Assessing isocyanate exposures in polyurethane industry sectors using biological and air monitoring methods.

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 being used by operators was not effective or that absorption may have occurred via dermal or other routes of exposure. This study demonstrates that biological monitoring is a useful tool when assessing worker exposure to isocyanates, providing a more complete picture on the efficacy of control measures in place than is possible by air monitoring alone. The results also demonstrated that where control measures were judged to be adequate, most biological samples were close to or < 1 micromol mol(-1) creatinine, the agreed biological monitoring benchmark.

Evaluation and further development of EASE model 2.0.

EASE (Estimation and Assessment of Substance Exposure) is a general model that may be used to predict workplace exposure to a wide range of substances hazardous to health. First developed in the early 1990s, it is now in its second Windows version. This paper provides a critical assessment of the utility and performance of the EASE model, and on the basis of this review, recommendations for the structure of a revised model are outlined. Twenty-seven stakeholders were interviewed about their previous use of EASE, perceived advantages and limitations of the model and suggestions for improvement. A subset of stakeholders was contacted on a second occasion to determine their views on the preferred outputs for an ideal exposure assessment model. Overall, stakeholders felt that the model should be updated to provide more accurate and precise exposure assessments. However, users also expressed the view that the simplicity and usability of the software model should not be compromised. Six studies investigating the validity of the inhalation exposure assessment section of EASE were identified. These showed that the model generally either predicted close to the measured exposures or overestimated exposure; though performance was highly variable. Two studies investigated the validity of the dermal exposure assessment and found that EASE produced considerable overestimates of actual dermal exposure (the amount of a substance that actually lands on the skin). A conceptual model of exposure was developed to investigate whether the structure of the EASE model is appropriate. Although EASE has a number of characteristics that describe exposure, it is a greatly simplified model and does not include all the important exposure determinants. More importantly, EASE can produce estimates of exposure that are ambiguous or incomplete. Our conceptual model may provide a rational basis for developing an improved version of EASE but further consultation is needed to decide the purpose and intended use of any successor to EASE.

A novel method of assessing the effectiveness of protective gloves--results from a pilot study.

We have devised a novel method for evaluating the effectiveness of protective gloves and have undertaken a small study to assess this approach. Three types of glove were tested in a standardised simulation test with a permethrin-based pesticide. Prewashed cotton gloves were used to collect the samples. One was worn over the protective glove on one hand to measure the potential deposition of pesticide on the hands had the gloves not been worn. A second was placed under the protective glove on the opposite hand to measure the actual deposition of permethrin on the hands when the gloves were worn. This regime was reversed half way through each test in an attempt to prevent bias. Measurable inner glove contamination occurred on 25 out of 30 occasions. Geometric mean protection factors were calculated from the ratio of outer and inner sampling glove contamination, with average protection factors of 470, 200 and 96 being obtained for the two nitrile and PVC gloves, respectively. The PVC gloves were the least effective in preventing inner glove contamination, probably because the glove was thick and fairly inflexible, causing more pesticide to enter the glove around the cuff. Although the tasks were standardised, variability occurred due to worker behaviour and equipment failure. The spray pump failed on five occasions, resulting in higher levels of inner glove contamination and a geometric mean protection factor of 32. On the occasions when the pump worked correctly, the level of protection provided by the gloves rose dramatically with mean protection factors of 220 and 450 being obtained for workers categorised as "messy" and "tidy", respectively.