Methylene diphenyl diisocyanate occupational exposure data in industry (1998-2020): A descriptive summary from an industrial hygiene perspective.

This paper provides an overview of airborne methylene diphenyl diisocyanate (MDI) concentrations in workplaces across North America and Europe. A total of 7649 samples were collected between 1998 and 2020 by producers of MDI during product stewardship activities at customer sites, primarily using validated OSHA or ISO sampling and analysis techniques. As would be expected from the low vapor pressure of MDI, 80% of the concentrations were less than 0.01 mg/m3 (1 ppb) and 93% were less than 0.05 mg/m3 (5 ppb). Respiratory protection is an integral part of Industrial Hygiene practices; therefore, its use was studied and summarized. While covering a variety of MDI applications, a large number of samples was obtained from composite wood manufacturing facilities, offering specific insight into potential exposures associated with different process sections and job types in this industry sector. Given the potential presence in industrial processes of MDI-containing dust or aerosols, future work should place increased emphasis on also investigating dermal exposure. The data reported in this paper provide valuable information for product stewardship and industrial hygiene purposes throughout the MDI-processing industry.

Comprehensive methylene diphenyl diisocyanate (MDI) evaluation method comparison using a laboratory generation system.

Isocyanates are reactive semivolatile contaminants that must be assessed in occupational environments, and specific evaluation methods are required to address the challenges related to isocyanate emission characteristics. Several standard methods exist, but significant differences remain regarding the diversity of industrial isocyanate emissions. This study presents a method to establish a baseline comparison of three sampling principles. A fine aerosol (mass median aerodynamic diameter of 250 nm) of pure methylene diphenyl diisocyanate (MDI) was produced (5-60 µg m-3) using a laboratory generation system (n = 31 generation experiments). Airborne MDI was measured with the following four methods, with an emphasis on the spatial distribution of the collected MDI within the sampler: (1) Swinnex cassette 13 mm, glass fibre filter (GFF), 9-(N-methylaminomethyl) anthracene (MAMA-Swin); (2) closed-face cassette (CFC) 37 mm, GFF (end filter and inner walls), MAMA-37; (3) impinger and backup GGF, 1,2-methoxyphenylpiperazine (MP) (ISO 16702/MDHS 25); and (4) denuder and GFF (Asset EZ4-NCO), dibutylamine (DBA) (ISO 17334-1). Bland and Altman analyses determined that there were no significant bias between the methods although Asset was not in agreement with MAMA-Swin (95% confidence interval above the ±20% criteria). Significant correlations (P < 0.05) were observed between airborne MDI concentration levels and their distribution within the Asset (denuder vs. end filter) and impinger (collecting solution vs. backup filter) subsections. The presence of impregnated inner walls in the CFC did not increase collection efficiency for the generated MDI aerosol. Non-uniform MAMA impregnation on GFF was demonstrated, whereas the collected MDI was evenly distributed in the air samples. These results provided the basis of comparison for other studies involving more complex isocyanate emissions.

A physiologically-based kinetic (PBK) model for work-related diisocyanate exposure: Relevance for the design and reporting of biomonitoring studies.

Diisocyanates are highly reactive substances and known causes of occupational asthma. Exposure occurs mainly in the occupational setting and can be assessed through biomonitoring which accounts for inhalation and dermal exposure and potential effects of protective equipment. However the interpretation of biomonitoring data can be challenging for chemicals with complex kinetic behavior and multiple exposure routes, as is the case for diisocyanates. To better understand the relation between external exposure and urinary concentrations of metabolites of diisocyanates, we developed a physiologically based kinetic (PBK) model for methylene bisphenyl isocyanate (MDI) and toluene di-isocyanate (TDI). The PBK model covers both inhalation and dermal exposure, and can be used to estimate biomarker levels after either single or chronic exposures. Key parameters such as absorption and elimination rates of diisocyanates were based on results from human controlled exposure studies. A global sensitivity analysis was performed on model predictions after assigning distributions reflecting a mixture of parameter uncertainty and population variability. Although model-based predictions of urinary concentrations of the degradation products of MDI and TDI for longer-term exposure scenarios compared relatively well to empirical results for a limited set of biomonitoring studies in the peer-reviewed literature, validation of model predictions was difficult because of the many uncertainties regarding the precise exposure scenarios that were used. Sensitivity analyses indicated that parameters with a relatively large impact on model estimates included the fraction of diisocyanates absorbed and the binding rate of diisocyanates to albumin relative to other macro molecules.We additionally investigated the effects of timing of exposure and intermittent urination, and found that both had a considerable impact on estimated urinary biomarker levels. This suggests that these factors should be taken into account when interpreting biomonitoring data and included in the standard reporting of isocyanate biomonitoring studies.

