Annals of Occupational Hygiene - current issue

How Safe is Control Banding? Integrated Evaluation by Comparing OELs with Measurement Data and Using Monte Carlo Simulation

Tischer, M., Bredendiek-KAmper, S., Poppek, U., Packroff, R. — 2009-07-03

The present study aims to explore the protection level that can be achieved by the German control banding (CB) tool Einfaches Massnahmenkonzept Gefahrstoffe, ‘Easy-to-use workplace control scheme for hazardous substances’. The rationale of our integrated approach is based on the Bewertungsindex (BWI), which is the quotient of the exposure level and the occupational exposure limit (OEL), with BWI <1 indicating compliance. The frequency distributions of the BWI were calculated in order to reflect statistically the variability of workplace conditions. The corresponding statistical values of the frequency distributions (percentiles etc.) are interpreted as an indicator of the level of protection that is achieved.

The occupational exposure data sets used in the calculation of the BWI frequency distribution were mainly collected from Bundesanstalt für Arbeitsschutz und Arbeitsmedizin field studies. The data sets taken into account were selected according to the criteria ‘hazard band, exposure potential, control approach’. Such a combination is called the ‘control banding scenario’ (CBS). Measurement data are only available for two CBS: in the case of the CBS ‘hazard band A, EPL3, CS1’ the only data that are available (n = 220) relate to propane-2-ol as used in the area of offset printing. Only 0.4 % of the BWI are above 1, this indicating a high level of compliance. In the case of the CBS ‘Hazard band B, EPL2, CS1’, exposure data are available from screen-printing firms (n = 50), optician workshops (n = 49), and from the area of furniture production (n = 13). The frequency distributions of the BWI reveal almost no instances of values being exceeded in the three branches.

In a subsequent step, a Monte Carlo Simulation was employed to explore whether the BWI frequency distributions can be generalized using a probabilistic model. The frequency distributions of the exposure levels and the OELs were used as the input data for the model. The simulation results show that the model distribution, called Modellierter Bewertungsindex distribution, can reproduce the BWI distribution if the data basis is homogeneous (data from one branch) and less correlated. In case of a heterogeneous data set (pooled data from different branches), the simulation results can be interpreted as generic statements about the attainable protection level. It was found that CB does not (at least potentially) guarantee compliance in either case. On the other hand, the generic simulation showed that compliance was high for volatile liquids used in closed systems (CBS: ‘hazard band C, EPL3, CS3’) and for solids in the presence of local exhaust ventilation (CBS: ‘hazard band B, EPS3, CS2’).

Evaluation of COSHH Essentials: Methylene Chloride, Isopropanol, and Acetone Exposures in a Small Printing Plant

Lee, E. G., Harper, M., Bowen, R. B., Slaven, J. — 2009-07-03

The current study evaluated the Control of Substances Hazardous to Health (COSHH) Essentials model for short-term task-based exposures and full-shift exposures using measured concentrations of three volatile organic chemicals at a small printing plant. A total of 188 exposure measurements of isopropanol and 187 measurements of acetone were collected and each measurement took ~60 min. Historically, collected time-weighted average concentrations (seven results) were evaluated for methylene chloride. The COSHH Essentials model recommended general ventilation control for both isopropanol and acetone. There was good agreement between the task-based exposure measurements and the COSHH Essentials predicted exposure range (PER) for cleaning and print preparation with isopropanol and for cleaning with acetone. For the other tasks and for full-shift exposures, agreement between the exposure measurements and the PER was either moderate or poor. However, for both isopropanol and acetone, our findings suggested that the COSHH Essentials model worked reasonably well because the probabilities of short-term exposure measurements exceeding short-term occupational exposure limits (OELs) or full-shift exposures exceeding the corresponding full-shift OELs were <0.05 under the recommended control strategy. For methylene chloride, the COSHH Essentials recommended containment control but a follow-up study was not able to be performed because it had already been replaced with a less hazardous substance (acetone). This was considered a more acceptable alternative to increasing the level of control.

