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PubMed1987

Sensory and pulmonary irritation of methyl isocyanate in mice and pulmonary irritation and possible cyanidelike effects of methyl isocyanate in guinea pigs.

Methyl isocyanate (MIC) was evaluated for sensory and pulmonary irritation in mice. MIC was found to be both a potent sensory and pulmonary irritant in this species. From these results, a safe level of exposure for a period of 8 hr was estimated to be about 0.02 ppm for humans. Guinea pigs were also exposed to MIC for a single 3-hr exposure at a concentration of 37 ppm. During exposure to MIC, coughing was observed in all animals. Pulmonary function was evaluated immediately following exposure and intermittently on the next 35 days using CO2 challenges and flow-volume loops. Highly abnormal responses to CO2 were observed immediately after exposure in all animals. Six of the eight animals exposed to MIC died. In the two survivors, an apparent recovery was seen during the 5 days following exposure, but a worsening effect was observed at days 21 and 28, with a partial recovery at day 35. The data clearly demonstrated that the primary pulmonary effect of MIC was one of airways obstruction. Oxygen uptake and carbon dioxide output were also measured in the guinea pigs following exposure to MIC. No evidence of a cyanidelike effect was observed, in contrast to a severe depression of oxygen uptake following exposure to hydrogen cyanide.

Airway Obstruction↗
PubMedDate not supplied

Effects of Si-functional isocyanate on the stability of oil-in-water emulsion with and without a carbon functional isocyanate.

The effects of silicon-functional isocyanates on the stability of oil-in-water emulsions with and without a carbon functional triisocyanate in the oil phase were investigated. The oil component was di-n-butyl-phthalate (DBP) containing Aerosol OT as an emulsifier. It was found that only CH3Si(NCO)3 among the (CH3)nSi(NCO)4 - n's was effective to contribute additional stability for the emulsion without a carbon functional triisocyanate. It was also found that a reaction product of CH3Si(NCO)3 with water reacted with a carbon functional triisocyanate.

Dibutyl Phthalate↗
PubMed1982

Non-specific bronchial hyper-reactivity in workers exposed to toluene di-isocyanate, diphenyl methane di-isocyanate and colophony.

Non-specific bronchial reactivity to histamine has been measured before specific occupational bronchial tests in the following groups: 51 workers exposed to toluene di-isocyanate (TDI); 40 workers exposed to diphenylmethane diisocyanate (MDI); 45 electronics workers exposed to colophony fumes and 13 unexposed controls. Finally 38 electronics workers had repeated measurements after moving their place of work. The results showed that histamine reactivity was an important, but not obligatory, factor in the development of occupational asthma, and that it appeared to be the result rather than the cause of occupational asthma, as it returned towards normal in workers removed from exposure. TDI and MDI were shown to be acting as specific causes of occupational asthma rather than nonspecific irritants at concentrations up to 0.02 ppm. There was evidence that some irritant reactions to colophony were occurring at exposure levels encountered at work, but that the majority of workers with colophony asthma were having specific reactions to the colophony fume.

Asthma↗
PubMed2005

Isocyanate acting as a carbonyl precursor: pyridyl group-assisted formation of 4H-pyrido[1,2-a]pyrimidin-4-ones from ketimines and isocyanates.

By the reactions of ketimines bearing a pyridyl or a picolyl group on a nitrogen atom of the imine moiety with tosylisocyanate, 4H-pyrido[1,2-a]pyrimidin-4-one derivatives could be obtained in quantitative yields. In these reactions, tosylisocyanate acts as a carbonyl precursor. The pyridyl or picolyl group is a key functional group because it is not only the constituent structure of the 4H-pyrido[1,2-a]pyrimidin-4-one framework but also the promoter of the formation of a ketene intermediate.

Journal Article↗
PubMed2006

Determination of airborne isocyanates generated during the thermal degradation of car paint in body repair shops.

