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Department of Environmental Health

Risk Science Center (RSC)

Occupational Alliance for Risk Science (OARS) Workplace Environmental Exposure Levels (WEELs)™

Occupational exposure limits (OELs) are developed for protection of healthy workers; they are not intended for the general public, which includes sensitive populations such as infants, the elderly, or the infirm. OELs are based on repeated daily exposures over a working lifetime. They are normally averaged over an 8-hour workday and serve to protect against acute and chronic health effects.

Click here for a PDF of OARS WEEL Table.

Substance CAS Source 8-Hour TWA Ceiling or Short-Term TWA Last Revised
Acetone Cyanohydrin 75-86-5 AIHA 2 ppm (skin) 5 ppm (15 min, skin) 1992
Acetophenone 98-86-2 AIHA 10 ppm 2007
Aldicarb 116-06-3 AIHA 0.01 mg/m3 (skin) 2009
Allyl Isothiocyanate 57-06-7 AIHA 1 ppm (15-min, skin, DSEN) 1993
Aminobenzoic Acid, para- 150-13-0 AIHA 5 mg/m3 2001
Aminotri (Methylenephosphonic Acid) 6419-19-8 AIHA 10 mg/m3 2004
Amyl Alcohol, n- 71-41-0 AIHA 100 ppm 2001
Benzaldehyde 100-52-7 AIHA 2 ppm 4 ppm (15-min, DSEN) 1998
Benzenesulfonic acid, 5-chloro-2((2-Hydroxy-1-napthalenyl)-azo)-4-methyl, barium salt (2:1) 5160-02-1 AIHA 1 mg/m3 2008
Benzophenone 119-61-9 AIHA 0.5 mg/m3 2003
Benzoyl Chloride 98-88-4 AIHA 5 ppm (ceiling, skin, DSEN) 2008
Benzyl Alcohol 100-51-6 AIHA 10 ppm 2008
Butylcatechol, 4-tert- 98-29-3 AIHA 2 mg/m3 (ceiling, skin, DSEN) 2001
Butyraldehyde 123-72-8 OARS 25 ppm (75 mg/m3) 2016
Chloramphenicol 56-75-7 AIHA 0.5 mg/m3 2008
Chloroisopropyl)Ether, bis-(2- 39638-92-9 AIHA 3 ppm 2009
Chloropropane, 2- 75-29-6 OARS 50 ppm (161 mg/m3) 2016
Chlorosulfonic Acid 7790-94-5 OARS 2016*
Chlorotrifluoroethylene 79-38-9 AIHA 5 ppm 2010
Cumene Hydroperoxide 80-15-9 AIHA 1 ppm (skin) 2009
Decabromodiphenyl Oxide 1163-19-5 AIHA 5 mg/m3 2009
Decamethylcyclopentasiloxane (D5) 541-02-6 OARS 10 ppm 2015
Decene, 1- 872-05-9 AIHA 100 ppm 2000
Dehydrolinalool 29171-20-8 AIHA 2 ppm 2007
Diallylamine 124-02-7 AIHA 1 ppm (skin) 2009
Dibromoneopentyl Glycol 3296-90-0 AIHA 0.2 mg/m3 2010
Dibutylamine 111-92-2 AIHA 5 ppm (ceiling, skin) 2003
Dichlorophenol, 2,4- 120-83-2 AIHA 1 ppm (skin*) 2004
Diethylbenzenes, mixed isomers 25340-17-4 AIHA 5 ppm 2005
Diethylene Glycol 111-46-6 OARS 10 mg/m3 2016
Diethylene Glycol Monoethyl Ether 111-90-0 AIHA 25 ppm 1991
Difluoroethane, 1,1- 75-37-6 AIHA 1000 ppm 2005
Difluoroethane, 1-Chloro-1,1- 75-68-3 AIHA 1000 ppm 1994
Difluoromethane 75-10-5 AIHA 1000 ppm 1997
Diisobutylene 25167-70-8 OARS 75 ppm (344 mg/m3 ) 2016
Dimethyl Ether 115-10-6 AIHA 1000 ppm 2010
Dimethyl Sulfoxide 67-68-5 AIHA 250 ppm 2003
Dimethyl Terephthalate 120-61-6 AIHA 5 mg/m3 (total) 2000
Dimethyldichlorosilane 75-78-5 AIHA 2 ppm (ceiling) 2001
Dimethylethylamine 598-56-1 AIHA 1 ppm 3 ppm 2011
Dimethyl-para-toluidine, n,n- 99-97-8 AIHA 0.5 ppm 2009
Dinitroanisole, 2,4- (DNAN) 119-27-7 OARS 0.1 mg/m3 (0.01 ppm) 2014
Dowtherm Q 612-00-0, 68987-42-8 AIHA 7.8 mg/m3 2002
Epoxybutane, 1,2- 106-88-7 AIHA 2 ppm 2003
Erythromycin 114-07-8 AIHA 3 mg/m3 2007
Fluoroethane, 1,1-dichloro-1- 1717-00-6 AIHA 500 ppm 3000 ppm (5-min STEL) 2008
Furan 110-00-9 AIHA Worker exposure by all routes should be minimalized to the fullest extent possible. 1993
GlycidylMethacrylate 106-91-2 AIHA 0.5 ppm (skin, DSEN) 2000
Glyoxal 107-22-2 AIHA 0.1 mg/m3 (DSEN) 2000
Hexadiene, 1,4- (mixed cis and trans) 592-45-0 AIHA 10 ppm 2009
Hexafluoro-2-butene, cis-1,1,1,4,4,4- (HFO 1336mzz-Z) 692-49-9 OARS 500 ppm (3350 mg/m3) 2014
Hexafluoro-2-butene, trans-1,1,1,4,4,4- (HFO 1336mzz-E) 66711-86-2 OARS 400 ppm (2680 mg/m3) 2018
Hexafluoropropane, 1,1,1,3,3,3- 690-39-1 AIHA 1000 ppm 1998
Hexamethyldisilazane (HMDZ) 999-97-3 OARS 10 ppm 50 ppm 2018
Hexamethylene Glycol 629-11-8 AIHA 10 mg/m3 2011
Hexanediamine, 1,6- 124-09-4 AIHA 1 ppm 2004
Hexanediol Diacrylate 13048-33-4 AIHA 1 mg/m3 (DSEN) 1998
Hexyl Alcohol, n- 111-27-3 AIHA 40 ppm (eye irritation) 2011
HFE-7100 163702-07-6,