Total Reactive Isocyanate Group (TRIG) Measurement: A Commentary.

Exposure to airborne isocyanates has, for decades, been a leading cause of occupational asthma. As respiratory sensitizers, isocyanates can induce allergic respiratory diseases with symptoms persisting even without further exposure. As this cause of occupational asthma is recognized it should be almost entirely preventable. In several countries isocyanates are assigned occupational exposure limits based on the total of reactive isocyanate groups (TRIG). The measurement of TRIG has some significant advantages over the measurement of individual isocyanate compounds. This exposure metric is explicit, simplifying calculations, and comparisons across published data. It reduces the risk of underestimating exposure by 'missing' important isocyanate compounds that may be present but are not the target analytes. It allows for quantification of exposure to complex mixtures of isocyanates, di-isocyanates monomers, prepolymers, polyisocyanates, oligomers, and/or intermediate forms. This is becoming increasingly important as more complex isocyanate products are being used in the workplace. There are many methods and techniques for measuring air concentrations/potential exposure to isocyanates. Several established methods have been standardized and published as International Organization for Standardization (ISO) methods. While some may be applied directly for determination of TRIG, others (developed for determination of individual isocyanates), require modification. This commentary aims to highlight the relative merits and limitations of those methods capable of determining TRIG and also considers potential future developments.

HBM4EU Diisocyanates Study-Research Protocol for a Collaborative European Human Biological Monitoring Study on Occupational Exposure.

Diisocyanates have long been a leading cause of occupational asthma in Europe, and recently, they have been subjected to a restriction under the REACH regulations. As part of the European Human Biomonitoring project (HBM4EU), we present a study protocol designed to assess occupational exposure to diisocyanates in five European countries. The objectives of the study are to assess exposure in a number of sectors that have not been widely reported on in the past (for example, the manufacturing of large vehicles, such as in aerospace; the construction sector, where there are potentially several sources of exposure (e.g., sprayed insulation, floor screeds); the use of MDI-based glues, and the manufacture of spray adhesives or coatings) to test the usability of different biomarkers in the assessment of exposure to diisocyanates and to provide background data for regulatory purposes. The study will collect urine samples (analysed for diisocyanate-derived diamines and acetyl-MDI-lysine), blood samples (analysed for diisocyanate-specific IgE and IgG antibodies, inflammatory markers, and diisocyanate-specific Hb adducts for MDI), and buccal cells (micronucleus analysis) and measure fractional exhaled nitric oxide. In addition, occupational hygiene measurements (air monitoring and skin wipe samples) and questionnaire data will be collected. The protocol is harmonised across the participating countries to enable pooling of data, leading to better and more robust insights and recommendations.

Development of a new SPE UPLC-MS/MS method for extraction and quantitation of toluene diamine on gloves following toluene diisocyanate exposure.

RATIONALE: Toluene diisocyanate (TDI) is a highly reactive isocyanate commonly used as a mixture of 2,4- and 2,6- isomers in the production of flexible foams. Exposure to TDI occurs primarily through vapour inhalation in workplaces where TDI is produced or used, but dermal exposure is also possible during some tasks. To ensure workplace safety, accurate monitoring of TDI and toluene diamine (TDA) levels is required. Methods of quantifying field effectiveness of gloves in preventing dermal exposure have not been established. Therefore, there is a need to develop a new practical method for assessing glove effectiveness for TDI/TDA. METHOD: A new offline SPE UPLC-MS/MS method for the quantitation of TDA isomers from TDI-exposed gloves was developed. Gloves were dipped in a solution of 1% acetic acid leading to a full conversion to TDA. TDA-free amine compounds were derivatized with acetic anhydride to increase chromatographic retention and signal intensity. RESULTS: 2,4-Diaminotoluene-α, α, α-d3 (2,4-d3 -TDA) was selected as a surrogate standard to minimise the variability in sample preparation and instrumental sensitivity. The choice of UPLC-MS/MS operated in multiple reaction monitoring (MRM) mode allowed to reach much lower limits of detection (LOD). The LOD of the method was 6.86 and 2.83 ng/mL (0.03 and 0.01 µg) for 2,6-TDA and 2,4-TDA, respectively. The limit of quantitation (LOQ) was 22.85 and 9.42 ng/mL (0.11 and 0.05 µg) for 2,6-TDA and 2,4-TDA, respectively. CONCLUSION: A new UPLC-MS/MS analytical method has been developed to determine field effectiveness of gloves for preventing dermal exposure to TDI/TDA. The new technique overcomes some limitations for measuring putative dermal exposure to isocyanates and may be useful in exposure monitoring and future research on isocyanate health risks.

