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

1,300

Reproductive/ Development; immune system; hematologic system

R

C

60

Hematologic & nervous systems; development

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]

M

8

9^[4,5]

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

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

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)

C

0.7^[4]

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

C

9

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]

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 – online at: http://oehha.ca.gov/air/hot_spots/tsd052909.html

C

-

-

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- & 2,6-)

C

0.07

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