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Brief Review of “Leaching and Toxicity of CCA-Treated and Alternative- Treated Wood Products.

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Presentation on theme: "Brief Review of “Leaching and Toxicity of CCA-Treated and Alternative- Treated Wood Products."— Presentation transcript:

1 Brief Review of “Leaching and Toxicity of CCA-Treated and Alternative- Treated Wood Products

2 Objectives Conduct a side-by-side comparison of CCA-treated wood and alternative chemical-treated wood with respect to relative chemical leaching and relative aquatic toxicity of leachates Gather basic data that can be used as part of overall assessment of preserved wood types

3 Wood Preservatives CCA- chromated copper arsenate ACQ- alkaline copper quaternary CBA- copper boron azole CC- copper citrate CDDC- copper dimethyldithiocarbamate

4 Leaching Tests SPLP- Synthetic Precipitation Leaching Procedure TCLP- Toxicity Characteristic Leaching Procedure Synthetic seawater (Instant Ocean) DI water

5 Chemical Leaching Results

6 Arsenic Concentrations Found in CCA-treated Wood Leachates DITCLPSPLPSW TC= 5 mg/L

7 Copper Concentrations Found in CCA-treated Wood Leachates SPLPDITCLPSW

8 Copper Boron Azole

9 General Observations about Leaching Tests For copper, TCLP and saltwater extract the most (DI and SPLP are equivalent) TCLP extracts the most chromium Arsenic leaching approximately equal for TCLP, SPLP and DI Organic chemicals for the most part leach independent of leaching fluid

10 Comparison of Copper Leachability (concentration in mg/l) SPLP

11 Comparison of Copper Leachability (mass leaching in %) SPLP

12 Aquatic Toxicity Assays Metplate Microtox Daphnia Algae

13 Toxicity Expressions EC 50 - mg/L or percent LC 50 - mg/L or percent IC 50 - mg/L or percent

14 Comparison of Toxicity Tests (SPLP Leaching of CDDC)

15 SPLP

16 Copper as a Surrogate Literature suggests that the copper leached from CCA is the primary toxicant to aquatic organisms Does this apply to the alternative wood preservatives as well?

17 Leachate EC 50 s (C.dubia) vs. Copper Concentrations

18 General Observations Alternative chemical treated wood chemicals exhibit a greater degree of aquatic toxicity Most sensitive tests are algae and daphnia, followed by Metplate and Microtox

19 Interpretation Results show that alternative treated wood products are expected to leach more copper to aquatic systems Since copper is a potent aquatic biocide, this raises a concern

20 Interpretation However, several additional factors will impact the true impact on an aquatic system: –Dilution –Sedimentation –Binding/Complexation

21 Relative Risk Results from previous work indicate risk from CCA-treated wood is greater with respect to human toxicity and waste management Results from this work indicates that risk from alternative-treated wood is greater with respect to aquatic toxicity

22 Initial Retention Level of Wood

23 Initial retentions measured by Timber Products Inspections Sept. & Nov Letter received from TPI on May 2002 stating the results for 1 sample were in error

24 How Was This Addressed? 40 g Sawdust SPIB XRF Spectrum Digest UM Digest UF Digest TPI, XRF

25 Results

26 Average of 5 Labs Used in Final Report Minor changes in % mass leached Did not affect overall conclusion

27 Updates to Report Text

28 Questions Updated draft at Will be finalized on Jan. 15, 2003


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