Health effects of exposure to isocyanates in a car factory.

OBJECTIVES: Isocyanates are known to induce occupational diseases. The aim of this work was to assess the health effects of exposure to isocyanates and to test the sensitivity of selected parameters for early detection of isocyanate-related allergic diseases. METHODS: In total, 35 employees from one factory were tested: 26 workers exposed to isocyanates (exposed group) and nine office workers (control group). All subjects filled in a questionnaire regarding possible health problems. Fractional exhaled nitric oxide (FeNO) and spirometry were measured for each subject at the same time during two consecutive working days. A urine sample was taken for a biological exposure test (BET). RESULTS: No significant difference was found between the exposed and control groups for spirometry parameters and FeNO. However, in the exposed group, FeNO was highly elevated (> 50 ppb) in five subjects (all reporting health problems at the workplace, all with normal spirometry and non-smokers). The BET revealed a significant difference (p < 0.001) between the exposed and control groups for 4,4´-methylenediphenyl diamine (MDA) in the urine. CONCLUSIONS: Our examination showed the usefulness of the BET in monitoring of workplace exposure to isocyanates and the importance of FeNO in monitoring of allergic inflammation of airways in non-smoking employees with normal spirometry.

Development and characterization of an adaptable aerosolized methylene diphenyl diisocyanate generation system.

Reactive semivolatile contaminants, such as isocyanates, can be particularly difficult to assess in occupational environments. While standard methods exist for isocyanates, there are still significant differences between the results they provide for various occupational environments or processes. This study presents the validation of a laboratory system for the generation of controlled atmospheres of isocyanates. A system consisting of different modules generated airborne methylene diphenyl diisocyanate (MDI) by nebulizing a solution into mixing and exposure chambers with control of flow rate, temperature, and relative humidity. Sampling was performed through an eight-port flow splitter that allowed only very slight within-test variability. MDI was measured using the Asset EZ4-NCO® and a modified version of the Iso-Chek® sampling system. MDI specific particle-size distribution was measured by a Marple Sierra cascade. Aerosol real-time monitoring was performed using a condensation particle counter, an electrical low-pressure impactor (ELPI+), and an aerosol optical spectrometer, providing additional information on system stability and particle-size distribution of the generated aerosol. The system was able to generate MDI concentration levels ranging from 4 to 233 µg m-3, with a steady-state level reached within 5 minutes, and with well-documented intra-test and inter-test variability (RSD of 4% and 15%, respectively). Accuracy and representativeness of MDI data were confirmed by the agreement between MAMA and Asset EZ4-NCO (used as reference), with a mean bias of 3%. Using the Asset EZ4-NCO capability, the vapor-particle partitioning of MDI was evaluated to be 8% and 92%, respectively, at a concentration ranging from 20 to 25 µg m-3. The system may therefore be used for exhaustive method intercomparison studies and could also be adapted to generate other emission types of semivolatile compounds.

On-site comparison of the OSHA 47, Asset EZ4-NCO, Iso-Chek, DAN, and CIP10 methods for measuring methylene diphenyl diisocyanate (MDI) at an oriented-strand board (OSB) factory.

