Assessing Isocyanate Exposures in Polyurethane Industry Sectors Using Biological and Air Monitoring Methods

Abstract

Isocyanates, as a chemical group, are considered to be the biggest cause of occupational asthma in the UK. Monitoring of airborne exposures to total isocyanate is costly, requiring considerable expertise, both in terms of sample collection and chemical analysis and cannot be used to assess the effectiveness of protection from wearing respiratory protective equipment (RPE). Biological monitoring by analysis of metabolites in urine can be a relatively simple and inexpensive way to assess exposure to isocyanates. It may also be a useful way to evaluate the effectiveness of control measures in place. In this study biological and inhalation monitoring were undertaken to assess exposure in a variety of workplaces in the non-motor vehicle repair sector. Companies selected to participate in the survey included only those judged to be using good working practices when using isocyanate formulations. This included companies that used isocyanates to produce moulded polyurethane products, insulation material and those involved in industrial painting. Air samples were collected by personal monitoring and were analysed for total isocyanate content. Urine samples were collected soon after exposure and analysed for the metabolites of different isocyanate species, allowing calculation of the total metabolite concentration. Details of the control measures used and observed contamination of exposed skin were also recorded. A total of 21 companies agreed to participate in the study, with exposure measurements being collected from 22 sites. The airborne isocyanate concentrations were generally very low (range 0.0005-0.066 mg m(-3)). A total of 50 of the 70 samples were <0.001 mg m(-3), the limit of quantification (LOQ), therefore samples below the LOQ were assigned a value of 1/2 LOQ (0.0005 mg m(-3)). Of the 70 samples, 67 were below the current workplace exposure limit of 0.02 mg m(-3). The highest inhalation exposures occurred during spray painting activities in a truck manufacturing company (0.066 mg m(-3)) and also during spray application of polyurethane foam insulation (0.023 mg m(-3)). The most commonly detected isocyanate in the urine was hexamethylene diisocyanate, which was detected in 21 instances. The geometric mean total isocyanate metabolite concentration for the dataset was 0.29 micromol mol(-1) creatinine (range 0.05-12.64 micromol mol(-1) creatinine). A total of 23 samples collected were above the agreed biological monitoring guidance value of 1.0 micromol mol(-1) creatinine. Activities that resulted in the highest biological monitoring results of the dataset included mixing and casting of polyurethane products (12.64 micromol mol(-1) creatinine), semi-automatic moulding (4.80 micromol mol(-1) creatinine) and resin application (3.91 micromol mol(-1) creatinine). The biological monitoring results show that despite low airborne isocyanate concentrations, it was possible to demonstrate biological uptake. This tends to suggest high sensitivity of the biological monitoring method and/or that in some instances the RPE bein...

Skin Exposure to Isocyanates: Reasons for Concern

“…Studies investigating urinary biomarkers of isocyanate exposure (the corresponding diamines) have provided additional indirect evidence for isocyanate skin uptake (Creely et al 2006; Kääriä et al 2001; Maitre et al 1996). Elevated levels of these urinary biomarkers have been detected in workers, in spite of very low or nondetectable documented inhalation exposures.…”

“…Elevated levels of these urinary biomarkers have been detected in workers, in spite of very low or nondetectable documented inhalation exposures. Greater than 2-fold higher urinary metabolite concentrations have been reported for operators with likely skin contamination compared to those without (Creely et al 2006). Maitre et al (1996) measured urinary hexamethylene diamine (HDA) of two HDI-exposed coworkers.…”

Occupational exposure to selected isocyanates in Polish industry

“…Although the measured TDI levels in the air were significantly higher than in the case of MDI, in the group of persons exposed to low levels of TDI (below LOQ), they also confirmed elevated levels of the metabolites of this compound in urine [29]. In studies conducted in 21 companies in Great Britain, Creely et al [18] found that only in 4% of collected air samples the concentration of the determined compound exceeded the OEL value, while levels of its metabolites in urine exceeded the British Biological Monitoring Guidance Value (BMGV -1 mmol/mol of creatinine) in 23 cases (33%) [5].…”

The role of isocyanates in fire toxicity

“…The selectivity of UV-FL absorbance detection for isocyanates is described as good for air samples (Ceballos et al 2011). However, this detection method generally suffers from slightly lower limit of detection (LOD) than MS, and a lower selectivity, especially in complex matrices (Corradini et al 1998). In addition, fire effluents are also likely contain polyaromatic species that can interfere with the UV/FL detection.…”