Isocyanate

In organic chemistry, isocyanate is the functional group with the formula R−N=C=O. Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Diisocyanates are manufactured for the production of polyurethanes, a class of polymers.^{[page needed][page needed]}

The isocyanate functional group

Isocyanates should not be confused with cyanate esters and isocyanides, very different families of compounds. The cyanate (cyanate ester) functional group (R−O−C≡N) is arranged differently from the isocyanate group (R−N=C=O). Isocyanides have the connectivity R−N≡C, lacking the oxygen of the cyanate groups.

Structure and bonding

In terms of bonding, isocyanates are closely related to carbon dioxide (CO₂) and carbodiimides (C(NR)₂). The C−N=C=O unit that defines isocyanates is planar, and the N=C=O linkage is nearly linear. In phenyl isocyanate, the C=N and C=O distances are respectively 1.195 and 1.173 Å. The C−N=C angle is 134.9° and the N=C=O angle is 173.1°.

Production

Isocyanates are usually produced from amines by phosgenation, i.e. treating with phosgene:

RNH₂ + COCl₂ → RNCO + 2 HCl

These reactions proceed via the intermediacy of a carbamoyl chloride (RNHC(O)Cl). Owing to the hazardous nature of phosgene, the production of isocyanates requires special precautions. A laboratory-safe variation masks the phosgene as oxalyl chloride. Also, oxalyl chloride can be used to form acyl isocyanates from primary amides, which phosgene typically dehydrates to nitriles instead.

Another route to isocyanates entails addition of isocyanic acid to alkenes. Complementarily, alkyl isocyanates form by displacement reactions involving alkyl halides and alkali metal cyanates.

Aryl isocyanates can be synthesized from reductive carbonylation of nitro- and nitrosoarenes; a palladium catalyst is necessary to avoid side-reactions of the nitrene intermediate.

Three rearrangement reactions involving nitrenes give isocyanates:

• Schmidt reaction, a reaction where a carboxylic acid is treated with ammonia and hydrazoic acid yielding an isocyanate.
• Curtius rearrangement degradation of an acyl azide to an isocyanate and nitrogen gas.
• Lossen rearrangement, the conversion of a hydroxamic acid to an isocyanate via the formation of an O-acyl, sulfonyl, or phosphoryl intermediate.

An isocyanate is also the immediate product of the Hofmann rearrangement, but typically hydrolyzes under reaction conditions.

Reactivity

With nucleophiles

Isocyanates are electrophiles, and as such they are reactive toward a variety of nucleophiles including alcohols, amines, and even water having a higher reactivity compared to structurally analogous isothiocyanates.

Upon treatment with an alcohol, an isocyanate forms a urethane linkage:

ROH + R'NCO → ROC(O)N(H)R'

where R and R' are alkyl or aryl groups. If a diisocyanate is treated with a compound containing two or more hydroxyl groups, such as a diol or a polyol, polymer chains are formed, which are known as polyurethanes.

Synthesis of polyurethane from a diisocyanate and a diol

Isocyanates react with water to form carbon dioxide:

RNCO + H₂O → RNH₂ + CO₂

This reaction is exploited in tandem with the production of polyurethane to give polyurethane foams. The carbon dioxide functions as a blowing agent.

Isocyanates also react with amines to give ureas:

R₂NH + R'NCO → R₂NC(O)N(H)R'

The addition of an isocyanate to a urea gives a biuret:

R₂NC(O)N(H)R' + R''NCO → R₂NC(O)NR'C(O)NHR''

Reaction between a di-isocyanate and a compound containing two or more amine groups produces long polymer chains known as polyureas.

Carbodiimides are produced by the decarboxylation of alkyl and aryl isocyanate using phosphine oxides as a catalyst:

C₆H₁₁NCO → (C₆H₁₁N)₂C + CO₂

Cyclization

Isocyanates also can react with themselves. Aliphatic diisocyanates can trimerise to from substituted isocyanuric acid groups. This can be seen in the formation of polyisocyanurate resins (PIR) which are commonly used as rigid thermal insulation. Isocyanates participate in Diels–Alder reactions, functioning as dienophiles.

Rearrangement reactions

Isocyanates are common intermediates in the synthesis of primary amines via hydrolysis:

• Hofmann rearrangement, a reaction in which a primary amide is treated with a strong oxidizer such as sodium hypobromite or lead tetraacetate to form an isocyanate intermediate.

