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At least 199 records · Page 11Linked to original sources
PubMed1997

An evaluation of the respiratory health status of automotive spray-painters exposed to paints containing hexamethylene di-isocyanates in the greater Durban area.

OBJECTIVE: A survey of automotive spray-painting establishments was undertaken to evaluate the respiratory health status of spray-painters exposed to paints containing hexamethylene di-isocyanates (HDIs). DESIGN: This was a cross-sectional study. SETTING: Spray-painting establishments in the Durban municipal area. PARTICIPANTS: Spray-painters from a random sample of 40 (25%) of the registered spray-painting establishments were studied. MAIN OUTCOME MEASURES: Responses to an Interviewer-administered standardised respiratory health questionnaire and a cross-shift spirometric lung function test were obtained for each spray-painter, questionnaires assessing the firm's compliance with the spray-painting safety requirements were also obtained. RESULTS: The mean cross-shift decrease in forced expiratory volume in 1 second (FEV1) was 130.5 ml (SD 203.19) (P = 0.0002). The lung function data indicated that of the 40 spray-painters examined, 10 (25%) showed clinically significant cross-shift decreases in FEV1, viz, decreases > 250 ml. Only 2 subjects had a diagnosis of asthma. Chronic respiratory symptoms of cough, wheeze and wheeze with breathlessness were similar to those noted in community-based studies. A high proportion had eye irritation (55%) and dermatitis of the hand (32%). The potential determinants of FEV1 were examined in a multiple linear regression analysis and only the isocyanate concentration levels approached statistical significance (P = 0.082), suggesting that other factors such as duration of exposure, spray-paint 'bounce-back' phenomenon, and 'healthy worker' effect may be more important. ('Bounce back' refers to the phenomenon whereby some of the mist from the spray-gun, after striking the surface being painted, is deflected back into the operator's breathing zone in the form of fine droplets or aerosols.) Forty per cent of the 40 spray booths had ventilation standards substantially below that specified in current South African legislation. Only 21 (55%) spray-painters were provided with the regulation respiratory protective equipment, and in the cases where it was provided, 7 (33%) of these spray-painters used the positive pressure air-line respiratory recommended by the leading manufacturers of isocyanate-based paints. CONCLUSIONS: The findings in this study confirm the risk of exposure to HDIs in the spray-painting industry and highlight the need for more stringent industrial hygiene controls.

Adult↗
PubMed1998

[Chronic hypersensitivity pneumonitis due to isocyanate in a patient presenting with acute symptoms 1 month after environmental exposure].

A 51-year-old man who had been working for 10 years with polyurethane paint containing isocyanate (MDI) was admitted to our hospital with complaints of fever and exertional dyspnea. Fine crackles were heard in both bases, and the patient had clubbed fingers. A chest X-ray film and computed tomograms of the lungs revealed patchy infiltrative shadows in both lung fields and subpleural honeycombing associated with irregular linear areas. Examination of bronchoalveolar lavage fluid showed increased T lymphocytes and a decreased CD 4/8 ratio. Specimens obtained by transbronchial lung biopsy revealed lymphoplasmacytic infiltration into the thickened alveolar walls, macrophage accumulation, and micro-epithelioid cell granulomas in the alveolar sacs. Hypersensitivity pneumonitis was suspected although the causative antigen was not identified because the results of short-term environmental provocation tests were negative in the patient's home and workplace. After discharge, the patient continued working as a paint sprayer. His acute symptoms recurred 1 month after exposure to isocyanate. Similar episodes occurred on two separate occasions. In addition, the patient tested positive for antibody to MDI-HSA in bronchoalveolar fluid. From the above observations, the patient was given a diagnosis of chronic hypersensitivity pneumonitis due to isocyanate (MDI). This condition is extremely rare. Furthermore, it is interesting that acute symptoms recurred 1 month after environmental exposure to the causative antigen.

Alveolitis, Extrinsic Allergic↗
PubMed1988

Isocyanates and respiratory disease: current status.

This paper reviews the known respiratory effects of isocyanates. There is good evidence to indicate that isocyanates: cause chemical bronchitis/pneumonitis; are potent pulmonary sensitizers capable of causing "isocyanate asthma"; cause nonspecific airways disease, including chronic bronchitis; can induce a general asthmatic state; and can cause hypersensitivity pneumonitis. Similar dose-response relationships are seen for both acute and chronic effects. There are plants operating in which exposures are well controlled and in which no respiratory effects can be detected. Suggestions are provided for preplacement assessment and periodic surveillance for workers exposed to these compounds.

