«Report on Copper, Chromium and Arsenic (CCA) Treated Timber Deborah Read April 2003 ISBN 0-478-21521-5 Acknowledgements This report was prepared by ...»
Report on Copper,
Chromium and Arsenic (CCA)
This report was prepared by Dr Deborah Read, public health physician, for ERMA New
The report was externally peer reviewed by:
Dr Michael Beasley, Medical Toxicologist, National Poisons Centre, School of Medicine,
University of Otago, Dunedin;
Dr Donald Campbell, Medical Officer of Health/Public Health Physician, MidCentral Health, Palmerston North; and Dr Peter Di Marco, Toxicologist, Perth, Australia.
The author gratefully acknowledges comments from members of the Inter-agency Coordinating Group and the assistance of Linda Campbell, Information Services Co-ordinator, ERMA New Zealand.
Table of Contents 1 Terms of Reference
3 Executive Summary
5 Copper, chromium and arsenic (CCA)
5.1 What is CCA?
5.2 CCA in New Zealand
5.3 Timber treatment in New Zealand
5.4 CCA-treated wood
5.5 Toxicity of CCA
6.1 What is copper?
6.2 General population exposure
7.1 What is chromium?
7.2 General population exposure
8.1 What is arsenic?
8.2 General population exposure
9 Migration of CCA
9.1 Migration from soil
9.2 Migration from treated wood
9.3 Levels of CCA components in soil/sand from treated wood structures................. 25
9.4 Dislodgeable CCA surface residue levels
9.5 Mitigation of CCA
10 Plant Uptake of CCA Components
11 Regulatory Approaches
11.1 New Zealand
11.2.1 European Union
11.2.2 United States
12 Health Risk Assessment
13 Exposure Assessment of Children
14 Epidemiological Studies
14.1 At risk population groups
14.2 Occupational studies
14.3 Non-occupational studies
15 Risk Assessments of Children’s Exposure to Arsenic from CCA-Treated Wood Structures
15.1 California Department of Health Services (1987)
15.2 US Consumer Product Safety Commission (1990)
15.3 WS Atkins International (1998)
15.4 Hazardous Substance and Waste Management Research (2000a, 2000b, 2001)... 48
15.5 Roberts and Ochoa (2001)
15.6 Gradient Corporation (2001)
15.7 Environmental Working Group (2001)
15.8 Maas et al. (2002)
15.9 US Consumer Product Safety Commission (2003)
16 Aggregate Exposure of New Zealand Children to Arsenic
17 Information Gaps and Uncertainties
18 Precautionary Health Advice
1 Terms of Reference
The objective is to produce a report that:
(1) reviews the report Release of Total Chromium, Chromium VI and Total Arsenic from New and Aged Pressure Treated Lumber by Dr R Maas et al. (2002) to provide guidance as to its scientific credibility, the extent to which it constitutes new information and the relevance of this information to New Zealand circumstances.
(2) reviews other relevant information about the public health (including occupational health) risks related to the use of CCA-treated timber particularly around homes and in children’s playgrounds, on a comparable basis to the review of the Maas report.
(3) identifies data and information gaps and uncertainties (including matters of dispute).
(4) provides advice on whether the levels of public and occupational health risk indicated may justify further regulatory action, taking account of the matters set out above.
The scope of the project is limited to undertaking a literatur e review and interpreting the findings in a New Zealand context that focuses on current public and occupational health risk.
Occupational risks related to the manufacture of copper, chromium and arsenic (CCA) treated timber, risks to the environment, and alternatives to CCA-treated timber are excluded.
2 Method A literature search of on-line bibliographic databases was undertaken using DIALOG for publications in English about the public and occupational health risks from use of CCAtreated wood in residential and public settings. Key words used in the search included synonyms and related terms for CCA. The search period focused on publications from 1990 to 2002. Some publications outside this period have been included. Since many of the reports, in particular the risk assessments, are not identifiable from bibliographic databases the bibliographies of identified reports and papers were also examined and organisational websites were searched. Not all articles that were viewed have been cited.
Although the Maas report has its own term of reference the author considered it more appropriate to review it in the context of all other risk assessments of CCA-treated wood, and therefore merged Terms of Reference 1 and 2. The Institute of Environmental Science and Research (ESR) reviewed the Maas report for the Ministry of Health from which a separate report is available.
This review focuses on the forms of the components of CCA that pertain to CCA-treated wood and gives more detail on arsenic than copper and chromium since it is the most toxic component and also appears to leach more from CCA-treated wood than chromium, the second most toxic component. For this reason the sections on copper and chromium are largely drawn from review documents rather than source references.
Copper, Chromium and Arsenic (CCA) Treated Timber Page 1 3 Executive Summary The wood preservative copper, chromium and arsenic (CCA) has been used in New Zealand since the 1950s but widespread exposure of the general population to CCA-treated wood did not occur until the late 1960s. Arsenic is the most toxic of the three components and has therefore been the focus of the health risk assessments that have been undertaken to date.
CCA-treated radiata pine is commonly used in outdoor settings. Uses in residential and public settings include decks, garden furniture, picnic tables, playground equipment, landscaping timbers, retaining walls, fences, gazebos and patios. However CCA is only one source of potential human exposure to inorganic arsenic. New Zealanders are exposed to low levels of arsenic present in food, water, air and soil, particularly in the central North Island where background levels are naturally high in the volcanic soil.
Decreasing amounts of copper, arsenic and chromium migrate from CCA-treated wood over time. All three components of CCA adsorb strongly onto soil so will be confined to the areas under the deck or immediately adjacent to the playground equipment.
Public exposure particularly that of children is most likely to occur through the ingestion of dislodgeable residues from the surface of, and contaminated soil adjacent to, CCA-treated wood structures such as playground equipment and decks. In contrast the main exposure for builders is inhalation of CCA dust.
