British Occupational Hygiene Society Research Articles

Workplace Exposure to Rosin-based Solder Flux Fume During Hand Soldering

The patterns and extent of exposure to rosin based solder flux fume have been investigated in two surveys and a number of individual site visits carried out by the UK Health and Safety Executive (HSE). Determination of solder fume was by measurement of airborne resin acid particulate. Both static and personal sampling was carried out over time periods ranging from 15 minutes to several hours. Resin acid concentrations were found to vary from less than 1 μgm-3 to 2289 μgm-3 . The effects of various types of local exhaust ventilation on resin acid concentrations have been observed. On-tool tip extraction systems were generally found to be the best control measure available; however good design, positioning and system maintenance is essential for efficient capture of the fume. The resin acid concentrations detected at these twenty-six sites suggest that the proposed British long and short term occupational exposure limits are realistically attainable targets, particularly where good working practices and:or effective fume control measures are in place. ©1998 British Occupational Hygiene Society. Published by Elsevier Science Ltd.

Respirable Fibres: Surfactant Coated Fibres Release More Fe3 than Native Fibres at Both pH 4.5 and 7.2

Exposure to asbestos is associated with several lung diseases. The carcinogenic action of asbestos is not fully understood but oxidative stress is considered to play a role. Iron on the surface can lead to Fenton chemistry and the Haber Weiss reaction producing free radicals such as the hydroxyl radical, which is likely to be important. Little is known of the pathogenic action of man- made fibres. This study involved the use of a panel of man-made fibres, some of which were shown to be pathogenic and others shown to be non-pathogenic in recent animal studies. A short term assay measuring Fe3+ release from the fibres over a 20 hour time period, and also a longer study of 12 weeks, found that pathogenic and non-pathogenic fibres could not be differentiated according to Fe3+ release only. Iron release from native fibres was compared with that from surfactant- coated fibres, and in all cases surfactant coated fibres released more Fe3+ inferring that in vivo lung lining fluid coats native fibres and therefore affects the fibre surface chemistry and hence reactivity.© 1998 Published by Elsevier Science Ltd on behalf of British Occupational Hygiene Society.

The Quartz Hazard: A Variable Entity

An IARC Working Group recently classified crystalline silica (quartz) into IARC|s Group 1, i.e. a carcinogen. This classification is based on evidence of carcinogenicity in experimental animals and in humans. However, the evaluation stated that in making the overall evaluation, the Working Group noted that carcinogenicity to humans was not detected in all industrial circumstances studied and that carcinogenicity may be dependent on inherent characteristics of the crystalline silica or on external factors affecting its biological activity. The present review seeks to put the apparently conflicting findings of cancer incidence in quartz-exposed industries into a unifying thesis, based on mechanistic studies. These mechanistic studies have enabled the events leading from deposition of quartz to silicosis and cancer to be partially elucidated and have demonstrated that the biological effects of quartz can be understood in terms of surface reactivity. Weparticularly emphasise the ability of quartz to generate free radicals and cause oxidative stress and the fact that this could be modified by a range of substances that affect the quartz surface; some of these modifying substances could originate from other minerals. We therefore propose that the hazard posed by quartz is not a constant entity, but one that may vary dramatically depending on the origin of the silica sample or its contact with other chemicals:minerals within its complex consti- tution. The mechanistic data described here could assist in the interpretation of epidemiological studies and pose further hypotheses that could be tested in order to help resolve the quartz carcinogenesis anomaly. The data suggest that quartz cannot be dealt with as a single hazard entity, as is the case with most other chemicals. ©1998 British Occupational Hygiene Society. Published by Elsevier Science Ltd.

The biopersistence and pathogenicity of man-made vitreous fibres after short- and long-term inhalation.

