Soil- and Soil-Gas Screening Numbers (California Human Health Screening Levels or CHHSLs)

Tables of OEHHA Soil and Soil-Gas Screening Numbers.

Table 1 - Soil-Screening Numbers (mg/kg soil) for Nonvolatile Chemicals Based on Total Exposure to Contaminated Soil: Inhalation, Ingestion and Dermal Absorption.

Table 2 - Soil-Gas-Screening Numbers for Volatile Chemicals below Buildings Constructed With Engineered Fill below Sub-slab Gravel.

Table 3 - Soil-Gas-Screening Numbers for Volatile Chemicals below Buildings Constructed Without Engineered Fill below Sub-slab Gravel

Chemical

Soil-Screening Number
(mg per kg of dry soil)

Table 1. Soil-and Soil-Gas-Screening Numbers (mg/kg soil) for Nonvolatile Chemicals Based on Total Exposure to Contaminated Soil: Inhalation, Ingestion and Dermal Absorption

Residential Scenario

Commercial/Industrial Scenario

Organic Acidic Chemicals

 

Basis1

 

Basis1

2, 4-D

6.9E+02

(nc)

7.7E+03

(nc)

2,4,5-T

5.5E+02

(nc)

6.1E+03

(nc)

Pentachlorophenol

4.4E+00

(ca)

1.3E+01

(ca)

Organic Neutral Chemicals

 

 

 

 

Aldrin

3.3E-02

(ca)

1.3E-01

(ca)

Benzo(a)pyrene

3.8E-02

(ca)

1.3E-01

(ca)

Chlordane

4.3E-01

(ca)

1.7E+00

(ca)

DDD

2.3E+00

(ca)

9.0E+00

(ca)

DDE

1.6E+00

(ca)

6.3E+00

(ca)

DDT

1.6E+00

(ca)

6.3E+00

(ca)

Dieldrin

3.5E-02

(ca)

1.3E-01

(ca)

1,4-Dioxane

1.8E+01

(ca)

6.4E+01

(ca)

Dioxin (2,3,7, 8-TCDD)

4.6E-06

(ca)

1.9E-05

(ca)

Endrin

2.1E+01

(nc)

2.3E+02

(nc)

Heptachlor

1.3E-01

(ca)

5.2E-01

(ca)

Lindane

5.0E-01

(ca)

2.0E+00

(ca)

Kepone

3.5E-02

(ca)

1.3E-01

(ca)

Methoxychlor

3.4E+02

(nc)

3.8E+03

(nc)

Mirex

3.1E-02

(ca)

1.2E-01

(ca)

PCBs

8.9E-02

(ca)

3.0E-01

(ca)

Toxaphene

4.6E-01

(ca)

1.8E+00

(ca)

Inorganic Chemicals

 

 

 

 

Antimony and compounds

3.0E+01

(nc)

3.8E+02

(nc)

Arsenic2

7.0E-02

(ca)

2.4E-01

(ca)

Barium and compounds

5.2E+03

(nc)

6.3E+04

(nc)

Beryllium and compounds

1.6E+014

(nc)

1.9E+024

(nc)

Beryllium oxide

1.6E+014

(nc)

1.9E+024

(nc)

Beryllium sulfate3

2.9E+004

(ca)

6.3E+004

(ca)

Cadmium and compounds

1.7E+00

(ca)

7.5E+00

(ca)

Chromium III

1.0E+05

(nc,max)

1.0E+05

(nc,max)

Chromium VI

1.7E+01

(ca)

3.7E+01

(ca)

Cobalt

6.6E+02

(nc)

3.2E+03

(nc)

Copper and compounds

3.0E+03

(nc)

3.8E+04

(nc)

Fluoride

4.6E+03

(nc)

5.7E+04

(nc)

Lead and lead compounds

8.0E+014

(nc)

3.2E+024

(nc)

Lead acetate3

2.3E+00

(ca)

1.0E+01

(ca)

Mercury and compounds

1.8E+01

(nc)

1.8E+02

(nc)

Molybdenum

3.8E+02

(nc)

4.8E+03

(nc)

Nickel and compounds

1.6E+03

(nc)

1.6E+04

(nc)

Nickel subsulfide3

3.8E-01

(ca)

1.1E+04

(ca)

Perchlorate

2.8E+015,6

(nc)

3.5E+025,6

(nc)

Selenium

3.8E+02

(nc)

4.8E+03

(nc)

Silver and compounds

3.8E+02

(nc)

4.8E+03

(nc)

Thallium and compounds

5.0E+00

(nc)

6.3E+01

(nc)

Vanadium and compounds

5.3E+02

(nc)

6.7E+03

(nc)

Zinc

2.3E+04

(nc)

1.0E+05

(nc)

1 (ca) denotes that the screening number is based on a carcinogenic potency factor, (nc) denotes that the screening number is based on a reference level in Table 3 for chronic toxic effects other than cancer, (max) denotes the screening number is based on the maximum concentration allowed, 100,000 mg/kg, and not toxicity.
2 The screening numbers for arsenic are for contamination resulting from human activity. Concentrations of naturally occurring arsenic may be far above the screening number. When levels of arsenic at a site are a concern, the agency with authority over remediation decisions should be consulted.
3 These metal salts are significantly (greater than 10-fold) more toxic than the values for the metals in general. If it is known that this chemical was used at the site, the screening number for this chemical should be used instead of the screening number for the metal and its compounds.
4 Revised in 2009
5 Added in 2010
6 While these CHHSLs are considered safe for exposure to perchlorate in soil, the potential for significant groundwater contamination from soil contaminated with perchlorate at the CHHSLs levels may exist, since the PHG level for drinking water is 6 ppb or 6 µg/L.

