a lot of wetness.

Here's what Naturepedic says about what they call Dry Sleep technology:

DrySleep™ - Waterproof & Breathable
 
Based on years of research, DrySleep technology effectively blocks liquids from passing through the fabric while still allowing the material to "breathe." It features a specially formulated non-toxic medical grade film which effectively blocks liquids while allowing a certain amount of water vapor (similar to humidity naturally found in the air) to pass through. This results in less "sweaty backs" and a drier, more comfortable sleep.
 
The DrySleep waterproof membrane does not contain any added fire retardants or antimicrobial treatments and is free of vinyl/PVC, phthalates and latex. It is also free of all chemicals listed on California's Proposition 65 bulletin. It has been tested for off-gassing and easily passes GREENGUARD's certification standards for eliminating chemical emissions. It is extremely thin (even thinner than the membranes used in the new environmentally friendly cloth diapers).
 
Vinyl/PVC, latex, and rubber, on the other hand, are very "sweaty". They block all moisture from passing through, creating a more uncomfortable sleeping environment. DrySleep provides full non-toxic waterproof protection without the associated discomfort.
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