Groundwater Arsenic Contamination in the United States

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Groundwater Arsenic Contamination in the United
States

• GIS Term Project, EWRE
• Fall 2000
• By Hazim Tugun

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Outline

• Background
• Objectives
• Mapping of data/findings related to As in the
  groundwater
• Preliminary Conclusions
• Future work

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Background

• A gray brittle semi-metal
• Naturally exists throughout the earths crust
  (often as Arsenic Sulfide, Metal Arsenates or
  Arsenites).
• Has many oxidation states, As(III) or As(V).

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Background

• Main sources
• Natural From dissolution of naturally existing
  minerals/ores or soils, upflow of geothermal
  water.
• Man-made Industrial effluents, copper smelting,
  atmospheric deposition.
• Adsorption-desorption, precipitation-dissolution
  with other environmental factors determine
  fate/transport in water.

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Background

• Human exposure via food, water and air.
• Regulated under EPA Drinking Water Standards 50
  ppb current limit ? 5 ppb proposed.
• Acute or chronic health effects
• Skin lesions, skin, bladder, other internal
  cancers, upon prolonged exposures.
• Poisoning / death can result upon ingestion of 60
  ppm in drinking water.

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Objectives

• Create a map to show the geospatial distribution
  of groundwater Arsenic concentrations in the
  United States.
• Use this distribution as a foundation to make
  general characterizations, if possible, of
  groundwater arsenic contamination with respect
  to
• Variations in the magnitude of contamination.
• Possible sources of contamination.
• Health effects.

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GW As data from USGS NAWQA
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GW As Mapping- Point Theme
TAB-delimited ASCII text ? .dbf ? Event Theme
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GW As Mapping- Interpolated Grid
Showing hot spots above EPA current 50 ppb limit
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Domestic, Public Supply and Recreational Uses of
GW
40 of all the sampled GW
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Public supply gt 50 ppb
1.4 of the public supply GW is above current EPA
limit
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Counties GW public supply gt 50 ppb
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Health Effects- National Atlas Cancer Mortality
Rate Data
50 of counties with GW supply gt 50 ppb have the
highest rates
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Preliminary Conclusions

• Western parts of the US seem to have higher GW As
  concentrations.
• May be due to more natural sources than man-made
  sources.
• Will become more clear when sources are looked
  at.
• Exposure to As in GW from public supply gt EPA
  limit is about 1.5. Significant?

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Preliminary Conclusions

• Health data is not very helpful in seeing
  patterns.
• Inadequate specific data in terms of the causes
  of cancer. Definitely needs further research /
  detailed epidemiological data.
• Probably, other factors, such as simply smoking,
  wipes out the effects that may be observed just
  due to exposure to low levels of As in GW.

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Future Work

• Look at more health data.
• Incorporate possible sources of As contamination
  in the GW of US.
• Soils/Mineral Data from SSURGO.
• EPA Toxic Release Information System.

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