Air Pollutants, Occupational↗
PubMed1988

Trace analysis of airborne aromatic isocyanates and related aminoisocyanates and diamines using high-performance liquid chromatography with ultraviolet and electrochemical detection.

A high-performance liquid chromatographic method was developed for trace analysis of complex air mixtures containing 2,6- and 2,4-toluenediisocyanates and related aminoisocyanates and diamines. The accuracy was tested at isocyanate concentrations of 2-1000 microg/m3 in air. The method is based on derivatization in the sampling step of isocyanate functions to corresponding urethane groups, with alkaline ethanol as the sampling and reacting medium. The derivatives formed, toluenediurethanes and tolueneaminourethanes, and unreacted diamines were detected by UV or electrochemically, the electrochemical detection being one order of magnitude more sensitive. Using an enrichment column, detection limits of ca. 0.05 pg/microl were obtained with electrochemical detection at a potential of 950 mV, which corresponds to air concentrations of 0.1 microg/m3 with 5 min sampling time at a rate of 11/min. The precision in the measurements were ca. 4% at concentrations of 6 microg/m3. A field measurement was performed concerning flame lamination of toluenediisocyanate-based polyurethane and cloth. Isocyanates, aminoisocyanates and diamines were found at air concentrations of 1-100 microg/m3.

Air Pollutants↗
PubMed1983

Simultaneous determination of amines and isocyanates in working atmospheres by gas-liquid chromatography.

A gas-liquid chromatographic method has been developed which permits trace analysis in a single run of amines and isocyanates occurring in relative concentrations of the order of 10,000:1. The amines were determined as free amines after alkalization of the sample and an extractive enrichment into toluene. The isocyanates were hydrolyzed to the corresponding amines during sampling in dilute sulphuric acid. This method gives the total isocyanate concentration. The use of a nitrogen sensitive detector and an alkali-treated packing, Pennwalt 223 with 4% KOH, are important prerequisites. Chromatographic parameters such as column liquid loading, injector impregnation and injector temperature were examined. Good separation between 2,4- and 2,6-toluenediamine isomers was obtained. The enrichment step was studied with respect to the degree of alkalization and to interferences from another amine present in large excess. The method was tested in the working atmospheres of two polyurethane foam factories. The substances determined were N-methylmorpholine, 1,4-diazabicyclo[2,2,2]octane and 2,4- and 2,6-toluenediisocyanates.

Air Pollutants↗
PubMed1980

Isocyanate-induced asthma in a car factory.

In a car factory employing 203 women machinists making seat covers more women complained of respiratory symptoms after the introduction of a new seat cover fabric, cropped nylon backed with flame-bonded polyurethane foam (CNPF). 68 women working in the trim shop were studied on the first day back at work after a week's holiday and then at the end of a working week; the incidence of wheezing and/or shortness of breath was greater than expected but there was no difference between peak flow rates. A second study of 192 of the 203 women working in the trim shop confirmed this recent increase in incidence of asthmatic symptoms and showed that significantly more machinists who had worked with this new fabric had a reduced peak flow rate than machinists who had not. Asthma developed in one subject when she was working in the factory sewing CNPF, when she was handling this fabric in the challenge cabinet in the laboratory, and on challenge with toluene di-isocyanate in the laboratory. Airways resistance increased in 3 other workers after exposure to CNPF in the laboratory. Low concentrations (between 0.0003 to 0.003 ppm) of toluene di-isocyanate were found in the air around this fabric. 4 of 9 women with symptoms had IgE antibodies to toluene di-isocyanate.

Asthma↗
PubMed2004

Metal-induced coordination inversion and carbon-nitrogen bond rearrangement. Structurally characterized phenyl isocyanate inserted into aluminum methyl compounds and O- and N-bound aluminum compounds.