Chemical 

Soil-Gas-Screening Number
(
μg per liter of soil gas)

Table 2. Soil-Gas-Screening Numbers for Volatile Chemicals below Buildings Constructed with Engineered Fill below Sub-slab Gravel

Residential Scenario

Commercial/Industrial Scenario

 

 

Basis1

 

Basis1

Benzene

8.5 E-02

(ca)2

2.8 E-01

(ca)

Carbon Tetrachloride

6.3 E-02

(ca)

2.1 E-01

(ca)

1,2-Dichloroethane

1.1 E-01

(ca)

3.6 E-01

(ca)

cis-1,2-Dichloroethylene

4.1 E+01

(nc)2

1.2 E+02

(nc)

trans-1,2-Dichloroethylene

8.4 E+01

(nc)

2.4 E+02

(nc)

Ethylbenzene

1.1 E+004

(ca)

3.6 E+004

(ca)

Mercury (elemental)

2.0 E-01

(nc)

5.6 E-01

(nc)

Methyl tert-Butyl Ether

8.6 E+00

(ca)

2.9 E+01

(ca)

Naphthalene

9.3 E-02

(ca)

3.1 E-01

(ca)

Tetrachloroethylene

4.7 E-01

(ca)

1.6 E+00

(ca)

Tetraethyl Lead

1.6 E-03

(nc)

4.5 E-03

(nc)

Toluene

3.2 E+02

(nc)

8.9 E+02

(nc)

1,1,1-Trichloroethane

2.5 E+03

(nc)

7.0 E+03

(nc)

Trichloroethylene

1.3 E+00

(ca)

4.4 E+00

(ca)

Vinyl Chloride

2.8 E-02

(ca)

9.5 E-02

(ca)

m-Xylene

8.5 E+02

(nc)

2.4 E+03

(nc)

o-Xylene

7.4 E+023

(nc)

2.1 E+033

(nc)

p-Xylene

8.0 E+02

(nc)

2.2 E+03

(nc)

1 (ca) denotes that the screening number is based on a carcinogenic potency factor, (nc) denotes that the screening number is based on a reference level in Table 3 for chronic toxic effects other than cancer, (max) denotes the screening number is based on the maximum concentration allowed, 100,000 mg/kg, and not toxicity.

2 (ca) denotes that the screening number is based on a carcinogenic potency factor, (nc) denotes that the screening number is based on a reference level in Table 3 for chronic toxic effects other than cancer.

3 Recommended soil-gas-screening number for xylenes. The representative value for xylenes is based on the calculated lowest health-protective one amongst the three isomers.

4 Added in 2010

Chemical

Soil-Gas-Screening Number
(
μg per liter of soil gas)

Table 3. Soil-Gas-Screening Numbers for Volatile Chemicals below Buildings Constructed without Engineered Fill below Sub-slab Gravel

Residential Scenario

Commercial/Industrial Scenario

 

 

Basis1

 

Basis1

Benzene

3.6 E-02

(ca)2

1.2 E-01

(ca)

Carbon Tetrachloride

2.5 E-02

(ca)

8.5 E-02

(ca)

1,2-Dichloroethane

5.0 E-02

(ca)

1.7 E-01

(ca)

cis-1,2-Dichloroethylene

1.6 E+01

(nc)2

4.4 E+01

(nc)

trans-1,2-Dichloroethylene

3.2 E+01

(nc)

8.9 E+01

(nc)

Ethylbenzene

4.2 E-014

(ca)

1.4 E+004

(ca)

Mercury (elemental)

4.5 E-02

(nc)

1.3 E-01

(nc)

Methyl tert-Butyl Ether

4.0 E+00

(ca)

1.3 E+01

(ca)

Naphthalene

3.2 E-02

(ca)

1.1 E-01

(ca)

Tetrachloroethylene

1.8 E-01

(ca)

6.0 E-01

(ca)

Tetraethyl Lead

2.1 E-04

(nc)

5.8 E-04

(nc)

Toluene

1.4 E+02

(nc)

3.8 E+02

(nc)

1,1,1-Trichloroethane

9.9 E+02

(nc)

2.8 E+03

(nc)

Trichloroethylene

5.3 E-01

(ca)

1.8 E+00

(ca)

Vinyl Chloride

1.3 E-02

(ca)

4.5 E-02

(ca)

m-Xylene

3.2 E+02

(nc)

8.9 E+02

(nc)

o-Xylene

3.2 E+023

(nc)

8.8 E+023

(nc)

p-Xylene

3.2 E+02

(nc)

8.9 E+02

(nc)

1 (ca) denotes that the screening number is based on a carcinogenic potency factor, (nc) denotes that the screening number is based on a reference level in Table 3 for chronic toxic effects other than cancer, (max) denotes the screening number is based on the maximum concentration allowed, 100,000 mg/kg, and not toxicity.
2 (ca) denotes that the screening number is based on a carcinogenic potency factor, (nc) denotes that the screening number is based on a reference level in Table 3 for chronic toxic effects other than cancer.
3 Recommended soil-gas-screening number for xylenes. The representative value for xylenes is based on the calculated lowest health-protective one amongst the three isomers.
4 Added 2010