Evaluation of self-reported skin problems among workers exposed to toluene diisocyanate (TDI) at a foam manufacturing facility

Causes of irritant contact dermatitis after occupational skin exposure: a systematic review

PURPOSE

Irritant contact dermatitis (ICD) is a major cause of occupational disease. The aim was to review the relation between exposure to occupational irritants and ICD and the prognosis of ICD.

METHODS

Through a systematic search, 1516 titles were identified, and 48 studies were included in the systematic review.

RESULTS

We found that the evidence for an association between ICD and occupational irritants was strong for wet work, moderate for detergents and non-alcoholic disinfectants, and strong for a combination. The highest quality studies provided limited evidence for an association with use of occlusive gloves without other exposures and moderate evidence with simultaneous exposure to other wet work irritants. The evidence for an association between minor ICD and exposure to metalworking fluids was moderate. Regarding mechanical exposures, the literature was scarce and the evidence limited. We found that the prognosis for complete healing of ICD is poor, but improves after decrease of exposure through change of occupation or work tasks. There was no substantial evidence for an influence of gender, age, or household exposures. Inclusion of atopic dermatitis in the analysis did not alter the risk of ICD. Studies were at risk of bias, mainly due to selection and misclassification of exposure and outcome. This may have attenuated the results.

CONCLUSION

This review reports strong evidence for an association between ICD and a combination of exposure to wet work and non-alcoholic disinfectants, moderate for metalworking fluids, limited for mechanical and glove exposure, and a strong evidence for a poor prognosis of ICD.

Testing of Disposable Protective Garments Against Isocyanate Permeation From Spray Polyurethane Foam Insulation

Background

Diisocyanates (isocyanates), including methylene diphenyl diisocyanate (MDI), are the primary reactive components of spray polyurethane foam (SPF) insulation. They are potent immune sensitizers and a leading cause of occupational asthma. Skin exposure to isocyanates may lead to both irritant and allergic contact dermatitis and possibly contribute to systemic sensitization. More than sufficient evidence exists to justify the use of protective garments to minimize skin contact with aerosolized and raw isocyanate containing materials during SPF applications. Studies evaluating the permeation of protective garments following exposure to SPF insulation do not currently exist.

Objectives

To conduct permeation testing under controlled conditions to assess the effectiveness of common protective gloves and coveralls during SPF applications using realistic SPF product formulations.

Methods

Five common disposable garment materials [disposable latex gloves (0.07 mm thickness), nitrile gloves (0.07 mm), vinyl gloves (0.07 mm), polypropylene coveralls (0.13 mm) and Tyvek coveralls (0.13 mm)] were selected for testing. These materials were cut into small pieces and assembled into a permeation test cell system and coated with a two-part slow-rise spray polyurethane foam insulation. Glass fiber filters (GFF) pretreated with 1-(9-anthracenylmethyl)piperazine) (MAP) were used underneath the garment to collect permeating isocyanates. GFF filters were collected at predetermined test intervals between 0.75 and 20.00 min and subsequently analyzed using liquid chromatography-tandem mass spectrometry. For each garment material, we assessed (i) the cumulative concentration of total isocyanate, including phenyl isocyanate and three MDI isomers, that effectively permeated the material over the test time; (ii) estimated breakthrough detection time, average permeation rate, and standardized breakthrough time; from which (iii) recommendations were developed for the use of similar protective garments following contamination by two-component spray polyurethane foam systems and the limitations of such protective garments were identified.

Results

Each type of protective garment material demonstrated an average permeation rate well below the ASTM method F-739 standardized breakthrough rate threshold of 100.0 ng/cm2 min-1. Disposable latex gloves displayed the greatest total isocyanate permeation rate (4.11 ng/cm2 min-1), followed by the vinyl and nitrile gloves, respectively. The Tyvek coverall demonstrated a greater average rate of isocyanate permeation than the polypropylene coveralls. Typical isocyanate loading was in the range of 900 to 15,000 ng MDI/cm2.

