About Arsenic
Arsenic has been the subject of recent debate among scientists and policy makers because of its relatively high toxicity and its persistence in the environment. Arsenic is a natural element that is ubiquitous in the world around us. It is present in air, water, soils, plants, animals, and humans.
Like most substances, low levels of arsenic present no danger, and mankind has lived in this environment since the beginning of time. But a fundamental toxicological principle applies to arsenic as well as all substances: the dose makes the poison. Even the most benign elements can become toxic at excessive levels of exposure. In comparison to most substances, arsenic is one of the more toxic elements, and that is why particular concentration levels in things we use are a general concern.
Can Arsenic Get Into Some Mulch At Elevated Levels?
The typical lawn and garden mulch used in the U.S. is not a concern. However, a recent limited study into mulch made from very new and specific kinds of recycled wood have become a concern to the industry.
Arsenic is a major ingredient in Chromated Copper Arsenate (CCA), a particular wood treatment commonly used for decades to prevent insect damage to decks, fencing, docks, and similar applications. This is the typical greenish-tinged wood sold in the U.S. that is now being voluntarily phased-out of consumer use by the wood preservative industry.
When CCA-treated wood is taken out of use (e.g., the demolition of a deck, porch, fence, playgrounds, etc., built with CCA-treated wood), some of this wood material may be recycled by companies involved in “Construction & Demolition” (C&D) waste disposal. Many states and localities have active C&D recycling programs, and there are numerous private companies that recycle C&D waste. If C&D is recycled and processed into mulch, some of it may contain CCA-treated wood that has high levels of arsenic.
Arsenic In Mulch: A Concern For All
Recently, even the intended use of some treated wood (for example insect-exposed structures such as decks, playground equipment, posts, etc.) has been controversial because of human and environmental exposure to the arsenic contained in the CCA treatment. The Mulch & Soil Council (MSC) completely supports the voluntary action of the wood preservative industry and the Environmental Protection Agency of the U.S. government in withdrawing CCA-treated wood from consumer use and consumer products effective January 1, 2004. However, CCA-treated wood’s recent appearance in mulch presents even greater concern than the originally approved use of this product.
This concern relates to how human and environmental exposure to arsenic are enhanced when CCA-treated wood is ground into mulch because recent research indicated that grinding CCA waste increases the opportunity for the chemical preservative to be more exposed to the environment. What was once a large solid timber with limited surface area is now numerous smaller pieces with greatly increased surface areas. When a board or timber is ground into mulch, the chemical concentration that was normally in the protected interior of the material is now exposed to the outside environment.
Not only is the exposure to CCA chemicals increased as a mulch, but also the areas in which mulch are used compound the concern. Mulch is used in landscape and playground settings where children and pets have direct contact with the material. Mulch is also used in gardens where edible plants could potentially absorb the arsenic. These uses, coupled with the enhanced exposure of the chemical, constitute potential hazards that must be avoided.
Is CCA-Treated Wood Being Used in Mulch?
Based upon current information, the mulch and soil industry believes only a very small percentage of mulch products (for example those using C&D wood) would be suspect of having any CCA-treated wood increasing the arsenic content potential of the product. The vast majority of mulch is made from virgin forest products such as tree bark and wood from sawmill operations. Some mulch is also made from recycled materials such as composted green waste or wood pallet grindings. But none of these materials, whether virgin or recycled, would contain “treated wood” or specifically CCA-treated wood. It appears the area of concern lies primarily with C&D wood that may contain CCA-treated materials.
A joint study by the University of Florida and the University of Miami reported that there are no viable and practical technologies to identify, and thus separate, CCA-treated wood from other non-treated C&D materials. After several years of aging, CCAtreated wood looses its greenish coloration or may have been painted or stained. Thus, it appears much like untreated wood and cannot be identified for separation. The study concludes that any wood recycling using C&D debris will likely contain some CCA-treated wood because of its presence in the waste stream and lack of detection and separation technologies.
What About “Red” or Other Colored Mulch?
One of the major reasons for using mulch is the decorative appearance it gives to a landscape. Mulch always looks best when it is new or freshly applied because it has the most vibrant and distinctive color at that time. So, color plays a major role in the overall quality of mulch.
