Disposable diapers contain traces of Dioxin, an extremely toxic by-product of the paper-bleaching process. It is a carcinogenic chemical, listed by the EPA as the most toxic of all cancer-linked chemicals. It is banned in most countries, but not the U.S
Disposable diapers contain Tributyl-tin (TBT) - a toxic pollutant known to cause hormonal problems in humans and animals.
Disposable diapers contain sodium polyacrylate, a type of super absorbent polymer (SAP), which becomes a gel-like substance when wet. A similar substance had been used in super-absorbancy tampons until the early 1980s when it was revealed that the material increased the risk of toxic shock syndrome
In May 2000, the Archives of Disease in Childhood published research showing that scrotal temperature is increased in boys wearing disposable diapers, and that prolonged use of disposable diapers will blunt or completely abolish the physiological testicular cooling mechanism important for normal spermatogenesis
Source: The Real Diaper Association. http://realdiaperassociation.org/