Conclusion

Permeation test data collected during this study indicated that each type of protective garment evaluated, provided a considerable level of protection (i.e. 10-110-fold reduction from the level of direct exposure) against the isocyanate component of the SPF insulation mixture. Nitrile gloves and polypropylene coveralls demonstrated the lowest rate of permeation and the lowest cumulative permeation of total isocyanate for each garment type.

Occupational asthma risk from exposures to toluene diisocyanate: A review and risk assessment

BACKGROUND

Toluene Diisocyanate (TDI) is a known respiratory sensitizer linked to occupational asthma (OA). To better manage worker risks, an appropriate characterization of the TDI-OA dose-risk relationship is needed.

METHODS

The literature was reviewed for data suitable for dose-response modeling. Previous study data were fit to models to derive prospective occupational exposure limits (OELs), using benchmark dose (BMD) and low-dose extrapolation approaches.

RESULTS

Data on eight TDI-exposed populations were suitable for analysis. There were 118 OA cases in a population contributing 13 590 person-years. The BMD-based OEL was 0.4 ppb. The OEL based on low-dose extrapolation to working lifetime extra risk of 1/1000 was 0.3 ppb.

CONCLUSIONS

This study synthesized epidemiologic data to characterize the TDI-OA dose-risk relationship. This approach yielded prospective OEL estimates below recent recommendations by the American Conference of Governmental Industrial Hygienists, but given significant study limitations, this should be interpreted with caution. Confirmatory research is needed.

A Role for Regulatory T Cells in a Murine Model of Epicutaneous Toluene Diisocyanate Sensitization

Toluene diisocyanate (TDI) is a leading cause of chemical-induced occupational asthma which impacts workers in a variety of industries worldwide. Recently, the robust regulatory potential of regulatory T cells (Tregs) has become apparent, including their functional role in the regulation of allergic disease; however, their function in TDI-induced sensitization has not been explored. To elucidate the kinetics, phenotype, and function of Tregs during TDI sensitization, BALB/c mice were dermally exposed (on each ear) to a single application of TDI (0.5-4% v/v) or acetone vehicle and endpoints were evaluated via RT-PCR and flow cytometry. The draining lymph node (dLN) Treg population expanded significantly 4, 7, and 9 days after single 4% TDI exposure. This population was identified using a variety of surface and intracellular markers and was found to be phenotypically heterogeneous based on increased expression of markers including CD103, CCR6, CTLA4, ICOS, and Neuropilin-1 during TDI sensitization. Tregs isolated from TDI-sensitized mice were significantly more suppressive compared with their control counterparts, further supporting a functional role for Tregs during TDI sensitization. Last, Tregs were depleted prior to TDI sensitization and an intensified sensitization response was observed. Collectively, these data indicate that Tregs exhibit a functional role during TDI sensitization. Because the role of Tregs in TDI sensitization has not been previously elucidated, these data contribute to the understanding of the immunologic mechanisms of chemical induced allergic disease.

Skin symptoms in bakery and auto body shop workers: associations with exposure and respiratory symptoms

Purpose

Despite the importance of skin exposure, studies of skin symptoms in relation to exposure and respiratory symptoms are rare. The goals of this study were to describe exposure–response relationships for skin symptoms, and to investigate associations between skin and respiratory symptoms in bakery and auto body shop workers.

Methods

Data from previous studies of bakery and auto body shop workers were analyzed. Average exposure estimates for wheat allergen and isocyanates were used. Generalized linear models were constructed to describe the relationships between exposure and skin symptoms, as well as between skin and respiratory symptoms.

Results

Data from 723 bakery and 473 auto body shop workers were analyzed. In total, 5.3 % of bakery and 6.1 % of auto body shop workers were female; subjects’ mean age was 39 and 38 years, respectively. Exposure–response relationships were observed in auto body shop workers for itchy or dry skin (PR 1.55, 95 % CI 1.2–2.0) and work-related itchy skin (PR 1.97, 95 % CI 1.2–3.3). A possible exposure–response relationship for work-related itchy skin in bakery workers did not reach statistical significance. In both groups, reporting skin symptoms was strongly and significantly associated with reporting respiratory symptoms, both work-related and non-work-related.