Common isocyanates

Methylene diphenyl 4,4'-diisocyanate (MDI);
numbering of the ring atoms shown with blue numbers

Isophorone diisocyanate

The global market for diisocyanates in the year 2000 was 4.4 million tonnes, of which 61.3% was methylene diphenyl diisocyanate (MDI), 34.1% was toluene diisocyanate (TDI), 3.4% was the total for hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), and 1.2% was the total for various others. A monofunctional isocyanate of industrial significance is methyl isocyanate (MIC), which is used in the manufacture of pesticides.

Common applications

MDI is commonly used in the manufacture of rigid foams and surface coating. Polyurethane foam boards are used in construction for insulation. TDI is commonly used in applications where flexible foams are used, such as furniture and bedding. Both MDI and TDI are used in the making of adhesives and sealants due to weather-resistant properties. Isocyanates, both MDI and TDI are widely used in as spraying applications of insulation due to the speed and flexibility of applications. Foams can be sprayed into structures and harden in place or retain some flexibility as required by the application. HDI is commonly utilized in high-performance surface-coating applications, including automotive paints.

Health and safety

The risks of isocyanates was brought to the world's attention with the 1984 Bhopal disaster, which caused the death of nearly 4000 people from the accidental release of methyl isocyanate. In 2008, the same chemical was involved in an explosion at a pesticide manufacturing plant in West Virginia.

LD50s for isocyanates are typically several hundred milligrams per kilogram. Despite this low acute toxicity, an extremely low short-term exposure limit (STEL) of 0.07 mg/m³ is the legal limit for all isocyanates (except methyl isocyanate: 0.02 mg/m³) in the United Kingdom. These limits are set to protect workers from chronic health effects such as occupational asthma, contact dermatitis, or irritation of the respiratory tract.

Since they are used in spraying applications, the properties of their aerosols have attracted attention. In the U.S., OSHA conducted a National Emphasis Program on isocyanates starting in 2013 to make employers and workers more aware of the health risks. Polyurethanes have variable curing times, and the presence of free isocyanates in foams vary accordingly.

Both the US National Toxicology Program (NTP) and International Agency for Research on Cancer (IARC) have evaluated TDI as a potential human carcinogen and Group 2B "possibly carcinogenic to humans". MDI appears to be relatively safer and is unlikely a human carcinogen. The IARC evaluates MDI as Group 3 "not classifiable as to its carcinogenicity in humans".

All major producers of MDI and TDI are members of the International Isocyanate Institute, which promotes the safe handling of MDI and TDI.

Hazards

Toxicity

Isocyanates can present respiratory hazards as particulates, vapors or aerosols. Autobody shop workers are a very commonly examined population for isocyanate exposure as they are repeatedly exposed when spray painting automobiles and can be exposed when installing truck bed liners. Hypersensitivity pneumonitis has slower onset and features chronic inflammation that can be seen on imaging of the lungs. Occupational asthma is a worrisome outcome of respiratory sensitization to isocyanates as it can be acutely fatal. Diagnosis of occupational asthma is generally performed using pulmonary function testing (PFT) and performed by pulmonology or occupational medicine physicians. Occupational asthma is much like asthma in that it causes episodic shortness of breath and wheezing. Both the dose and duration of exposure to isocyanates can lead to respiratory sensitization. Dermal exposures to isocyanates can sensitize an exposed person to respiratory disease.

Dermal exposures can occur via mixing, spraying coatings or applying and spreading coatings manually. Dermal exposures to isocyanates is known to lead to respiratory sensitization. Even when the right personal protective equipment (PPE) is used, exposures can occur to body areas not completely covered. Isocyanates can also permeate improper PPE, necessitating frequent changes of both disposable gloves and suits if they become over exposed.

Flammability

Methyl isocyanate (MIC) is highly flammable. MDI and TDI are much less flammable. Flammability of materials is a consideration in furniture design. The specific flammability hazard is noted on the safety data sheet (SDS) for specific isocyanates.

Hazard minimization

Industrial science attempts to minimize the hazards of isocyanates through multiple techniques. The EPA has sponsored ongoing research on polyurethane production without isocyanates. Where isocyanates are unavoidable but interchangeable, substituting a less hazardous isocyanate may control hazards. Ventilation and automation can also minimizes worker exposure to the isocyanates used.

