Are mulch colorants safe?

FellowsSummary & Conclusion
Current investigations indicate that mulch colorants pose no threat to people, pets or the environment.  The dyes currently used by the mulch and soil industry are similar to those used in the cosmetic and other manufacturing industries (i.e., iron oxide) and pose no health or environmental risk. 

In the early 2000’s, occasional media reports surfaced that questioned the human safety of colored mulches.  The MSC investigated these claims, undertaking its own detailed studies and literature search.  A Colorant Committee was formed in late 2006 and meetings were held throughout 2007. 

Mission and Goal
The mission of the committee was to document information on existing or emerging colorants and their components to address any concerns for human health and environmental safety by the public, regulators and media. The goal of the committee was to determine if standards are necessary for certified colored mulches.

Investigational Results
Below is a brief summary of the committee’s investigational findings:

a. Human Safety of Colorants

Iron Oxide (Red):
Iron Oxide is used extensively in facial cosmetics, paints, and other chemicals.  It has been used for centuries.  Following an extensive review of national and international literature and information, no specific concerns were identified.

Carbon Black:
Carbon black is virtually pure elemental carbon and is used in many consumer and industrial products such as tires, belts, virtually all other rubber goods, video and audiotapes, nearly all electric motors as the brush contacts, insulators, and dry cell batteries.  As a pigment, it is used as a toner for paper copiers and printers, inks for newspaper, and in most dark-colored paints and coatings. 

Given the wide manufacture of both pure carbon black and products containing carbon black, there is a wealth of information published on the human health aspects of this material. Occupational studies over 60 years do not show any increased health risk to workers exposed to carbon black compared to the general public.

The US EPA also concluded that no special considerations are necessary for carbon black as it pertains to exposure for infants and children.  There are no adverse effects for acute toxicity in humans and animal studies.  It is considered non-toxic.  Also, there were no problems with skin sensitization or eye irritation (beyond a simple physical irritant). 

b. Environmental fate
The committee did not find any evidence that any of the components of colorants were an environmental concern when used according to label directions and rates on mulch.

Committee Conclusions
The committee concluded that based on the available toxicological and environmental profiles of the ingredients commonly used in mulch colorants, there appears to be no significant areas of concern in using these materials in general, and in certified mulches.

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