Risk Assessment for Lead in Syracuse Children

1
Risk Assessment for Lead in Syracuse Children

• Philip Goodrum, Syracuse Research Corporation,
  goodrum_at_syrres.com
• Upstate NY SRA Symposium, June 13, 2005

2
Contributors

• David L. Johnson, SUNY ESF Chemistry
• Maria T. Mastriano, SRC

3
Overview

• Blood lead concentrations (PbB) - lead exposure,
  uptake, and biokinetics
• Why model PbB when we have measurements in
  children?
• Current challenges and opportunities for Syracuse

4
Lead Poisoning

• Physiological Effects
• neurological development and motor skills
• verbal skills, IQ performance
• Generally accepted that elevated PbBs are PbB gt
  10 ug/dL
• Majority of cases go undetected

5
Healthy People 2010 Objective Eliminate
Childhood Lead Poisoning (US Dept. HHS)

• NHANES III, Children 1-5 years with PbB gt 10
  ug/dL
• 1988-1991 8.9
• 1999-2002 1.6 (or 310,000)
• Sub-populations
• older homes
• non-Hispanic black children
• low-income families

6
Elevated PbB (gt 10 ug/dL) Trends
7
Risk Target for Lead P10 ? 5
..a typical child or group of similarly exposed
children should have an estimated risk of no more
than 5 of exceeding a PbB of 10 ?g/dL. - (U.S.
EPA, 1994)
Mean PbB
Probability
P10 PPbB gt 10 ?g/dL
0
0
10
20
30
40
PbB (?g/dL)
8
Spatial distribution of PbBs
Jennifer Bretsch, MS Thesis, ESF Grad. Prog. Env.
Sci. (1998)
9
Soil Pb in Syracuse, 1999
Maria Mastriano, MS Thesis, ESF Grad. Prog. Env.
Science (2001).
10
Variability in Blood Lead
11
PbB and Soil Pb in Syracuse
12

• EPA at BHSS in Idaho
• Structural Equation Model
• for Pb exposure showed
• 40 household dust
• 30 community soils
• 30 neighborhood soils

13
Soil Mapping
Ground cover
Dust Mapping
Outdoor Exposure
simple model
SUMMER ACTIVITIES
Indoor Exposure
CHILD
Observed BLL
Probabilistic Exposure model
Predicted BLL
14
Conceptual Model for Lead
Exposure Soil, Dust, Air, Diet, Water, Paint
Risk management minimizing exposure levels
15
Lead Paint is a Recognized Source
16
Paint or Gasoline?
paint
Howard Mielke (1999) Lead in the inner cities.
American Scientist, 87 62-73.
17
Estimate of Syracuse soil lead concentrations, der
ived from automotive emissions.

• assume
• Syracuse Pb deposition ratio to population
  fraction
• 25 of Syracuse driving is beyond city limits
• Pb deposition is mixed into top 10 cm of soil,
• and is uniform over 68.5 km2 of city,
• with soil bulk density 1.5 g cm-3
• Syracuse population 150,000
• USA population is 200,000,000

0.5 x 5.8 x 106 x 150,000 16 T Pb 16 g Pb
200,000,000 x 68.5 km2 km2
m2
18
Inside/outside Reservoir Comparison

• Avg paint (HUD Pb abatement, Syracuse) 2.6
  mg/cm2 2.4 g/ft2
• average room 10 x 10 x 8 420 sq. ft. with
  ceiling
• Average 7-room house contains 7 Kg. Pb in paint
• Average house lot 40 x 120 feet _at_ 200 ppm in soil
• assume Pb contained in top 10 cm
• 1200 x 3600 x 10 x 1.5 g/cm3
• Average city lot contains 13.2 Kg Pb in soil

19
Soil a Reservoir of Lead

• Strongest relationships between blood lead and
  (potential) environmental exposure measures is to
  loadingµg ft-2 or µg m2 not to concentration
• HUD clearance values are 40 µg ft2 (432 µg m2)
• Soil at 100 µg Pb g-1 per 1 cm depth
• 1.5 g cm-3 x 1cm x 100cm x 100cm x 100 x 10-6 g
  Pb
• 1 cm Soil loading of 1.5 g m-2 (1,500 µg m2)
• 10 cm Soil loading of 15 g m-2 (15,000 µg m2)

20
Urban Metal Mapping ProjectSyracuse, New York

• Door to door random house sampling (Summer
  2003-2004)
• Over 3500 soil samples taken
• Over 500 houses sampled
• Paired floor dust loading, metal loading and soil
  metal concentration data