A summary is given of the biopersistence and pathology after inhalation by rats of two different Man-made Vitreous Fibres, MMVF21 (traditional stone wool) and MMVF34 (HT stone wool), and the results are discussed in relation to biopersistence measured after intra-tracheal instillation. The results are given from a short-term inhalation biopersistence study, a completed chronic inhalation study, and interim results from an on-going chronic inhalation study. In both the short-term and chronic studies, laboratory rats were exposed by nose-only inhalation to well-characterised fibre test atmospheres that had been selected to be largely rat respirable. The short-term inhalation study included groups exposed to aerosols targeted at 150 fibres longer than 20 microns per cm3. The exposure duration was 6 hours/day for 5 days, with subsequent post-exposure periods lasting up to 12 months. For lung burden analyses, interim sacrifices were performed at regular intervals. The ongoing chronic study comprises a group of rats exposed to the MMVF34 fibre at one exposure level of 30 mg/m3. The negative control group is filtered air. The exposure duration is 6 hours/day, 5 days/week for 2 years, with a subsequent post-exposure period lasting until approximately 20% survival in the test fibre group. Interim sacrifices are performed at months 3, 6, 12, 18 and 24 and biopersistence monitored for rats exposed for 3 and 12 months, with subsequent post-exposure periods lasting 6 months. Effectively the main protocol for the previously conducted chronic study was the same, except that there were 3 fibre exposure groups (3, 16 and 30 mg/m3) and no specific biopersistence satellite groups were included. For MMVF34, the inhalation tests of different duration show a similar biopersistence pattern, while the intra-tracheal test gives longer elimination half-times especially for long fibres. The MMVF34 fibre is considerably less biopersistent than the traditional MMVF21 fibre when comparing the calculated elimination half-times after short-term inhalation. When comparing the pathology after 3, 6, 12 and 18 months exposure, MMVF34 showed minor histopathological changes compared to MMVF21. The carcinogenicity and toxicity results of the chronic study with MMVF21 suggest that this fibre does not pose a significant health risk to humans and the current results with MMVF34 indicate that this fibre consequently should pose an even smaller risk, if any.

Factors influencing personal magnetic field exposure: preliminary results for power utility and office workers.

Epidemiological studies and laboratory research suggest that exposure to extremely low frequency (< 300 Hz) magnetic fields is associated with an increase in risk of developing a number of rare diseases including leukaemia. Overall the risks to health appear to be small but a more accurate exposure assessment technique would help evaluate the true extent of any health effects. In this pilot study we aimed to identify and evaluate personal, work and environmental factors and their influence on measured exposure levels with a view to developing a method of reconstructing exposure. Office workers and power utility workers were studied using personal dosimeters to measure magnetic field exposure, along with frequent observation or measurement of factors related to exposure. Factors such as average and closest distance to source, time at position and current flow were combined in a series of metrics to investigate simple models of personal exposure. The results indicate that mean and peak magnetic field exposure levels are linked to current flow and the average distance of a worker from the source of the magnetic field. These factors are more accurate predictors of high exposures than they are of lower and average levels. It may be possible, with further work, to produce a model of exposure to magnetic fields for use in epidemiological studies.

The Biopersistence and Pathogenicity of Man-made Vitreous Fibres after Short- and Long-term Inhaltion

