Methods to lower the dust exposure of bag machine operators and bag stackers

This article reviews various dust control technologies developed over the years at the Pittsburgh Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) to provide various options and alternatives to lower bag machine operators' and bag stackers' dust exposures. Dust exposure records for the past 20 years show that bag machine operators and bag stackers normally have the highest respirable dust exposures of workers at mineral processing plants. A substantial amount of research has been performed over the years to minimize the dust exposure to these workers and the intent is to present all this information together in one article. Most of the research describes engineering controls that were adapted to existing facilities to reduce the dust generated during bag filling, bag conveying, and bag stacking. In some cases, a single technique succeeded in lowering respirable dust concentrations for all three processes, thus reducing the dust exposure to both the bag machine operator and the bag stacker. In other cases, a technique was developed to specifically reduce the dust exposure of one process or the other. This research also reviews various controls for secondary dust exposure, including general ventilation requirements to mill buildings, the effects of background dust sources, and personal work practices. This information is presented to help industrial hygienists, plant managers, engineers, and workers lower the dust exposure of bag machine operators and bag stackers.     

Factors affecting the Heubach and MRI dustiness tests

The effect of test parameters upon material dustiness measured by the Heubach dust measurement appliance and the MRI dustiness tester was studied. The users of these tests can alter test parameters such as flow rate, sampling time, mass of material tested, bulk density, and vibrator setting. The effect of these parameters upon the aerosol produced in the dustiness tester was experimentally studied. All of the parameters affected in a complicated manner, the amount of dust and the size distribution of the dust generated during these tests. Therefore, dustiness test results should not be adjusted for variations in test parameters. The users of dustiness tests need to carefully control dustiness test parameters in order to have reproducible dustiness tests.     

Dust inhalation exposures from the handling of small volumes of powders

Worker exposure to airborne particulates was stimulated in a laboratory under controlled conditions. Small volumes, 3.8 L (1 gal.), of finely divided powders were transferred at 1-min intervals to 23-L (6-gal.) containers over 30-min time intervals. A high-volume filter array in the exit vent of the specially designed exposure laboratory was used both to control the ventilation rate and to determine the emission factor of the pouring operation. The room ventilation rate, method of transfer, and drop height were varied, and the resulting particulate concentrations were monitored by personal and area samplers. The four powders studied were talc, sodium chloride, Portland cement, and Direct Yellow 4 dye. Based on this study, a model was developed to predict potential worker exposure from the pouring of small volumes of powders. The model is based on the following major conclusions. First, the space- and time-averaged concentration of suspended particulate matter at breathing height agrees well with the mean concentration of suspended particulate matter in the room air effluent. Second, material-specific suspended particulate emission factors vary approximately in direct proportion to the drop height. Third, emission factors for scooping/dumping operations agree well with factors for pouring operations for a given drop height. Fourth, emission factors compare well with dustiness indexes that were determined using a bench-scale dustiness test chamber described in a companion paper. Parameters of the exposure model include dustiness index, drop height of the pouring operation, total quantity of material poured, averaging time, and the fraction of respirable material. For the validation of the model, additional data would be necessary.     

Method to evaluate the dustiness of pharmaceutical powders

The trend among pharmaceutical companies to develop selective drugs of high potency has pushed the industry to consider the potential of each hazardous ingredient to become airborne. Dustiness issues are not unique to the pharmaceutical industry, but are relevant to any industry where powdered materials are mixed, transferred and handled. Interest in dustiness is also driven by concerns for worker health, the potential for plant explosions and the prevention of product loss. Unlike other industries, the pharmaceutical industry is limited by the milligram quantity of powdered material available for testing during product development. These needs have led to the development of a bench-top dustiness tester that requires only 10 mg of powder and fully contains the generated aerosol. The powder is dispersed within a 5.7 liter glass chamber that contains a respirable mass sampler and a closed-face sampler to quantify the respirable and total dust that are generated with a given energy input. The tester distinguished differences in dustiness levels of five different powders. Finer powders were dustier, and the respirable dust percentage was always less than that for total dust. Four testers have been built and evaluated using pharmaceutical grade lactose. Dustiness measurements determined using all four testers were comparable. The pharmaceutical industry uses surrogates such as lactose to represent active compounds in tests that estimate the dust concentration likely to occur in a new manufacturing operation. Differences between the dustiness of the active compound and its surrogate challenge the relevance of the surrogate tests to represent true exposures in the workplace. The tester can determine the dustiness of both the active compound and its surrogate, and the resultant ratio can help to interpret dust concentrations from surrogate tests. Further, dustiness information may allow the pharmaceutical researcher to select powder formulations that present low airborne concentrations in the workplace.     

