Dyes used in making colored mulch are usually vegetable-based and therefore harmless. Unfortunately, the question of whether dyed mulches are safe does not end with determining the composition of the dye.
The source of most dyed mulch is recycled wood. So far, so good. But the problem is that some of that recycled wood may be CCA-treated wood, which, used as a mulch, can raise the arsenic level in your soil. Although the use of arsenic in making pressure-treated lumber was largely banned after 2002, who's to say part of the source of the dyed mulch you're buying isn't old, leftover CCA-treated wood?
Enter the MSC Certification Logo, which certifies that a mulch or soil product is free of CCA-treated wood. MSC stands for Mulch and Soil Council. According to MSC's Product Certification program, "Certified mulches and soils can be found at major retailers and garden centers across the country." So look for MSC Certification Logo if you wish to improve the chances that the dyed mulch you're buying is safe for humans to handle.
So much for the issue of dyed mulch and human health. The next FAQ addresses a separate question: Does colored mulch affect plant growth?