Diisocyanates are occupational contaminants and known sensitizers causing irritation (skin and respiratory tract) as well as occupational asthma. Because of their physicochemical properties (semi-volatile and high reactivity) and low occupational limits, diisocyanate exposure evaluation is still a challenge nowadays for industrial hygienists and laboratories. The objective of this study was to compare the methylene diphenyl diisocyanate (MDI) concentrations measured by five methods using different collection or derivatization approaches in an oriented-strand board (OSB) factory. The methods used were: OSHA 47 (filter, 1-(2-pyridyl)piperazine) (OSHA), Asset EZ4-NCO (denuder and filter, dibutylamine) (Asset), Iso-Chek (double-filter, 9-(N-methylaminomethyl) anthracene and 1,2-methoxyphenylpiperazine), DAN (filter, 1,8-diaminonaphthalene), and CIP10 (centrifugation, 1,2-methoxyphenylpiperazine). Real-time monitoring of particle concentration and size distribution was performed to explain the potential bias between methods. The comparison study was performed over 3 consecutive days, generating at least 18 replicates for each of the 5 methods. The results of each methods were compared using linear mixed effect modeling. Compared to Asset, which yielded the highest concentrations overall, the OSHA method provided the smallest bias with -18% (95% CI [-61;24]) (not significant) for MDI monomer and the DAN method provided the smallest bias with -30 (95% CI [-70;9]) (not significant) for Total Reactive Isocyanate Group (TRIG). The CIP10 and Iso-Chek methods provided the largest biases for MDI monomer (-83% (95% CI [-115;-51]) and -78% (95% CI [-110;-46]), respectively) as well as for TRIG (-87% (95% CI [-120;-55]) and -75% (95% CI [-107;-44]), respectively). The underestimations of the CIP10 and Iso-Chek were explained by its inefficient sampling principle for fines particles and the use of a non-impregnated filter to collect aerosol MDI, respectively. This study confirms that impregnated filter, including denuding device such as the Asset EZ4-NCO sampler, collects the MDI-coated wood particles and MDI vapor with similar efficiency. It also demonstrates for the first time in this type of MDI emission a significant agreement for TRIG concentration between the DAN method in the impregnated filter configuration and an international standard one such as Asset.

Exposures and urinary biomonitoring of aliphatic isocyanates in construction metal structure coating.

BACKGROUND: Isocyanates are highly reactive chemicals used widely in metal structure coating applications in construction. Isocyanates are potent respiratory and skin sensitizers and a leading cause of occupational asthma. At present, there is no cure for isocyanate asthma and no biomarkers of early disease. Exposure reduction is considered the most effective preventive strategy. To date, limited data are available on isocyanate exposures and work practices in construction trades using isocyanates, including metal structure coatings. OBJECTIVES: The primary objectives of this work were: i) to characterize isocyanate inhalation and dermal exposures among painters during metal structure coating tasks in construction; and ii) to assess the adequacy of existing work practices and exposure controls via urinary biomonitoring pre- and post-shift. METHODS: Exposures to aliphatic isocyanates based on 1,6-hexamethylene diisocyanate (1,6-HDI) and its higher oligomers (biuret, isocyanurate and uretdione) were measured among 30 workers performing painting of bridges and other metal structures in several construction sites in the Northeastern USA. Exposure assessment included simultaneous measurement of personal inhalation exposures (n = 20), dermal exposures (n = 22) and body burden via urinary biomonitoring pre- and post-shift (n = 53). Contextual information was collected about tasks, processes, materials, work practices, personal protective equipment (PPEs) and exposure controls, work histories, and environmental conditions. RESULTS: Breathing zone concentrations were the highest for biuret (median, 18.4 µg/m3), followed by 1,6-HDI monomer (median, 3.5 µg/m3), isocyanurate (median, 3.4 µg/m3) and uretdione (median, 1.7 µg/m3). The highest exposures, measured during painting inside an enclosed bridge on a hot summer day, were: 10,288 µg/m3 uretdione; 8,240 µg/m3 biuret; and 947 µg/m3 1,6-HDI. Twenty percent of samples were above the NIOSH ceiling exposure limit for 1,6- HDI (140 µg/m3) and 35% of samples were above the UK-HSE ceiling for total isocyanate group (70 µg NCO/m3). Isocyanate loading on the gloves was generally high, with a median of 129 µg biuret/pair and maximum of 60.8 mg biuret/pair. The most frequently used PPEs in the workplace were half-face organic vapor cartridge (OVC) respirators, disposable palmar dip-coated polymer gloves, and cotton coveralls. However, 32% of workers didn't wear any respirator, 47% wore standard clothing with short-sleeve shirts and 14% didn't wear any gloves while performing tasks involving isocyanates. Based on biomonitoring results, 58.4% of urine samples exceeded the biological monitoring guidance value (BMGV) of 1 µmol hexamethylene diamine (HDA)/mol creatinine. Post-shift geometric mean HDA normalized to specific gravity increased by 2.5-fold compared to pre-shift (GM, 4.7 vs. 1.9 ng/mL; p value, < 0.001), and only 1.4-fold when normalized to creatinine. CONCLUSIONS: Exposure and biomonitoring results, coupled with field observations, support the overall conclusions that (i) substantial inhalation and dermal exposures to aliphatic isocyanates occur during industrial coating applications in construction trades; that (ii) the current work practices and exposure controls are not adequately protective. High urinary creatinine values in the majority of workers, coupled with significant cross-shift increases and filed observations, point to the need for further investigations on possible combined effects of heat stress, dehydration, and nutritional deficiencies on kidney toxicity. Implementation of comprehensive exposure control programs and increased awareness are warranted in order to reduce isocyanate exposures and associated health risks among this cohort of construction workers.

