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Examining Sources and Pathways of Lead Exposure in Toddlers: Insights from the LeadNL Study

The LeadNL study investigates lead exposure in toddlers (ages 0.5-6 years) in St. John's, focusing on soil, paint, and water as sources of lead. Blood lead levels (BLLs) were sampled from 249 children, revealing a geometric mean of 1.12 µg/dL, with elevated levels in homes built before 1970. Environmental lead levels were assessed across various housing cohorts, highlighting significant predictors of exposure. This study employs lead isotope ratio tracing to identify exposure sources, revealing crucial insights into environmental risks and the need for targeted interventions to protect children's health.

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Examining Sources and Pathways of Lead Exposure in Toddlers: Insights from the 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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