Ultrafine Particle Characteristics in Seven Industrial Plants

Elihn, K., Berg, P. — 2009-07-03

Ultrafine particles are considered as a possible cause of some of the adverse health effects caused by airborne particles. In this study, the particle characteristics were measured in seven Swedish industrial plants, with a special focus on the ultrafine particle fraction. Number concentration, size distribution, surface area concentration, and mass concentration were measured at 10 different job activities, including fettling, laser cutting, welding, smelting, core making, moulding, concreting, grinding, sieving powders, and washing machine goods. A thorough particle characterization is necessary in workplaces since it is not clear yet which choice of ultrafine particle metric is the best to measure in relation to health effects. Job activities were given a different order of rank depending on what particle metric was measured. An especially high number concentration (130 x 10³ cm^–3) and percentage of ultrafine particles (96%) were found at fettling of aluminium, whereas the highest surface area concentration (up to 3800 µm² cm^–3) as well as high PM10 (up to 1 mg m^–3) and PM1 (up to 0.8 mg m^–3) were found at welding and laser cutting of steel. The smallest geometric mean diameter (22 nm) was found at core making (geometric standard deviation: 1.9).

Exposure to Hazardous Substances in a Standard Molecular Biology Laboratory Environment: Evaluation of Exposures in IARC Laboratories

Chapot, B., Secretan, B., Robert, A., Hainaut, P. — 2009-07-03

Working in a molecular biology laboratory environment implies regular exposure to a wide range of hazardous substances. Several recent studies have shown that laboratory workers may have an elevated risk of certain cancers. Data on the nature and frequency of exposures in such settings are scanty. The frequency of use of 163 agents by staff working in molecular biology laboratories was evaluated over a period of 4 years by self-administered questionnaire. Of the agents listed, ethanol was used by the largest proportion of staff (70%), followed by ethidium bromide (55%). Individual patterns of use showed three patterns, namely (i) frequent use of a narrow range of products, (ii) occasional use of a wide range of products, and (iii) frequent and occasional use of an intermediate range of products. Among known or suspected carcinogens (International Agency for Research on Cancer Group 1 and 2A, respectively), those most frequently used included formaldehyde (17%), oncogenic viruses (4%), and acrylamide (32%). The type of exposure encountered in research laboratories is extremely diverse. Few carcinogenic agents are used frequently but many laboratory workers may be exposed occasionally to known human carcinogens. In addition, many of the chemicals handled by staff represent a health hazard. The results enabled the staff physician to develop an individual approach to medical surveillance and to draw a personal history of occupational exposures for laboratory staff.

Role of Associated Mineral Fibres in Chrysotile Asbestos Health Effects: The Case of Balangeroite

Turci, F., Tomatis, M., Compagnoni, R., Fubini, B. — 2009-07-03

Objectives: To evaluate the biodurability of balangeroite, present as contaminant of chrysotile asbestos in the Balangero mine, in order to have indication whether it might have been a confounding factor in the association of the mesothelioma cases reported among mine workers and employees.

Methods: The modifications taking place following incubation of the fibres in simulated phagolysosomal fluids have been measured on balangeroite, on one pure chrysotile sample (Val Malenco), on one chrysotile from Balangero with some associated balangeroite, and on two tremolite samples.

Results: The incubation modifies both chrysotile and balangeroite with substantial release in the medium of the metal ions which occupy the octahedral site in the mineral structure of the fibre while tremolite is virtually unaffected.

Conclusions: Considering the profound differences between the structure of balangeroite and amphiboles, previous results and observations on the poor ecopersistence of balangeroite, and the present data, we conclude that balangeroite traces may contribute to the overall toxicity of the airborne fibres in Balangero, but may not be compared to tremolite nor considered the sole responsible for the excess of mesothelioma found in Balangero.

A Survey of Occupational Exposure to 4,4'-methylene-bis (2-chloroaniline) (MbOCA) in the UK

Cocker, J., Cain, J. R., Baldwin, P., McNally, K., Jones, K. — 2009-07-03

Objectives: The main objective of the study was to gather information about the current controls and levels of exposure to 4,4'-methylene-bis (2-chloroaniline) (MbOCA) in a representative cross section of workplaces that use it to manufacture polyurethane elastomers. The study also aimed to investigate whether controls and guidance could be improved and to investigate exposure to isocyanates in these workplaces using biological monitoring.

Methods: An occupational hygienist and a field scientist visited the two UK suppliers and 20 out of the 25 workplaces known to be using MbOCA in the UK during 2005 and 2006. They collected air samples, surface wipes, gloves, and urine samples and made observations to assess exposure and the adequacy of controls. All samples were analysed for MbOCA and urine samples were additionally analysed for isocyanate metabolites. A statistical analysis was made of the results.

