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Arsenic Dislodged from CCA Surfaces – Effects of Coatings David Stilwell

Arsenic Dislodged from CCA Surfaces – Effects of Coatings David Stilwell. EFFECTS OF COATINGS ON ARSENIC DISLODGED FROM THE SURFACE. The Coatings Polyurethane (Sapolin, floor and deck enamel) Acrylic Latex (REZ, deck stain, Solid Color)

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Arsenic Dislodged from CCA Surfaces – Effects of Coatings David Stilwell

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  1. Arsenic Dislodged from CCA Surfaces – Effects of CoatingsDavid Stilwell

  2. EFFECTS OF COATINGS ON ARSENIC DISLODGED FROM THE SURFACE • The Coatings • Polyurethane (Sapolin, floor and deck enamel) • Acrylic Latex (REZ, deck stain, Solid Color) • Oil based, with alkyd resins (Olympic, Deck Stain, Semitransparent) • Spar varnish (Last n’ Last, marine and door) • Coat top surface of 2x8 CCA boards. • 16 Coupons from 4 boards (4 replicates for each coating)

  3. Average Arsenic Dislodged from Surface Before, After, and up to One Year After Coating Arsenic

  4. ARSENIC (ug/100cm^2)

  5. Oil Coating – By Board –Time Effects – High and Low Sample Days Match (Day 60 and 365 all high)

  6. Average Chromium Dislodged from Surface Before, After, and up to One Year After Coating Chromium

  7. Chromium (ug/100cm^2)

  8. Coatings Test Conclusions • Polyurethane, Acrylic, and Spar: >95% Reduction • Oil Based Finish: 80-97% Reduction, Average=90% • Oil Finish wears Uniformly and Does not Chip – May Be Preferred on Foot Traffic Surfaces • Application of these coatings effectively eliminated any surface removable arsenic for up to one year. • Better Side By Side Comparisons Need to be Carried Out (Different Coatings on Matched Surfaces compared to uncoated – Correct for time effects observed on a particular sample date)

  9. Coatings Test Conclusions • Spar Varnish Deteriorated after One Year • Test did not determine how well these coatings would stand up to wear and tear (Foot Traffic). • Consult with paint dealer. • See Consumer Reports (June 98, 99) “Exterior Deck Treatments Test”

  10. Durability of Finishes Feist and Ross, “Performance and Durability of Finishes on Previously Coated CCA-Treated Wood” 1995, Forest Products Journal • Fully Pigmented > Semitransparent > Unpigmented • Stains need refinishing after two years or less • Paints (Film Formers including Acrylics) Could Hold up for More Than Two Years • Wood Surfaces only Subjected to Weather, not Wear as in Foot Traffic • Results are in General agreement with Consumer Reports June 98 and 99

  11. California StudyPolyurethane and Oil Based Stains worked initially, but less clear over time. (n=?) As (ug/100 cm^2) • TimeOil BasedPolyu • Before 31-314 1100 (Pier) • After 6-11 10 • 6 Months 1-13 NA • 2 Years 54 12-65

  12. CPSC – Oil and Water Based Stains – No effect Sample Coating (n=3) As (ug/100cm^2) 1 None 22 ± 22 Oil Based 10 ± 3 Water Based 14 ± 7 2 None 32 ± 22 Oil Based 53 ± 35 Water Based 52 ± 26

  13. Do Coatings Reduce As Dislodged From Surface? • This Work Yes • California Yes • Riedel et al. (1991)* Mixed • CPSC NO • Lebow and Evans (1999)* NO * See Final Expo.doc, Lebow and Evans Fe2O3 + Acrylic Before Pressure Treatment (It would be good idea to try Fe2O3 Primer After)

  14. Coatings Future Work • Focus on Oil Based, Acrylic, Polyurethane and specialty coatings (Fe2O3 Primer, Linseed Oil- WeatherBos etc.). • Compare Environmental Test Chambers, To Real Weathering Applications With and Without Physical Wear (Such as Foot Traffic). • Water Repellent Stains? – Do any of Them Form Barrier?

  15. Arsenic Dislodged from CCA SurfacesDavid Stilwell

  16. WOOD PRESERVATIVES • Extends life of wood • Protects wood from harmful organisms such as termites and fungi • Reduces use of forest products • In trade, potential for harmful environmental effects caused by the preservatives

  17. ENVIRONMENTAL ISSUES ON THE USE OF CCA TREATED WOOD • Translocation of CCA to Soil and Water via; • Leaching of CCA from wood • Runoff from lumber yards • Sawdust and physical wearing of the wood • By Cleaning – Sanding and Power washing. • Human exposure to Arsenic in CCA • Dislodged from CCA wood surfaces (hand to mouth- children) • Exposure during construction (sawdust) • Plant uptake • Impact on Beneficial Marine Organisms • Cu and As Toxicity • Disposal of Old Wood

  18. STUDIES UNDERWAY AT CAES • Cu, Cr, and As in Soils • Under Decks and Highway Noise Barriers Built With CCA Wood • Arsenic Dislodged from CCA Wood Surfaces • Plant uptake of Arsenic • CCA Leaching Characterization (time, coating effects, etc...)

  19. Arsenic Dislodged From CCA Treated Wood Surfaces

  20. Copper, Chromium and Arsenic Dislodged from CCA Treated Wood Surfaces • Controversy on how much arsenic children are exposed to by physical contact with CCA treated wood surfaces. • Such surfaces include playground equipment and decks built with CCA treated wood. • Exposure is hand to mouth. • Our study attempts to estimate this exposure by analysis of copper, chromium, and arsenic in wipe samples taken on CCA wood surfaces.

