Airway symptoms and lung function in pipelayers exposed to thermal degradation products from MDI-based polyurethane

Associations of symptoms related to isocyanate, ureaformol, and formophenolic exposures with respiratory symptoms and lung function in coal miners

The respiratory effects of diphenylmethane diisocyanate (MDI)-based resins and ureaformol- and formophenolic-based resins, used in coal mining, are unknown. This cross-sectional study of 354 miners evaluated respiratory health in miners with MDI-related symptoms (IS) and ureaformol/formophenolic-related symptoms (UFS). The protocol included clinical examination, chest radiograph, questionnaire on respiratory symptoms, smoking habit, job history, resin handling, and spirometry. Resin handling concerned 27.7% of the miners. IS affected 5.6%, and 1.4% also after work. UFS affected 22.6%, and 2.3% also after work. Wheezing affected 35.6%; chronic cough, expectoration, or bronchitis about 10%; dyspnea 5.4%; and asthma 2.8%. The miners with UFS had significantly more frequent chronic cough, expectoration, chronic bronchitis, dyspnea, and wheezing, whereas those with IS at and after work had markedly lower FVC, FEV1, MMEF, FEF50%, and FEF25%. These findings raise the possibility of deleterious effects of exposures to MDI and ureaformol/formophenolic resins on respiratory health and lung function in coal miners during their working life.

Issues in diisocyanate antibody testing

Diisocyanates are used to produce a wide variety of polyurethane products; they are also recognized as an important cause of occupational asthma. Their chemical reactivity presents challenges to toxicologists and clinicians alike seeking to understand the mechanisms underlying diisocyanate asthma. In this article, we review the literature on immunoassay detection of IgE and IgG binding to diisocyanate-protein conjugates and assess the utility of such testing as a diagnostic tool and exposure indicator. Data from 29 studies of occupational exposure to diisocyanates revealed considerable variability in assay methodology and heterogeneity in the prevalence of positive antibody responses across laboratories. In studies that included both confirmed diisocyanate asthma subjects and exposed nonasthmatics, positive IgE responses identified cases with low sensitivity (18-27%), but high specificity (96-98%). Detection of IgG binding to diisocyanate conjugates is an indirect, qualitative indicator of disease status and past diisocyanate exposure. The utility of these assays is limited, however, due to a lack of (1) method standardization, (2) population norms to guide interpretation of results, and (3) demonstration that the assays improve either on disease prediction or on exposure confirmation beyond that of other indicators. Sources of assay heterogeneity are discussed and suggestions are offered for improving test performance and interpretability.

Evaluation of antibody binding to diisocyanate protein conjugates in a general population

BACKGROUND

Specific IgG binding to diisocyanate-human serum albumin (HSA) has been proposed as an indicator of diisocyanate exposure. One residential study reported IgG binding to diisocyanate conjugates in 8% of residents living near a factory using toluene diisocyanate (TDI). Because comparable assays were not performed using individuals distant from such facilities, the significance of this finding is uncertain.

OBJECTIVE

To determine the prevalence of diisocyanate specific antibodies in sera from individuals "not known to be exposed" to diisocyanates.

METHODS

Serum samples from 139 anonymous donors without known diisocyanate exposure were assayed by means of enzyme-linked immunosorbent assay for IgG or IgE specific for TDI-HSA, diphenylmethane diisocyanate (MOI)-HSA, and hexamethylene diisocyanate (HDI)-HSA. Positive responses (optical density > or = 0.1 and > or = 3 SDs above the mean of 8 laboratory controls) were run 3 times. Competitive inhibition was performed for sera exhibiting binding of optical density of at least 0.2.

RESULTS

We detected IgG reactive with HDI-HSA, diphenylmethane diisocyanate-HSA, and TDI-HSA in 18 (13%), 0, and 7 donors (5%), respectively. Inhibition (>50%) was demonstrated in 6 of 9 participants with elevated HDI-HSA levels and in 2 of 7 with elevated TDI-HSA levels. We detected IgE reactive with the same antigens in 3 donors (2%); however, none were confirmed to be positive using the biotin-streptavidin IgE assay.

CONCLUSIONS

Specific and nonspecific IgG binding to HDI-HSA and TDI-HSA were detected in individuals without known exposure to isocyanates. These antibody measurements may not be reliable indicators of diisocyanate exposure in nonoccupational populations and should not be interpreted as surrogates of diisocyanate exposure in the absence of defined referent populations.

Diffuse lamellar keratitis induced by toxic chemicals after laser in situ keratomileusis

PURPOSE

To assess whether toxic chemicals produced during autoclaving sterilization were 1 of the main causes of diffuse lamellar keratitis (DLK) and to analyze the clinical outcomes of patients developing DLK after laser in situ keratomileusis (LASIK) treated with intensive topical corticosteroids.