[Determination of diphenylmethane diisocyanate in workplace air by HPLC with impregnated filter membrane].

Objective: To develop a method for determining diphenylmethane diisocyanate in workplace air by HPLC with impregnated filter membrane. Methods: MDI in workplace air reacted with 1- (2-pyridyl) piperazine on impregnated filter membrane to form MDI-urea derivatives, after elution and filtration, it was detected by HPLC-UV. Results: Limit of detection was 0.003 8 µg/ml and limit of quantification was 0.013 µg/ml. Good linearity was obtained in the range of 0.013~2.000 µg/ml (r=0.999 7) . The precision was 3.10%~8.03% (n=6) , while the recovery was 96.3%~101.9%. Asorption capacity of the membrane was 40.8 µg MDI, and could be stored for 14 days in the light-proof environment of 2~8 ℃. Conclusion: The method optimized testing steps for MDI's standard curve, and provided good guidance for determination of MDI in workplace air with impregnated fiter membrane.

Characterization of Aerosol Release during Spraying of Isocyanate Products.

The aerosol release during the professional application of two different isocyanate based two component spray systems was identified and the physicochemical properties of the released airborne aerosols were characterized. For this purpose, aerosol release fractions were measured using a mass balance method described by Schwarz and Koch. Besides the release of total aerosol mass special emphasis was directed to the content of free monomeric MDI (4,4'- and 2,4'-diphenylmethane diisocyanate) in three particle size fractions relevant for inhalation uptake: inhalable, thoracic, and respirable size fraction. Two products were investigated: a two component PUR (polyurethane) spray foam (Elastopor) and a polyurea spray coating (Elastocoat). The mass fraction of the applied products released with the overspray as inhalable aerosol is 6.3 × 10-4 (Elastopor) and 4.0 × 10-4 (Elastocoat). Of the released total overspray aerosol 75 or 80% were in the thoracic size range, and 26 or 47% in the respirable regime for the PUR spray foam or the polyurea spray coating, respectively. At the time point of release the content of monomeric MDI in the aerosol corresponds to the composition of the bulk product. However, analysis of air samples indicates that <1% of the spray foam aerosol mass release fraction is attributed to free monomeric 4,4'- and 2,4'-MDI. For the Spray Coating the monomeric MDI fraction is <0.1%. Higher oligomers of MDI and prereacted oligomeric reaction products make up a few percent of the aerosol. This results in a total fraction of 0.0023% (spray foam) and 0.00015% (spray coating), respectively, of the sprayed monomeric MDI that is transferred into an inhalable aged aerosol. This data demonstrates, that during professional spraying only a small fraction of the total applied mass is released as airborne aerosol. The potential distribution of the theoretically inhalable aerosol in the respiratory tract and a low residual monomer content is described, significantly contributing to a refined safety assessment of the spray applications at the workplaces.

Evaluation of Disposable Protective Garments against Isocyanate Permeation and Penetration from Polyurethane Anticorrosion Coatings.

