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St. John’s LeadNL study

St. John’s LeadNL study. Sources and pathways of Pb exposure at low blood lead concentrations Trevor Bell ( tbell@mun.ca ). Co-authors : David Allison Jacinthe David Robert Foley Sarah Mackey Felicia Pickard Joanne Stares James Valcour. Funding by. Atlantic Ocean.

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St. John’s LeadNL study

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  1. St. John’s LeadNL study Sources and pathways of Pb exposure at low blood lead concentrations Trevor Bell (tbell@mun.ca) Co-authors: David Allison Jacinthe David Robert Foley Sarah Mackey Felicia Pickard Joanne Stares James Valcour Funding by

  2. Atlantic Ocean St. John’s harbour

  3. Why the LeadNL study? Soil lead levels < CCME > CCME

  4. LeadNLBiomonitoring survey Measured blood lead in 249 toddlers (0.5-6 yrs) Sampled across housing age cohorts Measured environmental lead levels in homes (194)

  5. Sample vs census pop.

  6. Blood lead distribution (n=257) GM= 1.12 µg/dL Range= 0.21 to 7.5 µg/dL 95th percentile 2.71µg/dL Canadian BLL reference

  7. BLLs by age & housing cohort

  8. BLLs by housing cohort • Children living in houses older than 1970 are at higher Pb exposure risk • have a significantly elevated BLL compared to the reference population • Housing age is a significant predictor of children’s mean blood Pb

  9. Soil Pb content • 36% of household soils above guideline • Dripline samples had highest levels

  10. Pb content of paint • Interior paint slightly higher Pb content than exterior paint • Statistical difference in paint Pb content across housing ages

  11. Pb in tapwater Highest in post-stagnation samples Vast majority below Canadian guidelines Only the first post-stagnation sample was significantly different in pre-1970 housing

  12. Associations between BLLs and ELLs Reference: 140ppm

  13. Potential Pb exposure sources Associations between BLLs and ELLs Significance level 95%

  14. Pb isotope ratio tracing • Can we use the isotope tracing method to source Pb exposure at low Pb concentrations

  15. Pb isotope ratio tracing • Participant selection • 90th percentile BLLs (2.29-7.5 μg/dL) (n=34) • 68% living in houses built before 1970 90th percentile 2.29µg/dL

  16. Pb isotope ratio tracing • Participant selection • 90th percentile BLLs (2.29-7.5 μg/dL) (n=34) • 68% living in houses built before 1970 ≥ 2 years ≥ 1 year to 2 years ≥ 6 months to 1 year ≥ 3 months to 6 months

  17. Pb isotope ratio tracing • Environmental sample selection by household • All soil samples • Highest Pb content water sample • Highest Pb content window trough dust sample • Floor and windowsill dust samples above COVs (Dixon et al. 2009 model)

  18. Environmental media samples

  19. Pb isotope ratio tracing • Blood Pb isotope analysis @ Bill Manton’s lab • Finnigan multi-collector TIMS • Environmental Pb isotope analysis @ MUN • Finnigan multi-collector ICP-MS

  20. PbB 206/207 ratios vs. PbBconc Blood 34 206/207 range = 1.1097-1.1948

  21. Dust Geological background 206/207 ratios for PbB & env media Water Paint Blood 8 Soil 30 Air 34 121 55 35

  22. Individual residential environment • 3 children had less radiogenic 206/207 values than sampled home env media • 17 children had moreradiogenic 206/207 values than sampled home envmedia • 14 children had 206/207 values that fell within the range of sampled home envmedia • Value in combining PbB concentration data with isotope data for interpretations

  23. Sourcing Pb exposure: case #1 µg/g All media samples have relatively low concentrations except water µg/dL,µg/ft2,µg/L Between 0.5 and 1 year old; BLL 2.71 ug/dL; 1981-2000 housing cohort; 6-12 month residency; Deteriorated paint on kitchen walls; PbW above guideline

  24. Sourcing Pb exposure: case #2 • PbBisotope ratio closest to child’s playroom floor, living room floor and front entrance floor, although relatively low Pb concentrations • All other samples less radiogenic than child’s blood – unlikely to be sources unless highly radiogenic media not sampled µg/g µg/dL,µg/ft2,µg/L 5-6 years old; BLL 2.5 ug/dL; home built 1961-70; residency >2 years; recent renovations to child’s bedroom and other rooms in house

  25. Sourcing Pb exposure: case #3 µg/dL,µg/ft2,µg/L PbB sample is closest to 206/207 ratios of home office floor and property soils Office floor dust is relatively high Soil samples are above guideline High exterior paint Pb content µg/g 2.5-3 years old; had highest BLL (7.5 ug/dL); >2 year residency; oldest housing category (>1946); Recent renovations in house and deteriorated paint observed on exterior and interior surfaces

  26. Community patterns • Using Euclidean distance between isotope ratios: • In 77% of cases, same source media was closest to blood lead whether using 206/207/208/207 ratio pair or all ratios together • Water (~40%), dust (~30%) and soil (~30%) were most frequently the closest source media to PbB isotope ratios

  27. Discussion? Is the success of Pb isotope tracing method site-specific? Does the long residency time of Pb in bone severely limit the method? Is the method useful at low Pb concentrations?

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