163702-08-7
AIHA 750 ppm 1999
Hydroxybenzoic Acid, 4- 99-96-7 OARS 5 mg/m3 2016
Isobutyraldehyde 78-84-2 AIHA 25 ppm 2002
Isocyanuric Acid 108-80-5 AIHA 10 mg/m3 (total);
5 mg/m3 (respirable)
2005
Isophthalic Acid 121-91-5 AIHA 10 mg/m3 (total);
5 mg/m3 (respirable)
1991
Isoprene 78-79-5 AIHA 2 ppm 2004
Limonene, d- 5989-27-5 AIHA 30 ppm 1993
Lithium Hydroxide 1310-65-2 AIHA 1 mg/m3 (ceiling) 1999
Lithium Oxide 12057-24-8 AIHA 1 mg/m3 (ceiling) 1999
Mancozeb 8018-01-7 AIHA 1 mg/m3 (total, DSEN) 2008
Melamine 108-78-1 OARS 3 mg/m3 2016
Menthol 1490-04-6 OARS 1 ppm 3 ppm (15 min) 2014
Mercaptobenzothiazole, 2- 149-30-4 AIHA 5 mg/m3 (skin, DSEN) 2010
Mercaptoethanol 60-24-2 AIHA 0.2 ppm (skin) 2002
Methoxypropylamine, 3- 5332-73-0 AIHA 5 ppm 15 ppm (15 min) 2009
Methyl Ethyl Ketoxime 96-29-7 AIHA 10 ppm (DSEN) 1990
Methyl-2-Pyrrolidone, n- 872-50-4 AIHA 10 ppm (skin) 2010
Methyltrichlorosilane 75-79-6 AIHA 1 ppm (ceiling) 2001
Monochloroacetic Acid 79-11-8 AIHA 0.5 ppm (skin) 2004
Nitro-1,2,4-Triazol-5-One, 3- (NTO) 932-64-9 OARS 2 mg/m3 2014
Nitroguanidine, 1- (NQ) 556-88-7 OARS 7 mg/m3 2016
Octamethylcyclotetrasiloxane (D4) 556-67-2 OARS 10 ppm 2014
Octanol, 1- 111-87-5 AIHA 50 ppm 2005
Octene, 1- 111-66-0 AIHA 75 ppm 2000
Pentaerythritol Triacrylate 3524-68-3 AIHA 1 mg/m3 (DSEN) 1999
Pentafluoroethane, 1,1,1,2,2- 354-33-6 AIHA 1000 ppm 2009
Pentafluoropropane, 1,1,1,3,3- 460-73-1 AIHA 300 ppm 2001
Phosphono-1,2,4 butanetricarboxylic, 2-acid 37971-36-1 AIHA 10 mg/m3 2006
Picolines 109-06-8, 108-99-6, 108-89-4 AIHA 2 ppm (skin) 5 ppm (15-min, skin) 1988
Piperidine 110-89-4 AIHA 1 ppm (skin) 1996
Polyethylene Glycols (MW > 200) 25322-68-3 AIHA 10 mg/m3 2009
Polypropylene Glycols 25322-69-4 AIHA 10 mg/m3 1997
Potassium Bromate 7758-01-2 AIHA 0.1 mg/m3 2004
Propargyl Bromide 106-96-7 AIHA 0.1 ppm (skin) 1997
Propenoic Acid, isooctyl ester, 2- 29590-42-9 AIHA 5 ppm 2010
Propionaldehyde 123-38-6 AIHA 20 ppm 2002
Propylene Glycol 57-55-6 AIHA 10 mg/m3 2004
Propylene Glycol Monomethyl Ether Acetate 108-65-6 AIHA 50 ppm 2005
Quinoline 91-22-5 AIHA 0.001 ppm (skin) 2006
Sodium Chloroacetate 3926-62-3 OARS 0.5 ppm (2.5 mg/m3 ) 2016
Sodium Hypochlorite 7681-52-9 AIHA 2 mg/m3 (15 min) 2010
