Chromated Copper Arsenate (CCA):
Final Probabilistic Risk Assessment for Children Who Contact CCA-Treated Playsets and Decks
CCA Table of Contents
Updated April 30, 2008
The final probabilistic risk assessment on chromated copper arsenate (CCA) that evaluates potential exposure and risk to children from CCA-treated wood is complete. This report entitled “A Probabilistic Risk Assessment for Children Who Contact CCA-Treated Playsets and Decks1” is available at regulations.gov in docket number EPA-HQ-OPP-2003-0250.
Although virtually all residential uses of CCA – including use on decks and playsets – have been voluntarily canceled, EPA is fulfilling its public commitment to revise the risk assessment based on new information as well as recommendations from the Scientific Advisory Panel (SAP) and Science Advisory Board (SAB). EPA wants to ensure that its procedures, processes, and decisions are transparent.
On this page:
- Significant changes incorporated in the final CCA probabilistic assessment
- Arsenic and potential risks to human health
- Role of a probabilistic risk assessment
- Coating study and its implications for the CCA risk assessment and consumers
- Next steps in the reregistration eligibility decision (RED) process for CCA
- Related information
- Consumer information links
- EPA’s overall conclusions regarding risk for children who contact CCA-treated playsets and decks have not changed.
- In the final probabilistic risk assessment, the Agency considered up-to-date exposure estimates published in Web 20051, skin contact rate information published in Freeman 20012, and the recommendations of several SAP and SAB reviews.
- Based on EPA’s revised cancer assessment guidelines, the Agency also applied the Cancer Assessment Review Committee’s reclassification of hexavalent chromium (CrVI) as “Likely to be Carcinogenic to Humans” via the oral route of exposure (currently pending EPA peer review) as well as age dependent adjustments factors to hexavalent chromium.
- In addition, the Agency included risk estimates based on exposure data from Kwon 20043.
Arsenic is a known human carcinogen and is acutely toxic at certain levels. When estimating the potential risks that a chemical may pose, one must consider two factors: toxicity and exposure.
- Toxicity is described as the harmful effects that the chemical may cause, which is often dependent on the amount or dose received.
- Exposure is the dose received, typically orally or through contact with the skin, or by inhaling, over a certain period of time.
Thus, whether any risk exists is dependent on both toxicity and exposure. Arsenic is a naturally occurring chemical that can also occur in drinking water, food crops, and soil.Leaching of arsenic from treated wood products into soil: Published results of scientific studies suggest that arsenic slowly leaches from CCA-treated wood products. The amount and rate at which arsenic leaches, however, varies considerably depending on numerous factors, such as local climate, acidity of rain and soil, and how much CCA was applied.
Presence of arsenic in the environment from other sources: Arsenic is a chemical element and is a natural constituent of the earth's crust. It occurs naturally in rocks and soil, water, air, and plants and animals. When in the natural environment, arsenic usually binds to other molecules, such as those found in soils, and does not tend to travel very far or “migrate.”
The average concentration of arsenic in soils in the United States varies considerably. Arsenic can be released into the environment through natural occurrences such as volcanic activity, erosion of rocks, and forest fires, or through human actions such as agricultural practices, mining, and smelting. The majority of industrial arsenic in the United States is believed to be used as a wood preservative, but it is also used in dyes, metals, and semiconductors.
Because of the statistical way in which a probabilistic assessment may be used to analyze a wide range of data, it provides a more scientifically robust analysis. A probabilistic assessment is able to indicate a range of risk estimates based on a range of assumptions as well as the likelihood of occurrence of any particular risk within the range.
EPA’s previous risk assessment was a deterministic assessment, which is only able to take into consideration specific point estimates in determining a single risk value. A probabilistic risk assessment provides for a much more accurate, advanced and robust analysis, thereby producing results that can be more closely correlated with exposure scenarios people experience in everyday life.
EPA’s Office of Research and Development and Office of Pesticide Programs and the Consumer Product Safety Commission conducted a study to determine whether or not the application of different wood coatings on CCA-treated wood affects the amount of CCA residues to which an individual may be exposed.
- This study suggest that applying certain penetrating coatings may reduce the migration of wood preservatives from CCA-treated wood.
The Agency is continuing to evaluate those CCA uses not included in the voluntary cancellation under the reregistration process. Once EPA completes the reregistration evaluation for CCA, the reregistration eligibility decision (RED) document for chromated arsenicals will be available at www.regulations.gov in docket number EPA-HQ-OPP-2003-0250, currently scheduled for late 2008.Consumer Advice Related to CCA-Treated Wood
Chromated Copper Arsenate (CCA) --
Consumer Safety Information Sheet (Consumer Awareness Program): Inorganic Arsenical Pressure-Treated Wood
1Zartarian V.G., J. Xue, H. A. Ozkaynak, W. Dang, G. Glen, L. Smith, and C. Stallings., 2005, “A Probabilistic Exposure Assessment for Children Who Contact CCA-treated Playsets and Decks Using the Stochastic Human Exposure and Dose Simulation Model for the Wood Preservative Scenario (SHEDS-WOOD)” Final Report. U.S. EPA. Washington, DC, EPA/600/X-05/
2Freeman N.C.G.; Jimenez, M.; Reed, K.J.; Gurunathan, S.; Edwards, R.D.; Roy, A.; Adgate, J.L.; Pellizzari, E.D.; Quackenboss, J.; Sexton, K., and Lioy, P.J. 2001. Quantitative analysis of Children’s microactivity patterns: The Minnesota Children’s Pesticide Exposure Study. Journal of Exposure Analysis and Environmental Epidemiology. 11(6): 501-509.
3Kwon, E.; Zhang, H.; Wang, Z.; Jhangri, G.; Lu, X.; Folk, N.; Gabos, S.; Li, X. And Le, X.C. 2004. Arsenic on the Hands of Children after Playing in Playgrounds. Environmental Health Perspectives. 112: 1375- 1380