Colorizing mulch is a popular method of improving the aesthetics of mulch materials. Today, both recycled wood and natural forest products are being colorized in the mulch industry. Coloration can improve the initial appearance of mulch and increase the longevity of its color. Most mulch products derived from natural forest products have an acceptable initial appearance without coloration, but coloration can extend the period of desirable color. However, many recycled mulches do not have V.7 an acceptable appearance initially. Adding color to these mulches is primarily done to improve their general appearance.
As stated previously, a minority of mulches derived from C&D wood (which may contain CCAtreated wood) is the primary area of concern with arsenic. But many C&D wood mulches are colorized to improve their initial appearance. As a result the issue, as reported by the news media, has generally been oversimplified and misrepresented by stating colorized mulch is the problem. Because red is the most popular color demanded by consumers, it has been further misreported that “red mulch contains arsenic”.
Coloration itself has no bearing on whether mulch may contain elevated levels of arsenic. There are many high-quality mulch products that are colored; so, the issue is C&D wood, not colorized mulch, and that distinction is very important.
Will the Ban on CCA-Treated Wood Lessen the Concern?
The U.S. Environmental Protection Agency has determined that chipped or ground CCA-treated wood is a hazardous waste. Accordingly, EPA does not allow the use of CCA wood as a garden mulch or composted soil product.
While the wood preservative industry’s voluntary ban would stop the sale of CCA-treated wood for consumer use and decrease the volume of additional material being added to the environment, it will not prevent the addition of CCA-treated wood for industrial uses or diminish the present problem with the disposal of products that have been in place for 20 years or more.
Currently it is estimated that over 92 billion board feet of CCA-treated wood is presently in service in the US. As demolition projects occur to meet the need for new construction, more C&D wood will likely appear in the waste stream, increasing the likelihood of more CCA-treated wood being used illegally in mulches that originate from C&D operations.
What is the MSC’s Position on C&D and CCA-Treated Wood in Mulch?
The Mulch & Soil Council opposes the use of C&D and CCA-treated wood as ingredients in any mulch or soil product. Further, the MSC will not certify any products containing C&D and CCA- treated wood as part of its product certification program.
These actions are based on a review of the scientific literature and the facts, as they are known today. The Council has adopted this position in an advisory capacity to the industry to encourage protection of human health and the environment. This position is subject to change pending the evolving science and testing now under study.
What is the MSC Doing Now about this Issue?
In addition to our position on C&D and CCA-treated wood in mulch, we are aggressively addressing the issue as outlined below:
1. Proper Labeling: The MSC believes strongly in promoting industry truth in labeling. The Council has long advocated this belief through promotion of its “Voluntary Uniform Product Guidelines for Horticulture Mulches, Growing Media, and Landscape Soils.” Proper labeling of mulches is addressed in the guideline document. However, the issue of CCA-treated and C&D wood has caused the need to go further in these guidelines. The Certification and Standards Committees of the MSC have proposed more rigorous and thorough guidelines to strengthen our commitment to truth in labeling. We anticipate amending our guidelines by the Summer of 2004.
2. A Testing Protocol and Standard for Arsenic in Mulch: The MSC has devised a test protocol to detect the presence of CCA-treated wood in mulches. We are now testing many mulches made from virgin forest products, colored mulches, and mulches deliberately mixed in a laboratory with known amounts of CCA-treated wood. We are also working with the US EPA and other officials in determining if existing standards can be applied to test results. The EPA routinely establishes such “environmental” standards and is the designated agency for protecting the environment in the United States.
3. Implementation of the Testing Protocol and Standards in Our Certification Program: Upon final adoption, the testing protocol and standards will become mandatory requirements for mulches certified by the MSC. This means that mulches certified by the MSC will have tested negative for CCA wood and met all other requirements outlined in the MSC guidelines and certification requirements. Also, periodic testing of random market samples is performed on certified products to ensure ongoing conformance to the standards.
Mulch in the Marketplace
We are aware that in most cases the general public cannot determine the quality of products just by looking at them. Whether the concern is the level of arsenic, truth in labeling, accurate quantity of content, etc., conformance to the MSC’s Voluntary Uniform Product Guidelines for Horticulture Mulches, Growing Media, and Landscape Soils is a good place to start. Although the MSC has no authority to mandate general industry compliance, member companies are actively encouraged to voluntarily follow these guidelines. However, products that are certified by the MSC must conform to these guidelines in order to achieve and maintain certification status. MSC certified products are identified with the MSC certification logo on the product label and on the MSC website .
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