Groundwater Arsenic Groundwater Arsenic Contamination in the United Contamination in the United StatesStates

GIS Term Project, EWRE

Fall 2000

By Hazim Tugun

OutlineOutline

Background Objectives Mapping of data/findings related to As in

the groundwater Preliminary Conclusions Future work

BackgroundBackground

A gray brittle semi-metal Naturally exists throughout the earth’s crust

(often as Arsenic Sulfide, Metal Arsenates or Arsenites).

Has many oxidation states, As(III) or As(V).

BackgroundBackground

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.

BackgroundBackground 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.

ObjectivesObjectives 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.

GW As data from USGS NAWQA

GW As Mapping- Point ThemeTAB-delimited ASCII text .dbf Event Theme

GW As Mapping- Interpolated GridShowing hot spots above EPA current 50 ppb limit

Domestic, Public Supply and Recreational Uses of GW

40% of all the sampled GW

Public supply > 50 ppb1.4% of the public supply GW is above current EPA limit

Counties – GW public supply > 50 ppb

0

200

400

600

800

1000

1200

1400

Ars

enic

Con

c. (

ppb)

1

Counties with Highest Max. GW Arsenic Conc.

Churchill / NV

Washington /ID

Worcester / MA

Yavapai / AZ

San Bernardino / CAEPA LIMIT = 50 ppb

Health Effects- National Atlas Cancer Mortality Rate Data50% of counties with GW supply > 50 ppb have the highest rates

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 > EPA limit is about 1.5%. Significant?

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.

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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