The Department of Environmental Protection (MassDEP) Office of Research and Standards (ORS) develops health-based air guidelines - Ambient Air Limits (AALs) and Threshold Effect Exposure Limits (TELs) - that are used to evaluate potential human health risks from exposures to chemicals in air. Theese guidelines are set at concentrations intended to protect the general population, including sensitive populations such as children, from adverse health effects over a lifetime of continuous exposure.

Background
Use of AALs & TELs
MassDEP Methods for Deriving AALs & TELs
Current AALs & TELs
For More Information

 


Background

To determine the AALs and TELs for individual chemicals, MassDEP first develops:

  • Non-Threshold Effects Exposure Limits (NTELs) based on known or suspected carcinogenic health effects. The NTEL is a concentration associated with a one in a million excess lifetime cancer risk over a lifetime of continuous exposure; and
  • Threshold Effects Exposure Limits (TELs) based on non-cancer health effects. The TEL is a concentration intended to protect the general population, including sensitive populations such as children, from adverse health effects over a lifetime of continuous exposure. TELs take into account the fact that people may be exposed to a chemical from other sources, including indoor air, food, soil and water.

MassDEP compares the NTEL and the TEL and designates the lower concentration as the AAL. Since, in general, NTELs are lower than TELs, most AALs are based on the NTEL, or risk of excess cancer. For chemicals that do not pose cancer risks, the AAL is based on the TEL, and in this case the published AAL and TEL values are the same.

Use of AALs & TELs

MassDEP uses AALs and TELs primarily in its air pollution control permitting program. The agency also uses AALs and TELs to evaluate the potential for health effects from chemicals present in ambient and indoor air.

It should be noted that exposure above an AAL or TEL does not automatically mean an individual will develop cancer or experience non-cancer health effects. However, the risk or probability of developing adverse effects increases with intensity and frequency of exposure.

MassDEP Methods for Deriving AALs & TELs

MassDEP updated its methods for deriving AALs and TELs in 2011 following a scientific peer review of the new updating methodology. MassDEP's new method makes use of existing peer reviewed air guidance levels developed by the U.S. Environmental Protection Agency (EPA), California Environmental Protection Agency (CalEPA) and other agencies. The Air Guidelines continue to consider cancer and non-cancer health effects. AALs and TELs for chemicals listed with evaluation dates of 1990 and 1995 were developed using the 1990 and 1995 methods respectively. AALs and TELs derived by earlier methods and published on this web site remain the state air guidelines until MassDEP updates them.

Current AALs & TELs

MassDEP releases AALs and TELs to the public by adding or updating guidelines and supporting information on its Air Guideline Values web page. You may sign up to be notified when new values are published.

AALs and TELs are health-based ambient air guidelines used to evaluate potential human health risks from exposures to chemicals in ambient air.

Air guideline values are set at concentrations intended to protect the general population, including sensitive populations such as children, from adverse health effects over a lifetime of continuous exposure.  

AIR GUIDELINES TABLE - FEBRUARY 2014
CHEMICAL
NAME &
CAS NUMBER
THRESHOLD EFFECTS
EXPOSURE
LIMIT (TEL)
(24-Hour Average)
ALLOWABLE
AMBIENT
LIMIT (AAL)
(Annual Average)
LAST
UPDATE
ug/m3
ppb[1]
ug/m3
ppb[1]
Acetaldehyde
75070
2
1.11
0.5
0.28
1995
Acrolein doc format of Acrolein
107028
0.070.030.070.032014
Acetone
67641
160.54
68.03
160.54
68.03
1990
Acrylonitrile
107131
0.4
0.18
0.01
0.0046
1995
Alkanes/Alkenes
(not to exceed 25% n-hexane)
95.24
-
47.62
-
1990
Ammonia doc format of MassDEP Air Guidelines for Ammonia
7664417
100
100
100
100
2011