Results: Only 2.5% of the 80 personal inhalation exposures to MbOCA exceeded the workplace exposure limit of 5 µg m^–3 8-h time-weighted average and 84% were below the limit of detection (LOD). Surface samples (n = 334) were collected from MbOCA users and suppliers and 60% had detectable levels of MbOCA ranging from 0.019 to 400 µg cm^–2. The highest levels were around a hopper, ovens, and the weighing and pouring areas. MbOCA was also detected in 8 of the 75 samples collected from areas not likely to be in contact with MbOCA. At the two suppliers, samples (n = 28) were collected from the outside surfaces of recently imported kegs, pallets, and the floor around kegs. Six samples had detectable levels and four of these (0.2, 0.8, 1, and 6 µg cm^–2) were from the floor and pallets in both suppliers. The other two positive results were found on the outside rim (18 µg cm^–2) and side (23 µg cm^–2) of a keg at one supplier indicating contamination by the manufacturer. Urine samples (n = 79) were collected and 49% were below the LOD for MbOCA and only three samples had levels of MbOCA that exceeded the biological monitoring guidance value (BMGV) of 15 µmol mol^–1 creatinine. The highest urinary MbOCA concentrations were in samples from workers casting and moulding. The 90th percentile of the urine MbOCA results was 8.6 µmol MbOCA per mol creatinine. Urine samples were also analysed for the diamine metabolites of toluene diisocyanate and hexamethylene diisocyanate and 33% had detectable levels with 22 and 13% of results, respectively, above the BMGV for isocyanates (1 µmol isocyanate-derived diamine per mol creatinine). The maximum urinary concentration of toluene diamine and hexane diamine were 15.6 and 10.1 µmol mol^–1 creatinine, respectively.

Conclusions: The survey found that the measures used to control exposure to MbOCA could be improved. Although air levels of MbOCA were generally low, there was evidence of spread of surface contamination and poor maintenance of controls such as local exhaust ventilation. A BMGV based on the 90th percentile of data from workplaces with good control would be less than the 90% value of 8.6 µmol mol^–1 creatinine found in this study and suggests that the current BMGV of 15 µmol mol^–1 creatinine is no longer acting as a stimulus to reduce exposure. The metabolites of isocyanates found in urine samples in this study could arise from inhalation exposure to isocyanates or from dermal exposure to either isocyanates or their diamine breakdown product and need further investigation.

Sampling Strategies for Occupational Exposure Assessment under Generalized Linear Model

Chen, C.-C., Chuang, C.-L., Wu, K.-Y., Chan, C.-C. — 2009-07-03

Objectives: Occupational exposure assessment is a major task in industrial hygiene studies. Although statistical analyses for magnitudes and variations of exposures to various types of working populations based on existing data sets are extensive, relatively few discussions on study designs appear in the literature, especially for sample size determination and number of repeated measurements.

Methods: In this paper, we propose a general framework of sampling strategies on sample size requirement together with the number of repeated measurements using the mixed-effects generalized linear model (GLM). As illustrative examples, we discuss sampling strategies separately under the log-normal assumption for hypotheses testing on (i) mean exposure differences of multiple worker groups and (ii) presence of a long-term exposure trend.

Results: Given a specified alternative hypothesis, the desired significance level and statistical power, the number of repeated measurements, within-worker and between-worker variances, and a correlation structure, we have derived and tabulated an explicit sample size requirement of the two hypothetical cases under log-normal distribution assumption.

Conclusions: On the basis of the tabulated outcomes, the sample size requirement is much more dominant than the number of repeated measurements for a group exposure comparison. Thus, in this case, recruiting more workers with fewer repeated measurements may be more economical than the opposite approach. For testing the presence of a long-term exposure trend, the sample size required decreases substantially with the number of repeated measurements. Also, equally spaced sampling times would be optimal because the effect of between-worker variance is algebraically cancelled out in sample size calculations.

