California Human Health Screening Levels (CHHSLs)

Go to downloads

California Human Health Screening Levels (CHHSLs) are concentrations of chemicals in soil or soil-gas below thresholds of concern for risks to human health—specifically, an excess lifetime cancer risk of one-in-a-million (10-6) and a hazard quotient of 1.0 for non-cancer health effects.  The CHHSLs were developed by OEHHA on behalf of the California Environmental Protection Agency, pursuant to Health and Safety Code Section 57008.

The CHHSLs have no regulatory effect and are not intended for use by regulatory agencies that have authority to require remediation of contaminated soil. The numbers are solely advisory and published as reference values for use by citizen groups, community organizations, property owners, developers, and local government officials to estimate the degree of effort that may be necessary to remediate a contaminated site.

The methodology for developing the CHHSLs is discussed in the report, Human-Exposure-Based Screening Numbers Developed to Aid Estimation of Cleanup Costs for Contaminated Soil (revised January 2005).  CHHSLs for approximately 60 chemicals are also presented in this report.  An earlier draft report, Proposed Methodology for Calculating Advisory Human-Exposure-Based Screening Numbers Developed to Aid Estimation of Cleanup Costs for Contaminated Soil, underwent a public comment period in March/April 2004.

After the publication of the final report, CHHSLs were added or revised for the following chemicals:

OEHHA CHHSLs (soil and soil-gas screening numbers) are compiled in tables in the document below.  OEHHA is in the process of updating existing CHHSLs and developing screening levels for additional chemicals.

Related information: 

Guidance, tools and other information on assessing contaminated sites can be found at: Department of Toxic Substances Control's Human Health Risk (HERO) Guidance and Tools

California Human Health Screening Levels (CHHSLs) News

Sep 23, 2010: Final Reports: California Human Health Screening Levels for Ethylbenzene and Perchlorate
The CHHSLs for ethlybenzene are soil gas levels of 1.1 µg/L and 0.42 µg/L for residential structures on engineered fill or base soil, respectively. The CHHSLs for ethlybenzene for commercial/industrial structures are soil gas levels of 3.6 µg/L and 1.4 µg/L on engineered fill or base soil, respectively. The CHHSLs for perchlorate are 28 mg/kg soil for residential property and 350 mg/kg soil for commercial/industrial property.
Dec 4, 2009: Draft reports: California Human Health Screening Levels for Ethylbenzene and Perchlorate
The 2009 draft CHHSLs for ethlybenzene are soil gas levels of 1.1 µg/L and 0.42 µg/L for residential structures on engineered fill or base soil, respectively.  The draft CHHSLs for ethlybenzene for commercial/industrial structures are soil gas levels of 3.6 µg/L and 1.4 µg/L on engineered fill or base soil, respectively.  The draft CHHSLs for perchlorate are 28 mg/kg soil for residential property and 350 mg/kg soil for commercial/industrial property.
Sep 17, 2009: Final Report: Revised California Human Health Screening Levels for Lead and Beryllium
The revised CHHSLs for lead and lead compounds are 80 mg/kg soil for residential property and 320 mg/kg soil for commercial/industrial property. The revised CHHSLs for beryllium and beryllium compounds and for beryllium oxide are 16 mg/kg soil for residential property and 190 mg/kg soil for commercial/industrial property. The revised CHHSLs for beryllium sulfate are 2.9 mg/kg soil for residential property and 6.3 mg/kg soil for commercial/industrial property.