If human workers must enter isocyanate-contaminated regions, personal protective equipment (PPE) can reduce their intake. In general, workers wear eye protection and gloves and coveralls to reduce dermal exposure For some autobody paint and clear-coat spraying applications, a full-face mask is required.

The US Occupational Safety and Health Administration (OSHA) requires frequent training to ensure isocyanate hazards are appropriately minimized. Moreover, OSHA requires standardized isocyanate concentration measurements to avoid violating occupational exposure limits. In the case of MDI, OSHA expects sampling with glass-fiber filters at standard air flow rates, and then liquid chromatography.

Combined industrial hygiene and medical surveillance can significantly reduce occupational asthma incidence. Biological tests exist to identify isocyanate exposure; the US Navy uses regular pulmonary function testing and screening questionnaires.

Emergency management is a complex process of preparation and should be considered in a setting where a release of bulk chemicals may threaten the well-being of the public. In the Bhopal disaster, an uncontrolled MIC release killed thousands, affected hundreds of thousands more, and spurred the development of modern disaster preparation.

Occupational exposure limits

Exposure limits can be expressed as ceiling limits, a maximal value, short-term exposure limits (STEL), a 15-minute exposure limit or an 8-hour time-weighted average limit (TWA). Below is a sampling, not exhaustive, as less common isocyanates also have specific limits within the United States, and in some regions there are limits on total isocyanate, which recognizes some of the uncertainty regarding the safety of mixtures of chemicals as compared to pure chemical exposures. For example, while there is no OEL for HDI, NIOSH has a REL of 5 ppb for an 8-hour TWA and a ceiling limit of 20 ppb, consistent with the recommendations for MDI.

Methylene bisphenyl isocyanate (MDI)

Organization (region)	Standard	Value
OSHA (USA)	Ceiling limit	20 ppb
NIOSH (USA)	Recommended exposure limit (REL) – ceiling limit	20 ppb
NIOSH (USA)	Recommended exposure limit (REL) – TWA	5 ppb
ACGIH (USA)	Threshold limit value (TLV)	5 ppb
Safe Work (Australia)	All isocyanates – TWA	0.02 mg/m^3 (approximately 2.5 ppb for comparison)
Safe Work (Australia)	All isocyanates – STEL	0.07 mg/m^3 (approximately 10 ppb for comparison)
Heath & Safety Executive (UK)	All isocyanates – TWA	0.02 mg/m3
Heath & Safety Executive (UK)	All isocyanates – STEL	0.07 mg/m^3

Toluene-2,4-diisocyanate (TDI)

Organization (region)	Standard	Value
OSHA (USA)	Ceiling limit	20 ppb
NIOSH (USA)	Recommended exposure limit (REL)	[none]
ACGIH (USA)	Threshold limit value (TLV)	5 ppb
ACGIH (USA)	Ceiling limit	20 ppb

Regulation

United States

The Occupational Safety and Health Administration (OSHA) is the regulatory body covering worker safety. OSHA puts forth permissible exposure limit (PEL) 20 ppb for MDI and detailed technical guidance on exposure assessment.

The National Institutes of Health (NIOSH) is the agency responsible for providing the research and recommendations regarding workplace safety, while OSHA is more of an enforcement body. NIOSH is responsible for producing the science that can result in recommended exposure limits (REL), which can be lower than the PEL. OSHA is tasked with enforcement and defending the enforceable limits (PELs). In 1992, when OSHA reduced the PEL for TDI to the NIOSH REL, the PEL reduction was challenged in court, and the reduction was reversed.

The Environmental Protection Agency (EPA) is also involved in the regulation of isocyanates with regard to the environment and also non-worker persons that might be exposed.

The American Conference of Governmental Industrial Hygienists (ACGIH) is a non-government organization that publishes guidance known as threshold limit values (TLV) for chemicals based research as constant work exposure level without ill-effect^[clarify]. The TLV is not an OSHA-enforceable value, unless the PEL is the same.

European Union

The European Chemicals Agency (ECHA) provides regulatory oversight of chemicals used within the European Union. ECHA has been implementing policy aimed at limiting worker exposure through elimination by lower allowable concentrations in products and mandatory worker training, an administrative control. Within the European Union, many nations set their own occupational exposure limits for isocyanates.

International groups

The United Nations, through the World Health Organization (WHO) together with the International Labour Organization (ILO) and United Nations Environment Programme (UNEP), collaborate on the International Programme on Chemical Safety (IPCS) to publish summary documents on chemicals. The IPCS published one such document in 2000 summarizing the status of scientific knowledge on MDI.

