Office of Environmental Health Hazard Assessment
Home Air Acute Reference Exposure Levels (RELs)

Air Toxicology and Epidemiology

Acute Reference Exposure Levels (RELs), Averaging Times, and Toxicologic Endpoints
(Follow links below to download individual chemical summaries. For conversion information, please see the individual chemical summaries.)

Download the entire Technical Support document.

All OEHHA Acute Reference Exposure Levels

Chemical Name (CAS #)

REL
(µg/m3)

Avg
time
(h)

Sp.1

Toxicologic Endpoints

Severity2

Acrolein (107-02-8)

1.9 x 10-1

1

H

Eye Irritation Mild
Acrylic Acid (79-10-7)

6 x 103

1

R

Respiratory Irritation Mild
Ammonia (7664-41-7)

3.2 x 103

1

H

Eye and Respiratory Irritation Mild
Arsenic and Inorganic Arsenic Compounds

1.9 x 10-1

4

M

Reproductive/ Developmental Severe
Arsine (7784-42-1)

1.6 x 102

1

M

Hematologic System Severe
Benzene (71-43-2)

1.3 x 103

6

R

Reproductive/ Developmental Severe
Benzyl Chloride (100-44-7)

2.4 x 102

1

M&R

Eye and Respiratory Irritation Mild
Carbon Disulfide (75-15-0)

6.2 x 103

6

R

Reproductive/ Developmental Severe
Carbon Monoxide3 (630-08-0)

2.3 x 104

1

H

Cardiovascular System Mild
Carbon Tetrachloride (56-23-5)

1.9 x 103

7

R

Reproductive/Developmental Severe
Chlorine (7782-50-5)

2.1 x 102

1

H

Respiratory Irritation Mild
Chloroform (67-66-3)

1.5 x 102

7

R

Reproductive/Developmental Severe
Chloropicrin (76-06-2)

2.9 x 101

1

M

Eye and Respiratory Irritation Mild
Copper and Compounds

1 x 102

1

H

Respiratory Irritation Mild
1,4-Dioxane (123-91-1)

3 x 103

1

H

Eye and Respiratory Irritation Mild
Epichlorohydrin (106-89-8)

1.3 x 103

1

H

Eye and Respiratory Irritation Mild
Ethylene Glycol Monobutyl Ether (111-76-2)

1.4 x 104

1

H

Eye and Respiratory Irritation Mild
Ethylene Glycol Monoethyl Ether (110-80-5)

3.7 x 102

6

R

Reproductive/Developmental Severe
Ethylene Glycol Monoethyl Ether Acetate (111-15-9)

1.4 x 102

6

Rb

Reproductive/Developmental Severe
Ethylene Glycol Monomethyl Ether (109-86-4)

9.3 x 101

6

R

Reproductive/Developmental Severe
Formaldehyde (50-00-0)

9.4 x 101

1

H

Eye Irritation Mild
Hydrogen chloride (7647-01-0)

2.1 x 103

1

H

Eye and Respiratory Irritation Mild
Hydrogen Cyanide (74-90-8)

3.4 x 102

1

Mk

CNS4 - serious Severe
Hydrogen Fluoride (7664-39-3)

2.4 x 102

1

H

Eye and Respiratory Irritation Mild
Hydrogen Selenide (7783-07-5)

5 x 100

1

GP

Eye and Respiratory Irritation Mild
Hydrogen Sulfide (7783-06-4)3

4.2 x 101

1

H

Respiratory Irritation Mild
Isopropyl Alcohol (67-63-0)

3.2 x 103

1

H

Eye and Respiratory Irritation Mild
Mercury (Inorganic) (7439-97-6)

1.8 x 100

1

R

Reproductive/Developmental Severe
Methanol (67-56-1)

2.8 x 104

1

H

CNS4 - mild Mild
Methyl Bromide (74-83-9)

3.9 x 103

1

H

CNS- mild (anorexia, nausea, headache; Mild
Methyl Chloroform (71-55-6)

6.8 x 104

1

H

CNS - mild Mild
Methyl Ethyl Ketone (78-93-3)

1.3 x 104

1

H

Eye and Respiratory Irritation Mild
Methylene Chloride (75-09-2)

1.4 x 104

1

H

CNS - mild Mild
Nickel and Nickel Compounds

6 x 100

1

H

Respiratory Irritation; Immune Response Mild
Nitric Acid (7697-37-2)

8.6 x 101

1

H

Respiratory Irritation Mild
Nitrogen Dioxide3(10102-44-0)

4.7 x 102

1

H

Respiratory Irritation Mild
Ozone3 (10028-15-6)

1.8 x 102

1

H

Eye and Respiratory Irritation Mild
Perchloroethylene (127-18-4)

2 x 104

1

H

CNS - mild; Eye and Respiratory Irritation Mild
Phenol (108-95-2)

5.8 x 103

1

H

Eye and Respiratory Irritation Mild
Phosgene (75-44-5)

4 x 100

1

R

Respiratory Irritation Mild
Propylene Oxide (75-56-9)

3.1 x 103

1

M

Eye and Respiratory Irritation Mild
Sodium Hydroxide (1310-73-2)

8 x 100

1

H

Skin, Eye, and Respiratory Irritation Mild
Styrene (100-42-5)

