Chemical Permeation through Disposable Gloves
Robert N. Phalen, Howard I. Maibach in Protective Gloves for Occupational Use, 2023
The need to test the permeation of isocyanates compounds through disposable gloves has arisen from isocyanates being a skin sensitizer and causative agent for allergic contact dermatitis.37–40 Isocyanate compounds are used in several industries beyond the collision repair industry and construction, as well as in many products and applications, e.g., in foams, bed liners, adhesives, insulation, varnishes, and isocyanate paints.41,42Figure 24.3 shows an example of the PPE worn by a worker using an isocyanate. Isocyanates include diisocyanates both in monomer and polymer forms. Monomer diisocyanates include methylenebis (phenyl isocyanate) (MDI), toluene diisocyanate (TDI), and hexamethylene diisocyanate (HDI), followed by less common naphthalene diisocyanate (NDI), methylene bis-cyclohexylisocyanate (HMDI) (hydrogenated MDI), and isophorone diisocyanate (IPDI). Examples of widely used polyisocyanates include HDI biuret and HDI isocyanurate.
Occupational respiratory diseases
Louis-Philippe Boulet in Applied Respiratory Pathophysiology, 2017
Occupational asthma can result from immune or nonimmune mechanisms. In the case of immune mechanisms, this type of asthma appears generally after a latency period of variable duration between the beginning of exposure and the onset of symptoms. In general, we consider HMW agents to act through the production of antibodies such as IgE as common allergens [22,23]. Atopic subjects have a slight increase in the risk of developing this type of asthma following the exposure to this type of agents. For LMW agents such isocyanates, the development mechanisms of asthma are uncertain. Some show sensitizing properties but others are irritants. Isocyanates can cause a RADS following inhalation accidents while in many other cases, they will also cause an occupational asthma after a prolonged exposure to lower concentrations of these substances. In case of LMW substances, IgE does not seem usually involved, although some workers can develop such antibodies. IgG can sometimes be involved but their role is uncertain. Sensitizing subjects could present asthmatic responses even at low concentration of these agents; it is therefore of major importance to stop the exposure when the diagnosis is established.
Scanning Angle Interference Microscopy (SAIM)
Qiu-Xing Jiang in New Techniques for Studying Biomembranes, 2020
Variations of intensity in laser illumination in wide-field microscopy could lead to interference fringes. To quantify such variation in intensity, reference slides with a monolayer of fluorescent dye can be prepared using silane conjugates of fluorescein and rhodamine B. The conjugates can be synthesized according to the protocol described in Paszek et al.22 Briefly, 1 mg of fluorescein isocyanate or 1.37 mg of rhodamine B isocyanate is made to react with 9.25 mg of APS in 1.25 mL anhydrous ethanol, under nitrogen gas at ~21°C for 2 hours with constant stirring. Immediately following the reaction, the conjugates are centrifuged at 20,000 g for 10 min to pellet unwanted aggregates, and then diluted 10-fold in absolute ethanol. Clean glass-bottom dishes (#1.5 glass) are incubated with the diluted silane conjugates for 30 minutes at ~21°C, rinsed with water and stored in water until imaging.
Microencapsulation of reactive isocyanates for application in self-healing materials: a review
Published in Journal of Microencapsulation, 2021
Amanda N. B. Santos, Demetrio J. dos Santos, Danilo J. Carastan
The term “isocyanate” may refer to the chemical group with formula R-N=C=O, but it is also the generic name of the chemical compounds which have one or more –NCO groups in their structure. The carbon atom in these compounds has an electropositive charge, making it extremely reactive with chemical groups which have an active atom of hydrogen (nucleophilic reagent), such as alcohols, amines and water. The reaction of NCO with the mentioned chemical groups usually forms urethane or urea bonds (Sharmin and Zafar 2012, Cherng et al.2013, Gogoi et al.2014). NCO is available in a large number of chemical compounds with a wide range of reactivity levels. They are usually classified as aliphatic, such as isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and 4,4′-bis-methylene cyclohexane diisocyanate (HMDI), or aromatic, such as toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI) and polyaryl polymethylene isocyanate (PAPI). The chemical structure of these isocyanates is presented in Figure 2. These compounds are usually combined with other monomers to form polymeric materials covering a vast array of properties, more often based on urethane and urea bonds.
Asthma and rhinitis in Greek furniture workers
Published in Journal of Asthma, 2021
Katerina Paraskevaidou, Konstantinos Porpodis, Theodoros Kontakiotis, Ioannis Kioumis, Dionisios Spyratos, Despina Papakosta
Our results are compatible with a cross-sectional epidemiological study by Mastragello et al. (12) who explored a sample of factory workers exposed to isocyanates and revealed that the risk of asthma was five times higher compared to unexposed workers. In another study, Talini et al. (33) showed that chemical workers have a greater risk of developing asthma symptoms, in contrast to Milanowski et al. (34) who demonstrated that the asthma-like symptoms were more frequent among employees in the wood department. Ucgun et al. (35) explored asthma prevalence in a region of Turkey and concluded that WRA was a common disease for furniture workers employed in the paint sector, they also suggested that smoking and atopy were significant contributors. In our study, chemical workers although exhibiting an increased frequency of asthma compared to the other two groups, did not show significant relation to smoking or to atopy.
Mass spectrometry-based analysis of murine bronchoalveolar lavage fluid following respiratory exposure to 4,4'-methylene diphenyl diisocyanate aerosol
Published in Xenobiotica, 2018
Justin M. Hettick, Brandon F. Law, Chen-Chung Lin, Adam V. Wisnewski, Paul D. Siegel
Diisocyanates are low molecular weight chemicals utilized as cross-linkers in polyurethane production. 4,4′-methylene diphenyl diisocyanate (MDI) is the most widely used diisocyanate, accounting for more than 60% of the global diisocyanate market (Allport et al., 2003). MDI is widely used in the manufacture of such products as rigid polyurethane spray foam insulation, truck bed liners, wood products and adhesives. Because of its low vapor pressure (5 × 10−6 mm Hg), MDI presents less of an inhalation hazard than the more volatile diisocyanates toluene diisocyanate (TDI) or hexamethylene diisocyanate (HDI); however, MDI is a potent lung and dermal sensitizer and a major cause of occupational asthma worldwide (NIOSH, 2004). This low volatility has, in part, driven the industry towards the use of the “safer” MDI rather than the more volatile diisocyanate, TDI. However, in many applications, MDI is heated and/or aerosolized via a spray gun, thus creating respirable vapor and/or aerosols. Furthermore, many hot applications and thermal processes such as fires can release free MDI fumes from products. However, after heating, MDI tends to recondense in the air at ambient temperatures (Karoly et al., 2004). Because MDI hydrolyzes slowly in the atmosphere (the half-life of MDI in the air is 0.92 d), exposures to aerosolized MDI in the workplace are likely to be to small particulates containing free isocyanate. The major occupational hazards to workers from MDI exposure are assumed to be MDI liquid, vapor, aerosol and MDI-coated particles such as wood dust (Woellner et al., 1997).
Related Knowledge Centers
- Carbodiimide
- Cyanate
- Functional Group
- Organic Chemistry
- Organic Compound
- Polymer
- Polyurethane
- Cyanate Ester
- Isocyanide
- Phenyl Isocyanate