Children who nibble on plastic toys containing polyvinyl chloride and phthalate additives are ingesting a considerable amount of possible endocrine disrupters, European and U.S. scientists said Friday in Tokyo.

PVC and several phthalates are considered highly likely to act as "environmental hormones," which are believed to disrupt the reproductive functions of animals and humans.

Dr. Suresh Rastogi of Denmark's National Environmental Research Institute said these toxic substances could also be carcinogenic. Phthalate additives are often used in the toy manufacturing process to soften PVC.

He said Denmark and Austria have already banned the use of phthalates in toy production for children under 3, adding that similar measures have been proposed in the EU Commission.

Rastogi said studies on both humans and wildlife have indicated that exposure to endocrine disrupters early in life is of great concern, since the young and fetuses may be unable to handle such substances.

Japan currently does not have any safety standards on the use of PVC and phthalates for any products, including toys designed for infants.

Joel Tickner, an associate professor at the University of Massachusetts, suggested that environmentally friendly materials replace PVC and phthalate additives.

Tickner urged toy manufacturers to stop using PVC and phthalates, although there is no conclusive scientific proof yet that they are endocrine disrupters.

As long as there is a possibility that they may harm children, they should be withheld from manufacturing children's products, he added.

The symposium, organized by Greenpeace Japan, revealed that more than half of the world's toy manufacturers they researched have already started to regulate the use of PVC and phthalate additives. But some major toy makers are still using the materials, it said.