Polyurethanes are widely used in car paint formulations. During thermal degradation, such polymeric systems can generate powerful asthmatic sensitizing agents named isocyanates. In body repair shops, the thermal degradation of car paint can occur during abrasive processes that generate enough heat to involve release of isocyanates in air. An environmental monitoring study was performed in two body repair training schools and in a body repair shop to evaluate the workers' exposure to isocyanates during cutting, grinding and orbital sanding operations. For sampling, cassettes containing two 1-(2-methoxyphenyl)piperazine (MOPIP)-coated glass fiber filters (MFs) ( approximately 5 mg of MOPIP per filter) and bubblers containing 15 ml of MOPIP solution in toluene (1.0 mg ml(-1)) backed at the outlet with cassettes containing two MFs were used. Tandem mass spectrometry was used to analyze the MOPIP derivatives of isocyanic acid (HNCO), all the linear aliphatic isocyanates ranging from methyl isocyanate (Me-i) to hexyl isocyanate, all the alkenyl isocyanates ranging from propylene isocyanate to hexylene isocyanate, 1,6-hexamethylene diisocyanate (HDI), trans- and cis-isophorone diisocyanate (IPDI), 2,4- and 2,6-toluene diisocyanate (TDI), 2,4'-; 2,2'- and 4,4'-methylenediphenyl diisocyanate (MDI), phenyl isocyanate (Ph-i) and p-toluene isocyanate (p-Tol-i). The instrumental detection limits (LOD) were in the 0.13-0.75 microg of NCO per m(3) range for 15 l air samples converted into 3 ml liquid samples. The isocyanate concentrations detected in the workers' breathing zone were in the 1.07-9.80 microg of NCO per m(3) range for cutting, 0.63-3.62 microg of NCO per m(3) range for grinding and 0-1.29 microg of NCO per m(3) range for sanding. However, a rapid decrease of the isocyanate concentration was observed while moving away from the emission source. Among the isocyanates detected the most abundant were the monomers (MDI, HDI, TDI and IPDI) and Me-i.

Air Pollutants, Occupational↗
PubMed2006

An FTIR investigation of isocyanate skin absorption using in vitro guinea pig skin.

Isocyanates may cause contact dermatitis, sensitization and asthma. Dermal exposure to aliphatic and aromatic isocyanates can occur in various exposure settings. The fate of isocyanates on skin is an important unanswered question. Do they react and bind to the outer layer of skin or do they penetrate through the epidermis as unreacted compounds? Knowing the kinetics of these processes is important in developing dermal exposure sampling or decontamination strategies, as well as understanding potential health implications such exposure may have. In this paper the residence time of model isocyanates on hairless guinea pig skin was investigated in vitro using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrometry. Model isocyanates tested were octyl isocyanate, polymeric hexamethylene diisocyanate isocyanurate (pHDI), polymeric isophorone diisocyanate isocyanurate (pIPDI) and methylenediphenyl diisocyanate (MDI). Isocyanates in ethyl acetate (30 microL) were spiked directly on the skin to give 0.2-1.8 micromol NCO cm(-2) (NCO = -N=C=O), and absorbance of the isocyanate group and other chemical groups of the molecule were monitored over time. The ATR-FTIR findings showed that polymeric isocyanates pHDI and pIPDI may remain on the skin as unreacted species for many hours, with only 15-20% of the total isocyanate group disappearing in one hour, while smaller compounds octyl isocyanate and MDI rapidly disappear from the skin surface (80+% in 30 min). Isocyanates most likely leave the skin surface by diffusion predominantly, with minimal reaction with surface proteins. The significance of these findings and their implications for dermal exposure sampling and isocyanate skin decontamination are discussed.

Animals↗
PubMed2002

Airway inflammation and functional changes after exposure to different concentrations of isocyanates.

