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ATSDR Presentation to the Washington, DC, Scientific Advisory Board

Regarding Exposure Investigations

Presented by Susan Metcalf, MD, MSPH on April 25, 2001


Slide 1
Agency for Toxic Substances
and Disease Registry
  • Susan W. Metcalf, MD, MSPH

Slide 2
Exposure Investigation
Spring Valley Chemical Munitions
Washington, DC
  • Ketna Mistry, M.D., F.A.A.P
  • Ken Orloff, Ph.D., DABT
Slide 3
ATSDR

The primary public health agency for addressing human health issues that might arise from exposure to hazardous substances
Slide 4

Continuum for Relating Environmental Contamination
with Clinical Disease

Slide 5
Purpose of an Exposure Investigation

To better characterize past, current, and possible future human exposures to hazardous substances in the environment.
Slide 6
Exposure Investigation: Data Gathering
  • Environmental samples
  • Biomarkers
  • Exposure-dose reconstruction
Slide 7
Arsenic Biomarkers: Blood
  • Quantifies the absorbed Arsenic
  • Clears within a few hours
  • Not useful for low-level exposure
slide 8
Arsenic Biomarkers: Urine
  • Good marker of recent exposure
    • (3-4 days)
  • Includes both inorganic and organic forms
  • Reference range available
slide 9
Total Arsenic in Urine
  • Inorganic As (As+3, As+5)
  • MMA (monomethylarsonic acid)
  • DMA (dimethylarsenic acid)
  • Trimethylated forms
    • Arsenobetaine
    • Arsenocholine
slide 10
Arsenic Biomarkers: Hair
  • Measures several months of exposure
  • Collection is non-invasive
slide 11
Limitations of Hair as Biomarker
  • Possibility of external contamination
  • Paucity of reference range data for unexposed populations
slide 12
Playground Arsenic Levels
  • Soil arsenic levels
    • Average 57 ppm
    • Highest level 498 ppm
  • Children immediately relocated to another area of the campus
slide 13
Playground Characteristics
  • Covered with 2 inches of mulch or grass in some areas
  • Playground is periodically remulched
slide 14
Target Population
  • Daycare roster:
    • 28 children
    • 4 adult staff
  • Length of time at daycare:
    • ~50% present: < 7 months
    • ~50% present: > 1 year
slide 15
Other Sources of Arsenic
  • Wood preservatives
  • Pesticides
  • Arsenic containing herbal medicines
  • Parental occupational exposure
  • Hobbies
  • Consumption of seafood
  • Pica (soil eating) behavior
slide 16
Results
  • Hair samples for arsenic:
  • 24/ 32 hair samples : not detected
  • 8 / 32 hair samples: detected
  • 8 Arsenic detected hair samples ranged from 0.10 ppm to 0.14 ppm
slide 17
Background Hair Arsenic Levels
  • Textbooks: < 1 ppm
  • National Research Council: 0.2 ppm
  • NCEH: 95th percentile: 0.28 ppm
slide 18
Conclusion
  • Hair arsenic levels were not elevated in the 32 participants of this exposure investigation
  • Therefore, no unusual exposure to arsenic was found in the participants at the Child Daycare Center
slide 19
Speciated Urine Arsenic (µg/L)(Kalman, 1990)

Age Group
(boys)
Rushton Control
0-6 years 65 11
7-13 years 30 13
14-20 years 10 9
Mean As soil conc 353 ppm 7-57 ppm
slide 20
Hwang 1997
  • Measured speciated urinary As in 300 children near smelter site
  • Average soil levels 121-236 ppm
  • Average urinary arsenic levels 8.6 µg/L
slide 21
Panther Creek, 1998
  • Mining site
  • Soil levels up to 3500 ppm
  • Urine samples tested for As
    • 20/23 below detection levels
    • 6-8 µg/g Cr As in samples where As detected
slide 22
Panther Creek, ID
  • Hair analysis
    • 26/36 below level of detection
    • 7 had elevated hair levels
      • Urine levels not elevated
      • All were remediation workers
      • Likely due to external contamination
slide 23
Past studies of exposure to Arsenic in soil
  • At soil levels < 100 ppm, average urine arsenic is similar to background levels
  • At soil levels > 100 ppm, urinary levels may show exposure but are below levels associated with health effects

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