Is PUL Safe to use in nappies?

This is a question we've come across several times recently. Apparently the suggestion is being made that ammonia from urine can react with the chemicals in PUL/TPU (the laminated waterproof fabric used in many modern cloth nappies), causing nappy rashes or eczema.

While PUL/TPU is a type of plastic, therefore various chemicals/compounds are used in its production, in the state we have it in - a waterproof layer in our nappies - it is an inert material. This means that it has no active properties and is unable to form compounds. Under normal use circumstances it can't react with ammonia, for example, to create toxic fumes.  PUL/TPU is only capable of releasing chemicals if it changes state. This should only happen at temperatures above 428F/120C degrees - the lowest temperature at which it can melt and change states.

PUL/TPU is actually still widely used for what it was originally invented: medical purposes. That includes as the waterproof film used to dress open wounds.

There is such a thing as PUL/TPU allergy, though - even if it doesn't relate to a chemical reaction occurring in the nappy. Reactions to PUL are usually due to contact dermatitis or a sensitivity to synthetic fabrics.  Like some of us can't wear wool, others can't wear synthetic fabrics, including PUL. A child who reacts to PUL, will usually react to other synthetic fabrics and substances.

Certification standards with specific reference to chemicals that can apply to PUL/TPU in cloth nappies (and worth looking out for if you'd like further assurance) are Oeko-tex100 (where every step along the supply chain - from raw materials, fibres, dyes and fabrics to the final product including all components like snaps, threads and labels - are tested for harmful, or potentially harmful, chemicals) and CPSIA (Consumer Product Safety Improvement Act) covering all children's products sold in the USA.

Further Reading
A look at the safety of PUL & Cloth Diapers (New & Green)