BACKGROUND: Isocyanates are a common cause of occupational asthma (OA). OBJECTIVES: We sought (1) to examine whether asthmatic reactions to isocyanates could be induced at concentrations as low as 1 ppb in subjects with OA caused by isocyanates previously diagnosed in our center and (2) to compare the inflammatory and functional changes after exposure to 1 and 15 ppb of isocyanates with similar total doses (concentration of isocyanates x duration of exposure). METHODS: Specific inhalation challenges were performed in 12 asthmatic subjects with previously confirmed OA caused by isocyanates. Eight subjects were exposed to 1 ppb at 10% of the dose of isocyanates that induced an asthmatic reaction at the time of the diagnosis. Seven subjects were exposed to the same total dose of isocyanates by using concentrations of 1 and 15 ppb 1 month apart. RESULTS: Exposure to 1 ppb at 10% of the dose that had induced functional changes at the time of diagnosis induced an asthmatic reaction in 3 of 8 subjects. There was a significant correlation between the percentage of maximum decrease in FEV(1) after exposure to 1 ppb and the increase in sputum neutrophils (rho = 0.8). By keeping the total dose (concentration of isocyanates x duration of exposure) of isocyanates similar, 4 of 7 subjects experienced an asthmatic reaction after exposure to 1 ppb, whereas only one subject experienced an 18.5% decrease in FEV(1) after exposure to 15 ppb. CONCLUSION: Isocyanates can induce functional and inflammatory changes (mainly neutrophilic) at concentrations as low as 1 ppb. For the same total dose of exposure, low concentrations of isocyanates are as harmful as or even more harmful than higher concentrations for subjects with OA to isocyanates.

Administration, Inhalation↗
PubMed2005

Validation of a solvent-free sampler for the determination of low molecular weight aliphatic isocyanates under thermal degradation conditions.

During the thermal degradation of 1,6-hexamethylenediiso- cyanate-based (HDI) car paint, the eight most abundant isocyanates generated are isocyanic acid, methyl isocyanate, ethyl isocyanate, propyl isocyanate, butyl isocyanate, pentyl isocyanate, hexyl isocyanate, and 1,6-hexamethylenediisocyanate. For the first time, a method using solvent-free samplers is proposed and validated for the simultaneous sampling of all these isocyanates. The sampling efficiency during thermal degradation of car paint can be affected by the formation of dust and aerosols and by the emission of many chemicals, such as isocyanic acid, anhydrides, amines, and alcohols that consume the reagent or interfere in the derivatization procedure. Sampling was performed using cassettes containing two 1-(2-methoxyphenyl)piperazine (MOPIP)-coated glass fiber filters (MFs) (approximately 4.9 mg per filter) and compared with bubblers containing 15 mL of MOPIP solution in toluene (1.0 mg/mL(-1)) and with bubblers backed with MFs. A DIN 53436 laboratory scale furnace was used to generate the isocyanates under thermal degradation conditions. For an aliphatic isocyanate concentration of approximately 42 microg(NCO) m(-3), no significant difference in sampling efficiency was observed between the three techniques studied, thus confirming the sampling efficiency of the MFs. The samples were analyzed using high-performance liquid chromatography coupled with electrospray/tandem mass spectrometry. Quantification was performed in daughter mode monitoring (MOPIP+H)(+) fragments. For concentrations between 0.013 microg(NCO) mL(-1) and 0.52 microg(NCO) mL(-1) for the monoisocyanates, and between 0.026 microg(NCO) mL(-1) and 1.04 microg(NCO) mL(-1) for the HDI, the correlation coefficients were in the 0.9974-0.9996 range (n = 18). Analytical reproducibility and precision were better than 95.4% and 94.9%, respectively, for all the isocyanates. The instrumental detection limits, defined as three times the standard deviation measured at the lowest point on the calibration curve were in the 1.8-3.0 ng(NCO) mL(-1) range (n = 8), which corresponds to about 0.37-0.60 microg(NCO) m(-3) for a 15-L air sample when the filters are desorbed in 3 mL.

Air Pollutants, Occupational↗
PubMed2004

Determination of technical grade isocyanates used in the production of polyurethane plastics.

