The Occupational Alliance for Risk Science (OARS) is an initiative to facilitate sharing of information with workers and occupational health and safety professionals. OARS provides a forum for information exchange about exposure guidance for chemical stressors, methods for improving occupational risk assessments, and training opportunities. The OARS serves as the home of exposure guide values, and related guideline documents, for chemical stressors. These guide values and supporting documentation related to worker and community exposure levels for chemical and physical agents and stressors are published by the OARS. OARS is managed by Toxicology Excellence for Risk Assessment (TERA).
• October 2023: The semi-annual OARS WEEL committee meeting will be held on October 26-27 in South San Francisco, CA. The session is in-person and also via Zoom.
• September 2023: OARS WEEL documentation for bis-(2-Chloroisopropyl) Ether is available for public comment from September 23 through October 22, 2023. To obtain a copy and submit comments please contact Dr. Patricia McGinnis at mcginnis@tera.org.
• September 2023: OARS WEEL documentation for Methyltrimethoxysilane is available for public comment from September 23 through October 22, 2023. To obtain a copy and submit comments please contact Dr. Patricia McGinnis at mcginnis@tera.org.
• April 2023: The “Workplace environmental exposure level guide (WEEL) for Triethylenetetramine (TETA)” was published in Toxicology an Industrial Hygiene 39(4): 183-187.
• March 2023: The semi-annual OARS WEEL committee meeting was held March 23-24 in Nashville, TN.
• March 2023: The poster, “The Impact of Workplace Environmental Exposure Levels (WEELs)” was presented by TERA at the March 2023 Society of Toxicology Meeting. Click on image below to view full size version.
• March 2023: The WEEL Committee welcomes four new members:
Lisa Michelle Cooper, MS; Theresa Repaso-Subang, RPBio, DABT, ERT, QPRA;
Bradley Thomson, MS; Elizabeth Vancza, PhD, DABT
• March 2023: The semi-annual OARS WEEL committee meeting will be held on March 23, 1-4pm CDS and March 24, 10am-3pm CDS in Nashville, TN. The session is in-person and also via Zoom.
• February 2023: OARS WEEL documentation for Triethyleneamine (TETA) has been finalized, posted, and submitted to Toxicology and Industrial Health.
The OARS-WEEL Committee consists of volunteer experts dedicated to the science of setting occupational exposure levels. The Committee strives for a balance of toxicology and industrial hygiene professionals with a broad base of experience from industry, government, academia, and consulting services. Each member serves on the Committee solely in his/her individual capacity and not as a representative of his/her employer, organization and/or agency.
Chair: Jessica Graham, PhD, DABT
Vice Chair: Stacy Barnett, BS
Secretary: Ann Parker, MS
Past Chair: Leslie Beyer, MS, DABT, CIH
Daniel E. Arrieta, MS, PhD, DABT, ERT
Joel Bercu, PhD, MPH, DABT
Courtney M. Callis, MPH, DABT
Patrick Coin, PhD
Michelle Deveau, PhD, ROH, CRSP
Christine Glatt, MS, DABT
Janet Gould, PhD., DABT, CIH
Andrew A. “Tony” Havics, CIH, PE
Sophie Jia, MD, PhD, DABT
Mark Jonesku, MS, CSP, CIH
Mark Korchinski, MSc, DABT, ERT
Tom Lewandowski, PhD, DABT, ERT, ATS
Andrew Maier, PhD, DABT, CIH
Melisa Masuda-Herrera, MS
Robert Roy, PhD, DABT, Fellow ATS
Lawrence M. Segal, PhD, ERT
Robert Skoglund, PhD, DABT, CIH, CPPS
Andrew Soiefer, PhD, DABT (1990-2020)
Kenneth Still, PhD, ATS, CIH, CSP, CHMM
Ann Tveit, PhD, DABT
James Weldy, CIH, CPH
Bill Brock, PhD, DABT, Fellow ATS
David Clapin, PhD, MPA, DABT (2003-2018)
Lisa Michelle Cooper, MS
Michael Cooper, MS, MPH, NRRPT, CIH
Chandrika Moudgal, MS
Sandeep Mukhi, PhD, DABT
Robert Nocco, MS, DABT, CIH, CSP, CFPS, RRPT
Theresa Repaso-Subang, RPBio, DABT, ERT, QPRA
Bradley Thomson, MS
Henry Trochimowicz, MS, ScD
Elizabeth Vancza, PhD, DABT
Brittany Wheldon, PhD
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 to download the PDF version of the 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 lsothiocyanate | 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 |
| Benzenesulfonicacid, 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 | |
| ChIoroisopropyI)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 | |
| Decafluoropentane, 1,1,1,2,3,4,4,5,5,5- (HFC- 4310mee) | 138495-42-8 | OARS | 225 ppm (2320 mg/m3) | 700 ppm (7217 mg/m3) |
2020 |
| 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-ChIoro-1,1- | 75-68-3 | AIHA | 1000 ppm | — | 1994 |
| Difluoroethylene, (E)-1,2 (HFO-1132 (E) | 1630-78-0 | OARS | 350 ppm | 2022 | |
| Difluoromethane | 75-10-5 | AIHA | 1000 ppm | 1997 | |
| Diisobutylene | 25167-70-8 | OARS | 75 ppm (344 mg/m3 ) | 2016 | |
| Dimethyl Ether | 115-10-6 | OARS | 1000 ppm | 2022 | |
| 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 |
| Methoxytridecafluoroheptene isomers (MPHE) | Variable | OARS | 200 ppm | — | 2020 |
| Methyl Ethyl Ketoxime | 96-29-7 | AIHA | 10 ppm (DSEN) | 1990 | |
| Methyl-2-PyrroIidone, n- (NMP) | 872-50-4 | OARS | 15 ppm (60 mg/m3) Skin | 30 ppm (120 mg/m3) | 2021 |
| Methyltrichlorosilane | 75-79-6 | AIHA | 1 ppm (ceiling) | 2001 | |
| Monochloroacetic Acid | 79-11-8 | AIHA | 0.5 ppm (skin) | 2004 | |
| Nitro-1,2,4-TriazoI-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-ChIoro-1,1,1,2- | 2837-89-0 | AIHA | 1000 ppm | — | 2005 |
| Tetrafluoropropene, (Z)-1-ChIoro-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 | OARS | 1 ppm (skin) | 2023 | |
| Triethylphosphate | 78-40-0 | AIHA | 7.45 mg/m3 | 2010 | |
| TrifIuoro-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
Copyright © 1995 - 2022
OARS-WEEL
1250 Ohio Pike, Suite 197, Cincinnati, OH 45102
Phone: 513.542.7475
Webmaster: tera@tera.org
