QUANTIFYING ISOCYANATES FROM MEDICAL DEVICES AND PRODUCTS: A PILOT STUDY

Purpose: Isocyanates can cause asthma. This study was conducted to identify and quantify methylene diphenyl diisocyanate (MDI) species in medical devices and products used in the neonatal intensive care setting. Methods: Thirteen medical devices and products were tested. Foams and suspected isocyanate-containing parts of the test items were separated from the rest of the devices. Two small pieces (~0.5 g) from each device or product were sampled and pre-weighed, and then extracted following a standardized protocol. The foam-type materials were placed into a glass syringe and infused with 10 mL of the 2E-4M 1-(9-anthraceny lmethyl)piperazine in toluene solution for one minute and then extracted from the syringe through a filter. The procedure was repeated ten times. A second extraction using a new aliquot of 10 mL solution (same procedure) was performed. The solution was evaporated to dryness, reconstituted to 1 mL in acetonitrile and analyzed for extractable MDI species with 2 injections. Chemical analysis for isomers of MDI (4,4'-, 2,4'-, and 2,2'-), MDI trimer, tetramer and pentamer was accomplished using a hyphenated liquid chromatography/mass spectrometry (LC-UV-MS/MS) analytical method. The limit of detection was 25 pg/mL for 4,4'-MDI, 5 pg/mL for 2,4'-MDI and ~1 ng/mL for trimer. In statistical analysis, quantities (ng) of MDI isomers from 2 injections were averaged. Quantities from two extractions were added together and divided by the sample weight (mg) to derive the concentration for the replicate. Two replicate concentrations were then averaged to calculate the mean for each device or product. Results: Mean (? standard deviation: SD) concentration (ng/mg) of 4,4'-MDI ranged from 0.0005 (? 0.0001) for the forehead pad to 0.1401 (? 0.1972) for a diaper, and 2,4'-MDI ranged from 0.00001 for a diaper, foam-based arm board, neonatal SpO2 adhesive sensor (sensor portion), forehead pad to 0.0045 for neonatal SpO2 adhesive sensor (foam portion). Mean concentrations of both 4,4'- and 2,4'-MDI for other devices and products were in between the ranges. No 2,2'-MDI, and MDI trimer, tetramer and pentamer were detected. Conclusions: 4,4'- and 2,4'-MDI species were detectable in all medical devices and products tested, but concentrations were low. Although MDI species were detectable, it is not clear whether low levels identified will be absorbed through the skin and have a potential clinical or long-term adverse effect. Further studies are needed to evaluate these implications.