A method for determination of technical grade isocyanates used in the production of polyurethane (PUR) is presented. The isocyanates in technical grade products were characterised as di-n-butylamine (DBA) derivatives using LC-MS and LC-chemiluminescent nitrogen detection (CLND) and the total isocyanate content was compared to a titration assay. For collection of isocyanates in air, an impinger-filter sampling technique with DBA as derivatisation reagent was used. Characterised DBA and nonadeuterium labelled DBA derivatives of isocyanates in technical products were used as calibration standards and internal standards, respectively, in the analysis of air samples. Three workplaces were studied where PUR products were produced either by spraying or by moulding. In both technical products and in air samples, a number of monomeric, oligomeric and prepolymeric isocyanates of e.g. methylenebisphenyl diisocyanate (MDI) and hexamethylene diisocyanate (HDI) were characterised. Several of these have not previously been described in workplace atmospheres. In the technical isocyanate products, between 69 and 102% of the NCO content determined by titration was accounted for by LC-CLND. Quantifications of a wide range of isocyanates in air samples were performed with correlation coefficients in the range 0.988-0.999 (n= 8) and the instrumental detection limits were 0.7-25 pg. At the two workplaces where MDI- and HDI isocyanurate-based products were sprayed, the isocyanate composition in the air reflected the composition in the technical product. At the workplace where a MDI-based product was used in a moulding process, only the monomeric isocyanates were found in the air. The advantage of using characterised technical grade isocyanates as analytical standards was clearly demonstrated and the possibility of using index compounds when monitoring isocyanate exposure is discussed.

Air Pollution, Indoor↗
PubMed1995

Investigation of the ability of MDHS method 25 to determine urethane-bound isocyanate groups.

Method 25 for the Determination of Hazardous Substances (MDHS 25) of the Health and Safety Executive of the United Kingdom attempts to identify and quantify all isocyanate species in an air sample. Isocyanate species are derivatized with 1-(2-methoxyphenyl)piperazine (MOPP) and analyzed by high-performance liquid chromatography (HPLC) with tandem ultraviolet/electrochemical (UV/EC) detection. The method identifies peaks as being isocyanate-derived if the EC/UV detector response ratio is between 0.75 and 1.5 times that of the derivatized monomer. This investigation sought to determine if the method correctly identifies and accurately quantifies intermediates created during polyurethane formation that possess free isocyanate groups. Model compounds derived from 2,4-toluene diisocyanate (2,4-TDI) and ethylene glycol were prepared. These urethane species contained two ("dimer") and three ("trimer") TDI units and terminal MOPP-derivatized isocyanate groups. Like monomeric 2,4-TDI/MOPP urea, each contained two derivatized isocyanate groups per molecule. This investigation found that neither the UV nor the EC response is proportional to the number of isocyanate groups present in the model compounds. Therefore, it is concluded that MDHS 25 is neither capable of correctly identifying TDI-urethane intermediates possessing MOPP-derivatized isocyanate groups nor is it capable of accurately quantifying these isocyanate groups. The proposed solution to this problem is the utilization of a derivatizing reagent that yields derivatized isocyanate species whose detector responses come more exclusively from the derivatized isocyanate moiety and, therefore, are more proportional to the number of derivatized isocyanate groups.

Chromatography, High Pressure Liquid↗
PubMed2006

Assessing isocyanate exposures in polyurethane industry sectors using biological and air monitoring methods.