Conclusions

Exposure–response relationships were observed for skin symptoms in auto body shop workers. The lack of significant exposure–response associations in bakery workers should be interpreted cautiously. Workers who reported skin symptoms were up to four times more likely to report respiratory symptoms. Improved awareness of both skin and respiratory outcomes in exposed workers is needed.

Electronic supplementary material

The online version of this article (doi:10.1007/s00420-012-0760-x) contains supplementary material, which is available to authorized users.

Classification of skin sensitizing substances: a comparison between approaches used by the DFG-MAK Commission and the European Union legislation

A systematic classification of substances (or mixtures of substances) with regard to various toxicological endpoints is a prerequisite for the implementation of occupational safety strategies. As its principal task the "Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area" of the "Deutsche Forschungsgemeinschaft" (DFG-MAK Commission) derives and recommends maximum workplace concentrations and biological tolerance values (MAK and BAT values) based exclusively on scientific arguments. Several endpoints are evaluated separately in detail, e.g. carcinogenicity, risks during pregnancy, germ cell mutagenicity or contribution to systemic toxicity after cutaneous absorption. Skin- and airway sensitization is also considered; the present paper focuses on these two endpoints.

Hand/face/neck localized pattern: sticky problems--resins

Plastic resin systems have an increasingly diverse array of applications but also induce health hazards, the most common of which are allergic and irritant contact dermatitis. Contact urticaria, pigmentary changes, and photoallergic contact dermatitis may occasionally occur. Other health effects, especially respiratory and neurologic signs and symptoms, have also been reported. These resin systems include epoxies, the most frequent synthetic resin systems to cause contact dermatitis, (meth)acrylics, polyurethanes, phenol-formaldehydes, polyesters, amino resins (melamine-formaldehydes, urea-formaldehydes), polyvinyls, polystyrenes, polyolefins, polyamides and polycarbonates. Contact dermatitis usually occurs as a result of exposure to the monomers and additives in the occupational setting, although reports from consumers, using the raw materials or end products periodically surface. Resin- and additive-induced direct contact dermatitis usually presents on the hands, fingers, and forearms, while facial, eyelid, and neck involvement may occur through indirect contact, eg, via the hands, or from airborne exposure. Patch testing with commercially available materials, and in some cases the patient's own resins, is important for diagnosis. Industrial hygiene prevention techniques are essential to reduce contact dermatitis when handling these resin systems.

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.

Dermal, inhalation, and internal exposure to 1,6-HDI and its oligomers in car body repair shop workers and industrial spray painters

OBJECTIVES

To study inhalation and dermal exposure to hexamethylene diisocyanate (HDI) and its oligomers as well as personal protection equipment (PPE) use during task performance in conjunction with urinary hexamethylene diamine (HDA) in car body repair shop workers and industrial spray painters.

METHODS

Personal task based inhalation samples (n = 95) were collected from six car body repair shops and five industrial painting companies using impingers with di-n-butylamine (DBA) in toluene. In parallel, dermal exposure was assessed using nitril rubber gloves. Gloves were submerged into DBA in toluene after sampling. Analysis for HDI and its oligomers was performed by LC-MS/MS. Urine samples were collected from 55 workers (n = 291) and analysed for HDA by GC-MS.

RESULTS

Inhalation exposure was strongly associated with tasks during which aerosolisation occurs. Dermal exposure occurred during tasks that involve direct handling of paint. In car body repair shops associations were found between detectable dermal exposure and glove use (odds ratio (OR) 0.22, 95% confidence interval (CI) 0.09 to 0.57) and inhalation exposure level (OR 1.34, 95% CI 0.97 to 1.84 for a 10-fold increase). HDA in urine could be demonstrated in 36% and 10% of car body repair shop workers and industrial painting company workers respectively. In car body repair shops, the frequency of detectable HDA was significantly elevated at the end of the working day (OR 2.13, 95% CI 1.07 to 4.22 for 3-6 pm v 0-8 am). In both branches HDA was detected in urine of approximately 25% of the spray painters. In addition HDA was detected in urine of a large proportion of non-spray painters in car body repair shops.

CONCLUSION

Although (spray) painting with lacquers containing isocyanate hardeners results in the highest external exposures to HDI and oligomers, workers that do not perform paint related tasks may also receive a considerable internal dose.