Pesticides: Topical & Chemical Fact Sheets

January 8, 2007

EPA is taking legal action to deny all applications for registration of acid copper chromate, known as ACC, as a wood preservative pesticide intended for residential use. ACC contains hexavalent chromium, which is a skin irritant and sensitizer and a known human carcinogen when inhaled.

EPA’s deliberate and scientific review process has concluded that the proposed residential uses of ACC would pose cancer, and non-cancer risks of concern to workers during the manufacturing process and non-cancer risks to contractors and residential users. The Agency is concerned that the proposed uses would pose skin irritation risk of concern to children who come in contact with the treated wood.

In addition, disposal of the ACC-treated wood by either contractors or residential users after its useful lifespan could require that it be handled and disposed of as a hazardous waste since the wood could contain high levels of chromium. This evaluation has also concluded that the risks of concern associated with the proposed residential uses of ACC outweigh the minimal benefits.

Basis of EPA’s Decision

• The human health risks of the proposed use of ACC to treat wood for use in residential applications are high.
• The widespread use of ACC in residential applications, as proposed, would pose unacceptable risks to workers and residents.
• Wood treated with ACC raises disposal issues that could add to the cost of ACC-treated wood and/or could result in health and environmental impacts.
• The risks associated with the proposed residential use of ACC outweigh its benefits.
• ACC does not meet the standard of registration under FIFRA Section 3

Risk Assessment Findings

EPA has reviewed data submitted in support of applications for registration of ACC. Findings from the risk assessment include the following:

• Risks due to inhalation exposures to hexavalent chromium for treatment plant workers exceed the Agency’s level of concern for both cancer and non-cancer effects.
• Skin exposures to hexavalent chromium for children contacting treated wood surfaces exceed the Agency’s level of concern for skin sensitization.
• Introduction of ACC-treated wood into the residential marketplace would have hazardous waste generation and disposal implications.
• Risks to manufacturing workers making finished wood products exceed the Agency’s level of concern for both the cancer and non-cancer effects due to inhalation exposure to wood dust containing hexavalent chromium.
• Retail and transport workers could be exposed to some residues of hexavalent chromium via skin contact with wood surfaces that exceed the Agency’s level of concern.
• Reliable data on the carcinogenicity of hexavalent chromium via the oral route of exposure is currently unavailable. The National Toxicology Program is conducting a study to determine whether hexavalent chromium is a carcinogen by the oral route of exposure. Preliminary results currently are expected to be available in March or April 2007.

Risk Mitigation Considered

Inhalation Exposure

The Agency conducted an inhalation risk assessment for wood treatment plant workers. Currently, ACC is registered to treat wood for industrial/commercial use only. Workers would be likely to treat significantly more wood if residential uses were allowed than in the current industrial-use-only scenario. Although use of properly worn respirators reduces risk of inhalation exposure in some occupational risk scenarios, in others it does not.

Workers in manufacturing facilities that make finished wood products also can be potentially exposed to hexavalent chromium by contacting wood surfaces and by inhalation resulting from sawing operations. Since treated wood products are exempt from FIFRA regulation as treated articles they do not have detailed label instructions that could require that these persons wear respirators.

The Agency believes that there are no labeling requirements that could reliably reduce exposure to acceptable levels either in the occupational or residential setting. Labels for CCA and ACC products have required placement of tags on wood in an attempt to provide some information to end users. However, they may not always be put on the treated wood, they can fall off, their current limited size could preclude the inclusion of detailed safety information, and there is no evidence that users pay any attention to them. Respirators are not considered a feasible mitigation measure for do-it-yourself residents. While some contractors might be able to correctly use this equipment, it is not likely that they regularly use such personal protective equipment.

Skin Exposure

Holding periods are the primary option that has been considered to mitigate residential risks. A holding period would require wood treaters to hold treated wood for a designated period of time before allowing the wood to move in commerce. While a product label could require a holding period, the Agency does not believe that such a requirement would likely be practical or effective to mitigate risk for the highest exposure scenarios (more than 23 days to more than 36 days). The typical turnover of treated wood in the marketplace results in treated wood leaving the treatment site and entering retail outlets within as little as seven days of treatment. Issues include:

• Cost of carrying inventory
• Size of storage facilities needed and cost of construction
• Existence of treatment-service-only operations that do not buy wood but simply treat wood for an outside customer, generally with minimal holding periods.

Thus, the Agency believes that requiring holding periods would be in direct conflict with customary practice in the industry, creating an inherent conflict that would likely present serious challenges to compliance with a holding period requirement. There may also be difficulties in establishing an enforceable method for ensuring that wood would not be available before the prescribed holding period had elapsed and thus ensuring that wood would not reach consumers before the hexavalent chromium was reduced to acceptable levels. If holding periods were observed, it would likely add to the price of ACC-treated wood.

Another possible mitigation measure is that treated wood could be heated by processes such as kiln drying before shipment to accelerate the chromium conversion process. However, heating the wood would be an expensive added process step and could present compliance and enforcement challenges not unlike those that would be expected for holding periods.

Benefits Related to ACC

Registration of pesticides under the Federal Insecticide Fungicide, and Rodenticide Act (FIFRA) requires EPA to consider both risks and benefits. Currently, at least eight chemical wood preservatives are registered for use in the residential lumber and timber market. These include ACQ-C and D, copper azole -A and B, copper naphthenate, copper citrates, copper dimethyldithiocarbamate, copper-HDO, and polymeric betaine. Of these chemicals, ACQ currently is the most widely used wood preservative for residential applications. It also has relatively low risks, based on its components of copper and quaternary ammonium compounds.

EPA considered the cost of treatment of wood using ACC versus available alternatives, the use of wood such as redwood and cedar, as well as the use of non-wood alternative materials such as plastics. The cost of treated wood for a deck between ACC and ACQ is very similar. Other materials would be more expensive. However, the analysis did not take into account any potential cost of a required holding period before sales of ACC-treated wood or additional cost associated with hazardous waste disposal.

Based on the weight of the evidence, EPA concludes that the benefits of the use of ACC-treated wood for residential applications are minimal. Moreover, the likely costs to society of disposal of ACC-treated wood would exceed these benefits. The risks to workers and consumers that would be posed by widespread use of this chemical, if registered as proposed, far outweigh the benefits.

More about the disposal of Hazardous Waste.

Top of page