Bio-monitoring Methylene Diphenyl Diisocyanate (MDI) exposure and body burden

DESCRIPTION (provided by applicant): Exposure to isocyanate, the essential cross-linker for making polyurethane, is a leading cause of occupational asthma world-wide. Three major types of isocyanate are used commercially, methylene-diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI), or aliphatic, hexamethylene diisocyanate (HDI). Despite being the newest of the three, MDI has overtaken the isocyanate market in production and consumption, for many reasons, including its unique applications and properties. Importantly, at room temperature, MDI has a much lower vapor pressure than HDI or TDI, and exists as a solid, rather than a (volatile) liquid. Thus, MDI is presumed to be safer , because the potential for respiratory tract exposure is thought to be restricted to times when the chemical is heated or aerosolized (sprayed), i.e. during application. MDI is widely used in making flexible and rigid foams, coatings, elastomers and numerous other polyurethane-based products. Exposure to MDI is the best-recognized risk factor for the development of MDI asthma and exposure reduction is the primary strategy of disease prevention. Contemporary methods of monitoring MDI exposure are severely limited, and new approaches are needed to help protect millions of people exposed at work. Our laboratory is currently investigating new approaches to MDI exposure surveillance based upon serum biomarkers, which offer distinct advantages over (workplace) environmental surveillance. Our new approach uses immunoassays to quantitate two biomarkers we hypothesize provide important MDI exposure information and, which can greatly improve current surveillance programs. One biomarker is MDI-specific IgG, which should serve as an effective exposure surrogate, according to principles we outline in the Background (Section B), and can be measured through an indirect enzyme-linked immunosorbant assays (ELISA). A second biomarker is MDI itself, circulating in the peripheral blood attached to self proteins, which we propose to capture in a sandwich -type ELISA. Our vision is for these serum biomarkers, and immunoassays for their quantitation, to become part of integrated multi-disciplinary MDI exposure monitoring programs, which help protect the health of millions of workers throughout the world. Development of the proposed immunoassays will be facilitated by previous experience of the research personnel, and preliminary data acquired to date. The Specific Aims of the project are the following: Aim 1) Generate and characterize candidate MDI (conjugated albumin) antigens. Aim 2) Develop methods to measure MDI-specific antibodies (biomarker 1). Aim 3) Generate and characterize (rabbit) polyclonal and (mouse) monoclonal MDI-specific antibodies. Aim 4) Develop immunoassays that detect and quantitate MDI in human serum (biomarker 2). PUBLIC HEALTH RELEVANCE: This application will develop two new immunoassays to bio-monitor MDI exposure in the workplace, thus, ensuring adequate safety in polyurethane manufacture, and protecting the health of the US workforce.