OEHHA Acute, 8-hour and Chronic Reference Exposure Level (REL) Summary

All OEHHA Acute, 8-hour and Chronic Reference Exposure Levels (chRELs) as of June 2014

Documentation available in the Air Toxics Hot Spots Program Guidance Manual for the Preparation of Health Risk Assessments 2015 (Appendices 1, 2 and 3)

 

OEHHA Acute, 8-hour and Chronic Reference Exposure Level (REL) Summary1

Substance

REL type[1]

Inhalation REL
(
ug/m3)

Oral REL
(
ug/kg BW-day)

Hazard Index
Target Organs

Species[2]

Acetaldehyde (75-07-0)

A

470[5]

 

Eyes; respiratory system (sensory irritation)

H

8

300[4,5]

 

Respiratory system

R

C

140[4,5]

 

Respiratory system

R

Acrolein  (107-02-8)

A

2.5[5]

 

Eyes, respiratory system (sensory irritation)

H

8

0.7[5]

 

Respiratory system

R

C

0.35[5]

 

Respiratory system

R

Acrylic Acid  (79-10-7)

A

6,000

 

Respiratory system; eyes

R

Acrylonitrile (107-13-1)

C

5[4]

 

Respiratory system

R

Ammonia (7664-41-7)

A

3200[4]

 

Respiratory system; eyes

H

C

200

 

Respiratory system

H

Arsenic (7440-38-2) & inorganic arsenic compounds (including arsine)

A

0.20[5]

 

Development; cardiovascular system; nervous system

M

8

0.015[5]

 

Development; cardiovascular system; nervous system; respiratory system; skin

H

C

0.015[5]

0.0035[5]

Inhalation & oral: Development; cardiovascular system; nervous system; respiratory system; skin

H

Benzene  (71-43-2)

A

27

 

Developmental; Immune system; Hematologic system

M

8

3

 

Hematologic system

H

C

3

 

Hematologic system

H

Benzyl Chloride(100-44-7)

A

240

 

Respiratory system; eyes

M, R

Beryllium& beryllium compounds (7440-41-7)

C

0.007

2.0

Inhalation: Respiratory system; immune system Oral: Alimentary system (Gastrointestinal tract)

H

Butadiene (106-99-0)

A

660[4,5]

  Development

M

8

9[4,5]

  Reproductive system

M

C

2[4,5]

 

Reproductive system

M

Cadmium & cadmium compounds (7440-43-9)

C

0.02

0.5

Inhalation: Kidney; respiratory system
Oral: kidney

H

Carbon disulfide (75-15-0)

A

6,200

 

Reproductive/ Development; nervous system

R

C

800[4]

 

Nervous system; reproductive system

H

Carbon monoxide (630-08-0)

A

23,000

 

Cardiovascular system

H

Caprolactam (105-60-2)

A

50

 

Eyes (sensory irritation)

H

8

7

 

Respiratory system

R

C

2.2

 

 

Respiratory system

R

Carbon tetrachloride (56-23-5)

A

1,900

 

Alimentary system (liver); Reproductive/ Developmental; nervous system

R

C

40

 

Alimentary and nervous systems; development

GP

Chlorinated dibenzo-p dioxins and
dibenzofurans 

Unspeciated mixtures treated as 2,3,7,8-tetrachlorodibenzo-p-dioxin (1746-01-6)

C

0.00004

1 x 10-5

Inhalation and Oral: Alimentary (liver) reproductive, endocrine, respiratory, hematologic systems; development

R

Chlorine (7782-50-5)

A

210

 

Respiratory system; eyes

H

C

0.2[4]

 

Respiratory system

R

Chlorine dioxide (10049-04-4)

C

0.6

 

Respiratory system

R

Chlorobenzene (108-90-7)

C

1,000

 

Alimentary system (liver); kidney; reproductive system

R

Chloroform (67-66-3)

A

150

 

Reproductive/ Developmental; respiratory system; nervous system

R

C

300

 

Alimentary system; kidney; development

R

Chloropicrin (76-06-2)

A

29

 

Respiratory system; eyes

M

C

0.4[4]

 

Respiratory system

M

Chromic trioxide (as chromic acid mist)

C

0.002

20

Inhalation: Respiratory system
Oral: Hematologic system

H

Chromium (hexavalent) (18540-29-9) & soluble hexavalent chromium compounds (except chromic trioxide)

C

0.2[4]

20

Inhalation: Respiratory system
Oral: Hematologic system

R

Copper and compounds

A

100

 

Respiratory system

H

Cresol mixtures (1319-77-3)

C

600

 

Nervous system

R

Dichlorobenzene (1,4-) (106-46-7)

C

800

 

Nervous and respiratory; alimentary systems (liver); kidney

R

Dichloroethylene (1,1) (75-35-4)

C

70

 

Alimentary system (liver)

GP

Diesel Exhaust

C

5[3]

 

Respiratory system

R

Diethanolamine  (111-42-2)

C

3

 

Respiratory and hematologic systems

R

Dimethylformamide (N,N-) (68-12-2)

C

80

 