[C(4)H(3)N(CH(2)NMe(2))-2]AlMe(2) (1) is prepared in 88% yield by the reaction of substituted pyrrole [C(4)H(4)N(CH(2)NMe(2))-2] with 1 equiv of AlMe(3) in methylene chloride. Reaction of compound 1 with 1 equiv of phenyl isocyanate in toluene generates a seven-membered cycloaluminum compound [C(4)H(3)N[CH(2)NPh(CONMe(2))]-2] AlMe(2) (2). The phenyl isocyanate was inserted into the aluminum and dimethylamino nitrogen bond and induced an unusual rearrangement which results in C-N bond breaking and formation. A control experiment shows that the reaction of substituted pyrrole [C(4)H(4)N(CH(2)NMe(2))-2] with 1 equiv of phenyl isocyanate in diethyl ether yields a pyrrolyl attached urea derivative [C(4)H(3)N(CH(2)NMe(2))-2-[C(=O)NHPh]-1] (3). The demethanation reaction of AlMe(3) with 1 equiv of 3 in methylene chloride at 0 degrees C afforded O-bounded and N-bounded aluminum dimethyl compounds [C(4)H(3)N(CH(2)NMe(2))-2-[C(=O)NPh]-1]AlMe(2) (4a) and [C(4)H(3)N(CH(2)NMe(2))-2-[CO(=NPh)]-1]AlMe(2) (4b) in a total 78% yield after recrystallization. Both 4a and 4b are observed in (1)H NMR spectra; however, the relative ratio of 4a and 4b depends on the solvent used. Two equivalents of AlMe(3) was reacted with 3 in methylene chloride to yield a dinuclear aluminum compound AlMe(3)[C(4)H(3)N(CH(2)NMe(2))-2-[C(=O)NPh]-1] AlMe(2) (5). Reaction of 5 with another equivalent of ligand 3 results in the re-formation of compounds 4a and 4b.

Journal Article↗
PubMed2000

Synthesis of MII[N(SiMe3)2][Me3SiNC(tBu)NSiMe3] (M = Sn, Ge) from amidinate precursors: active catalysts for phenyl isocyanate cyclization.

Mixed amidinato amido complexes [Me3SiNC(tBu)NSiMe3]M[N(SiMe3)2] (M = Sn 2, Ge 3) were prepared by the reaction of [Me3SiNC(tBu)NSiMe3]Li (1a) with SnCl2 and GeCl2(dioxane) in ether. The N(SiMe3)2 ligand in these compounds is derived from the rearrangement of the [Me3SiNC(tBu)NSiMe3]- anion with extrusion of tBuCN. The susceptibility of [Me3SiNC(tBu)NSiMe3]- to rearrangement appears to be dependent on reaction solvent and on the coordinated metal center. Single-crystal X-ray diffraction studies of 2 and 3 are presented. Replacement of Me for tBu in the ligand allowed [Me3SiNC(Me)NSiMe3]2SnII (4) to be isolated, and an X-ray structure of this compound is reported. The isolation of 4 indicates that steric factors also play a role in the stability of [Me3SiNC(tBu)NSiMe3]-. Compounds 2 and 3 are outstanding catalysts for the cyclotrimerization of phenyl isocyanates to perhydro-1,3,5-triazine-2,4,6-triones (isocyanurates) at room temperature. In contrast, complex 4 catalytically reacts with phenyl isocyanate to produce isocyanate dimer and trimer in a 52:35 ratio.

Journal Article↗
PubMed1996

Addition-Rearrangement of Aryl- and Alkoxysulfonyl Isocyanates with 5-Methyl-Substituted 3,4-Dihydro-2-methoxy-2H-pyrans. Selective Synthesis of Functionalized 2-Piperidones(1).

3,4-Dihydro-2-methoxy-5-methyl-2H-pyran and 3,4-dihydro-2-methoxy-5,6-dimethyl-2H-pyran undergo addition-rearrangement reactions with arylsulfonyl isocyanates to generate the corresponding 3-formyl- and 3-acetyl-6-methoxy-3-methyl-1-(arylsulfonyl)-2-piperidones. For example, 3,4-dihydro-2-methoxy-5-methyl-2H-pyran and phenylsulfonyl isocyanate afforded 3-formyl-6-methoxy-3-methyl-1-(phenylsulfonyl)-2-piperidone as a separable trans/cis mixture in high yield. The more reactive phenoxysulfonyl and alkoxysulfonyl isocyanates provided analogous results.

Journal Article↗
PubMed2006

An ab initio study on the allene-isocyanic acid and ketene-vinylimine [2 + 2] cycloaddition reaction paths.