BACKGROUND: Polyurethanes are a class of isocyanate-based organic coatings commonly used to control corrosion on high-value metallic structures. Despite their widespread use, dermal exposure to these isocyanate-containing coatings presents a significant occupational health risk to workers, including the development of allergic and irritant contact dermatitis and systemic sensitization. At present, little is known about the effectiveness of the protective garments commonly used to prevent dermal exposure to polyurethane coatings in construction trades. OBJECTIVES: The primary objective of this study was to measure the permeation and penetration of isocyanates from polyurethane anticorrosion coatings though a selection of protective garments. In addition, a standardized spray procedure using a fixed-position spraying technique was evaluated as an option to minimize variability in coating application. METHODS: Five disposable garment materials were evaluated for resistance to isocyanates during this study: latex gloves (0.076 mm), nitrile gloves (0.078 mm), Tyvek coveralls (0.105 mm), polypropylene/polyethylene (PP/PE) coveralls (0.116 mm), and a cotton t-shirt (0.382 mm). A permeation test cell system was used to evaluate each garment material against two products: a polyurethane zinc-rich primer based on 4,4'-methylene diphenyl diisocyanate and an aliphatic finish coating based on prepolymers of 1,6-hexamethylene diisocyanate. Glass fiber filters pretreated with 1-(9-anthracenylmethyl)piperazine were used to collect penetrating isocyanates during the 120-min test period, which were analyzed by liquid chromatography-tandem mass spectrometry. Polytetrafluoroethylene loading filters were sprayed in series with permeation test cells and analyzed gravimetrically to assess the homogeneity of coating application. RESULTS: The latex gloves demonstrated the highest rate of isocyanate permeation of all evaluated garments during testing with both coatings (primer: 27.38 ng cm-2 min-1; finish coating: 7.39 ng cm-2 min-1). Nitrile gloves were much more resistant than latex gloves (primer: 1.89 ng cm-2 min-1; finish coating: 1.26 ng cm-2 min-1) and were not permeated by the finish coating until after 15 min. The PP/PE coverall provided the most consistent resistance to both coatings (primer: 0.08 ng cm-2 min-1; finish coating: 1.27 ng cm-2 min-1), whereas the Tyvek coverall was readily permeated by the primer (primer: 3.47 ng cm-2 min-1; finish coating: 0.87 ng cm-2 min-1). The cotton t-shirt was rapidly permeated by the primer during the first 5 min of exposure (primer: 146.65 ng cm-2 min-1; finish coating: 4.64 ng cm-2 min-1). In addition, the fixed-position spraying technique used during this study demonstrated a significant reduction in loading variability within each batch of test cells when compared to manual spray application. CONCLUSION: Nitrile gloves demonstrated superior resistance to both isocyanate-containing coatings in comparison to latex gloves. Although both coverall materials were resistant to permeating isocyanate within the established thresholds, the PP/PE coverall provided more consistent resistance to both coatings. Owing to the cotton t-shirt's high rate of penetration with both coatings, it is recommended only as a secondary barrier. Study results showed that the use of fixed-position spray techniques provided consistent and reproducible results within each batch of test cells. Additional test design modifications are necessary to further reduce variability between batches and ensure more consistent coating thickness.

Assessment and control of exposures to polymeric methylene diphenyl diisocyanate (pMDI) in spray polyurethane foam applicators.

In this work we characterize personal inhalation and dermal exposures to diphenyl methane diisocyanate (MDI) and other species in polymeric MDI (pMDI) formulations during spray polyurethane foam (SPF) insulation at 14 sites in New England. We further assess the adequacy of current workplace practices and exposure controls via comparative urinary biomonitoring of the corresponding methylene diphenyl diamine (MDA) pre- and post-shift. MDI and pMDI are potent dermal and respiratory sensitizers and asthmagens, strong irritants of the skin, eyes, and the respiratory tract, and may cause skin burns. This study is the first comprehensive report to-date on the work practices, inhalation and dermal exposures to isocyanates and effectiveness of existing controls during SPF applications. Breathing zone exposures to 4,4' MDI (n = 31; 24 sprayers, 7 helpers) ranged from 0.9 to 123.0 µg/m3 and had a geometric mean (GM) of 13.8 µg/m3 and geometric standard deviation (GSD) of 4.8. Stationary near field area samples (n = 15) were higher than personal exposures: GM, 40.9 (GSD, 3.9) µg/m3, range 1.4-240.8 µg/m3. Sixteen percent of personal air samples and 35% of area samples exceeded the National Institute for Occupational Health and Safety's (NIOSH) full shift recommended exposure limit (REL) of 50 µg/m3, assuming zero exposure for the unsampled time. 4,4' MDI load on the glove dosimeters had a GM of 11.4 (GSD 2.9) µg/glove pair/min, suggesting high potential for dermal exposures. Urinary MDA had a GM of 0.7 (GSD, 3.0) µmol MDA/mol creatinine (range, nd-14.5 µmol MDA/mol creatinine). Twenty-five % of urine samples exceeded the Health and Safety Executive (HSE) biological monitoring guidance value (BMGV) of 1 µmol MDA/mol creatinine. We further report on field observations regarding current exposure controls, discuss implications of these findings and opportunities for improving work practices to prevent isocyanate exposures during SPF insulation.