The Evaluation of CBRN Canisters for Use by Firefighters during Overhaul

Currie, J., Caseman, D., Anthony, T. R. — 2009-07-03

Air-purifying respirators (APRs) have been proposed to provide an additional respiratory protection option for structural firefighters involved in overhaul operations and wildland firefighters, where particulate and aldehyde exposures have been documented. Previous studies (Anthony et al., 2007) developed test methods to evaluate APR cartridges and canisters for use in overhaul activities, where initial findings indicated that multi-gas cartridges may not be effective. This study evaluated the performance of three chemical, biological, radiological, and nuclear (CBRN) canisters (MSA, 3M, and Scott) and one multi-gas canister similar in appearance to CBRN canisters but without CBRN certification (3M FR-64040). Challenge concentrations typical of overhaul exposures were generated by combusting common household materials. Twelve tests were conducted, using random canister selection, where challenge air and air filtered by the canisters were tested. All tests examined penetration of CO; NO₂; SO₂; respirable dust; aldehydes, including formaldehyde, acrolein, and glutaraldehyde; and hydrogen cyanide. Six of the tests also investigated naphthalene, benzene, and hydrogen chloride, but challenge concentrations from the simulated overhaul smoke were near the limit of detection (LOD) and were two orders of magnitude below short-term or ceiling concentrations of concern and were eliminated from further study with the combustion materials used in this study. In all tests, an irritant index was computed to evaluate the aggregate penetration of contaminants in the smoke mixture, using 15- and 30-min occupational exposure limits as well as assessing individual penetrations. In all cases, the challenge concentration irritant index exceeded unity, ranging from 2.3 to 21. For all 12 tests, the APR canister reduced the overall irritant index to levels below unity, indicating that these canisters would provide protection for firefighters working in overhaul environments. However, in some tests, levels of carbon monoxide were higher than recommended for persons wearing APRs. Since these canisters do not protect against carbon monoxide, firefighters must still rely on direct reading warning to indicate high CO levels, indicating the need to leave the area if wearing an APR, as these APR canisters would be inappropriate.

Vibrotactile Perception and Effects of Short-Term Exposure to Hand-Arm Vibration

Burstrom, L., Lundstrom, R., Hagberg, M., Nilsson, T. — 2009-07-03

This study clarifies whether the established frequency weighting procedure for evaluating exposure to hand-transmitted vibration can effectively evaluate the temporary changes in vibrotactile perception thresholds due to pre-exposure to vibration. In addition, this study investigates the relationship between changes of the vibrotactile perception thresholds and the normalized energy-equivalent frequency-weighted acceleration. The fingers of 10 healthy subjects, five male and five female, were exposed to vibration under 16 conditions with a combination of different frequencies, intensities, and exposure times. The vibration frequencies were 31.5 and 125 Hz and exposure lasted between 2 and 16 min. According to International Organization for Standardization (ISO) 5349-1, the energy-equivalent frequency-weighted acceleration for the experimental time of 16 min is 2.5 or 5.0 m s^–2 root-mean-square, corresponding to a 8-h equivalent acceleration, A(8), of ~0.5 and 0.9 m s^–2, respectively. A measure of the vibrotactile perception thresholds was conducted before the different exposures to vibration. Immediately after the vibration exposure, the acute effect was measured continuously on the exposed index finger for the first 75 s, followed by 30 s of measures every minute for a maximum of 10 min. If the subject's thresholds had not recovered, the measures continued for a maximum of 30 min with measurements taken every 5 min. Pre-exposure to vibration significantly influenced vibrotactile thresholds. This study concludes that the influence on the thresholds depends on the frequency of the vibration stimuli. Increased equivalent frequency-weighted acceleration resulted in a significant change in threshold, but the thresholds were unaffected when changes in the vibration magnitude were expressed as the frequency-weighted acceleration or the unweighted acceleration. Moreover, the frequency of the pre-vibration exposure significantly influenced (up to 25 min after exposure) recovery time of the vibrotactile thresholds. This study shows that the frequency weighting procedure in ISO 5349-1 is unable to predict the produced acute changes in the vibrotactile perception. Moreover, the results imply that the calculation of the ‘energy-equivalent’ frequency-weighted acceleration does not reflect the acute changes of the vibration perception thresholds due to pre-exposure to vibration. Furthermore, when testing for the vibrotactile thresholds, exposure to vibration on the day of a test might influence the results. Until further knowledge is obtained, the previous practice of 3 h avoidance of vibration exposure before assessment is recommended.

NIOSH Definition of Closed-System Drug-Transfer Devices

Nygren, O., Olofsson, E., Johannson, L. — 2009-07-03