Microbial dustiness and particle release of different biofuels

Exposure to organic dust originating from biofuels can cause adverse health effects. In the present study we have assessed the dustiness in terms of microbial components and particles of various biofuels by using a rotating drum as a dust generator. Microbial components from straw, wood chips, wood pellets and wood briquettes were quantified by several methods. Excellent correlations (r >/= 0.85, P < 0.0001) were found: between lipopolysaccharide (LPS) (as determined by 3-hydroxy fatty acid analysis) and endotoxin (as determined by a Limulus test), cultivable bacteria, total number of bacteria and muramic acid; between endotoxin and cultivable bacteria, total number of bacteria and muramic acid; between total number of bacteria and muramic acid; between cultivable fungi and total number of fungi. Straw was dustier than the other biofuels in terms of actinomycetes, bacteria, muramic acid, endotoxin, LPS, particle mass and number of particles. One of the wood chips studied and the straws had comparatively high dustiness in terms of fungi, while both wood pellets and wood briquettes had comparatively low dustiness in terms of all microbial components. An initially high particle generation rate of straw and wood chips decreased over time whereas the particle generation rate of wood briquettes and wood pellets increased during a 5 min rotation period. Particles of non-microbial origin may be the determining factor for the health risk in handling briquettes and pellets. Straw dust contained significantly more microorganisms per particle than did wood chip dust, probably because bacteria were most abundant in straw dust. The concentrations of endotoxin and fungi were high in wood and straw dust; dust from one of the straws contained 3610 EU/mg and dust from one of the chips contained 7.3 x 10(6) fungal spores/mg. An exposure to 3 mg of straw or wood chips dust/m(3) (the Swedish and Danish OEL of unspecific inhalable dust) could cause exposures to endotoxin and fungi higher than levels were health symptoms are seen to develop. The very different levels of dustiness in terms of particles and microbial components of different biofuels shows that dustiness is an important health-relevant factor to consider when choosing among biofuels and when designing worksites for handling of biofuels.     

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 dustiness 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.     

Allergen and dust exposure as determinants of work-related symptoms and sensitization in a cohort of flour-exposed workers; a case-control analysis

OBJECTIVES: To estimate the incidence of specific IgE sensitization and allergic respiratory symptoms among UK bakery and flour mill workers; and to examine the roles of flour aeroallergen and total dust exposures in determining these outcomes. METHODS: A cohort of 300 new employees, without previous occupational exposure to flour, were followed prospectively for a median (range) of 40 (1-91) months. Cases-defined as those developing work-related symptoms or a positive skin prick test to flour or alpha-amylase during follow up--were compared with controls, matched for duration of employment. Exposures to flour aeroallergen and total inhalable dust were estimated using a questionnaire and personal sampling techniques. RESULTS: Incidence rates for work-related eye/nose and chest symptoms were 11.8 and 4.1 cases per 100 person years (py), respectively. Fewer employees developed positive skin prick tests to flour (2.2 cases per 100 py) or alpha-amylase (2.5 cases per 100 py). Positive skin tests to occupational allergens were more common among those with new work-related symptoms. There were clear relationships between the risks of developing work-related symptoms or a positive skin prick test and three categories of estimated exposure to total dust or flour aeroallergen. Atopic employees were more likely to develop a positive skin prick test-but not work-related symptoms. These findings were unaffected by age, sex or cigarette smoking. CONCLUSIONS: In this population, many work-related symptoms which develop after first employment in modern UK bakeries or flour mills were not accompanied by evidence of IgE sensitization to flour or alpha-amylase. Although average dust exposures were within current occupational standards, the risks of development of upper and lower respiratory symptoms and of specific sensitization were clearly related to total dust and/or flour aeroallergen exposure. The incidence of work-related chest symptoms in the presence of a positive skin test to flour or alpha-amylase in this setting was approximately 1 case per 100 py.     