The reaction paths of [2 + 2] cycloadditions of allene (H2C=C=CH2) to isocyanic acid (HN=C=O) and ketene (H2C=C=O) to vinylimine (H2C=C=NH), leading to all the possible 14 four-membered ring molecules, were investigated by the MP2/aug-cc-pVDZ method. In the two considered reactions, the 2-azetidinone (beta-lactam) ring compounds were predicted to be the most stable thermodynamically in the absence of an environment. Although 4-methylene-2-azetidinone is the most stable product of the ketene-vinylimine cycloaddition, its activation barrier is higher than that for 4-methylene-2-iminooxetane by ca. 6 kcal/mol. Therefore, the latter product can be obtained owing to kinetic control. The activation barriers in the allene-isocyanic acid reactions are quite high, 50-70 kcal/mol, whereas in the course of the ketene-vinylimine cycloaddition they are equal to ca. 30-55 kcal/mol. All the reactions studied were found to be concerted and mostly asynchronous. Simulation of the solvent environment (toluene, tetrahydrofuran, acetonitrile, and water) by using Tomasi's polarized continuum model with the integral equation formalism (IEF-PCM) method showed the allene-isocyanic reactions remained concerted, yet the activation barriers were somewhat higher than those in the gas phase, whereas the ketene-vinylimine reactions became stepwise. The larger the solvent dielectric constant, the lower the activation barriers found. The lowest-energy pathways in the gas phase and in solvent were confirmed by intrinsic reaction coordinate (IRC) calculations. The atoms in molecules (AIM) analysis of the electron density distribution in the transition-state (TS) structures allowed us to distinguish pericyclic from pseudopericyclic from nonplanar-pseudopericyclic types of reactions.

Alkadienes↗
PubMed2006

The heat of formation of chlorine-isocyanate and the relative stability of isoelectronic molecules: an experimental and theoretical study.

Accurate thermochemical data of small molecules are invaluable to the progress of every aspect of chemistry, especially in the atmosphere, combustion and industry. In this work, photofragmentation translational spectroscopy and 1st principles electronic structure theory reveal the literature value of the heat of formation of chlorine-isocyanate to be in error by more than 40 kcalmol. We report a revised experimental value for D0(Cl-NCO) = 51+/-3 kcal/mol which leads to a Delta Hf (ClNCO) = 8.5+/-3 kcal/mol. High level ab initio (CCSD(T)) electronic structure calculations extrapolated to the complete basis set limit give D0(Cl-NCO) = 6.3 kcal/mol, in good agreement with experiment. In light of the present results, the destabilization of azides relative to isoelectronic isocyanates has been evaluated empirically for three pairs of related molecules. It is found to be 90-110 kcal/mol, and has been attributed mainly to the weakening of the N-NN bond relative to the N-CO bond. Electronic structure calculations employing decomposition analysis suggest that, compared to homopolar N2, the (+delta)CO(-delta) pi polarity provides better orbital interaction (charge transfer) and electrostatic attraction and results in a closer encounter and larger stabilization between the fragments and that this is the origin of isoelectronic destabilization of azides relative to the isocyanates.

Journal Article↗
PubMed1990

The health and safety executive interlaboratory quality control scheme for isocyanates.

The inclusion of isocyanate analysis within the AQUA (Analytical Quality Assurance) interlaboratory quality assurance scheme was established in 1984. (The AQUA interlaboratory quality assurance scheme is equivalent to external quality assessment, in North America the term proficiency testing is preferred.) The participants include university, industrial, occupational consultant and government laboratories, both in the U.K. and abroad. The AQUA isocyanate scheme is linked to a specific analytical method. MDHS 25 [Health and Safety Executive, Organic isocyanates in air: laboratory method using 1-(2-methoxyphenyl) piperazine solution and high performance liquid chromatography. H.M. Stationery Office, London (1987)]. Results from the first 4 years of the scheme's operation are reviewed and individual laboratory performance indices assessed against the mean interlaboratory performance indices. Most of the laboratories in the scheme show a marked improvement with time, which in some instances has followed help and advice from the HSE. There has also been an overall reduction in intralaboratory variability over this period.

Air Pollutants, Occupational↗
PubMed1987

Clinical and socio-professional fate of isocyanate-induced asthma.

