This article summarizes a large body of industry air sampling data (8134 samples) in which airborne MDI concentrations were measured in a wide variety of manufacturing processes that use either polymeric MDI (PMDI) or monomeric (pure) MDI. Data were collected during the period 1984 through 1999. A total of 606 surveys were conducted for 251 companies at 317 facilities. The database includes 3583 personal (breathing zone) samples and 4551 area samples. Data demonstrate that workplace airborne MDI concentrations are extremely low in a majority of the manufacturing operations. Most (74.6%) of the airborne MDI concentrations measured in the personal samples were nondetectable, i.e., below the limits of quantification (LOQs). A variety of validated industrial hygiene sampling/analytical methods were used for data collection; most are modifications of OSHA Method 47. The LOQs for these methods ranged from 0.1-0.5 microg/sample. The very low vapor pressures of both monomeric MDI and PMDI largely explain the low airborne concentrations found in most operations. However, processes or applications in which the chemical is sprayed or heated may result in higher airborne concentrations and higher exposure potentials if appropriate control measures are not implemented. Data presented in this article will be a useful reference for employers in helping them to manage their health and safety program as it relates to respiratory protection during MDI/PMDI applications.

This study provides support for the current American Conference of Governmental Industrial Hygienists threshold limit value time-weighted average of 5 ppb.

No abstract

A majority of all the flexible polyurethane foams are produced by the continuous slabstock process using toluene diisocyanate (TDI) and polyether polyol. The commercially available TDI product is predominantly an 80:20 mixture of the 2,4-TDI and 2,6-TDI isomers. TDI can be used in many applications, but the market is dominated by the flexible slabstock foam industry. Even though there has been a considerable amount of industrial hygiene sampling conducted for airborne TDI in this industry, the focus of the sampling has generally included long-term (time-weighted average) monitoring with a limited amount of sampling for short-term (peak) episodes. By conducting only long-term sampling, which averages the exposure over some extended time period, these short-term episodes (i.e., tasks or activities) of peak exposure were often not characterized. To investigate whether long-term sampling was adequately predictive of short-term excursions, simultaneous (side-by-side) short-term and long-term breathing zone samples were collected on 31 flexible slabstock foam line employees at six manufacturing facilities throughout the United States. Four hundred three short-term samples averaging 15 minutes in length, and 78 long-term samples averaging 124 minutes in length were collected for four operator categories. From these 78 long-term samples, 31 eight-hour TWAs were projected (assuming no further exposure to airborne TDI for the remainder of the work shift) for comparison to the short-term samples. Based on the data collected, compliance with the current ACGIH TLV TWA of 5 ppb would also ensure compliance with the OSHA PEL-C of 20 ppb in a majority of the cases associated with the flexible slabstock foam industry provided that (1) the TLV TWA accounted for the 2,6-TDI isomer in addition to the 2,4-TDI isomer (at this time, exposure limits are published for only the 2,4-TDI isomer), and (2) the TLV TWA was compared to the partial shift TWA measured over the operational time of the workday rather than as an average over an eight-hour workday. Further, exceedences of the 20 ppb PEL-C did occur (e.g., when the foam line tunnel was entered, where there was an "upset" condition, or where there was close contact with hot [fresh cut] buns), but can be protected against with (1) improved work practices, (2) engineering controls, and (3) respiratory protection.

Consistent with a previous study, no cases of occupational asthma were identified from exposure to 1,6-hexamethylene diisocyanate, isophorone diisocyanate, methylene bis(4-cyclohexyl isocyanate), or their polyisocyanates even though many employees reported detection of odors (93%) or skin exposures (53%).