Size selective dustiness and exposure; simulated workplace comparisons

A simulated workplace study was conducted to investigate the relation between inhalation exposure and dustiness determined with a rotating drum dustiness tester. Three powders were used in the study, i.e. magnesium stearate, representing a very dusty powder, and aluminium oxide and calcium carbonate, representing low and very low dusty powders, respectively. Two scenarios of handling small volume of powders were included; sweeping/cleaning and scooping/weighing/adding. Size-selective dust exposure was assessed using MultiDust (dual-fraction) IOM and RespiCon sampling heads. For the present operation scenarios, dustiness showed itself to be the major determinant of exposure and explained approximately 70% of the exposure variances. The ratios of respirable and inhalable fractions as determined by dustiness tests were comparable with the ratios observed for exposure. The results emphasize the relevance of dustiness as a parameter to characterize substances according to potential for exposure.     

Dust exposure indices and lung function changes in Longshoremen and Dock workers

A group of Dutch harbor workers involved in loading and unloading bulk products from sea vessels such as coal, cokes, and some other products like alumina, borax, phosphate ore, and vermiculite was studied. Exposures were characterized by personal and environmental monitoring. This information was subsequently used to estimate several dust exposure indices and to study relationships with lung function variables and respiratory symptoms. Average respirable dust exposure levels ranged from 0.3–4.0 mg/m³. Workers involved in unloading products from sea vessels were exposed to the highest dust levels. Supervisors and workers with tasks in the dock had an intermediate to low exposure. Office workers had the lowest exposure to respirable dust. Inhalable dust levels were considerably higher and average exposures ranged from 0.3–80 mg/m³. The ranking of occupational titles by inhalable dust exposure was almost identical to the rank order of respirable dust levels. Workers with higher current and cumulative dust exposures tended to have a lower lung function, and only shortness of breath had a statistically significant relationship with current and cumulative inhalable dust exposure. In general, relationships between lung function and inhalable dust levels tended to be somewhat stronger in terms of statistical significance, because inhalable dust is an estimate of dust deposition in the upper airways and lung function is a measurable parameter of airway obstruction in that region. However, the differences with respirable dust were minimal, and variability in dust exposure levels was extremely large for this population. It was concluded that harbor workers involved in unloading ships containing coal and various kinds of ore can be exposed to high dust levels. Relationships between dust exposure and lung function illustrate that these exposures are a respiratory hazard. Our finding that inhalable dust levels have a somewhat stronger relationship with lung function level than respirable dust levels deserves further attention.     