The IARC evaluates the hazard data on chemicals and assigns a rating on the risk of carcinogenesis. In the case of TDI, the final evaluation is possibly carcinogenic to humans (Group 2B). For MDI, the final evaluation is not classifiable as to its carcinogenicity to humans (Group 3).

The International Isocyanate Institute is an international industry consortium that seeks promote the safe utilization of isocyanates by promulgating best practices.

See also

• Isothiocyanate
• Polymethylene polyphenylene isocyanate

References

1. Christian Six; Frank Richter (2005). "Isocyanates, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a14_611. ISBN 978-3-527-30673-2.
2. Patai, Saul, ed. (1977a). Cyanates and Their Thio Derivatives. The Chemistry of Functional Groups. Vol. 1. Wiley. doi:10.1002/9780470771525. ISBN 978-0-470-77152-5.
3. Patai, Saul, ed. (1977b). Cyanates and Their Thio Derivatives. The Chemistry of Functional Groups. Vol. 2. doi:10.1002/9780470771532. ISBN 978-0-470-77153-2.
4. Byrn, Marianne P.; Curtis, Carol J.; Hsiou, Yu; Khan, Saeed I.; Sawin, Philip A.; Tendick, S. Kathleen; Terzis, Aris; Strouse, Charles E. (1993). "Porphyrin sponges: conservative of host structure in over 200 porphyrin-based lattice clathrates". Journal of the American Chemical Society. 115 (21). American Chemical Society (ACS): 9480–9497. Bibcode:1993JAChS.115.9480B. doi:10.1021/ja00074a013. ISSN 0002-7863.
5. Smith (2020), March's Organic Chemistry, rxn. 16-7.
6. Patai 1977a, p. 447.
7. Patai 1977b, pp. 619–818.
8. Manov-Yuvenskii, V. I.; Redoshkin, B. A.; Belyaeva, G. P.; Nefedov, B. K. (March 1981) [21 Jan 1980]. "Effect of carbon monoxide pressure, pyridine concentration, and temperature on synthesis of 1-methyl­benzene 2,4-diisocyanate by carbonylation of 2,4-dinitro­toluene". Izvestiya Akademii Nauk SSSR. Seriya Khimicheskaya. 3. Plenum: 614–617. doi:10.1007/BF00949595. UDC 542.91:541.12.034:546.262.3-31:547.546.
9. Manov-Yuvenskii, V. I.; Redoshkin, B. A.; Belyaeva, G. P.; Nefedov, B. K. (January 1980) [13 Oct 1978]. "Synthesis of aromatic diisocyanates by carbonylation of dinitro compounds with carbon monoxide on palladium catalysts". Izvestiya Akademii Nauk SSSR. Seriya Khimicheskaya. 1. Plenum: 133–136. doi:10.1007/BF00951891. UDC 542.91:541.128:547.546:546.263.3-31.
10. Wallis, Everett S.; Lane, John F. (2011), "The Hofmann Reaction", Organic Reactions, John Wiley & Sons, Ltd, pp. 267–306, doi:10.1002/0471264180.or003.07, ISBN 978-0-471-26418-7, retrieved 2025-01-21
11. Li, Zhen; Mayer, Robert J.; Ofial, Armin R.; Mayr, Herbert (2020-04-27). "From Carbodiimides to Carbon Dioxide: Quantification of the Electrophilic Reactivities of Heteroallenes". Journal of the American Chemical Society. 142 (18): 8383–8402. Bibcode:2020JAChS.142.8383L. doi:10.1021/jacs.0c01960. PMID 32338511. S2CID 216557447.
12. Coleman, M.M.; Painter, P. (2019). Fundamentals of Polymer Science: An Introductory Text, Second Edition. CRC Press. p. 39. ISBN 978-1-351-44639-6.
13. Campbell, T. W.; Monagle, J. J. (1963). "Diphenylcarbodiimide". Organic Syntheses. 43: 31. doi:10.15227/orgsyn.043.0031.
14. http://alpha.chem.umb.edu/chemistry/orgchem/CH20Handout.pdf Archived 2006-09-11 at the Wayback Machine, Ch20Handout, University of Massachusetts Boston
15. Mann, F. G.; Saunders, B. C. (1960). Practical Organic Chemistry, 4th Ed. London: Longman. p. 128. ISBN 978-0-582-44407-2. {{cite book}}: ISBN / Date incompatibility (help)