Thirty-one patients with isocyanate-induced asthma were studied 6-54 months after diagnosis. Four had the same work conditions and unchanged or worse respiratory symptoms; seven had an alternative job or safer work conditions at the same work-place and suffered from mild to severe symptoms. The remaining twenty subjects were definitely removed from exposure; of these, ten (50%) remained symptomatic after being removed from exposure for an average of 19 months. Asymptomatic patients appeared to be younger and to have shorter durations of total and symptomatic exposures, while symptomatic patients were more reactive to acetylcholine at diagnosis. For patients removed from isocyanate exposure and for those re-employed at the same work-place, quality of the new work site seems to play a role in the evolution of isocyanate-induced asthma.

Adult↗
PubMed1971

Alkyl isocyanates as active site-specific inhibitors of chymotrypsin and elastase.

Alkyl isocyanates react specifically with the two serine proteinases, chymotrypsin and elastase, to yield inactive enzyme derivatives containing 1 male of reagent per mole of enzyme. Octyl isocyanate inactivates chymotrypsin only, while butyl isocyanate inactivates both enzymes but shows greater efficiency toward elastase than toward chymotrypsin. These reagents may thus represent unique chemical "yardsticks" for the measurement of the relative dimensions of the active sites of the two very similar enzymes.

Alkylation↗
PubMed1979

Peak flow rate records in the diagnosis of occupational asthma due to isocyanates.

Peak expiratory flow rate (PEFR) has been recorded hourly or two-hourly from waking to sleeping in workers with respiratory symptoms who were exposed to isocyanate fumes at work. Twenty-three recordings averaging 33 days duration were recorded in 20 workers. Each worker was also admitted for bronchial provocation testing to toluene di-isocyanate (TDI) or diphenylmethane di-isocyanate (MDI) fumes or both. A final assessment of work-related asthma made from subsequent work exposure was compared with the results of bronchial provocation testing and a subjective assessment of the peak flow records. Both techniques were specific and sensitive. Physiological patterns of occupational asthma were defined from the records of PEFR. The most striking finding was the slow recovery from work-induced asthma. This commonly took several days to start and in one worker took 70 days to complete after leaving work. Several workers developed a pattern resembling fixed airways obstruction after repeated exposure at work. The consequences of these findings for the recording of symptoms of occupational asthma are discussed and recommendations are made for the recording of PEFR in workers in general.

Asthma↗
PubMed1992

[Occupational asthma caused by isocyanates].

The aim of our study is to find whether the percentage of RAST positives to isocyanates within a company is a reflection of the exposure of the workers. Specific IgE was sought in 199 workers from ten companies where isocyanates were used. Twenty of them were followed for some time (june 87 to september 90). A non-exposed reference group was used for comparison. Measurements were made by the Pharmacia RAST-ELISA Method. In some cases, controls were made by RAST-RIA and CAPS ELISA/RIA. Results show that the proportion of positive RAST varies from one organisation to another and is probably a measure of the type and intensity of the exposure; the improvement of the working conditions to reduce the ambient concentration reduces, in time, the proportion of positive RAST; there were no positive RAST in the reference group; the conditions of taking and storage of blood samples before analysis influences the result. In conclusion, measurement of specific IgE may be an useful alternative to measurement of ambient concentration for following workers exposed to isocyanates.

Antibody Specificity↗
PubMed1977

[Immunologic diagnostic pulmonary diseases caused by inhaled isocyanates (author's transl)].

Besides the strong irritative effect on the respiratory tract the isocyanates probably also have an allergenic effect. The paper gives a review of literature about immunologic in vitro- and in vivo-methods in this question. Difficulties arise especially with preparation of antigen. Isocyanates are thought to link with proteins to give antigenic conjugates. Specifity firstly depends on the isocyanate hapten.

Animals↗
PubMed1990

You're the flight surgeon. Isocyanates are the most common cause of occupational asthma.

Isocyanates are the most common cause of occupational asthma. They are used to produce polyurethanes for the manufacture of plastics, adhesives, surface coatings, and both flexible and rigid foams. Of the several types of isocyanates commonly used, toluene diisocyanate (TDI) is the most significant commercially and toxicologically. Asthma develops in approximately 5 to 10% of workers regularly exposed to TDI. Once sensitized, asthma can develop after exposure to extremely low concentrations of TDI. Although suggestive, an immunologic mechanism remains unclear since studies vary in their findings of positive skin tests and specific IgE. Once developed, isocyanate asthma persists with continued exposure and in some even after removal from exposure.

Aerospace Medicine↗