A summary is given of the biopersistence and pathology after inhalation by rats of two different Man-made Vitreous Fibres, MMVF21 (traditional stone wool) and MMVF34 (HT stone wool), and the results are discussed in relation to biopersistence measured after intra-tracheal instillation. The results are given from a short-term inhalation biopersistence study, a completed chronic inhalation study, and interim results from an on-going chronic inhalation stiuly. In both the short-term and chronic studies, laboratory rats were exposed by nose-only inhalation to well-characterised fibre test atmospheres that had been selected to be largely rat respirable. The short-term inhalation study included groups exposed to aerosols targeted at 150 fibres longer than 20 μm per cm3 The exposure duration was 6 hours/day for 5 days, with subsequent post-exposure periods lasting up to 12 months. For lung burden analyses, interim sacrifices were performed at regular intervals. The ongoing chronic study comprises a group of rats exposed to the MMVF34 fibre at one exposure level of 30mg/m3 The negative control group is filtered air. The exposure duration is 6 hours/day, 5 days/week for 2 years, with a subsequent post-exposure period lasting until approximately 20% survival in the test fibre group. Interim sacrifices are performed at months 3, 6, 12, 18 and 24 and biopersistence monitored for rats exposed for 3 and 12 months, with subsequent post-exposure periods lasting 6 months. Effectively the main protocol for the previously conducted chronic study was the same, except that there were 3 fibre exposure groups (3, 16 and 30 mg/m3 and no specific biopersistence satellite groups were included. For MMVF34, the inhalation tests of different duration show a similar biopersistence pattern, while the intra-tracheal test gives longer elimination half-times especially for long fibres. The MMVF34 fibre is considerably less biopersistent than the traditional MMVF2I fibre when comparing the calculated elimination half-times after short-term inhalation. When comparing the pathology after 3, 6, 12 and 18 months exposure, MMVF34 showed minor histopathological changes compared to MMVF2I. The car cinogenicity and toxicity results of the chronic study with MMVF2I suggest that this fibre does not pose a significant health risk to humans and the current results with MMVF34 indicate that this fibre consequently should pose an even smaller risk, if any. © 1998 British Occupational Hygiene Society. Published by Elsevier Science Ltd.

National versus International Asbestos Fibre Counting Schemes: Comparison between the Spanish Interlaboratory Quality Control Programme (PICC-FA) and the Asbestos Fibre Regular Informal Counting Arrangement (AFRICA)

An interchange of eight asbestos reference slides was planned informally between the Spanish national proficiency testing scheme, PICC-FA, and its international counterpart, AFRICA. The fibre counting levels, the reference values and the differences in performance assessments for individual counts and laboratories were analysed to test the level of agreement between the schemes. Comparisons were based on the proportions of fibre counts within and outside limit values. Discrepancies were found between schemes in the classification of counts, with the position of the limits of satisfactory performance being the most important factor of disagreement. The AFRICA limits are over twice as wide as the PICC-FA limits, though only 17% of the counts are affected by this large difference. There were not found to be significant differences in the assessment of the performances of Spanish laboratories—87.5% would have achieved a satisfactory classification in both schemes. A possible new approach to harmonizing proficiency testing schemes is discussed. © 1998 British Occupational Hygiene Society. Published by Elsevier Science Ltd.

Monitoring of Occupational Exposure to Polycyclic Aromatic Hydrocarbons in a Carbon-electrode Manufacturing Plant

An investigation is presented of occupational exposure to polycyclic aromatic hydrocarbons (PAH) in a carbon-electrode manufacturing plant, as assessed by three monitoring methods, viz. environmental monitoring of the external dose by analysis of personal air samples, biological monitoring of the internal dose by analysis of urinary 1-hydroxypyrene (1-OHpyrene), and biological effect monitoring by dosimetry of PAH-DNA adducts in blood lymphocytes. On the basis of job conditions, workers at the plant were divided into three groups with presumed low, intermediate and high exposure to air-borne PAH, respectively. All air samples showed levels of total PAH below the current MAC-value in the Netherlands, which is 200µg/m3, whereas the benzo[a]pyrene level was occasionally higher than the recommended concentration of 2 µg/m3 The values of 1-OHpyrene in urine from the intermediate and high exposure groups were significantly higher than those of the low exposure group, namely 3.6- and 8.2-fold, respectively. Clear external and internal exposure was thus demonstrated for workers of the high and intermediate exposure groups, but this did not result in a measurable effect at the DNA level in blood lymphocytes. Tobacco smoking, on the other hand, caused a significant increase of the levels of PAH-DNA adducts but did not affect 1 -OHpyrene values. These data suggest that smoking is a more important risk factor for adverse health effects, i.e. cancer, than occupational exposure to PAH in this plant. © 1998 British Occupational Hygiene Society. Published by Elsevier Science Ltd.