Wood dust and formaldehyde exposures in the cabinet-making industry

Time-weighted average (TWA) personal total and respirable dust exposures were determined gravimetrically for 48 subjects in 4 cabinet-making plants. TWA personal formaldehyde exposures also were obtained, with the use of 3M 3750 passive monitors. Selective area sampling for formaldehyde was undertaken using two methods. The results obtained with the passive monitors were compared to the standard chromotropic acid impinger method. Considerable variation was noted in the dust exposures. Cabinet-makers exposed to softwoods were found to have a mean exposure of approximately one half of the current applicable ACGIH TWA-TLV, while hard-wood exposure was twice the applicable TWA-TLV. The highest dust exposures were recorded for those workers sanding, the mean total dust being 2.91 mg/m3 (S.E. 0.70) and respirable dust 0.63 mg/m3 (S.E. 0.20). Sanding operations also were found to produce a higher proportion of respirable dust (22%) than other woodworking operations (6%-14%). Workers in assembly areas also were found to have higher dust exposures, likely reflecting the fact that conventional dust collection devices for stationary woodworking equipment are not appropriate for hand held tools and hand sanding. The importance of making respirable dust measurements is discussed. The poor correlation between paired total and respirable dust concentrations indicates that both measurements should be made. Some potential limitations to respirable wood dust sampling using 10 mm nylon cyclones are noted, however. Area dust concentrations were found to be significantly lower than personal exposures, emphasizing the importance of personal sampling data. Formaldehyde vapor exposures were very low, with a mean of 0.06 ppm (S.E. 0.01).     

Locomotor and cardiorespiratory impairments after retirement in relation to certain occupational exposures during working life

The relationships between locomotor and cardiorespiratory impairments and occupational exposures during working life were examined, using a sample of 627 retired persons in the greater Paris area. Among men, there was a significant statistical association between carrying heavy weights and locomotor impairment. There were also significant associations between exposure to toxic products, tiring postures and vibrations and cardiorespiratory impairment among men. Concerning women, associations between exposure to dust and tiring postures during working life and cardiorespiratory impairment were observed. These results were obtained after adjusting for age, socio-professional status, tobacco use, living alone and after adjusting also for the other occupational exposures. These results are compatible with the hypothesis of long-term effects of occupational exposures on the principal health characteristics of the aged.     

Occupational exposure and 12-year spirometric changes among Paris area workers.

A follow-up study over 12 years was conducted among 556 men aged 30 to 54 in 1960 and working at that time in factories around Paris (France). Various occupational exposures were recorded at the time of the 1960 survey after a technical study of each workplace. The annual rate of decline of FEV1 during 12 years was estimated for each subject from the measurements in 1960 and 1972. This rate (the FEV1 slope) was related independently of FEV1 level (which reflects the loss since the beginning of adult life) and of smoking habits to occupational exposure to dust, gases, and heat. FEV1 slope was significantly related to inhalation of mineral dust (even in the absence of silica) as well as to grain dust, and the slope was steeper with increased intensity of exposure to dust. Analysis of job changes showed that among heavily exposed subjects, those who changed jobs had a less steep slope than those who did not. Our results support the hypothesis of a causal role of exposure to dust in the development of chronic airflow obstruction and of a benefit when exposure to dust ceases. Exposure to dust, gas, and heat usually occurred together so data on gas and heat were analysed after taking account of exposure to dust. The influence of heat on FEV1 decline showed a clear trend. Results suggest that exposure to gases associated with exposure to dust or heat or both had a deleterious effect. After adjusting for age, smoking, and FEV1 level (ASLA) the following average slopes were obtained: 44 ml/a (for exposure to none or to only a slight amount of dust, or to gases alone), 51 ml/a (heat), 53 ml/a (noticeable dust), 55 ml/a (noticeable dust and heat), 60 ml/a (noticeable dust, heat, and high concentration of gases). Independently of the occupational exposures, ASLA FEV1 slopes among manual workers were related to skill, being 44 ml/a for skilled and 51 ml/a for unskilled men. Independently of social class and occupational exposures recorded, there were differences in FEV1 slopes by factory, suggesting that one should not rely on using one factory as the control of studies of occupational exposure to another.     

