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

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 LeachingResults

6. Arsenic Concentrations Found in CCA-treated Wood Leachates TC= 5 mg/L DI TCLP SPLP SW

7. DI TCLP SPLP SW Copper Concentrations Found in CCA-treated Wood Leachates

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 • EC50- mg/L or percent • LC50- mg/L or percent • IC50- 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 EC50s (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 Retention Level of Wood • Initial retentions measured by Timber Products Inspections Sept. & Nov. 2000 • 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 UF Digest UM 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 www.ccaresearch.org Will be finalized on Jan. 15, 2003