2.1 x 104

1

H

Eye and Respiratory Irritation Mild
Sulfates3

1.2 x 102

1

H

Respiratory Irritation Mild
Sulfur Dioxide3 (7446-09-5)

6.6 x 102

1

H

Respiratory Irritation Mild
Sulfuric Acid and Oleum

1.2 x 102

1

H

Respiratory Irritation Mild
Toluene (108-88-3)

3.7 x 104

1

H

CNS - mild; Eye and Respiratory Irritation Mild
Triethylamine (121-44-8)

2.8 x 103

1

H

CNS - mild; Eye Irritation Mild
Vanadium Pentoxide (1314-62-1)

3 x 101

1

H

Respiratory Irritation Mild
Vinyl Chloride (75-01-4)

1.8 x 105

1

H

CNS - mild; Eye and Respiratory Irritation Mild
Xylenes (m,o,p-isomers)

2.2 x 104

1

H

Eye and Respiratory Irritation Mild
1 Species used in key study for REL development: D = dog; GP = guinea pig: H = human; M = mouse; Mk = monkey; R = rat; Rb = rabbit
2 Refers to effect severity levels-- see Hazard Identification section of main text or Table 6
3 California Ambient Air Quality Standard
4 CNS = Central Nervous System.
Hazard Index Target Organs

Chemical Name (CAS #)

Target Organs

Acrolein (107-02-8) Respiratory System; Eye
Acrylic Acid (79-10-7) Respiratory System; Eye
Ammonia (7664-41-7) Respiratory System; Eye
Arsenic and Inorganic Arsenic Compounds Reproductive/Developmental
Arsine (7784-42-1) Hematologic System
Benzene (71-43-2) Reproductive/Developmental; Immune System; Hematologic System;
Benzyl Chloride (100-44-7) Respiratory System; Eye
Carbon Disulfide (75-15-0) Reproductive/Developmental; Nervous System
Carbon Monoxide (630-08-0) Cardiovascular System
Carbon Tetrachloride (56-23-5) Reproductive/Developmental; Nervous System; Alimentary Tract
Chlorine (7782-50-5) Respiratory System; Eye
Chloroform (67-66-3) Nervous System; Reproductive/Developmental
Chloropicrin (76-06-2) Respiratory System; Eye
Copper and Compounds Respiratory System
1,4-Dioxane (123-91-1) Respiratory System; Eye
Epichlorohydrin (106-89-8) Respiratory System; Eye
Ethylene Glycol Monobutyl Ether (111-76-2) Respiratory System; Eye
Ethylene Glycol Monoethyl Ether (110-80-5) Reproductive/Developmental
Ethylene Glycol Monoethyl Ether Acetate (111-15-9) Reproductive/Developmental; Nervous System
Ethylene Glycol Monomethyl Ether (109-86-4) Reproductive/Developmental
Formaldehyde (50-00-0) Eye; Respiratory System; Immune System
Hydrogen Chloride (7647-01-0) Respiratory System; Eye
Hydrogen Cyanide (74-90-8) Nervous System
Hydrogen Fluoride (7664-39-3) Respiratory System; Eye
Hydrogen Sulfide (7783-06-4) Headache and Nausea in Response to Odor
Isopropyl Alcohol (67-63-0) Respiratory System; Eye
Mercury (Inorganic) (7439-97-6) Reproductive/Developmental
Methanol (67-56-1) Nervous System
Methyl Bromide (74-83-9) Nervous System; Respiratory Irritation; Reproductive/Developmental
Methyl Chloroform (71-55-6) Nervous System
Methyl Ethyl Ketone (78-93-3) Respiratory System; Eye
Methylene Chloride (75-9-2) Nervous System
Nickel and Nickel Compounds Respiratory System; Immune System
Nitric Acid (7697-37-2) Respiratory System
Nitrogen Dioxide (10102-44-0) Respiratory System
Ozone (10028-15-6) Eye; Respiratory System
Perchloroethylene (127-18-4) Nervous system; Eye; Respiratory System
Phenol (108-95-2) Respiratory System; Eye
Phosgene (75-44-5) Respiratory System
Propylene Oxide (75-56-9) Respiratory System; Eye; Reproductive/Developmental
Selenium: He2S Respiratory System; Eye
Sodium Hydroxide (1310-93-2) Eye; Skin; Respiratory System
Styrene (100-42-5) Respiratory System; Eye;
Sulfates Respiratory System
Sulfur Dioxide (7446-09-5) Respiratory System
Sulfuric Acid and Oleum Respiratory System
Toluene (108-88-3) Nervous System; Eye; Respiratory System; Reproductive/Developmental
Triethylamine (121-44-8) Nervous System; Eye
Vanadium Pentoxide (1314-62-1) Respiratory System; Eye
Vinyl Chloride (75-01-4) Nervous System; Eye; Respiratory System
Xylenes (m,o,p-isomers) Eye; Respiratory System

 

 
Flex Your Power Website
Energy efficiency and conservation information. Find incentives/rebates, technical assistance, retailers, product guides, case studies and more.
AMBER ALERT: Save a Child Amber Alert logo
AMBER ALERT empowers law enforcement, the media and the public to combat abduction by sending out immediate information.

OEHHA Logo