Laboratory evaluation of pressure differential-based respirable dust detector tube

Assessment of exposure to occupational dusts is a first step in reducing exposures to harmful dust concentrations. A new type of respirable dust sampler was developed and compared side-by-side to personal gravimetric samplers in the laboratory. The new sampler correlates filter back pressure with mass accumulation to provide mid-shift- and end-of-shift determinations of cumulative exposure. The sampler uses a small low flow rate pump to draw dust through a small detector tube that contains a porous urethane foam respirable classification section and glass fiber filter that collects respirable dust. Six different coal dusts were aerosolized in a laboratory dust chamber and a total of 119 triplicate observations were obtained. For individual coal types, the correlation coefficients were between 0.87 and 0.97. The precision of the two methods was similar, with the percent relative standard deviation of the personal samplers of 12 percent and the new detector method of 14 percent. For all coal types tested th data were best described by a power function where delta P = 1.43 mass (0.85), with a correlation coefficient of 0.73. The method becomes more accurate at higher dust loadings such that all laboratory data with mass loadings greater than an equivalent concentration of 2 mg/m3 fall within +/- 25 percent of the power function. Assessment of the method under field conditions is in progress.     

Characterization of paint dust aerosol generated from mechanical abrasion of TiO2-containing paints

The purpose of the study was to determine the potential for release of titanium dioxide nanoparticles in paint dust. The coatings aerosol resuspension system was developed and used for testing the generation and physical, chemical, and morphological properties of paint dust particles from mechanical abrasion (i.e., sanding) of coated wood surfaces. The paint dust emissions from bare and coated wood surfaces with multiple coatings using variable sandpaper grits were evaluated. Substantially higher particle number concentrations were measured for paint dust containing particles in the nano range (particles with aerodynamic diameter less than 100?nm) than those measured for wood dust. The variability of particle number concentration and size distribution of paint dust derived under different conditions indicated that considerable quantities of nanoparticles might be released from mechanical abrasion of painted surfaces that may induce unhealthy exposure conditions. Moreover, spectroscopic and microscopic analysis identified the presence of paint and wood components in paint dust, including titanium dioxide agglomerates that were originally embedded in the paint. The agglomerates were mostly attached to particles with sizes <100?nm, enabling them to potentially penetrate into the lower respiratory tract. These results demonstrated that the paint dust exposure generation system can provide qualitative and quantitative information on particle emissions and the abundance of nanoparticles from paint sanding in realistic conditions and they may be used to assess occupational and environmental exposures and risks. Furthermore, the prevalence of titanium dioxide nanoparticles in paint dust highlights the potential for exposures of painters and other occupational groups to hazardous paint dust and the need for protective devices and strategies aiming to reduce exposures to nanoparticles.     

Exposure assessment to alpha- and beta-pinene,delta(3)-carene and wood dust in industrial production of wood pellets

The main aim of the study was to measure the exposure to monoterpenes (alpha- and beta-pinene and Delta(3)-carene) and wood dust during industrial production of wood pellets and briquettes. Additional aims were to compare the results from wood dust sampled on a filter with real time measurements using a direct reading instrument and to identify peak exposures to dust. Twenty-four men working at six companies involved in industrial production of wood pellets and briquettes participated in the study. Monoterpenes were measured by diffusive sampling and wood dust was measured as total dust. A data logger (DataRAM) was used for continuous monitoring of dust concentration for 18 of the participants. The sampling time was approximately 8 h. The personal exposure to monoterpenes ranged from 0.64 to 28 mg/m(3) and a statistically significant (Kruskal-Wallis test, P = 0.0002) difference in levels of monoterpenes for workers at different companies was seen. In the companies the personal exposure to wood dust varied between 0.16 and 19 mg/m(3) and for 10 participants the levels exceeded the present Swedish occupational exposure limit (OEL) of 2 mg/m(3). The levels of wood dust during the morning shift were significantly (Mann-Whitney test, P = 0.04) higher compared with the afternoon shift. Continuous registration of dust concentration showed peak values for several working operations, especially cleaning of truck engines with compressed air. For 24 workers in six companies involved in industrial production of wood pellets the personal exposure to monoterpenes was low and to wood dust high compared with the present Swedish OEL and previous studies in Swedish wood industries. Since the DataRAM can identify critical working tasks with high wood dust exposure a reduction in exposure levels could probably be achieved by changes in working routines and by the use of protective equipment.     

