• January 2025: OARS WEEL documentation for Methyltrimethoxysilane (MTMS) was published online in Toxicology and Industrial Health. Available at: https://journals.sagepub.com/doi/full/10.1177/07482337241301523 

• January 2025: OARS WEEL documentation for (E)-1,1,1,2,2,5,5,6,6,6-Decafluoro-3-hexene (HFO-153-10mczz-E) was published online in Toxicology and In• November 2024: OARS WEEL documentation for Vinyltrimethoxysilane (VTMS) as been submitted to Toxicology and Industrial Health for publication.

• November 2024: OARS WEEL documentation for Vinyltrimethoxysilane (VTMS) as been submitted to Toxicology and Industrial Health for publication.

• June 2024: OARS WEEL documentation for Bis-(2-Chloroisopropyl) Ether (BCIPE) was published online in Toxicology and Industrial Health. Available at: https://journals.sagepub.com/doi/10.1177/07482337241245745. For questions, please contact Dr. Patricia McGinnis at mcginnis@tera.org.

• June 2024: OARS WEEL documentation for HFO-153-10mczz-E has been submitted to Toxicology and Industrial Health for publication.

• June 2024: OARS WEEL documentation for Methyltrimethoxysilane (MTMS) has been submitted to Toxicology and Industrial Health for publication.



NEWS ARCHIVES


   

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.

   


The development of new or revision of existing WEELs is typically assigned to voluntarily designated subcommittees. A subcommittee usually comprises 3 – 4 members from the WEEL Committee. New WEELs are developed using the OARS-WEEL administrative standard operating procedure (SOP), while existing WEELs are usually revised every 10 years, unless the availability of significant new data which may impact the existing WEEL value compels the committee to make a revision sooner. The OARS-WEEL SOP contains procedures and guidelines governing conflicts of interest, draft document preparation, literature searches, draft document review, balloting process, post-ballot WEEL documentation quality assurance scientific review, and publication.

 

Once a subcommittee has prepared a draft WEEL document, a review of the draft is scheduled for the next available Committee meeting. The WEEL Committee members are expected to have reviewed all such drafts prior to the meeting. If no major changes are necessary to a draft, the attending Committee membership may, by a simple majority, approve the WEEL for balloting. Alternatively, the Committee may direct the subcommittee to revise the WEEL and present it for further discussion at a future meeting. If a ballot is not approved by a two-thirds majority of non-abstaining Committee members, it is discussed at the next Committee meeting to determine the appropriate course of action. Once the WEEL is approved by a two-thirds majority of non-abstaining Committee members, copies of ballot comments are forwarded to the designated subcommittee and all substantive comments must be addressed in the final draft. If resolution of a substantive comment results in a change to the WEEL value or a change in the basis for the value, the draft must be re-balloted.

 

Once all comments have been addressed on a successfully balloted draft, document formatting and editorial review are performed by TERA, before the draft WEEL document is made available for public comment (usually for a period of 30 days but may be extended if the need arises). After the public comment period has elapsed, comments are addressed by the subcommittee responsible for that specific draft, after which the WEEL documentation is submitted to Toxicology and Industrial Health (TIH), a peer-reviewed medical journal that covers research in the fields of occupational health and toxicology, for publication. A thorough review of the galley proof by the scientific content quality coordinator at TERA, and proofreaders and editors at TIH is the penultimate step before eventual publication of the WEEL documentation.



   

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.

  Workplace Environmental Exposure Levels (WEELs) are health-based guide values for chemical stressors. The WEELs provide air concentrations intended to protect most workers from adverse health effects related to occupational chemical exposures.  

 

   

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
Decafluoro-3-hexene, (E)- 1,1,1,2,2,5,5,6,6,6- (HFO-153-10mczz-E) 1256353-26-0 OARS 200 ppm (2160 mg/m3)   2024
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

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Got a question, comment, or want more information? Please drop us a note. or email Dr. Patricia McGinnis at: mcginnis@tera.org