Dust Exposure and Lung Cancer in Quebed Chrysotile Miners and Millers

A large cohort of men born between 1891 and 1920 and employed for at least a month in the chrysotile producing industry of Quebec has been under study since 1966. These men were followed from first employment (the earliest in 1904) to 1992, by which time over 8000 had died, 657 from lung cancer. The current study is of 488 cases of lung cancer formerly employed at three places, viz, a major complex, here called Company 3, in the region of Thetford Mines (243 cases), the mine and mill in the town of Asbestos (206) and a small asbestos-products factory in the same town (39). For each case, four referents were sought by random selection from among survivors to a greater age, after matching on place of employment, age of starting work, smoking habit and date of birth. This process was highly successful, although six cases had less than four referents. For each man (the 488 cases with 1941 referents) and for each calendar year of employment, we obtained the fraction of the year worked at various levels of intensity, assessed in 13 ‘dust categories’ of mpcf (million particles per cubic foot). We then calculated how many years each man spent at these various levels; these years, adjusted for the length of the working week (66 h until 1937; 48h 1938–1949; and 40h 1950–1985), were accumulated up to ten years before the death of the case. The men were classified according as they were non- or ex-smokers, or smokers, of cigarettes. For each man at Company 3 and one referent for each, his years of work in a central area of five mines and in a peripheral area of ten mines were differentiated; contamination of the chrysotile by fibrous tremolite was known to be much greater in the central than in the peripheral area. Case-referent comparisons, within place of employment, were made by conditional logistic regression. As anticipated from earlier subject-years analyses, lung cancer risks were found to be negligible for years worked in dust categories I and 2 (averaging 0.5 and 2 mpcf), regardless of place; as the upper limit of category I is considerably higher than permitted nowadays, the lung cancer risk from exposure to chrysotile at permitted levels can be taken as extremely small. Patterns of exposure-response for higher categories were irregular. At Company 3, some risks appeared elevated for years spent in the higher dust categories: 3–4, 5–7, 8–10 and 11–13, with averages around 9, 20, 36 and 92 mpcf, respectively. For categories 3–4 and 8–10, the odds ratios were high for some or all work in the central area, but minimal for years spent in the peripheral area only. Odds ratios were fairly low for cigarette smokers who worked in categories 5–7 and also for years spent in the highest categories (11–13). At the mine and mill in Asbestos, all risks were low except for years worked by non- and ex-smokers in categories 7–13 (ca. 40 mpcf). There were no increased risks at the factory. It was known from the subject-years analyses that most of the excess had occurred at Company 3, but it is now clear that for all practical purposes it was confined to the central area there, probably due largely to fibrous tremolite and in dust conditions of at least dust category 3. The average of this category was 7 mpcf or very roughly 24 fibres/ml, about two orders of magnitude higher than today's hygiene standards. © 1998 British Occu pational Hygiene Society. Published by Elsevier Science Ltd.

EXPOSURE LEVELS AND DETERMINANTS OF INHALABLE DUST EXPOSURE IN BAKERIES

The study's objectives were to measure full-shift exposure to inhalable dust in bakeries and define the determinants of full-shift exposure. Inhalable dust was measured gravimetrically. Ninety-six bakery workers, employed in seven different bakeries, participated in the study. Two side-by-side full-shift inhalable dust samples were obtained from each study participant on a single occasion. Samples were collected on 18 days selected at random. During the entire sampling period, bakers were observed and information on 14 different tasks was recorded at 15 min intervals. Other production characteristics were also recorded for each sampling day. These task and production variables were used in statistical modelling to identify significant predictors of exposure. The mean full-shift inhalable dust exposure was 8.2 mg/m3 (range: 0.1–1 10 mg/m3). A regression model explained 79% of the variability in exposure. The model indicated that tasks such as weighing, pouring and operating dough-brakers and reversible sheeters increased the exposure, while packing, catching and decorating decreased the exposure. Bread and bun production lines were associated with increased full-shift inhalable dust exposure, while cake production and substitution of dusting with the use of divider oil were associated with decreased exposure. Production tasks and characteristics are strong predictors of personal full-shift exposures to flour dust among bakers; these can be altered to reduce exposure levels. © 1997 British Occupational Hygiene Society. Published by Elsevier Science Ltd.

