Worker safety is important to the diisocyanates industry. Occupational health and safety professionals, called industrial hygienists, use chemical sampling and analysis to assess workplace chemical concentrations and the potential for worker exposures. The validity of an assessment is based in part on the procedures used for sample collection and analysis, and on data interpretation. In many instances, industrial hygienists use approaches that have been refined over many years and are accepted by professionals as good practice. However, the multitude of variables within a specific workplace requires the professional to exercise judgment in the design of a particular assessment.
Industrial Hygiene and Workplace Monitoring
Protecting Worker Health through Safe Occupational Exposure Levels
Occupational Exposure Limits (OELs) are intended to set the airborne concentrations of substances to which workers can be exposed, on a daily basis without significant risk of material adverse effects. OELs are normally set for an eight-hour day and are expressed as an eight-hour time-weighted average. In many cases, a short-term (15-minute) exposure limit or Ceiling (not to be exceeded at during any part of the working exposure) value is also established. Occupational exposure limits can be called by different names such as: threshold limit values (TLV); permissible exposure limits (PEL) and short-term exposure limit (STEL) in the United States; maximalearbeitplatzkonzentrationen (MAK) in Germany; and indicative and binding limit values (ILV) in the European Union.
Regulatory authorities in many countries have devised and adopted occupational exposure limits in the air for MDI and TDI. For MDI and TDI in the U.S., these are commonly 20 parts per billion (ppb) (short-term exposure limit) and 5 ppb (for eight-hour time-weighted average value). These OELs have been set by the Occupational Safety and Health Administration (OSHA) or the American Conference of Governmental and Industrial Hygienists (ACGIH). On February 1, 2016, the American Conference of Governmental Industrial Hygienists (ACGIH) lowered its recommended occupational exposure levels, known as TLVs, for Toluene-2,4-diisocyanate and Toluene-2,6-diisocyanate (TDI) from 5 parts per billion (ppb) to 1 ppb and the 15-min STEL from 20 ppb to 5 ppb. Current regulations should always be consulted for compliance purposes.
To learn more about concentration limits for diisocyanates, consult with OSHA, ACGIH (or other country specific regulatory agencies) and the product manufacture. To protect workers, the DII industry uses many tools to monitor worker exposure as outlined below.
Industrial Hygiene and Workplace Monitoring Resources
American Chemistry Council
- Considerations for Modifications to NIOSH 5521 and OSHA 47 Air Sampling Methods for Diphenylmethane Diisocyanate (MDI)
- Considerations for Modifications to OSHA Method 42, Air Monitoring Method: Toluene Diisocyanate (TDI)
- Considerations for Modifications to OSHA Method 47, Air Monitoring Method: Diphenylmethane Diisocyanate (MDI)
- Occupational Hygiene Air Monitoring for MDI and TDI Guidance
OSHA Sampling and Analytical Methods
- Diisocyantes (TDI) (Organic Method #42 - Withdrawn)
- Methylene Bisphenyl Isocyanate (MDI) (Organic Method #47 - Withdrawn)
Wipe Method
- OSHA Technical Manual (OTM) Section II: Chapter 2 (Wipe Sampling Methodology)
ASTM Standards
- ASTM D5932 – 20 Standard Test Method for Determination of 2,4-Toluene Diisocyanate (2,4-TDI) and 2,6-Toluene Diisocyanate (2,6-TDI) in Air (with 9-(N-Methylaminomethyl) Anthracene Method) (MAMA) in the Workplace
- ASTM D5836 - 20 Standard Test Method for Determination of 2,4-Toluene Diisocyanate (2,4-TDI) and 2,6-Toluene Diisocyanate (2,6-TDI) in Workplace Atmospheres (1-2 PP Method)
NIOSH Manual of Analytical Methods
- Isocyanates (including 2,4-TDI, 2-6 TDI and 4,4'-MDI (Method 5522)
- Isocyanates, Monomeric (including 2,4-TDI, 2-6 TDI and 4,4'-MDI (Method 5521)
- Toluene-2,4-diisocyanate (Method 2535)
- International Organization for Standardization (ISO) Workplace air –Guidelines for selecting analytical methods for sampling and analyzing isocyanates in air (available for purchase)