Is Recycled Rubber Mulch Safe?

Significance

• Tire mulch leaches potentially toxic compounds into the environment; these materials can kill algae, zooplankton, snails, and fish, according to the Washington State University Extension. Tire mulch can contain contaminants and heavy metals.

Considerations

• Ground rubber should never be used in garden soil, agricultural soil, or in any potting medium. The rubber can lead to zinc toxicity in plants.

Warnings

• Some bacteria species use rubber as an energy source, and rubber tire mulch exposed to fungal diseases such as white rot and brown rot loses the ability to kill bacteria. Additionally, the Washington State University Extension notes that "ground rubber is more likely to ignite and more difficult to extinguish" than many other types of mulch.