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IDEM Announces New Arsenic Soil Screening Levels


By Andy Bowman, Attorney, Bingham Greenebaum Doll LLP

On July 10, 2013, the Indiana Department of Environmental Management (IDEM) announced that it will allow responsible parties to use optional revised soil direct contact screening levels for arsenic in the interim period before IDEM publishes its annual update of the Remediation Closure Guide Screening Levels Table in January 2014.  IDEM’s decision is in response to U.S. EPA’s revision of its Regional Screening Levels in May 2013 that reduced the default relative bioavailability factor for arsenic exposure from 100% to 60%.  Relative bioavailability refers to the amount of arsenic that is absorbed into the body’s circulation during dermal contact with soil containing arsenic.  The interim optional screening levels and current screening levels are shown in the table below.

Exposure Scenario Current Screening Levels Interim Optional Screening Levels
Soil Direct Contact (mg/kg) (mg/kg)
Residential 5.5 8.5
Commercial/Industrial 16 24
Excavation 430 640

Screening levels are used as one of several risk-based screening tools to assess whether potential exposure pathways at a site may need further investigation or the use of a site-specific risk assessment.  IDEM’s screening levels are adapted from U.S. EPA’s Regional Screening Levels and are updated annually.  IDEM provided the optional arsenic screening level as an exception to the annual update process because the magnitudes of the increases are significant and arsenic is often a compound of potential concern at sites.

To view a complete PDF of the May/June 2013 issue of the Environmental Letter, click HERE.


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