Isocyanates and hydrogen cyanide in fumes from heated proteins and protein-rich foods.

Toxic compounds in cooking fumes could cause respiratory problems. In the present study, the formation of isocyanic acid (ICA), methyl isocyanate (MIC), and hydrogen cyanide (HCN) was studied during the heating of proteins or frying of protein-rich foods. Heating was performed in an experimental setup using a tube oven set at 200-500°C and in a kitchen when foods with different protein content were fried at a temperature around 300°C. ICA, MIC, and HCN were all generated when protein or meat was heated. Individual amino acids were also heated, and there was a significant positive correlation between their respective nitrogen content and the formation of the measured compounds. Gas from heated protein or meat also caused carbamylation in albumin. ICA, MIC, and HCN were also present in fumes generated when meat, egg, and halloumi were fried in a kitchen pan. The levels of ICA were here twice that of the Swedish occupational exposure limit. If ICA, MIC, and HCN in fumes from heated protein-rich foods could contribute to the risk of airway dysfunction among those exposed is not clear, but it is important to avoid inhaling frying and grilling fumes and to equip kitchens with good exhaust ventilation.

Wasabia koreana Nakai: A Preliminary Study on Nutrients and Chemical Compounds That May Impact Sensory Properties.

In this study, the nutritional, functional, and chemical measurements of sensory attributes of different parts of wasabi, namely, leaf, petiole, and rhizome, were investigated. Proximate composition analysis showed the presence of high amounts of carbohydrates in the rhizome and amino acid composition analysis confirmed high proportions of glutamic acid and aspartic acid in all three parts. While proximate composition showed low lipid content in wasabi, ω-3 fatty acids accounted for a high proportion (>44%) of the total lipids. Wasabi leaves had high vitamin C and total phenolic contents, and thus demonstrated antioxidant capacity. Allyl isothiocyanate, which gives wasabi its characteristic pungent taste, was identified by gas chromatography/mass spectrometry and an electronic nose. On an electronic tongue, wasabi leaves showed compounds associated with sourness and saltiness while the petiole had high content of compounds associated with sweetness and bitterness. This study provides basic data for the utilization of wasabi parts as food materials based on their nutritional, functional, and chemical measure of sensory attributes.

Stability of Isocyanates Sampled in Fire Smokes.

Inhalation of airborne isocyanates is associated with acute asthma attacks and inflammation in the respiratory tract as well as cancer. These highly reactive compounds are used as monomers in various applications such as foams for insulation materials and upholstery furniture and are therefore commonly found in fire smoke from insulation materials, such as rigid polyisocyanurate (PIR) foams. Consequently, there is an increasing concern regarding the potential adverse health effects they may cause during this type of exposure.The aim of this study was to investigate the stability of generated isocyanates from aerobic pyrolysis of PIR after sampling in the derivatization solution as well as after sample preparation to establish the optimal storage conditions and rate of degradation. Both airborne and particle-bound isocyanates were collected, using dibutylamine as derivatization agent in a midget impinger and impregnated filter after the impinger. The rapid degradation of the generated isocyanates after sampling emphasizes the need for a prompt sample preparation and analysis, in particular for the collected mono-isocyanates, as the concentration decreased by 50% within 4-8 h.

Analysis of isocyanates in indoor dust.

Isocyanates are harmful semi-volatile organic compounds that are emitted from various consumer products like polyurethane foam-based mattresses. Although it is a concern that isocyanates might accumulate in indoor dust, causing infants and toddlers, in particular, to be exposed to them, little information is available on the levels of isocyanates in the indoor environment. In this study, we investigated the suitability of an analytical method for determining the presence and level of isocyanates in the indoor dust. The method we developed displayed acceptable linearity, accuracy, and precision in the analysis of eleven different isocyanates. By using this analytical method, we could detect five isocyanates (ICA, MIC, EIC, PIC, and PHI) and quantify three isocyanates (MIC, EIC, and PHI) in indoor dust collected in different houses. This study is the first to focus on the pollution of indoor dust by isocyanates, and the tested method is suitable for the estimation of the level of isocyanate exposure. Graphical abstract ᅟ.

Testing of Disposable Protective Garments Against Isocyanate Permeation From Spray Polyurethane Foam Insulation.