Alimentary (liver) and respiratory systems

H

Dioxane (1,4-) (123-91-1)

A

3,000

 

Respiratory system; eyes

H

C

3,000

 

Alimentary system; kidney; cardiovascular system

R

Epichlorohydrin (106-89-8)

A

1,300

 

Respiratory system; eyes

H

C

3

 

Respiratory system; eyes

R

Epoxybutane (1,2-) (106-88-7)

C

20

 

Respiratory system; cardiovascular system

M

Ethylbenzene(100-41-4)

C

2,000

 

Alimentary system (liver); kidney; endocrine system; development

M, R

Ethyl chloride (75-00-3)

C

30,000

 

Development; alimentary system (liver)

M

Ethylene dibromide (106-93-4)

C

0.8

 

Reproductive system

H

Ethylene dichloride (107-06-2)

C

400

 

Alimentary system (liver)

R

Ethylene glycol (107-21-1)

C

400

 

Respiratory system; kidney; development

H

Ethylene glycol monobutyl ether (111-76-2)

A

14,000

 

Respiratory system; eyes

H

Ethylene glycol monoethyl ether (110-80-5)

A

370

 

Reproductive/ Development

R

C

70

 

Reproductive system; hemotologic system

Rb

Ethylene glycol monoethyl ether acetate (111-15-9)

A

140

 

Reproductive/ Development; nervous system

R

C

300

 

Development

Rb

Ethylene glycol monomethyl ether (109-86-4)

A

93

 

Reproductive/ Development

R

C

60

 

Reproductive system

Rb

Ethylene glycol monomethyl ether acetate (110-49-6)

C

90

 

Reproductive system

Rb

Ethylene oxide (75-21-8)

C

30

 

Nervous system

R

Fluorides (except Hydrogen Fluoride - listed below separately)

C

13[4]

40

Inhalation: Bone and teeth; respiratory system

Oral: Bone and teeth

H

Formaldehyde (50-00-0)

A

55[5]

 

Eyes (Sensory irritation)

H

8

9[5]

 

Respiratory system

H

C

9[5]

 

Respiratory system

H

Glutaraldehyde (111-30-8)

C

0.08[4]

 

Respiratory system

M

Hexane (n-)(110-54-3)

C

7000

 

Nervous system

H

Hydrazine  (302-01-2)

C

0.2

 

Alimentary system (liver); endocrine system

Ha

Hydrogen chloride (7647-01-0)

A

2,100

 

Respiratory system; eyes

H

C

9

 

Respiratory system

H

Hydrogen cyanide (74-90-8)

A

340

 

Nervous system

H

C

9

 

Nervous system; endocrine system; cardiovascular system

H

Hydrogen fluoride (7664-39-3)

A

240

 

Respiratory system; eyes

H

C

14[4]

40

Inhalation: Bone and teeth; respiratory system (See “fluorides” summary)

Oral: Bone and teeth

H

Hydrogen selenide (7783-07-5)

A

5

 

Respiratory system; eyes

GP

Hydrogen sulfide (7783-06-4)

A

42

 

Nervous system

H

C

10

 

Respiratory system

M

Isophorone (78-59-1)

C

2,000

 

Development; alimentary system (liver)

R, M

Isopropanol (67-63-0)

A

3,200

 

Eyes; respiratory system

H

C

7,000

 

Kidney; development

R, M

Maleic anhydride (108-31-6)

C

0.7[4]

 

Respiratory system

R,Ha, Mk

Manganese (7439-96-5) & manganese compounds

8

0.17[4,5]

 

Nervous system

H

C

0.09[4,5]

 

Nervous system

H

Mercury (7439-97-6) & inorganic mercury compounds

A

0.6[5]

 

Nervous system; development

R

8

0.06[5]

 

Nervous system; development; kidney

H

C

0.03[5]

0.16[5]

Inhalation & Oral: Nervous system; development; kidney

H

Methanol (67-56-1)

A

28,000

  Nervous system

H

C

4,000[4]

 

Development

M

Methyl bromide (74-83-9)

A

3900

 

Nervous system; respiratory system; Reproductive/ development

H

C

5

 

Respiratory system; nervous system; development

R

Methyl chloroform (71-55-6)

A

68,000

 

Nervous system

H

C

1000

 

Nervous system

Gb

Methylene chloride (75-09-2)

A

14,000

 

Cardiovascular system; Nervous system

H

C

400

 

Cardiovascular system; nervous system

H

Methylene dianiline(4,4’-) (101-77-9)

C

20

 

Eyes; alimentary system (liver)

GP

Methylene diphenyl isocyanate (101-68-8) and polymeric methylene diphenyl diisocyanate (9016-87-9)

A 12[5]   Respiratory system R
8 0.16[5]   Respiratory system R

C

0.08[5]

 

Respiratory system

R

Methyl ethyl ketone (78-93-3)

A

13,000

 

Respiratory system; eyes

H

Methyl isocyanate (624-83-9)

C

1

 

Respiratory system; reproductive system

R

Methyl t-butyl ether (1634-04-4)

C

8,000

 

Kidney; eyes; alimentary system (liver)