Tetrachloropyridine, 2,3,5,6- 2402-79-1 OARS 5 mg/m3 2016
Tetrachlorosilane 10026-04-7 AIHA 1 ppm (ceiling) 1999
Tetraethylene Glycol Diacrylate 17831-71-9 AIHA 1 mg/m3 (skin, DSEN) 1981
TetraethylenePentamine 112-57-2 AIHA 5 mg/m3 (skin, DSEN) 2004
Tetrafluoroethane, 1,1,1,2- (HFC-134a) 811-97-2 AIHA 1000 ppm 2003
Tetrafluoroethane, 1,1,2,2- (HFC-134) 359-35-3 OARS 1000 ppm 2018
Tetrafluoroethane, 2-Chloro-1,1,1,2- 2837-89-0 AIHA 1000 ppm 2005
Tetrafluoropropene, (Z)-1-Chloro-2,3,3,3- (HCFO-1224yd(Z)) 111512-60-8 OARS 1000 ppm 2017
Tetrafluoropropene, 2,3,3,3,- (HFO-1234yf) 754-12-1 AIHA 500 ppm 2009
Tetrafluoropropylene, 1,3,3,3- 1645-83-6 AIHA 800 ppm 2011
Tetrahydrofurfuryl Alcohol 97-99-4 AIHA 0.5 ppm (skin) 1993
Titanium Tetrachloride 7550-45-0 AIHA 0.5 mg/m3 2009
Toluene Diamine, 2,4- and mixed isomers 95-80-7; 25376-45-8 AIHA 0.005 ppm (skin) 2010
Toluenesulfonyl Chloride, para- 98-59-9 AIHA 5 mg/m3 (ceiling) 2009
trans-1-Chloro-3,3,3-trifluoropropylene (HCFO-1233zd(E)) 102687-65-0 OARS 800 ppm 2013
Trichlorosilane 10025-78-2 AIHA 0.5 ppm (ceiling) 1998
Triethoxysilane 998-30-1 AIHA 0.05 ppm 2000
Triethylene Glycol Diacrylate 1680-21-3 AIHA 1 mg/m3 (skin) 1981
Triethylenetetramine 112-24-3 AIHA 1 ppm (skin) 2009
Triethylphosphate 78-40-0 AIHA 7.45 mg/m3 2010
Trifluoro-2,2-Dichloroethane, 1,1,1- 306-83-2 AIHA 50 ppm 2001
Trifluoroethane, 1,1,1- 420-46-2 AIHA 1000 ppm 1996
Trifluoroethanol, 2,2,2- 75-89-8 OARS 0.3 ppm 2016
Trifluoroiodomethane (CF3I) 2314-97-8 OARS 500 ppm 1500 ppm 2018
Trimethoxysilane 2487-90-3 AIHA 0.05 ppm 2010
Trimethylamine 75-50-3 AIHA 1 ppm 2005
Trimethylchlorosilane 75-77-4 AIHA 5 ppm (ceiling) 2001
Trimethylolpropane Triacrylate 15625-89-5 AIHA 1 mg/m3 (skin) 1981
Trimethylolpropane Trimethacrylate 3290-92-4 AIHA 1 mg/m3 (skin) 1981
Trisodium Phosphate 7601-54-9 AIHA 5 mg/m3 (15 min) 2009
Urea 57-13-6 AIHA 10 mg/m3 2007
Vanillin 121-33-5 AIHA 10 mg/m3 2009
Vinylcyclohexene 100-40-3 AIHA 1 ppm 2009
Vinyltrichlorosilane 75-94-5 AIHA 1 ppm (ceiling) 2002

*Value withdrawn

Substances Considered But Determined to Have an Inadequate Minimum Data Set:

  • Chlorine Monoxide
  • Methylene Butanedioic Acid
  • 1,3-Pentadiene