某矿井及选煤厂煤尘作业场所现状调查

目的 通过对某矿井及选煤厂工作场所煤尘的检测,了解职业危害现状,并对其职业危害控制效果进行评价.方法 根据生产工艺流程及GBZ159-2004<工作场所空气中有害物质监测的采样规范>等标准确定煤尘采样点和采样方法.结果 井下采掘工序受检的21个工种的煤尘时间加权平均浓度(TWA)合格率为28.6%,其中有5个工种的粉尘危害等级为Ⅱ级,6个工种的粉尘危害等级为0级,其余工种的粉尘危害等级均为Ⅰ级.选煤厂检测6个工种的煤尘TWA合格率为83.3%,只有1个工种的粉尘危害等级为Ⅰ级,其余全部为0级.18个作业点定点采样,煤尘浓度合格率为72.2%.结论 喷雾及风流净化水幕对煤尘起到了一定的控制作用,但因井下作业工艺条件和工作环境的限制,大部分工作场所煤尘浓度不符合职业接触限值要求,建议加强除尘或防尘设备的日常管理和维护,强化通风,加强操作人员的个人防护.

Abstract：

Objective through a detection of dust in the coal mines workplace, to understand the status of occupational hazards, and the evaluation of occupational hazards, provide subject to control occupational hazards. Method according to production process and "hazardous substances in workplace air monitoring, sampling norms" and other standards to determine the sampling points and sampling of coal dust.Result underground mining operations in 21 subjects with time-weighted average concentration of dust types pass rate of 28.6%, of which five types of dust hazard grade Ⅱ, six types of dust hazard rating of 0, and the remaining types of grade Ⅰ dust hazard levels. Coal dust test six types of time-weighted average concentration of 83.3% pass rate, only one types of dust hazard grade Ⅰ, all the rest is 0. Calculated by the detection of dust overrun 18 times operating sites, the pass rate of 72.2% results. Conclusion purified water spray and air flow curtain of dust control has played a certain role, but the work of underground working conditions and environmental constraints, most of the dust concentration in workplace occupational exposure limits do not meet the requirements, recommended the strengthening of dust or Dust the daily management and maintenance of equipment, strengthen the ventilation, personal protection officers to strengthen operations.     

A measure of goodness-of-fit for the lognormal model applied to occupational exposures.

The lognormal distribution is often applied to occupational exposures, yet the assumption of lognormality is rarely verified. This lack of rigor in evaluating the appropriateness of the lognormal model has resulted, in part, from the difficulty of applying formal goodness-of-fit tests. When evaluation of model fit has been attempted, occupational hygienists have relied upon probability plotting of exposures rather than upon formal statistical methods. The goal of this work was to develop for the occupational hygienist a simple quantitative evaluation to supplement the probability plot. A measure of goodness-of-fit to the lognormal model based on the ratio of two estimators of the mean of the distribution, the simple or direct estimate of the mean and the maximum likelihood estimate of the mean of a lognormal distribution, is described. This new measure, the ratio metric, is a simple extension of calculations made routinely by many occupational hygienists. Results from using the ratio metric were compared to probability plotting and to two traditional measures of goodness-of-fit, the Lilliefors test and the W test, for two occupational exposure data sets. The results of the ratio and W tests are comparable for a variety of occupational exposure data, but the Lilliefors test is overly conservative and does not detect several cases of gross deviations from lognormality. The ratio metric is an effective alternative to the Lilliefors test and is easier to perform than the W test for the range of data usually encountered by occupational hygienists. Occupational hygienists are encouraged to use the ratio metric in conjunction with the probability plot in evaluating the lognormal assumption.     

