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Arsenic Dislodged from CCA Surfaces – Effects of Coatings David Stilwell.

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Presentation on theme: "Arsenic Dislodged from CCA Surfaces – Effects of Coatings David Stilwell."— Presentation transcript:

1 Arsenic Dislodged from CCA Surfaces – Effects of Coatings David Stilwell

2 EFFECTS OF COATINGS ON ARSENIC DISLODGED FROM THE SURFACE u The Coatings u Polyurethane (Sapolin, floor and deck enamel) u Acrylic Latex (REZ, deck stain, Solid Color) u Oil based, with alkyd resins (Olympic, Deck Stain, Semitransparent) u Spar varnish (Last n’ Last, marine and door) u Coat top surface of 2x8 CCA boards. u 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 u Polyurethane, Acrylic, and Spar: >95% Reduction u Oil Based Finish: 80-97% Reduction, Average=90% u Oil Finish wears Uniformly and Does not Chip – May Be Preferred on Foot Traffic Surfaces u Application of these coatings effectively eliminated any surface removable arsenic for up to one year. u 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 u Spar Varnish Deteriorated after One Year u Test did not determine how well these coatings would stand up to wear and tear (Foot Traffic). u Consult with paint dealer. u 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 u Fully Pigmented > Semitransparent > Unpigmented u Stains need refinishing after two years or less u Paints (Film Formers including Acrylics) Could Hold up for More Than Two Years u Wood Surfaces only Subjected to Weather, not Wear as in Foot Traffic u Results are in General agreement with Consumer Reports June 98 and 99

11 California Study Polyurethane and Oil Based Stains worked initially, but less clear over time. (n=?) As (ug/100 cm^2) u Time Oil Based Polyu u Before (Pier) u After u 6 Months1-13NA u 2 Years

12 CPSC – Oil and Water Based Stains – No effect SampleCoating (n=3)As (ug/100cm^2) 1None22 ± 22 Oil Based10 ± 3 Water Based14 ± 7 2None32 ± 22 Oil Based53 ± 35 Water Based52 ± 26

13 Do Coatings Reduce As Dislodged From Surface? u This WorkYes u CaliforniaYes u Riedel et al. (1991)*Mixed u CPSCNO u 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 u Focus on Oil Based, Acrylic, Polyurethane and specialty coatings (Fe2O3 Primer, Linseed Oil- WeatherBos etc.). u Compare Environmental Test Chambers, To Real Weathering Applications With and Without Physical Wear (Such as Foot Traffic). u Water Repellent Stains? – Do any of Them Form Barrier?

15 Arsenic Dislodged from CCA Surfaces David Stilwell

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

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

18 STUDIES UNDERWAY AT CAES u Cu, Cr, and As in Soils u Under Decks and Highway Noise Barriers Built With CCA Wood u Arsenic Dislodged from CCA Wood Surfaces u Plant uptake of Arsenic u 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 u Controversy on how much arsenic children are exposed to by physical contact with CCA treated wood surfaces. u Such surfaces include playground equipment and decks built with CCA treated wood. u Exposure is hand to mouth. u 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 u Boards Purchased at Lumber Yards u Amounts, Variability, Weathering and Coating Effects u CCA Wood Surfaces u Playgrounds u Decks (Not Done) u Picnic Tables (Not Done)

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

23 Wipe Apparatus – Following CPSC

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

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

26 Board Survey – (0.4 lbs/ft^3). WR is Water Repellent + CCA Type (SET)Boards Coupons Samples Duration 2x8(1&2) /4x6WR(3) /4x6WR(4) /4x6WR(5) /4x6(6) /4x6(7) TOTAL

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 Setug As/100cm^ / / / /-8 Variability Example, Day 35 Sets 4-7

31

32 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

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

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

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

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

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

38 Amounts of Arsenic Dislodged from the Surface u Coupons u Playscapes u Comparisons

39 OVERALL RESULTS- TEST COUPONS (µg As/100 cm^2) TYPERANGEAVG.MEDIAN Reg.(n=192) ±2018 WR (n=180) ±2040 ALL ±2227 (n=372)