A COMPREHENSIVE STRATEGY FOR THE ASSESSMENT OF NOISE EXPOSURE AND RISK OF HEARING IMPAIRMENT

A comprehensive strategy is presented for the evaluation of the daily noise exposure level [LEX,d in dB(A)] and the assessment of the risk of hearing impairment. The risk is defined as the probability for a worker with a given exposure history to noise to develop a hearing deficit above a given threshold. It is shown that for a given accuracy to be obtained on the risk prediction, the precision required on the LEX,d is low at levels around 90 dB(A) and increases at higher levels. The strategy uses the concepts of homogeneous group of exposure (HGE) and stationarity interval (S.I.), defined as the period over which the exposure distribution is the same for the members of the HGE. The number of workers to sample, the number of samples to take for each worker and their duration are discussed. A semi-random sampling is recommended, excluding the periods with low noise exposure. Tests are proposed for the homogeneity of the group and the validity of the S.I.. A corrected standard deviation is defined in order to take into account the skewness of the distribution of the noise equivalent levels of the samples and formulas are presented to estimate the LEx.d, its standard error and the corresponding risk of hearing impairment, © 1997 British Occupational Hygiene Society. Published by Elsevier Science Ltd

DEVELOPMENT OF A MODEL TO PREDICT AIR CONTAMINANT CONCENTRATIONS FOLLOWING INDOOR SPILLS OF VOLATILE LIQUIDS

A personal computer spreadsheet model which predicts air contaminant concentrations following indoor spills of volatile liquids has been developed. Three mass transfer models are compared for predicting evaporative flux in the model, the flat plate mass transfer theory, Penetration Theory, and Mackay and Matsugu models. Two methods of predicting spill temperature during evaporation are presented, the isothermal method, which assumes spill temperature remains at ambient throughout evaporation, and the spill temperature method, which predicts spill temperature using equations developed from a heat balance over the spill pool. Dispersion is approximated in the model as a well-mixed room with short-circuiting. Model equations are programmed into a Lotus 1,2,3 spreadsheet. Calculations of room concentration, spill pool surface temperature, and spill area are made at consecutive 20-s intervals following the spill. Model predictions are compared with concentration measurements made after two test spills in a laboratory. The model gives a good first estimate of room concentration, performing best when the spill is assumed to be isothermal and the Penetration Theory or Mackay and Matsugu methods are used to predict evaporation rate. © 1997 British Occupational Hygiene Society. Published by Elsevier Science Ltd

VOLATILISATION PROCESSES IN WASTEWATER TREATMENT PLANTS AS A SOURCE OF POTENTIAL EXPOSURE TO VOCs

The results of a survey estimating volatilisation rates (as gas exchange constants and flux rates) of a range of hazardous alkane, aromatic, organohalogen, organosulphide, ketone and alcohol volatile organic compounds (VOCs) from a water bay are presented. More than 73 experimental test runs were carried out over a year under varying seasonal conditions to measure the simultaneous concentrations of VOCs in air and water phases. The data were processed employing new advances in ‘surface renewal’ volatilisation models. Based on the experimental data, estimates of theoretical equilibrium constants, gas exchange constants and flux rates for each VOC were made. Within the ranges of concentration which may reasonably be encountered by process workers, the fluxes for a broad range of VOCs ranged from approximately 0.04× 10−8 to 9.0×10−1 g cm−2 h−1. The results were used to make predictions about the relationship between volatilisation processes and their implications for occupational hygiene risk assessment. © 1997 British Occupational Hygiene Society. Published by Elsevier Science Ltd

BIOAEROSOL EXPOSURE IN WASTE COLLECTION: A COMPARATIVE STUDY ON THE SIGNIFICANCE OF COLLECTION EQUIPMENT, TYPE OF WASTE AND SEASONAL VARIATION