It is assumed that the form of arsenic in CCA-treated wood surface residues and soil is pentavalent and the chromium is trivalent. Pentavalent arsenic is less toxic than trivalent arsenic and trivalent chromium is significantly less toxic than hexavalent chromium.
Conversion of trivalent chromium to hexavalent chromium has been reported following use of commercial deck wash treatments containing oxidising agents and in some soil conditions.
Chronic exposure to arsenic through ingestion is associated with skin, lung and bladder cancer and through inhalation with lung cancer. Hexavalent chromium is also carcinogenic but only through inhalation.
There are no epidemiological studies or human case reports involving disease related to direct contact with CCA-treated wood and the low level exposures that most of the general population will experience from contact with CCA-treated wood are extremely unlikely to result in acute health effects. CCA-treated wood has also been in use for many years without discernible adverse health effects suggesting that if there is a true increased risk it is very small.
The studies and risk assessments that have been carried out overseas are relevant to New Zealand. The CCA formulations used in New Zealand are similar to CCA Type C used in the United States. Radiata pine is also similar to southern pine species which are the predominant wood treated with CCA in the United States. The main limitation in extrapolating American results for residues and soil from CCA-treated wood to New Zealand relates to climate, particularly rainfall. In addition in the United States almost all CCA-treated decking and playground equipment is treated to a higher CCA retention specification than in New Zealand which means the dislodgeable residue concentrations reported there may be higher than what would be found on such structures in New Zealand.
Copper, Chromium and Arsenic (CCA) Treated Timber Page 2 Since children under seven years are most likely to exhibit mouthing behaviour children aged 2-6 years are considered the most at risk group in risk assessments of CCA-treated wood structures. The risk assessments cover a variety of exposure scenarios. In the absence of data on New Zealand children’s activity patterns it is not possible to accurately assess how applicable these are for New Zealand. However several playground visits a week for children aged 2-6 years in towns and cities may be plausible and some children are likely to have more frequent exposure from a sand-pit, deck and/or play equipment at home.
It is difficult to compare assessments with one another as the values used for some exposure parameters vary widely and hence there is a large variation in the risk estimates. No standardised study protocol has been used for assessing exposure to dislodgeable CCA residues and prior to the recent US Consumer Product Safety Commission (US CPSC) study (2003) sampling methodology appears not to have been validated. Assessments based on wipe data are likely to have overestimated the amount of dislodgeable arsenic residue that would be transferred to hands and there is high variability among the reported results. Until the CPSC study (2003) little attempt had been made to correlate wipe and hand loading data. Wipe arsenic concentrations were found to overestimate hand arsenic concentrations approximately five- fold. Future use of this conversion factor is likely to give more realistic measures.
For those risk assessments that are well described in terms of assumptions made and exposure parameters used, the risk estimates for lung and bladder cancer range from about one additional case in a million people (1 x 10-6 ) exposed above the background lifetime risk of developing lung or bladder cancer due to other factors to one in ten thousand (1 x 10-4 ) people exposed. In other words the additional lifetime cancer risk ranges from less than the risk level of one in one hundred thousand (1 x 10-5 ) regarded as tolerable for carcinogens by New Zealand regulatory agencies to an order of magnitude higher. Any increased risk for skin cancer is in addition to the risk for lung and bladder cancer.
Available New Zealand data on inorganic arsenic intake are insufficient for a risk assessment to be carried out with reasonable certainty. On the basis of limited data the estimated aggregate inorganic arsenic intake for an average New Zealand 2-6 year old child from food, drinking water and a daily playground visit (assuming the CPSC value of 3.5 µg ingested arsenic from CCA-treated wood surface residues applies in New Zealand) is below the tolerable intake of about 2 µg/kg body weight/day set by the Joint Food and Agriculture Organisation / World Health Organisation Expert Committee on Food Additives (JFECFA) (FAO/WHO, 1989). The tolerable intake is the amount that can be ingested daily per kilogram of body weight that represents a level of no appreciable health risk for a lifetime exposure.
However aggregate exposure may be high for some children depending on their age, geographical location, home characteristics and daily activity.
Much of the information identified during this review was available only in the form of technical reports and was unpublished in the peer reviewed scientific literature. It was only possible to confirm that two risk assessments (WS Atkins International, 1998; US CPSC,
2003) had undergone independent scientific peer review.
There are no New Zealand data on the prevalence of CCA-treated wood decks or playground equipment and their age, the number of children likely to be exposed, activity patterns of New Zealand children involving these structures, and dislodgeable residue results from CCAtreated radiata pine structures.
Copper, Chromium and Arsenic (CCA) Treated Timber Page 3 Uncertainty still remains about the transfer rate of surface residues from CCA-treated wood to skin over time, the hand-to- mouth transfer efficiency, and relative bioavailability of ingested arsenic residues and to a lesser extent soil arsenic compared to ingested arsenic in water.
Most risk assessments use toxicity values that have been developed by the US Environmental Protection Agency (EPA) for both cancer and non-cancer effects. Recently the CPSC has also used the National Research Council’s (NRC) value for cancer effects. The Atkins report (WS Atkins International, 1998) used the World Health Organisation’s (WHO) value for lung cancer from inhalation. Acceptance of these values varies depending on the perspective of the risk assessor with some emphasising their limitations more than others. The main uncertainty for the cancer toxicity values is that the mechanism of carcinogenesis of arsenic is not well established. In the absence of certainty linear extrapolation has been used to predict cancer risk at low levels of arsenic intake from the risks at moderate to high intakes. There is also uncertainty associated with averaging low dose arsenic short-term exposure over a lifetime.