Background: Diisocyanates (isocyanates), including methylene diphenyl diisocyanate (MDI), are the primary reactive components of spray polyurethane foam (SPF) insulation. They are potent immune sensitizers and a leading cause of occupational asthma. Skin exposure to isocyanates may lead to both irritant and allergic contact dermatitis and possibly contribute to systemic sensitization. More than sufficient evidence exists to justify the use of protective garments to minimize skin contact with aerosolized and raw isocyanate containing materials during SPF applications. Studies evaluating the permeation of protective garments following exposure to SPF insulation do not currently exist. Objectives: To conduct permeation testing under controlled conditions to assess the effectiveness of common protective gloves and coveralls during SPF applications using realistic SPF product formulations. Methods: Five common disposable garment materials [disposable latex gloves (0.07 mm thickness), nitrile gloves (0.07 mm), vinyl gloves (0.07 mm), polypropylene coveralls (0.13 mm) and Tyvek coveralls (0.13 mm)] were selected for testing. These materials were cut into small pieces and assembled into a permeation test cell system and coated with a two-part slow-rise spray polyurethane foam insulation. Glass fiber filters (GFF) pretreated with 1-(9-anthracenylmethyl)piperazine) (MAP) were used underneath the garment to collect permeating isocyanates. GFF filters were collected at predetermined test intervals between 0.75 and 20.00 min and subsequently analyzed using liquid chromatography-tandem mass spectrometry. For each garment material, we assessed (i) the cumulative concentration of total isocyanate, including phenyl isocyanate and three MDI isomers, that effectively permeated the material over the test time; (ii) estimated breakthrough detection time, average permeation rate, and standardized breakthrough time; from which (iii) recommendations were developed for the use of similar protective garments following contamination by two-component spray polyurethane foam systems and the limitations of such protective garments were identified. Results: Each type of protective garment material demonstrated an average permeation rate well below the ASTM method F-739 standardized breakthrough rate threshold of 100.0 ng/cm2 min-1. Disposable latex gloves displayed the greatest total isocyanate permeation rate (4.11 ng/cm2 min-1), followed by the vinyl and nitrile gloves, respectively. The Tyvek coverall demonstrated a greater average rate of isocyanate permeation than the polypropylene coveralls. Typical isocyanate loading was in the range of 900 to 15,000 ng MDI/cm2. Conclusion: Permeation test data collected during this study indicated that each type of protective garment evaluated, provided a considerable level of protection (i.e. 10-110-fold reduction from the level of direct exposure) against the isocyanate component of the SPF insulation mixture. Nitrile gloves and polypropylene coveralls demonstrated the lowest rate of permeation and the lowest cumulative permeation of total isocyanate for each garment type.

An indoor air quality evaluation in a residential retrofit project using spray polyurethane foam.

Understanding of indoor air quality (IAQ) during and after spray polyurethane foam (SPF) application is essential to protect the health of both workers and building occupants. Previous efforts such as field monitoring, micro-chamber/spray booth emission studies, and fate/transport modeling have been conducted to understand the chemical exposure of SPF and guide risk mitigation strategies. However, each type of research has its limitation and can only reveal partial information on the relationship between SPF and IAQ. A comprehensive study is truly needed to integrate the experimental design and analytical testing methods in the field/chamber studies with the mathematical tools employed in the modeling studies. This study aims to bridge this gap and provide a more comprehensive understanding on the impact of SPF to IAQ. The field sampling plan of this research aims to evaluate the airborne concentrations of methylene diphenyl diisocyanate (MDI), formaldehyde, acetaldehyde, propionaldehyde, tris(1-chlor-2-propyl)phosphate (TCPP), trans-1-chloro-3,3,3-trifluoropropene (SolsticeTM), and airborne particles. Modifications to existing MDI sampling and analytical methods were made so that level of quantification was improved. In addition, key fate and transport modeling input parameters such as air changes per hour and airborne particle size distribution were measured. More importantly, TCPP accumulation onto materials was evaluated, which is important to study the fate and transport of semi-volatile organic compounds. The IAQ results showed that after spray application was completed in the entire building, airborne concentrations decreased for all chemicals monitored. However, it is our recommendation that during SPF application, no one should return to the application site without proper personal protection equipment as long as there are active spray activities in the building. The comparison between this field study and a recent chamber study proved surface sorption and particle deposition is an important factor in determining the fate of airborne TCPP. The study also suggests the need for further evaluation by employing mathematical models, proving the data generated in this work as informative to industry and the broader scientific community.