Recent Danish studies on waste collectors' bioaerosol exposure are summarized. Generally the median exposure levels ranged from 105 to 106 cells m−3 (total microorganisms), 104 to 105 cfu m−3 (culturable fungi) and 103 to 104 cfu m−3 (culturable bacteria). The type of waste was a governing factor for exposure. Garden waste collectors frequently experienced concentrations exceeding 105 cfu m−3 for mesophilic fungi and 104 cfu m−3 for the thermophilic fungus Aspergillus fumigatus, Workers collecting compostable, mixed and sorted waste occasionally experienced similar concentrations of the fungal groups while workers collecting ‘bulky waste’ and paper had low exposure. Type of collection vehicle was identified as another governing factor for exposure. Vehicles loaded from the top (approximately 3 m above the ground) caused lower exposure (by a factor of 25) to fungi than vehicles loaded at the level or the breathing zone of the workers. Exposure was also affected by season of the year—the concentration of total microorganisms, culturable fungi, Aspergillus fumigatus and endotoxin was low in winter. Exposure to total microorganisms counted by microscopy was found to have a fairly high validity (Va) as an indicator of exposure to culturable fungi (Va = 1·45) or culturable bacteria (Va = 1·25). Likewise, dust may also be used as an indicator of exposure to total microorganisms (Va = 1·36), culturable fungi (Va = 1·31) and culturable bacteria (Va = 1·35). © 1997 British Occupational Hygiene Society. Published by Elsevier Science Ltd

GROUPING STRATEGIES FOR EXPOSURE TO INHALABLE DUST, WHEAT ALLERGENS AND α-AMYLASE ALLERGENS IN BAKERIES

This paper describes repeated measurements of inhalable flour dust, wheat allergens and α-amylase allergens in the bakery industry. A total of 571 full-shift personal dust samples was collected. Wheat allergens and α-amylase allergens were measured in 449 and 507 samples, respectively, by the use of recently developed immunoassays. For all three measures of exposure, the main components of exposure variability were determined. Different grouping strategies for studying exposure-response relationships were compared. The specific job of a bakery worker was identified as the most important source of variability in inhalable flour dust concentrations. For exposure to wheat allergens, the job performed was also the most important source of variation, but type of bakery also explained some of the variability. For α-amylase allergen exposure, information on type of bakery was more important then job information. For exposure to inhalable dust and wheat allergens, a classification by job title would lead to sufficient contrast in average exposure levels. By contrast, a grouping strategy based on a combination of job and type of bakery appeared to be essential to obtain a useful classification of exposure to α-amylase allergens. © 1997 British Occupational Hygiene Society Published by Elsevier Science Ltd

MONITORING AND MODELLING OF EXPOSURE TO ETHANOL IN HAIRDRESSING SALONS

Personal exposure to solvents was studied among hairdressers in 28 salons in two regions during two seasons in The Netherlands. Ethanol was used as a marker for solvent exposure. Auxiliary data, such as salon and work characteristics, meteorological conditions and information on the presence of control measures, were collected during the measurements. The average exposure to ethanol was almost a factor of 200 below the occupational exposure limit, but differences in average ethanol concentrations up to a factor of 30 were present between salons. Exposure concentrations were significantly higher on Fridays than on other days of the week. Contrary to expectation, exposures were somewhat lower in the spring than in the summer and in an urban than a semi-rural area. An empirical statistical model based on exposure data collected during the first measurement period appeared not to be valid for the encountered circumstances in the second measurement period. An alternative classification scheme based on two easily obtainable salon and task characteristics was elaborated. This scheme will be applied in an ongoing epidemiological study on reproductive disorders among hairdressers and their offspring. © 1997 British Occupational Hygiene Society. Published by Elsevier Science Ltd.