16. Cohen, Julius (1900). Practical Organic Chemistry 2nd Ed. London: Macmillan and Co., Limited. p. 72. Practical Organic Chemistry Cohen Julius.
17. Baumgarten, Henry; Smith, Howard; Staklis, Andris (1975). "Reactions of amines. XVIII. Oxidative rearrangement of amides with lead tetraacetate". The Journal of Organic Chemistry. 40 (24): 3554–3561. doi:10.1021/jo00912a019.
18. Randall, D. (2002). The Polyurethanes Book. Wiley. ISBN 978-0-470-85041-1.
19. US EPA, OCSPP (2015-08-14). "Chemicals and Production of Spray Polyurethane Foam – Why It Matters". US EPA. Retrieved 2018-12-08.
20. "CSB Issues Report on 2008 Bayer CropScience Explosion: Finds Multiple Deficiencies Led to Runaway Chemical Reaction; Recommends State Create Chemical Plant Oversight Regulation". www.csb.gov. CSB. Retrieved 2018-11-21.
21. Allport D. C., Gilbert, D. S. and Outterside S. M. (eds) (2003). MDI and TDI: safety, health & the environment: a source book and practical guide. Chichester, Wiley.
22. EH40/2005 Workplace exposure limits (PDF) (4th ed.). TSO. 2020. ISBN 9780717667338. OCLC 1429445127.
23. "Isocyanates – Controlling hazardous substances – Managing occupational health risks in construction". www.hse.gov.uk.
24. "CDC – Isocyanates – NIOSH Workplace Safety and Health Topic". www.cdc.gov. 2018-11-09. Retrieved 2018-11-21.
25. "Isocyanate Exposure, Reaction and Protection – Quick Tips #233 – Grainger Industrial Supply". www.grainger.com. Retrieved 2018-11-21.
26. "OSHA announces new National Emphasis Program for occupational exposure to isocyanates". www.osha.gov. Occupational Safety and Health Administration. Retrieved 2018-11-21.
27. Riedlich, C. (2010). "Risk of isocyanate exposure in the construction industry" (PDF). CPWR – the Center for Construction Research and Training: 1–8. Archived (PDF) from the original on 2014-04-08.
28. IXOM. "Safety Data Sheet – TOLUENE DIISOCYANATE (TDI)" (PDF). Archived (PDF) from the original on 2018-04-17. Retrieved 2018-11-24.
29. "Health Effects of Diisocyanates: Guidance for Medical Personnel" (PDF). American Chemistry Council. Archived (PDF) from the original on 2013-08-09. Retrieved 2018-11-24.
30. "SAFETY DATA SHEET" (PDF). Everchem. Archived (PDF) from the original on 2017-03-16. Retrieved 2018-11-24.
31. Reeb-Whitaker, Carolyn; Whittaker, Stephen G.; Ceballos, Diana M.; Weiland, Elisa C.; Flack, Sheila L.; Fent, Kenneth W.; Thomasen, Jennifer M.; Trelles Gaines, Linda G.; Nylander-French, Leena A. (2012). "Airborne Isocyanate Exposures in the Collision Repair Industry and a Comparison to Occupational Exposure Limits". Journal of Occupational and Environmental Hygiene. 9 (5): 329–339. doi:10.1080/15459624.2012.672871. PMC 4075771. PMID 22500941.
32. "Preventing Asthma and Death from MDI Exposure During Spray-on Truck Bed Liner and Related Applications" (PDF). www.cdc.gov. Archived (PDF) from the original on 2006-09-21. Retrieved 2018-12-07.
33. Bogaert, Pieter; Tournoy, Kurt G.; Naessens, Thomas; Grooten, Johan (January 2009). "Where Asthma and Hypersensitivity Pneumonitis Meet and Differ". The American Journal of Pathology. 174 (1): 3–13. doi:10.2353/ajpath.2009.071151. ISSN 0002-9440. PMC 2631313. PMID 19074616.
34. Kimber, Ian; Dearman, Rebecca J.; Basketter, David A. (2014-07-25). "Diisocyanates, occupational asthma and IgE antibody: implications for hazard characterization". Journal of Applied Toxicology. 34 (10): 1073–1077. doi:10.1002/jat.3041. ISSN 0260-437X. PMID 25059672. S2CID 29989837.
35. OSHA. "Do You Have Work-Related Asthma? A Guide for YOU and YOUR DOCTOR" (PDF). Retrieved 2018-11-21.
