Diisocyanates (dNCOs) are the most commonly reported cause of chemically induced occupational asthma, but the ultimate antigenic form is unknown. Reactions of the three most common monomeric dNCOs, hexamethylene dNCO (HDI), methylene diphenylisocyanate (MDI), and toluene dNCO (TDI), with cysteine methyl ester (CME) gave the corresponding bis-dithiocarbamates (HDI-CME, TDI-CME, and MDI-CME). The dissociation kinetics of these bis-thiocarbamates, in aqueous conditions, was followed spectrophotometrically under varying pH and temperature conditions. Reaction of the adducts with methylamine or human serum albumin (HSA) produced diurea, monourea, and diamine products, and this was consistent with the base-catalyzed elimination reaction (E1cB) pathway being the dominant, but not exclusive, dissociation mechanism. The hydrolysis of the adducts was first-order with respect to OH(-) concentration and overall second-order (HDI-CME, k = 3.36 x 10(2) M(-)(1) min(-)(1); TDI-CME, k = 2.49 x 10(4) M(-)(1) min(-)(1); and MDI-CME, k = 5.78 x 10(4) M(-)(1) min(-)(1) at pH 7.4) with deviation from second-order when the dNCO had an aromatic functional group. Arrhenius plots gave activation energies (HDI-CME, E(a) = 70.6 kJ/mol; TDI-CME, E(a) = 46.1 kJ/mol; and MDI-CME, E(a) = 44.5 kJ/mol) that were consistent with the following order of stability: HDI-CME > TDI-CME > MDI-CME. Therefore, the stability of different dNCO-derived thiocarbamates in aqueous environments can vary greatly. Thiocarbamate dissociation rates and type of products formed may potentially influence antigenicity and subsequent hypersensitivity/toxic reactions following dNCO exposures.

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2-Mercaptobenzothiazole and zinc dialkyldithiocarbamates are commonly used sulfur-containing rubber vulcanization accelerators known to cause allergic contact dermatitis. Exposure to these agents occurs through clothing such as undergarments and shoes, latex medical devices and latex and nitrile gloves. A simple, inexpensive screening method for total sulfur accelerator and a high performance liquid chromatographic speciation method were developed in the present study. These methods were applied to screen and quantify the sulfur accelerator content from 38 brands of 'off-the-shelf' latex and nitrile gloves obtained from commercial vendors. It was found that accelerator levels ranged from not detectable to 7.35 mg/g in the gloves analysed. Brands were found to contain single and multiple accelerator species within the glove. Powdered gloves had significantly higher accelerator levels than powder-free gloves from the same manufacturer; however, these chemical accelerators do not preferentially partition to the powder. The present analytical methodology is suitable for both manufacturing quality validation purposes, as well as for accelerator allergy research.

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