Aniline
62533

0.2
0.053
0.1
0.026
1995

Antimony
7440360

2
-
1
-
1995

Arsenic doc format of MassDEP Air Guidelines for Arsenic
7440382

0.003
-
0.0003
-
2011
Asbestos
1332214
0.0002
f/cm3
-
0.000004
f/cm3
-
1990
Benzene doc format of Benzene
71432
2
0.6
0.1
0.03
2014
Benzyl Chloride
100447
14.08
2.72
0.94
0.18
1990
Beryllium
7440417
0.001
-
0.0004
-
1990
1,3-Butadiene
106990
1.20
0.54
.003
0.002
1990
n-Butyl Alcohol
71363
412.24
136.05
412.24
136.05
1990
Cadmium doc format of Cadmium
7440439
0.002
-
0.0002
-
2014
Calcium Chromate
13765190
0.003
-
0.0001
-
1990
Carbon Disulfide
75150
0.1
0.032
0.1
0.032
1995
Carbon Tetrachloride
56235
85.52
13.61
0.07
0.01
1990
Carbonyl Sulfide
463581
0.1
0.041
0.1
0.041
1995
Chlordane
57749
0.14
0.008
0.03
0.002
1990
Chlorine
7782505
3.95
1.36
3.95
1.36
1990
Chlorobenzene
108907
93.88
20.41
6.26
1.36
1990
Chloroethane
75003
717.55
272.11
358.78
136.05
1990
Chloroform
67663
132.76
27.21
0.04
0.01
1990
Chloroprene
126998
0.98
0.27
0.98
0.27
1990
Chromic Acid
7738945
0.003
-
0.0001
-
1990
Chromium (metal)
7440473
1.36
-
0.68
-
1990
Chromium (VI) Compounds
0.003
-
0.0001
-
1990
Copper
7440508
0.54
-
0.54
-
1990
p-Cresol
106445
24.05
5.44
12.02
2.72
1990
Cyclohexane
110827
280.82
81.63
280.82
81.63
1990
o-Dichlorobenzene
95501
81.74
13.61
81.74
13.61
1990
p-Dichlorobenzene
106467
122.61
20.41
0.18
0.03
1990
1,2-Dichloroethane
107062
11.01
2.72
0.04
0.01
1990
1,2-Dichloroethylene
540590
215.62
54.42
107.81
27.21
1990
Dichloromethane doc format of Dichloromethane
(Methylene Chloride)
75092
100
30
60
20
2014
1,2-Dichloropropane
78875
0.9
0.19
0.05
0.01
1995
Diethylamine
109897
8.13
2.72
4.07
1.36
1990
Di(2-ethylhexyl)phthalate
117817
1.36
0.09
0.77
0.05
1990

Dimethylformamide
68122

6
2.01
3
1.004
1995
1,4-Dioxane
123911
24.49
6.80
0.24
0.07
1990
Diphenyl
92524
0.34
0.05
0.09
0.01
1990
Diphenylamine
122394
2.72
0.39
0.68
0.10
1990

Epichlorohydrin
106898

0.08
0.021
0.08
0.021
1995
Ethanol
64175
51.24
27.21
51.24
27.21
1990
Ethyl Acetate
141786
391.84
108.84
391.84
108.84
1990
Ethyl Acrylate
140885
0.56
0.14
0.28
0.07
1990

Ethylbenzene
100414

300
69.09
300
69.09
1995
Ethylene Glycol
107211
34.50
13.61
34.50
13.61
1990
Ethyl Ether
60297
329.80
108.84
164.90
54.42
1990
Fluoride
16984488
6.80
8.76
6.80
8.76
1990
2
2
0.08
0.06
2011
Furan
110009
0.40
0.14
0.02
0.007
1990
Heptachlor
76448
0.14
0.009
0.001
0.0001
1990
Hexachlorocyclopentadiene
77474
0.006
0.0005
0.006
0.0005
1990
Hexachloroethane
67721
0.53
0.05
0.25
0.03
1990
2-Hexanone
591786
10.88
2.66
10.88
2.66
1990
Hydrazine doc format of MassDEP Air Guidelines for Hydrazine
302012
0.04
0.03
0.0002
0.0002
2011

Hydrogen Bromide
10035106

5
1.51
5
1.51
1995

Hydrogen Chloride
7647010

7
4.69
7
4.69
1995

Hydrogen Cyanide
74908

0.6
0.54
0.3
0.27
1995

Hydrogen Fluoride
7664393

0.68
0.83
0.34
0.42
1990

Hydrogen Sulfide
7783064

0.9
0.65
0.9
0.65
1995
Isoamyl Acetate
123922
144.76
27.21
144.76
27.21
1990
Isobutyl Acetate
110190
193.77
40.82
193.77
40.82
1990
Isobutyl Alcohol
78831
41.22
13.61
41.22
13.61
1990
Isopropyl Acetate
108214
283.81
68.03
283.81
68.03
1990
Lead
7439921
0.14
-
0.07
-
1990
Lead Subacetate
1335326
0.14
-
0.01
-
1990
Lindane
58899
0.14
0.11
0.003
0.0002
1990
0.1
0.02
0.1
0.02
2011
Mercury (elemental)
7439976
0.14
-
0.07
-
1990
Mercury (inorganic)
0.14
-
0.01
-
1990
Mercury (methyl-)
22967926
0.003
-
0.0014
-
1990
Methanol
67561
7.13
5.44
7.13
5.44
1990