Airborne exposure to heavy metals and total particulate during abrasive blasting using copper slag abrasive

This research investigates occupational exposure to metal and total particulate aerosols during abrasive blasting operations using one substitute abrasive, copper slag. Airborne exposures to metal (As, Be, Pb, Cr, Cd, V, and Ti) and total particulate aerosols from two copper slag sources are evaluated by the collection and analysis of personal breathing zone samples during abrasive blasting operations in both indoor and outdoor settings. Results from this research indicate that abrasive blasting operations using copper slag abrasive can generate, in a relatively short time, total particulate, lead, arsenic, and chromium exposures that exceed permissible exposure limits (PELs) set by the Occupational Safety and Health Administration (OSHA). Results also show statistically significant differences in exposure concentrations between slag sources. A correlation between total particulate concentrations and metal concentrations is indicated in both slag sources and in both indoor and outdoor settings. Results of this research allow occupational health and safety professionals to make a more informed determination of the degree of health risk posed to workers during abrasive blasting operations using commercially obtained copper slag abrasive.     

Immune response to flour and dust mites in a United Kingdom bakery.

In a study of 279 United Kingdom bakery workers a high prevalence of immunological response to storage mites was found. To determine whether this was the consequence of exposure to storage mites in bakery work, a population of salt packing workers was examined as a comparison group not at occupational risk of exposure to storage mites. Forty two per cent of both groups were atopic (had a positive skin prick response greater than negative controls to D pteronyssinus, grass pollen, or cat fur by 2 mm or more) and 33% had an immediate skin prick test response to at least one of four storage mites (L destructor, G domesticus, T putrescentiae, A Siro). A higher percentage of the salt packing workers than the bakery workers had a positive radioallergosorbent test (RAST) (greater than or equal to 0.35 PRU) to D pteronyssinus and to the four storage mites. Logistic regression analysis identified atopy as the most significant variable for a positive skin test and RAST response to storage mites in both groups of workers. RAST inhibition was used to analyse extracted area and personal air samples. Analysis of static area samples for aeroallergen showed immunological identity with flour but L destructor was found in only one of seven exposed filters. The concentration of airborne flour was related to exposure rank of perceived dustiness and gravimetric measurement of total dust. Nineteen out of 32 filters from workers in jobs with higher dust exposure (rank >/=6) had a level of > 10 microgram/m(3) flour whereas this concentrations was exceeded in only one of 23 filters from workers in low dust exposure (< rank 6). It is concluded that storage mites are not of special significance in allergic responses in bakery workers. The development of immunological (and airway) responsiveness to inhaled flour dust is increased in those exposed to higher concentrations of airborne allergen, which appears to be predominantly flour and not storage mites.     

Immune response to flour and dust mites in a United Kingdom bakery.

In a study of 279 United Kingdom bakery workers a high prevalence of immunological response to storage mites was found. To determine whether this was the consequence of exposure to storage mites in bakery work, a population of salt packing workers was examined as a comparison group not at occupational risk of exposure to storage mites. Forty two per cent of both groups were atopic (had a positive skin prick response greater than negative controls to D pteronyssinus, grass pollen, or cat fur by 2 mm or more) and 33% had an immediate skin prick test response to at least one of four storage mites (L destructor, G domesticus, T putrescentiae, A Siro). A higher percentage of the salt packing workers than the bakery workers had a positive radioallergosorbent test (RAST) (greater than or equal to 0.35 PRU) to D pteronyssinus and to the four storage mites. Logistic regression analysis identified atopy as the most significant variable for a positive skin test and RAST response to storage mites in both groups of workers. RAST inhibition was used to analyse extracted area and personal air samples. Analysis of static area samples for aeroallergen showed immunological identity with flour but L destructor was found in only one of seven exposed filters. The concentration of airborne flour was related to exposure rank of perceived dustiness and gravimetric measurement of total dust. Nineteen out of 32 filters from workers in jobs with higher dust exposure (rank >/=6) had a level of > 10 microgram/m(3) flour whereas this concentrations was exceeded in only one of 23 filters from workers in low dust exposure (< rank 6). It is concluded that storage mites are not of special significance in allergic responses in bakery workers. The development of immunological (and airway) responsiveness to inhaled flour dust is increased in those exposed to higher concentrations of airborne allergen, which appears to be predominantly flour and not storage mites.