SETTING

Department of Ophthalmology, Taichung Veterans General Hospital, Taichung, Taiwan, Republic of China.

METHODS

A total of 14 eyes of 7 patients received technically smooth LASIK and developed DLK, including 6 severe and 8 mild DLK cases. In all eyes the same microkeratome was used; it was contaminated with toxic chemical materials produced accidentally by coautoclaving instruments and a foam piece.

RESULTS

Six eyes of 3 patients developed severe DLK on the same day, and 8 eyes of 4 patients developed mild DLK during the next LASIK surgery. After intensive topical corticosteroid treatment, lamellar infiltrates disappeared in 3 days in mild DLK eyes and 2 weeks in severe DLK eyes. No eye was treated with flap lifting and interface irrigation. For grade 4 DLK, the corneal opacity and flap folds disappeared in 4 weeks. There were no instances of permanent corneal scarring or loss of best spectacle-corrected visual acuity.

CONCLUSIONS

Toxic chemicals produced during instrument autoclaving sterilization are a possible cause of DLK. Immediate diagnosis and treatment with intensive corticosteroid drops are critical and can resolve severe DLK.

Symptom onset in the first 2 years of employment at a wood products plant using diisocyanates: some observations relevant to occupational medical screening

BACKGROUND

Questionnaires are essential tools for medical screening, but their role in monitoring workers at increased risk of occupational asthma (OA) remains indeterminate.

METHODS

Employees who were at a newly established wood products plant without previous exposure to methylene diphenyl diisocyanate (MDI) completed an initial questionnaire and from one to four follow-up questionnaires during a 2-year period. Onset of symptoms in 132 workers was assessed by exposure groups and modeled using generalized estimating equations.

RESULTS

Onset of attacks of dyspnea with wheeze, attacks of dyspnea or cough at rest, and chest tightness were significantly associated with MDI exposure after controlling for age, smoking, and wood dust exposure. Onset of cough on most days was significantly related to smoking and dust. Onset of phlegm production was significantly related to both MDI and dust exposure.

CONCLUSIONS

Onset of certain symptoms is significantly associated with MDI exposure. Early detection of MDI-associated health effects using a short screening questionnaire appears feasible.

Exposure biomarkers and risk from gluing and heating of polyurethane: a cross sectional study of respiratory symptoms

OBJECTIVES

To define the relation between exposure to polyurethane (PUR) glue, biomarkers of exposure and effect, and work related symptoms that occur at least once a week.

METHODS

In a cross sectional study, 152 workers and 14 clerks in a factory with exposure to sprayed and heated PUR glue containing 4, 4'-diphenylmethane (MDI) or 1,6-hexamethylene (HDI) di-isocyanate were examined with gas chromatography-mass spectrometry (GC-MS) for metabolites of MDI in plasma (P-MDX) and urine (U-MDX), 2,4- and 2, 6-toluene di-isocyanate (TDI; P-TDX, U-TDX) and HDI in plasma and urine, specific serum IgG (S-IgG-MDI, S-IgG-HDI, and S-IgG-TDI, respectively) and IgE (S-IgE-MDI). Work related symptoms of the eyes and airways (nose or lower airways, or both), and lung function were also evaluated.

RESULTS

P-MDX was detected in 65% of the workers, U-TDX in 47%, HDX in none. Three per cent were positive for S-IgE-MDI, 33% for S-IgG-MDI, 32% for S-IgG-TDI, and 12% for S-IgG-HDI. A few clerks had metabolites, and some had antibodies. Most metabolites and immunoglobulins were slightly correlated-for example, P-MDX v S-IgG-MDI: r(s)=0.21. Workers who heated glue had increased P-MDX (odds ratio (OR)=12 for a value above the median) and S-IgG-MDI (OR=3.7), sprayers P-2,4-TDX (OR=6.2) and P-2,6-TDX (OR=16). Twenty six per cent of the workers had work related symptoms of the airways, 21% from the nose, 11% from the lower airways. Spraying of glue increased the risk of work related symptoms and slightly decreased lung function. U-MDX was associated with work related symptoms from the airways (OR=3.7) and P-2,6-TDX with work related symptoms from the lower airways (OR=6.6). S-IgG-MDI was related to work related symptoms from the airways (OR=2.6).

CONCLUSIONS

There were relations between exposures to sprayed and heated PUR glue based on MDI and HDI, concentrations of metabolites of MDI and TDI in plasma and urine, specific IgG serum antibodies against MDI, TDI, and HDI, and work related symptoms.