Kriosa

Here is PEER's news release containing additional links on the subject:
http://www.peer.org/news/news_id.php?row_id=1202

In 2008, the US EPA's Region 8 office issued this warning about various concerns they think should be investigated with respect to using shredded tire crumb products as playground surfaces. The report points out various research that has been done by other groups on shredded tire products with respect to a variety of different concerns (chemical leaching, particulate matter, VOCs, effects on aquatic organisms, heavy metals). The paper calls for further investigation into valid concerns that have not yet been adequately researched.

http://www.peer.org/docs/epa/09_1_6_epa_tire_warnings.pdf

I think it's reasonable to assume that the risks and warnings for shredded tire rubber mulch would be about the same.

In 2008, the US EPA's Region 8 office issued this warning about various concerns they think should be investigated with respect to using shredded tire crumb products as playground surfaces. The report points out various research that has been done by other groups on shredded tire products with respect to a variety of different concerns (chemical leaching, particulate matter, VOCs, effects on aquatic organisms, heavy metals). The paper calls for further investigation into valid concerns that have not yet been adequately researched.

http://www.peer.org/docs/epa/09_1_6_epa_tire_warnings.pdf

I think it's reasonable to assume that the risks and warnings for shredded tire rubber mulch would be about the same.