  21. SURVEY ON ARSENIC DISLODGED FROM WOOD • Boards Purchased at Lumber Yards • Amounts, Variability, Weathering and Coating Effects • CCA Wood Surfaces • Playgrounds • Decks (Not Done) • Picnic Tables (Not Done)

  22. Method That Was Used – (Similar to CPSC) • Attach Polyester wipe to 3x5 wood block and place on sample surface. • Place a 1.25 kg mass on block • Pull swipe/block assembly across sample surface 5 cycles • Remove the wipe by folding inward, return it to sample cup, and add 100ml of 10% HNO3. • Digest for 2 hours at 60 degrees C.

  23. Wipe Apparatus – Following CPSC

  24. Procedure Test- Recovery of CCA Extract on Glass Cu, Cr, As Recovery >90 % Using Damp Wipes DAMP >> DRY

  25. Survey- Wood Purchased at Lumber Yards • 6 Sets of 8 ft. boards from 3 Lumber Yards • Each Set 3-4 Boards • Each Board Cut into 1-2 ft. coupons • Test between 2-4 Coupons from Each Board • 4 Sets consisted of Regular CCA Wood and 3 Sets Consisted of CCA Wood Plus Water Repellent Treatment (WR) • Sampling Duration; 1-2 years each Set

  26. Board Survey – (0.4 lbs/ft^3). WR is Water Repellent + CCA Type (SET) BoardsCoupons Samples Duration 2x8(1&2) 4 16 120 2 5/4x6WR(3) 3 12 108 2 5/4x6WR(4) 3 6 36 1 5/4x6WR(5) 3 6 36 1 5/4x6(6) 3 6 36 1 5/4x6(7) 3 6 36 1 TOTAL 19 52 372

  27. Variability and Time (weathering) Effects

  28. Sampling Scheme – Nested Design Coupons (2 or 4 per board) … ….. Boards (3-4 per set) Sets (n=6) Over Time (one or two years)

  29. Test Coupons

  30. Variability Example, Day 35 Sets 4-7 Set ug As/100cm^2 4 57 +/- 9 5 51+/- 23 6 79 +/- 33 7 23 +/-8

  31. Variability – Between Boards Within a Set and Over Time –Tends to Follow Same Order (10>11>12, 13>14,15)WR Boards – No Marked Decrease Over 1 Year

  32. Variability – Between Boards Within a Set and Over TimeTends to Follow Same Order, STD CCA Boards – Decrease Over 1 Year, to Steady State?- See 2 Year Data

  33. Variability – Between Boards Within a Set and Over Time2 YEAR RESULTS - One Regular CCA (2x8) the Other WR CCA (Set3) NO MAJOR TREND OVER 2 YEARS

  34. Time Effects - All Sets (Normalized to D=1)

  35. Cr/As Ratio - Tends to Increase over Time – Suggests Surface Becomes Relatively Depleted in Arsenic (Theory Cr/As = 1.1)

  36. Variability and Time Effects- Conclusions • Within Board Variability (17%) much less than other sources. • Variability Between Boards, Sets and Time about Equal (39, 45, 36 %). • Within a Set the As dislodged tended to follow the same board order over time (High Boards stayed High Low Ones Stayed Low). • Cr/As Ratio increases with weathering • Decrease in As over time not shown by this data.

  37. Amounts of Arsenic Dislodged from the Surface • Coupons • Playscapes • Comparisons

  38. OVERALL RESULTS-TEST COUPONS (µg As/100 cm^2) TYPERANGEAVG.MEDIAN Reg.(n=192) 5-122 24±20 18 WR (n=180) 8-110 43±20 40 ALL 5-122 34±22 27 (n=372)

  39. Histogram All Sets (from Avg. Freq.. of Each Set)

  40. Average Arsenic Dislodged- By set-Avg. Deviation (error bars); 49%

  41. OVERALL RESULTS (n=372)-TEST COUPONS Cu, Cr, As (µg As/100 cm^2) ElementRangeAvg. Median Cu 3-69 22±12 20 Cr 4-231 51±37 42 As 5-122 34±22 27

  42. Playscape Surfaces

  43. Playscape Surfaces

  44. Arsenic Dislodged (µg/100 cm^2) From Municipal CCA Wood Playscape Surfaces # Planks(Decking) Supports (Poles)* n Range Avg. n Range Avg.. 1 14 2-45 10.5 3 15-67 36 2 16 2-17 7.8 4 51-632 216 3 15 3-22 8.2 3 21-135 63 Overall 2-45 7.6 15-632116 Supports > Planks. But Supports Sampled In Different Manner (By Hand, Not Block). Pole Results Should Only be Considered Indicative.

  45. Why Were Test Coupons > Playscape Surface? • Arsenic dislodged (µg/100 cm^2) from coupon surfaces averaged 34, but those from playscapes averaged 8. • Time Effects (Playscapes Sampled 1x) • Aging Effects/Weathering • Physical Wearing (By Repeated Physical Contact )

  46. EFFECTS OF CONSECUTIVE PASSES ON THE SAME SURFACE • Relevant to planks, hand-rails and other surfaces that are frequently contacted. • 7 test coupons from 5 separate batches of boards (2x8, 5/4x6 reg and WR) • 5 Passes each board following Standard Procedure (Each Pass is 5 Repetitions Back and Forth)

  47. EFFECTS OF CONSECUTIVE PASSES ON THE SAME SURFACE

  48. EFFECTS OF CONSECUTIVE PASSES ON THE SAME SURFACE

  49. AVERAGE AMOUNTS OF ARSENIC DISLODGED AFTER CONSECUTIVE SAMPLINGS Normalized to Rep. 1 = 100%

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