36. Daniels, Robert D. (2018-02-01). "Occupational asthma risk from exposures to toluene diisocyanate: A review and risk assessment". American Journal of Industrial Medicine. 61 (4): 282–292. doi:10.1002/ajim.22815. ISSN 0271-3586. PMC 6092631. PMID 29389014.
37. Bello, Dhimiter; Herrick, Christina A.; Smith, Thomas J.; Woskie, Susan R.; Streicher, Robert P.; Cullen, Mark R.; Liu, Youcheng; Redlich, Carrie A. (2006-11-28). "Skin Exposure to Isocyanates: Reasons for Concern". Environmental Health Perspectives. 115 (3): 328–335. doi:10.1289/ehp.9557. ISSN 0091-6765. PMC 1849909. PMID 17431479.
38. Ceballos, Diana M.; Fent, Kenneth W.; Whittaker, Stephen G.; Gaines, Linda G. T.; Thomasen, Jennifer M.; Flack, Sheila L.; Nylander-French, Leena A.; Yost, Michael G.; Reeb-Whitaker, Carolyn K. (2011-08-10). "Survey of Dermal Protection in Washington State Collision Repair Industry". Journal of Occupational and Environmental Hygiene. 8 (9): 551–560. doi:10.1080/15459624.2011.602623. ISSN 1545-9624. PMID 21830873. S2CID 33905218.
39. Pubchem. "Methyl isocyanate". pubchem.ncbi.nlm.nih.gov. Retrieved 2018-11-21.
40. ISOPA. "Dealing with fires involving MDI and TDI" (PDF). Archived (PDF) from the original on 2015-09-19. Retrieved 2018-11-21.
41. Weiss-Hills, Samantha (2018-05-28). "Is Your Couch Poisoning You?". Architectural Digest. Retrieved 2018-12-08.
42. "Finding a substitute for methyl isocyanate". Chemistry World. Retrieved 2018-11-21.
43. "Final Report | Isocyanate-Free Polyurethane Coatings | Research Project Database | Grantee Research Project | ORD | US EPA". cfpub.epa.gov. Retrieved 2018-12-07.
44. "Isocyanates – Controlling hazardous substances – Managing occupational health risks in construction". www.hse.gov.uk. Retrieved 2018-11-21.
45. Ceballos, Diana; Reeb-Whitaker, Carolyn; Glazer, Patricia; Murphy-Robinson, Helen; Yost, Michael (2014-03-28). "Understanding Factors That Influence Protective Glove Use Among Automotive Spray Painters". Journal of Occupational and Environmental Hygiene. 11 (5): 306–313. doi:10.1080/15459624.2013.862592. ISSN 1545-9624. PMC 5514320. PMID 24215135.
46. "Chemical Resistant Gloves > Painters and Repairers Education Program | Internal Medicine". medicine.yale.edu. Yale School of Medicine. Archived from the original on 2017-11-23. Retrieved 2018-11-21.
47. American Chemistry Council. "Guidance for Selection of Protective Clothing for MDI Users" (PDF). Archived (PDF) from the original on 2013-08-09. Retrieved 2018-11-21.
48. "Safety and Health Topics | Isocyanates – Additional Resources". www.osha.gov. Occupational Safety and Health Administration. Retrieved 2018-11-21.
49. "Sampling and Analytical Methods | Methylene Bisphenyl Isocyanate (MDI) – (Organic Method #047)". www.osha.gov. Occupational Safety and Health Administration. Retrieved 2018-11-22.
50. Tarlo, S. M.; Liss, G. M.; Yeung, K. S. (2002-01-01). "Changes in rates and severity of compensation claims for asthma due to diisocyanates: a possible effect of medical surveillance measures". Occupational and Environmental Medicine. 59 (1): 58–62. doi:10.1136/oem.59.1.58. ISSN 1351-0711. PMC 1740212. PMID 11836470.
51. Hu, Jimmy; Cantrell, Phillip; Nand, Aklesh (2017-07-29). "Comprehensive Biological Monitoring to Assess Isocyanates and Solvents Exposure in the NSW Australia Motor Vehicle Repair Industry". Annals of Work Exposures and Health. 61 (8): 1015–1023. doi:10.1093/annweh/wxx064. ISSN 2398-7308. PMID 29028250. S2CID 2072874.
