Unlike gravel or wood chips, rubber mulch has no sharp edges that can cause children at play to get scrapes and cuts. It does not stain like grass or sand filler. Additionally, rubber does not encourage the growth of mold and mildew.
As compared to other loose fill materials such as sand or gravel, rubber mulch does not need to be replaced as often. It is less likely to drift off of the playground since it is heavier than wood chips or sand. Occasional raking or cleaning with a leaf blower is all the maintenance rubber mulch requires.
In the garden, rubberized mulch can be dyed in various colors making it an attractive choice for landscaping, although the colors can fade over time. As it is nonporous, it helps to keep moisture in the soil and does not attract insects as opposed to organic substances like wood mulch.
Toxic substances are used in the manufacture of rubber tires. Tires are also likely to have been exposed to hazardous chemicals, which may be absorbed into the material prior to recycling. Toxic minerals and chemicals can eventually leach out from the rubber, causing serious health hazards. Additionally, rubber takes a long time to extinguish if ignited, releasing hazardous chemicals as it burns. Rubber is not likely to combust without a source of ignition, however.
Public concerns have been expressed that the presence of lead and other hazardous chemicals contained in rubber filler could represent a danger to children. As a result of these concerns, several states including New York and California have conducted studies to assess the level of contaminants in recycled tires. In a January 2007 report, the California Office of Environmental Health concluded that rubber mulch did not represent long-term health risks. The US Environmental Protection Agency also conducted a limited study and concluded that the levels of potentially hazardous chemicals are too low to represent a health hazard. Still, the US EPA recommends that children wash hands after playing in areas with rubber filler -- a good practice to follow, regardless of where children play. Further studies are planned by the US EPA as well as various state agencies.