OEHHA Acute, 8-hour and Chronic Reference Exposure Level (REL) Summary
All OEHHA Acute, 8-hour and Chronic Reference Exposure Levels (RELs) as of August, 2020
Documentation available in the Air Toxics Hot Spots Program Guidance Manual for the Preparation of Health Risk Assessments 2015 (Appendices A, B and C)
|
OEHHA Acute, 8-hour and Chronic Reference Exposure Level (REL) Summary1 |
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|---|---|---|---|---|---|
|
Substance |
REL type[1] |
Inhalation REL |
Oral REL |
Hazard Index |
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 |
|
1-Bromopropane (106-94-5) |
A |
3300[4, 5] |
|
Developmental |
R |
|
8 |
3.4[5] |
|
Nervous system; respiratory system |
H |
|
|
C |
1.7[5] |
|
Nervous system; respiratory system |
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 |
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 |
|
Carbonyl Sulfide (463-58-1) |
A |
660[5] | Nervous system | R | |
|
8 |
10[4, 5] | Nervous system | R | ||
|
C |
10[4, 5] | Nervous system | R | ||
|
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 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 |
H |
|
Chromium (hexavalent) (18540-29-9) & soluble hexavalent chromium compounds (except chromic trioxide) |
C |
0.2[4] |
20 |
Inhalation: Respiratory system |
R |
|
Chromium (trivalent) inorganic water-soluble compounds (Inhalation concentrations as µg Cr(III)/m3) |
A |
0.48[5] |
|
Respiratory system |
Ha |
|
8 |
0.12[4,5] |
|
Respiratory system |
R |
|
|
C |
0.06[4,5] |
|
Respiratory 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 |
4700 |
|
Eyes and respiratory system |
H |
|
8 |
164 |
|
Respiratory system |
R |
|
|
C |
82 |
|
Respiratory system |
R |
|
|
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 |
|
Hexamethylene diisocyanate (monomer, 822-06-0) |
A |
0.3[5] |
|
Respiratory system |
R |
|
8 |
0.06[5] |
|
Respiratory system |
H |
|
|
C |
0.03[5] |
|
Respiratory system |
H |
|
|
Hexamethylene diisocyanate (polyisocyanate mixtures, including, but not limited to isocyanurate (3779-63-3) and biuret (4035-89-6)) |
A |
4.5[5] |
|
Respiratory system |
R |
|
8 |
0.8[5] |
|
Respiratory system |
R |
|
|
C |
0.4[5] |
|
Respiratory system |
R |
|
|
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] |
|
Inhalation: Respiratory system; hematologic system |
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 |
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) |
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) |
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 (1310-73-2) |
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 | 5,000 | Respiratory, nervous systems; eyes | H | |
| 8 | 830 | Eyes | H | ||
|
C |
420 |
|
Eyes |
H |
|
|
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 |
||
|
Trimethylbenzenes (25551-13-7): 1,3,5- (108-67-8), 1,2,4- (95-63-6), 1,2,3- (526-73-8) |
A |
2400[4, 5] |
|
Nervous System |
R |
|
8 |
8[4, 5] |
|
Nervous system |
R |
|
|
C |
4[4, 5] |
|
Nervous system |
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)].