2-Methoxy Ethanol
109864

3
0.96
2
0.64
1995
Methyl Acrylate
96333
9.57
2.72
4.79
1.36
1990
Methyl Bromide
74839
5.28
1.36
2.64
0.68
1990
Methyl Ethyl Ketone (MEK)
78933
200
67.82
10
3.39
1995
Methyl Isobutyl Ketone (MIBK)
108101
55.70
13.61
55.70
13.61
1990
Methyl Methacrylate
80626
22.27
5.44
22.27
5.44
1990
Naphthalene (including 2-methylnaphthalene)
91203
14.25
2.72
14.25
2.72
1990
Nickel (metal)
7440020
0.27
-
0.18
-
1990
Nickel Oxide
1313991
0.27
-
0.01
-
1990
Nitrobenzene
98953
13.69
2.72
6.84
1.36
1990
Pentachlorophenol
87865
0.01
0.001
0.01
0.001
1990
Phenol
108952
52.33
13.61
52.33
13.61
1990
Phosphoric Acid
7664382
0.27
0.07
0.27
0.07
1990
Phthalic Anhydride
85449
1.65
0.27
0.82
0.14
1990
PCBs
1336363
0.003
-
0.0005
-
1990
Propyl Alcohol
71238
133.63
54.42
133.63
54.42
1990

Propylene Oxide
75569

6
2.53
0.3
0.13
1995
Resorcinol
108463
12.24
2.72
3.06
0.68
1990
Selenium
7782492
0.54
-
0.54
-
1990
Selenium Sulfide
7446346
0.54
-
0.05
-
1990
Styrene
100425
200
46.96
2
0.47
1995
Sulfuric Acid
7664939
2.72
0.68
2.72
0.68
1990
1,1,2,2-Tetrachloro-
1,2-Difluoroethane
76120
1133.33
136.05
566.67
68.03
1990
1,1,2,2-Tetrachloroethane
79345
18.67
2.72
0.02
0.003
1990
50
7
0.1
0.01
2011
Tetrahydrofuran
109999
160.35
54.42
80.18
27.21
1990
Toluene
108883
80
21.23
20
5.31
1995
Toluene Diisocyanate
584849
0.10
0.01
0.10
0.01
1990
o-Toluidine
95534
2.38
0.54
0.17
0.04
1990
1,1,1-Trichloroethane
71556
1038.37
190.48
1038.37
190.48
1990
1,1,2-Trichloroethane
79005
14.84
2.72
0.06
0.01
1990
Trichloroethylene
79016
36.52
6.80
0.61
0.11
1990
2,4,6-Trichlorophenol
88062
-
-
0.16
-
1990
Triethylamine
121448
1
0.24
0.7
0.17
1995
Vanadium
1314621
0.27
-
0.27
-
1990
Vanadium Pentoxide
1314621
0.14
0.02
0.03
0.005
1990

Vinyl Acetate
108054

30
8.52
8
2.27
1995
Vinyl Chloride
75014
3.47
1.36
0.38
0.15
1990
Vinylidene Chloride
75354
1.08
0.27
0.02
0.01
1990
Xylenes (m-,o-,p- isomers)
1330207
11.80
2.72
11.80
2.72
1990

[1] All new and revised values are expressed in ug/m3 to one significant figure. Values are also presented in units of ppb for the convenience of users. From 2011 forward, values in units of ppb are calculated from the value in units of ug/m3 after it has been rounded to one significant figure. Concentrations measured in units of ppb can be transformed to ug/m3 using all significant figures applicable to the measured concentration in ppb, assuming the molecular conversion factor has an infinite number of significant figures, and then rounded to one significant figure for comparison to the Air Guidelines. Values derived in 1995 are presented in ppb without rounding.

For More Information

How AALs & TELs are Derived: 
Contact Sandra Baird of the MassDEP Office of Research & Standards, 617-654-6587 or sandra.baird@state.ma.us

Potential Health Effects from Individual Chemicals