21
Geographic Patterns of Lead and Zinc in House
Dusts and Surface Soils of Syracuse, NY,
USA D.L. Johnson, J. Hager, J. Brooks, H.
StellaLevinsohn, A. Hunt, S. Blount, S.
Ellsworth, A. Lanciki, S. Lee and D.A. Griffith
SUNY College of Environmental Science and
Forestry, Syracuse, NY UNYSPEC,
Baldwinsville, NY Dept. Geography, Univ. Miami
Lead in Soil Samples
22
Data Sources for Exposure Variables

• Site-Specific
• Concentrations
• Soil
• House Dust
• Tap Water
• Bioavailability
• Soil, Dust

• Literature / Judgment
• Concentrations
• Diet, Air
• Other (garden, paint)
• Ingestion Rates
• Fraction soil
• Exposure Frequency
• Bioavailability
• Water, Diet, Air

X
X
X
X
23
Data Sources for Exposure Variables

• Site-Specific
• Concentrations
• X Soil
• X House Dust
• X Tap Water
• Bioavailability
• X Soil, Dust

• Literature / Judgment
• Concentrations
• Diet, Air
• Other (garden, paint)
• Ingestion Rates
• Fraction soil
• Exposure Frequency
• Bioavailability
• Water, Diet, Air

X
X
X
24
Soil and Dust Ingestion Rate
Source Griffin et al., 1999. HERA 5(4) 845-868.
25
Dust Exposure Pathways
26
Temporal Variability

• Environment
• season / climate
• Behavior
• hand-to-mouth activity
• location
• frequency of contact
• Physiology
• GI status

27
Modeling Objective
To develop a scientifically sound approach to the
quantitative uncertainty analysis of lead risk
estimates.

• How do we best represent variability and
  uncertainty in model variables?
• How can these estimates be propagated through
  risk models?
• What are the critical assumptions and data gaps?
• How do we interpret and communicate the output of
  these analyses?

28
Models are often cheaper than sampling. How can
we construct a model, and what can we learn?
Deposition
Removal
29
Modeling Assumptions

• Time Step
• Exposure Unit
• Concentration Term (Soil and Dust)
• Intake - Uptake Interval
• Blood Lead Age Grouping
• Probability Distribution for PbB Variability

30
Truncation of Soil Ingestion Rate
IRsd (mg/day) min 0 25th ile 10 50th
ile 45 75th ile 88 90th ile
186 95th ile 208 99th ile 225 max ?
Source Stanek and Calabrese (1995)
31
Averaging over Time
Arithmetic mean intake for averaging time
x3
x4
x5
x6
x2
x1
Monthly Time Step n 12
x2
x1
Quarterly Time Step n 4
x1
Annual Time Step n 1
32
Time Step (annual vs. monthly)
P10 9.5
P10 5.0
33
Spatial Variability

• Sampling Design
• location
• sample size
• Receptor
• random movement
• Exposure Unit
• residence
• study zone

For residential exposure, typically Csoil mean
34
Median Household Dust Metal Concentrations (ppm)
REFs-2
REFs-3
REFs-4
35
Indoor Dust Loading Is there a pattern of dirty
houses?
36
(No Transcript)
37
(No Transcript)
38

• Why ESF (external soil fraction)?
• kids spend more time inside than outside
• model indoor exposure from high resolution
  outdoor maps

• How ESF?
• tracer element ratio Mg, Sr, Zr, Fe, Mn
• works if local external soil is sole source

10.3 ?g Mn/sq. ft.
33 mg soil per square foot
313 ?g Mn/g soil
10.3 ?g/sq. ft.
313 ?g/g soil
house dust
39
Calculation of ESF

• Soil Fe conc. 0.14 gFe/gsoil (14000ppm)
• Dust loading 0.067 gdust/ft2 (67mg/ft2)
• Fe loading 12010-6 gFe/ft2 (120µgFe/ft2)

40
(No Transcript)
41
(No Transcript)
42
Dust loading (mg/ft2)
How does dust loading vary with time?
50
10
Time (days? Weeks?)
43
When was that sample taken?

• Time elapsed between date of abatement and date
  of PbB test collection

44
Current Challenges in Modeling PbBs

• Temporal Variability
• Activity Patterns - Do individuals exhibit
  patterns in soil ingestion as they age?
• Should different time steps apply to different
  inputs?
• Indoor Dust
• Source apportionment
• Connection to risk management strategies
• Biokinetics at what rate does PbB decline?