What is causing deformed amphibians?

Today I finished reading the chapter about amphibian deformations by S. Sessions. There is no consensus in the literature if the correct name would be malformations (caused by developmental errors) or deformations (caused by trauma), because on amphibians a trauma can cause a developmental error. There are different possible causes of deformities: Pollution (retinoids), UVB radiation, predation, parasites (trematode infections). Pollution and UVB radiation haven’t been well proved yet, but predation and parasites are the most probable causes. Predation in tadpoles, including cannibalism, (especially in early stages, when they haven’t lost the ability to regenerate tissues) has been proved to cause deformations. Parasites, specially the trematode Ribeiroia, forms cyst in tadpoles, which changes the arrangement of developing limb cells, causing polymelia (numerous limbs) and other deformities observed in natural amphibian populations. The reason why more deformations have been reported recently is not very clear: one hypothesis is that pollution or another type of habitat perturbation could be affecting the trematode cycle, increasing the number of parasites.