R

Naphthalene (91-20-3)

C

9

  Respiratory system

H

Nickel & nickel compounds (except nickel oxide for chronic inhalation exposures) (Inhalation concentrations as µg Ni/m3: oral dose as µg Ni/kg-day)

A

0.2[5]

 

Immune system

M

8

0.06[5]

  Respiratory, immune systems

R

C

0.014[5]

11[5]

Inhalation: Respiratory system; hematologic system
Oral: Development

R

Nickel oxide (1313-99-1) (Inhalation concentration as µg Ni/m3: oral dose as µg Ni/kg-day)

C

0.02[5]

11[5]

Inhalation: Respiratory system
Oral: Development

M

R

Nitric acid  (7697-37-2)

A

86

 

Respiratory system

H

Nitrogen dioxide (10102-44-0)

A

470

 

Respiratory system

H

Ozone (10028-15-6)

A

180

 

Respiratory system; eyes

H

Perchloroethylene (127-18-4)
(syn. Tetrachloroethylene)[3]

A

20,000

 

Nervous system; respiratory system; eyes

H

C

35

 

Kidney; alimentary system (liver)

M

Phenol  (108-95-2)

A

5,800

 

Respiratory system; eyes

H

C

200

 

Alimentary system; cardiovascular system; kidney; nervous system

R

Phosgene (75-44-5)

A

4

 

Respiratory system

R

Phosphine (7803-51-2)

C

0.8

 

Respiratory system; alimentary system (liver); nervous system; kidney; hematologic system

M

Phosphoric acid (7664-38-2)

C

7[4]

 

Respiratory system

R

Polychlorinated biphenyls (PCBs)
Individual congeners evaluated using TEF methodology, relative to as 2,3,7,8-tetrachlorodibenzo-p-dioxin (see Appendix C in the TSD for Cancer Potency Factors

C

-

-

Inhalation & oral: Alimentary (liver) reproductive, endocrine, respiratory, hematologic systems; development

R

Phthalic anhydride (85-44-9)

C

20

 

Respiratory system

H

Propylene(115-07-1)

C

3,000

 

Respiratory system

R

Propylene glycol monomethyl ether (107-98-2)

C

7,000

 

Alimentary system (liver)

R

Propylene oxide (75-56-9)

A

3,100

 

Respiratory system; eyes; reproductive/development

H

C

30

 

Respiratory system

R

Selenium and selenium compounds (other than hydrogen selenide)

C

20

5

Inhalation & oral: Alimentary system (liver); cardiovascular system; nervous system

H

Silica (crystalline, respirable)

C

3[4]

 

Respiratory system

H

Sodium hydroxide (1310-93-2)

A

8

 

Respiratory system; eyes; skin

H

Styrene (100-42-5)

A

21,000

 

Respiratory system; eyes; reproductive/development

H

C

900[4]

 

Nervous system

H

Sulfates

A

120

 

Respiratory system

H

Sulfur dioxide (7446-09-5)

A

660

 

Respiratory system

H

Sulfuric acid (7664-93-9) [& oleum, acute only]

A

120

 

Respiratory system

H

C

1

 

Respiratory system

Mk

Toluene (108-88-3)

A

37,000

 

Respiratory, nervous systems; eyes reproductive/development

H

C

300

 

Nervous system; respiratory system; development

R

Toluene diisocyanates: 2,4- (584-84-9)and 2,6- (91-08-7) isomers and mixed isomers (26471-62)

A 2[5]   Respiratory system H
8 0.015[5]   Respiratory system H

C

0.008[5]

 

Respiratory system

H

Trichloroethylene (79-01-6)

C

600

 

Nervous system; eyes

H

Triethylamine  (121-44-8)

A

2,800

 

Nervous system; eyes

H

C

200

 

Eyes

R

Vanadium pentoxide(1314-62-1)

A

30

 

Respiratory system; eyes

H

Vinyl acetate (108-05-4)

C

200

 

Respiratory system

R, M

Vinyl chloride (75-01-4)

A

180,000

 

Nervous system; respiratory system; eyes

H

Xylenes: technical mixture (1330-20-7) and o-xylene (95-47-6), m-xylene (108-38-3) and p-xylene (106-42-3) isomers.

A

22000

 

Nervous & respiratory systems; eyes

H

C

700

 

Nervous & respiratory systems; eyes

H

Footnotes:
[1]REL types: A = acute, 8 = 8-hour, C = chronic. Exposure averaging time for acute RELs is 1 hour.  For 8-hour RELs, the exposure averaging time is 8 hours, which may be repeated.  Chronic RELs are designed to address continuous exposures for up to a lifetime: the exposure metric used is the annual average exposure.

[2]Species used in key study for REL development: D = dog; Gb = gerbil; GP = guinea pig: H = human; Ha = hamster; M = mouse; Mk = monkey; R = rat; Rb = rabbit

[3]These peer-reviewed chronic REL values were developed under the Toxic Air Contaminant (TAC) Program mandated by AB1807.

[4]REL based on benchmark dose (BMC) approach.

[5]REL developed using the revised methodology (OEHHA, 2008)].