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May-08-2007 05:34printcomments

Bark Mulches Sold in Oregon Could Pose Health Risk

The low-cost mulch was promoted as a bark mulch substitute for its low flammability and weed control properties.

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(PORTLAND ) - Since late 2000, bark mulches composed of old asphalt roofing wastes have been produced and sold in the Portland and Eugene/Springfield areas.

The material was called “Budget Bark” in the Portland area and “No Spark Bark” in Eugene/Springfield. The low-cost mulch was promoted as a bark mulch substitute for its low flammability and weed control properties.

In 2004, DEQ became concerned about soil and groundwater contamination from application of these mulches, and analyzed samples of the products. Results showed levels of contaminants in quantities of concern for human health and aquatic life.

DEQ analyses of the bark mulches detected several chemical constituents, including polynuclear aromatic hydrocarbons (PAHs) and arsenic, at levels exceeding those considered “safe” for soils located in residential and commercial settings.

The chemicals of primary concern are arsenic and five petroleum-derived PAHs. Arsenic and several of the PAHs are considered probable human carcinogens by the US Environmental Protection Agency.

Health and Ecological Risks

The mulches are not immediately hazardous to human health or aquatic life, but people should avoid repeated exposure by getting it in their mouths or by breathing the dust. The contaminants in the material are not very soluble, so they would not be expected to contaminate groundwater when thinly spread as landscaping mulch.

Human exposure to the toxics in the mulch can occur primarily through skin contact or oral ingestion from unwashed hands, and inhalation of dust. Gardening and landscaping activities will increase the possibility of exposure.

Children are especially at risk by ingesting the mulch or breathing its dust. Children are likely to play close to the ground and often put their fingers and hands in their mouths, which adds to their exposure risk. Because young bodies grow and develop rapidly, toxins have the ability to cause lasting harm if children are repeatedly exposed to these substances.

Advice for use of mulch products

DEQ advises that homeowners and commercial property owners who use landscaping mulch avoid these two products and any mulch product containing asphalt roofing wastes. Many other safe mulch products are available for use as weed control.

If asphalt roofing mulch has already been used, DEQ recommends removal if the material has been placed in residential areas or commercial areas with frequent human activity.

Should I have the mulch tested for toxics?

Testing is not needed to identify the material.

The material is ground up asphalt roofing and should be fairly easy to visually identify. The asphalt will appear as dark black bits or chunks, often speckled with colored sand-sized particles.

Individuals wanting to have their material tested should contact an analytical laboratory. Chemical constituents to be tested for include: 1) total metals and 2) polynuclear aromatic hydrocarbons.

How do I remove the material from my property?

As with any potentially toxic material, property owners may want to consider hiring a professional cleanup company to remove this material.

Homeowners can remove this material themselves. If you decide to do your own work, make sure you minimize your contact with the material by wearing a long sleeved shirt or jacket, long pants, and closed-toed shoes, and be sure to moisten the material to minimize generating dust that you could inhale. Any suspected bark mulch material can be raked or shoveled into sealed plastic bags and disposed with other garbage.

If mulch particles have been tracked into your home, remove them using a wet mop or equivalent.

DEQ recommends having your carpet cleaned if soiled by this material. Finally, carefully wash your clothes, tools, and body after handling the material.

Is it safe to cover this material with a layer of regular bark mulch?

DEQ does not recommend covering the mulch with regular bark mulch as a long term or environmentally sound protective measure. While burial under regular bark dust will minimize exposure risks in the short term, the petroleum-derived contaminants will eventually be exposed once the organic bark decomposes.

If used at all, DEQ suggests that “No Spark Bark” or “Budget Bark” be used as mulch only in an industrial setting, away from water, where people are only periodically exposed to the mulch products.

Regulatory Authority

While DEQ does not have authority over the manufacture, sale, or safety of “products,” we do have authority over wastes and their re-use. A DEQ solid waste materials recovery site permit for RoofGone, Inc. (the Eugene producer of “No Spark Bark”) allows operation of the facility only if “No Spark Bark” is not distributed for use near waterbodies or in residential or commercial areas.

DEQ is working to ensure the safe removal and cleanup of the bark product or asphalt shingles at some sites, especially those with large stockpiles of the material.

For more information contact Bob Barrows, DEQ, Eugene, (541) 687-7354.

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