Isocyanates, as a chemical group, are considered to be the biggest cause of occupational asthma in the UK. Monitoring of airborne exposures to total isocyanate is costly, requiring considerable expertise, both in terms of sample collection and chemical analysis and cannot be used to assess the effectiveness of protection from wearing respiratory protective equipment (RPE). Biological monitoring by analysis of metabolites in urine can be a relatively simple and inexpensive way to assess exposure to isocyanates. It may also be a useful way to evaluate the effectiveness of control measures in place. In this study biological and inhalation monitoring were undertaken to assess exposure in a variety of workplaces in the non-motor vehicle repair sector. Companies selected to participate in the survey included only those judged to be using good working practices when using isocyanate formulations. This included companies that used isocyanates to produce moulded polyurethane products, insulation material and those involved in industrial painting. Air samples were collected by personal monitoring and were analysed for total isocyanate content. Urine samples were collected soon after exposure and analysed for the metabolites of different isocyanate species, allowing calculation of the total metabolite concentration. Details of the control measures used and observed contamination of exposed skin were also recorded. A total of 21 companies agreed to participate in the study, with exposure measurements being collected from 22 sites. The airborne isocyanate concentrations were generally very low (range 0.0005-0.066 mg m(-3)). A total of 50 of the 70 samples were <0.001 mg m(-3), the limit of quantification (LOQ), therefore samples below the LOQ were assigned a value of 1/2 LOQ (0.0005 mg m(-3)). Of the 70 samples, 67 were below the current workplace exposure limit of 0.02 mg m(-3). The highest inhalation exposures occurred during spray painting activities in a truck manufacturing company (0.066 mg m(-3)) and also during spray application of polyurethane foam insulation (0.023 mg m(-3)). The most commonly detected isocyanate in the urine was hexamethylene diisocyanate, which was detected in 21 instances. The geometric mean total isocyanate metabolite concentration for the dataset was 0.29 micromol mol(-1) creatinine (range 0.05-12.64 micromol mol(-1) creatinine). A total of 23 samples collected were above the agreed biological monitoring guidance value of 1.0 micromol mol(-1) creatinine. Activities that resulted in the highest biological monitoring results of the dataset included mixing and casting of polyurethane products (12.64 micromol mol(-1) creatinine), semi-automatic moulding (4.80 micromol mol(-1) creatinine) and resin application (3.91 micromol mol(-1) creatinine). The biological monitoring results show that despite low airborne isocyanate concentrations, it was possible to demonstrate biological uptake. This tends to suggest high sensitivity of the biological monitoring method and/or that in some instances the RPE being used by operators was not effective or that absorption may have occurred via dermal or other routes of exposure. This study demonstrates that biological monitoring is a useful tool when assessing worker exposure to isocyanates, providing a more complete picture on the efficacy of control measures in place than is possible by air monitoring alone. The results also demonstrated that where control measures were judged to be adequate, most biological samples were close to or < 1 micromol mol(-1) creatinine, the agreed biological monitoring benchmark.

Air Pollutants, Occupational↗
PubMed2004

Leukotrienes and isocyanate-induced asthma: a pilot study.

BACKGROUND: The role of leukotrienes (LTs) in the pathophysiology of isocyanate-induced asthma is not well known. OBJECTIVE: We sought to characterize the type of airway inflammation induced by exposure to isocyanates and to investigate whether exposure to isocyanates induced an increase in LT receptor cysteinyl leukotriene ((CysLT)(1), CysLT(2) and leukotriene B(4) receptor (BLT(1))) expression, as well as a release of LT (LTC(4) and leukotriene B(4) (LTB(4))) and IL-8 in both asthmatics with isocyanate-induced asthma and healthy subjects. METHODS: We investigated eight subjects with isocyanate-induced asthma and eight healthy subjects. Both groups underwent specific inhalation challenges to isocyanates in the laboratory. Induced sputum was collected before and after exposure to isocyanates. CysLT(1), CysLT(2) and BLT(1) expression was assessed by flow cytometry, whereas LTC(4), LTB(4) and IL-8 were measured in the sputum supernatants by enzyme immunoassay. RESULTS: Exposure to isocyanates induced an increase in sputum neutrophils only in subjects with occupational asthma. There was a significant increase in CysLT(1) and BLT(1) receptor expression, as well as a release of LTB(4) and IL-8 after exposure to isocyanates compared with the baseline, only in subjects with isocyanate-induced asthma, whereas there was no increase in LTC(4). Exposure to isocyanates did not induce any change in LT receptor expression nor in the levels of LTC(4), LTB(4) and IL-8, in healthy subjects. CONCLUSION: The neutrophilia observed after exposure to isocyanates is likely to be related to the release of LTB(4), probably enhanced by the increased expression of BLT(1) on neutrophils as well as by the release of IL-8. The significance of the increase of CysLT1 receptor expression on neutrophils is unknown and needs further investigation.

Adult↗