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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 CoatingsDavid 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) • 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)
Average Arsenic Dislodged from Surface Before, After, and up to One Year After Coating Arsenic
Oil Coating – By Board –Time Effects – High and Low Sample Days Match (Day 60 and 365 all high)
Average Chromium Dislodged from Surface Before, After, and up to One Year After Coating Chromium
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)
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”
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
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
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
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)
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?
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
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
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...)
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.
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)
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.
Procedure Test- Recovery of CCA Extract on Glass Cu, Cr, As Recovery >90 % Using Damp Wipes DAMP >> DRY
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
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
Sampling Scheme – Nested Design Coupons (2 or 4 per board) … ….. Boards (3-4 per set) Sets (n=6) Over Time (one or two years)
Variability Example, Day 35 Sets 4-7 Set ug As/100cm^2 4 57 +/- 9 5 51+/- 23 6 79 +/- 33 7 23 +/-8
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
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
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
Cr/As Ratio - Tends to Increase over Time – Suggests Surface Becomes Relatively Depleted in Arsenic (Theory Cr/As = 1.1)
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.
Amounts of Arsenic Dislodged from the Surface • Coupons • Playscapes • Comparisons
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)
Average Arsenic Dislodged- By set-Avg. Deviation (error bars); 49%
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
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.
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 )
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)
AVERAGE AMOUNTS OF ARSENIC DISLODGED AFTER CONSECUTIVE SAMPLINGS Normalized to Rep. 1 = 100%