The average disposable nappy weighs around 40g. The bulk of it (about 60%) is wood pulp. Some of the other materials it contains are polypropylene, polyethylene or bonded carded web for the top and back sheets, and other materials for fasteners, elastic and adhesives.
Many brands also contain polyacrylate, a superabsorbent material in powder form, which can absorb many times its weight in liquid. In contact with moisture, it solidifies into a gel and traps the liquid inside. Nappies without superabsorbent material generally contain more wood pulp to increase their absorbency.
You may have heard claims that the chemicals sodium polyacrylate and dioxin in disposable nappies pose a significant health risk to babies and toddlers. We’ve seen these claims too — on the websites of those promoting the use of cloth nappies — but couldn’t find them substantiated in the scientific literature.
As far as we could establish, there have been no long-term studies of the effects of superabsorbent materials on infants. However, two studies in the early 1990s found that polyacrylate polymers (superabsorbent material) had no toxic effect on the genetic material of laboratory animals, and didn’t cause birth defects in them.
There’s some disagreement about the benefits of nappies containing superabsorbent materials. Some studies found that the type of nappy made no difference to nappy rash, but many others have confirmed that disposables with superabsorbent materials have led to drier skin and hence, fewer incidences and reduced severity of nappy rash.
As far as dioxins are concerned, they’re a family of organochlorines that includes one of the most toxic chemicals yet made. In the past, dioxin traces were found in chlorine-bleached white paper and pulp products, including disposable nappies. However, nowadays nappies are usually oxygen-bleached (using hydrogen peroxide), which forms no dioxin.