52. "MEDICAL SURVEILLANCE PROCEDURES MANUAL AND MEDICAL MATRIX (EDITION 11)" (PDF). Navy And Marine Corps Public Health Center. Archived from the original (PDF) on 2016-12-08. Retrieved 2018-11-21.
53. Rose, Dale A.; Murthy, Shivani; Brooks, Jennifer; Bryant, Jeffrey (2017-09-11). "The Evolution of Public Health Emergency Management as a Field of Practice". American Journal of Public Health. 107 (S2): S126 – S133. doi:10.2105/ajph.2017.303947. ISSN 0090-0036. PMC 5594387. PMID 28892444.
54. "CDC – NIOSH Pocket Guide to Chemical Hazards – Hexamethylene diisocyanate". www.cdc.gov. Retrieved 2018-12-08.
55. "1910.1000 TABLE Z-1 Limits for Air Contaminants". www.osha.gov. Occupational Safety and Health Administration. Retrieved 2018-11-24.
56. "Methylene bisphenyl isocyanate". CDC. Retrieved 2018-11-24.
57. Allport, D. C.; Gilbert, D. S.; Outterside, S. M. (2003). MDI and TDI: Safety, Health and the Environment. England: John Wiley & Sons, LTD. p. 346. ISBN 978-0-471-95812-3.
58. Safe Work Australia. "Guide to handling isocyanates" (PDF). Archived (PDF) from the original on 2018-11-25. Retrieved 2018-11-21.
59. HSE (2018). EH40/2005 Workplace exposure limits. United Kingdom: The Stationery Office. p. 17. ISBN 978-0-7176-6703-1.
60. "Toluene-2,4-diisocyanate". CDC. Retrieved 2018-11-24.
61. "Request for assistance in preventing asthma and death from diisocyanate exposure". 1996-03-01. doi:10.26616/NIOSHPUB96111. {{cite journal}}: Cite journal requires |journal= (help)
62. US EPA, OCSPP, OPPT, EETD (2015-06-06). "Spray Polyurethane Foam (SPF) Insulation and How to Use it More Safely". US EPA. Retrieved 2018-11-22.{{cite web}}: CS1 maint: multiple names: authors list (link)
63. "Restriction proposal on diisocyanates and several authorisation applications agreed by RAC and SEAC". echa.europa.eu. ECHA. Retrieved 2018-11-22.
64. Vincentz Network GmbH & Co. KG. "Proposed restriction of diisocyanates". European Coatings. Retrieved 2018-11-22.
65. Sekizawa J., Greenberg M. M. (2000). "Concise International Chemical Assessment Document 27: DIPHENYLMETHANE DIISOCYANATE (MDI)" (PDF). Retrieved 2018-11-18.
66. "TOLUENE DIISOCYANATES" (PDF). IARC. 1987. Archived (PDF) from the original on 2018-11-25. Retrieved 2018-11-18.
67. "4,4′-METHYLENEDIPHENYL DIISOCYANATE AND POLYMERIC 4,4′-METHYLENEDIPHENYL DIISOCYANATE" (PDF). Archived (PDF) from the original on 2018-11-25. Retrieved 2018-11-18.
68. "Welcome to the International Isocyanate Institute". Retrieved 2018-11-18.

External links

• NIOSH Safety and Health Topic: Isocyanates, from the website of the National Institute for Occupational Safety and Health (NIOSH)
• Health and Safety Executive, website of the UK Health and Safety Executive, useful search terms on this site — isocyanates, MVR, asthma
• International Isocyanate Institute | dii International Isocyanate Institute
• Safe Working Procedure for Isocyanate-Containing Products, June 200. Archived 2016-03-09 at the Wayback Machine
• Isocyanates – Measurement Methodology, Exposure and Effects, Swedish National Institute for Working Life Workshop (1999)
• Health and Safety Executive, Guidance Note (EH16) Isocyanates: Toxic Hazards and Precautions (1984)
• The Society of the Plastics Industry – Technical Bulletin AX119 MDI-Based Polyurethane
• Foam Systems: Guidelines for Safe Handling and Disposal (1993)
• An occupational hygiene assessment of the use and control of isocyanates in the UK by Hilary A Cowie et al. HSE Research Report RR311/2005. Prepared by the Institute of Occupational Medicine for the Health and Safety Executive