EXPOSURE TO SOLUBLE NICKEL IN ELECTROLYTIC NICKEL REFINING

Past and present exposure to nickel was studied in an electrolytic nickel refinery, where an increased incidence of nasal cancer had been reported, using nickel analyses in air, blood and urine. Genotoxic effects were studied using analysis of micronuclei from acridine orange-stained smears from the buccal mucosa of the workers. Workers used respirators or masks in tasks where the exposure was expected to be high. Inside the mask, nickel concentrations were 0.9–2.4 μgm–3 in such tasks. In those tasks where masks were not used, nickel concentrations in the breathing zone were 1.3–21 μg m–3. Air-borne nickel concentrations (stationary sampling) varied between 230 and 800 μg m–3 in 1966–1988 with no systematic change; thereafter lower concentrations (170–460 μg m–3) have been observed. After-shift urinary concentrations of nickel were 0.1–2/ μmol l.–1; they showed no correlation with nickel concentrations in the air. Concentrations of nickel in the urine were still elevated after a 2–4 week vacation. The frequency of micronucleated epithelial cellsc in the buccal mucosa of nickel refinery workers was not significantly elevated by comparison with referents. No relationship was observed between micronucleus frequencies and levels of nickel in air, urine or blood. © 1997 British Occupational Hygiene Society. Published by Elsevier Science Ltd.

EVALUATION OF EVAPORATION AND CONCENTRATION DISTRIBUTION MODELS — A TEST CHAMBER STUDY

Occupational exposure to airborne volatile organic compounds is governed by the source strength and dispersion of the pollutant into workroom air. The purpose of the present test chamber study was to validate suggested models for the prediction of evaporation rates and concentration distributions. The study design was organized into different scenarios to simulate workplace conditions. Evaporation rates of organic compounds of different volatilities were recorded gravimetrically and the corresponding concentrations in air were measured at various locations equally distributed in the test chamber. The evaporation models generally showed a fair agreement with experiments but tended to underestimate the evaporation rate especially at low air velocity. Based on factorial experiments a new simple evaporation model was suggested. The performances of the concentration distribution models were of different quality. The model developed by Roach (Annuls of Occupational Hygiene 24, 105–132, 1981) cannot be used in predicting the concentration distribution in case of a convective air flow. If knowledge of the evaporation rate and pollutant concentration at some distances from the source were available, the model suggested by Scheff et al. (Applied Occupational and Environmental Hygiene 7, 127–134, 1992) generated a concentration distribution in reasonable agreement with the observed data. The box-model (Sinden, Building und Environment 13, 21–28, 1978) generally offered a fair performance but tended to underestimate the pollutant concentration in a region close to the source in the direction of the main air flow. © 1997 British Occupational Hygiene Society. Published by Elsevier Science Ltd.

DOCUMENTATION OF A DUSTINESS DRUM TEST

A rotating drum dustiness test is described and the results with this device run at standardized conditions from 1989 to 1994 are presented. The measured dustinets indices covered a range of about a factor 2000. The test was good at ranking different materials. Influences of the test conditions on the drum method were studied in a 24 factorial design using super ground alumina with small particles and a narrow size distribution. The variables mass, flow, rotation speed and sampling time were run at base and high level and the air humidity was kept fixed at 50% RH. An analysis of variance showed a correlation between these different variables with a particularly strong interaction between the mass and the rotation speed. Time resolved dust measurements showed the importance of being able to monitor the dust release during time. For some test conditions a continuous dust release was found, while most tests showed primarily an initial dust release. Copyright © 1996 British Occupational Hygiene Society.

MAPPING AIR CONTAMINANTS INDOORS USING A PROTOTYPE COMPUTED TOMOGRAPHY SYSTEM

Single and multiple plumes of sulphur hexafluoride were measured and mapped using a prototype open-path Fourier transform infrared spectrometer (OP-FTIR)-computed tomography (CT) system in an indoor exposure chamber. The OP-FTIR-CT system accurately mapped the position of concentration peaks at different locations in the chamber, and estimated concentrations within a range of 4–50% when compared with point samples measured by gas chromatography with an electron capture detector. Two OP-FTIR spectrometer ray configurations, one with 100 rays and the other with 136 rays, were used to scan the chamber and reconstruct the concentration maps. Ray configuration and time to scan the entire chamber were found to have a profound effect on the quality of the reconstructed maps. The ability to obtain real-time, non-invasive measurements, and to generate spatially and temporally resolved maps of multiple chemicals, makes the OP-FTIR-CT system a promising technique for monitoring source emissions and evaluating exposures to air contaminants in a workplace. Copyright © 1996 British Occupational Hygiene Society.