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

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

42 OVERALL RESULTS (n=372)- TEST COUPONS Cu, Cr, As (µg As/100 cm^2) ElementRangeAvg.Median Cu ±1220 Cr ±3742 As ±2227

43 Playscape Surfaces

44

45 Arsenic Dislodged (µg/100 cm^2) From Municipal CCA Wood Playscape Surfaces #Planks(Decking)Supports (Poles)* nRangeAvg.n Range Avg Overall Supports > Planks. But Supports Sampled In Different Manner (By Hand, Not Block). Pole Results Should Only be Considered Indicative.

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

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

48 EFFECTS OF CONSECUTIVE PASSES ON THE SAME SURFACE

49

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

51 EFFECTS OF CONSECUTIVE PASSES ON THE SAME SURFACE -WR CCA Boards (Weathered for 0,60 and 207 days) Rejuvenation

52 EFFECTS OF CONSECUTIVE PASSES ON THE SAME SURFACE –2x8 CCA Boards (Weathered for 0,60 and 207 days)

53 Rejuvenation EFFECTS OF CONSECUTIVE PASSES ON THE SAME SURFACE -Reg CCA Boards (Weathered for 0,60 and 207 days)

54 Rejuvenation EFFECTS OF CONSECUTIVE PASSES ON THE SAME SURFACE –Average Each Set (Weathered for 0,60 and 207 days)

55 CONCLUSIONS ON THE EFFECTS OF CONSECUTIVE PASSES ON THE SAME SURFACE u The amounts of CCA material dislodged from the surfaces tends to decrease with increased contact frequency u So, comparatively less CCA could be dislodged from wood surfaces that are frequently contacted. u Most Consistent with new boards u Rejuvenation Effect after 60 Days Weathering u Weathered boards may approach steady state

56 Comparisons - Reference – Table 5 in EPA’s FINAL EXPO.DOC

57 From Table 5 - Summary of Dislodged Arsenic on Wet Wipes – 6 Groups, 18 Data Sets

58 From Table 5 - Summary of Dislodged Arsenic on Wet Wipes - – 6 Groups, 18 Data Sets

59 From Table 5 - Summary of Dislodged Arsenic - 10 Groups, 43 Data Sets

60

61 Comparisons and Conclusions u Huge Variations Between Groups, Within Groups Comparing Surfaces, and Within a Group of Samples (Min to Max) u Variation in Results u Methods u Surfaces – Retention, Age, etc. u Limited Data on Method Comparison u Vac Brush > Wet > Dry > Dry Hand ? u For Wet, Dry and Hand Methods u Median ug As/100 cm^2 u Average ug As/100 cm^2

62 Comparisons and Conclusions u Arsenic Above The Detection Limits Were Found in Most Studies u Results Highly Variable u Need for Uniform Method u Need For Lab Studies – Leach Model – Arsenic on Surface as a function of Diffusion From Interior, Leaching From Surface, Particles Removed From Surface

63 Comparisons and Conclusions u Vacuum Brush Much Higher Than Other Methods – Suggests a Potential Hazard When Scrubbing, Sanding, or Power Washing Old Wood Surfaces

64 Theory - Amount of As in a Volume ( 100cm^2 * Thickness) – Removed by Contact, Sanding or Power Washing Retention (lbs/ft^3) Human Hair 20 to 150 microns Higher Values in Wipe Samples (> ) May Indicate High Retention

65 SUGGESTIONS u No Animal or Children’s Play areas under decks u Paint or Stain CCA Wood Surfaces Regularly u Alternative Materials for Contact Surfaces u Wood treated with preservatives which contain no arsenic Cedar u Composite Woods- Trex etc. u Plastic Timber u Stone or Concrete Blocks

66 TREX

67 Acknowledgements u Katja Gorny, Mike Toner, Eric Mull, TJ Graetz, Becca Ostman (interns) u Craig Musante (CAES)


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