Effectiveness of a worksite intervention to reduce an occupational exposure: the Minnesota wood dust study

OBJECTIVES

This study assessed the effectiveness of an intervention to reduce wood dust, a carcinogen, by approximately 26% in small woodworking businesses.

METHODS

We randomized 48 businesses to an intervention (written recommendations, technical assistance, and worker training) or comparison (written recommendations alone) condition. Changes from baseline in dust concentration, dust control methods, and worker behavior were compared between the groups 1 year later.

RESULTS

At follow-up, workers in intervention relative to comparison businesses reported greater awareness, increases in stage of readiness, and behavioral changes consistent with dust control. The median dust concentration change in the intervention group from baseline to follow-up was 10.4% (95% confidence interval = -28.8%, 12.7%) lower than the change in comparison businesses.

CONCLUSIONS

We attribute the smaller-than-expected reduction in wood dust to the challenge of conducting rigorous intervention effectiveness research in occupational settings.

[Reduction of dust during manual grinding of cast iron]

The method for determining the emission of dust and the effectiveness of dust removal from machines and devices by local exhaust ventilation to the workplace air is presented. This method consists in determining concentrations of air pollution in the measuring duct through which it is sucked off from the chambers with tested devices. At the same time the volume of air flow rate is measured. A laser dust analyzer is used to measure dust concentrations in the air. Air is sampled with isokinetic sampling heads. It was shown that dust emission at different kinds of manual grinding of cast iron without ventilation was between 24 mg/min and 8131 mg/min, whereas with the use of local exhaust ventilation it decreased below 35 mg/min. The efficiency of the exhaust elements was over 95% at optimum use of local ventilation.

Designing intervention effectiveness studies for occupational health and safety: The Minnesota Wood Dust Study

BACKGROUND

A planning model was used to guide the design of a randomized controlled study of the effectiveness of tailored interventions in lowering dust exposures in small woodworking shops.

METHODS

Guided by Green's PRECEDE-PROCEED model, we used a planning committee, focus groups and a pilot study to gain information on small woodworking shops, causes of and controls for high dust levels, and barriers and incentives surrounding availability and use of dust controls.

RESULTS

The planning committee identified key characteristics of small woodworking shop owners. Focus groups with owners and employees served to further elucidate why dust control was considered unimportant. The pilot study gave measures of dust exposures, tasks, and use of controls. Interventions focused on providing owners with technical and economic assistance to lower dust levels and an educational program for employees discussing health effects and effective methods of dust control.

CONCLUSIONS

The PRECEDE-PROCEED model proved a useful framework for designing an intervention in the occupational setting.

Reducing airborne pathogens, dust and Salmonella transmission in experimental hatching cabinets using an electrostatic space charge system

Electrostatic charging of particles in enclosed spaces has been shown to be an effective means of reducing airborne dust. Dust generated during the hatching process has been strongly implicated in Salmonella transmission, which complicates the cleaning and disinfecting processes for hatchers. Following two preliminary trials in which dust reduction was measured, four trials were conducted to evaluate the effectiveness of an electrostatic space charge system (ESCS) on the levels of total aerobic bacteria (TPC), enterobacteriaceae (ENT), and Salmonella within an experimental hatching cabinet. The ESCS was placed in a hatching cabinet that was approximately 50% full of 18-d-old broiler hatching eggs. The ESCS operated continuously to generate a strong negative electrostatic charge throughout the cabinet through hatching, and dust was collected in grounded trays containing water and a degreaser. An adjacent hatching cabinet served as an untreated control. Air samples from hatchers were collected daily, and sample chicks from each hatcher were grown out to 7 d of age for cecal analysis in three of the trials. The ESCS significantly (P < 0.05) reduced TPC and ENT by 85 to 93%. Dust concentration was significantly reduced (P < 0.0001) during the preliminary trials with an average reduction of 93.6%. The number of Salmonella per gram of cecal contents in birds grown to 7 d of age was significantly (P < 0.001) reduced by an average log10 3.4 cfu/g. This ionization technology is relatively inexpensive and could be used to reduce airborne bacteria and dust within the hatching cabinet.

[House-dust mites and mold fungi as a source of indoor allergens]

In this work information on the biology and ecology of synanthropic mites and mold fungi, proved to be the sources of indoor allergens in different premises, is presented. The authors propose the algorithm of the ecological monitoring of dwellings, developed on the basis their investigations. The types of dwellings, the time and situations when ecological monitoring should be carried out are analyzed. Grounds for the necessity of controlling the number of mites and the concentration of Micromyces spores, as well as their elimination from the environment, are given.

Allergic rhinitis in children

Epidemiologic and pathophysiologic evidence indicates that allergic rhinitis, whether seasonal or perennial, is one piece of a larger atopic clinical picture that often occurs concomitantly with asthma. Allergic rhinitis usually develops during childhood and has a prevalence of up to 40% in the pediatric population. Careful attention to food allergies and the presence of household allergens during infancy and early childhood may limit potential sensitizations. Many antihistamines and topical corticosteroids now are available for the treatment of allergic rhinitis in children, which is all the more important because optimal management may improve quality of life and curtail the development of serious sequelae.

Comparison of filter bag, cyclonic, and wet dust collection methods in vacuum cleaners

In this study, methods were developed for comparative evaluation of three primary dust collection methods employed in vacuum cleaners: filter bag, cyclonic, and wet primary dust collection. The dry collectors were evaluated with KCl test aerosols that are commonly used in filter testing. However, these aerosols cannot be used for evaluating wet collectors due to their hygroscopicity. Therefore, the wet collectors were evaluated with nonhygroscopic test particles. Both types of test aerosol indicated similar collection efficiencies in tests with dry collectors. The data show that high initial collection efficiency can be achieved by any one of the three dust collection methods: up to 50% for 0.35 microm particles, and close to 100% for 1.0 microm and larger particles. The degree of dependence of the initial collection efficiency on airflow rate was strongly related to the type and manufacturing of the primary dust collector. Collection efficiency decreased most with decreasing flow rate for the tested wet collectors. The tested cyclonic and wet collectors showed high reentrainment of already collected dust particles. After the filter bag collectors had been loaded with test dust, they also reemitted particles. The degree of reentrainment from filter bags depends on the particulate load and the type of filter material used. Thus, the overall particle emissions performance of a vacuum cleaner depends not only on the dust collection efficiency of the primary collector and other filtration elements employed, but also on the degree of reentrainment of already collected particles.

Filtration in industrial hygiene

Filters used in industrial hygiene are of two basic types, corresponding with the two basic airborne hazards: particulate and vapor. They are as different in their construction as they are in their purpose, and each gives negligible protection against the other hazard. By use of the correct type, adequate filtration efficiency can usually be achieved. Most particulate filters are made from fibers, and finer fibers result in higher efficiency. Filters can capture particles much smaller than the fiber diameter, as a result of diffusional motion of the airborne particles and, in the case of filters that hold a permanent electric charge, electrostatic attraction. Most vapor filters are made from granules of activated carbon, which have an extremely large effective surface area, where molecules of contaminant are adsorbed. The performance of all filters tends to alter as the filter material becomes loaded. Electrically neutral particulate filters become more efficient but at the expense of increased resistance to airflow. Particulate filters that act by electric forces may become less efficient, and are often less inclined to clog. Vapor filters usually have a high initial efficiency, but the penetration of vapor increases as the filters become saturated with adsorbed vapor, and the performance of these filters is normally expressed in terms of their lifetime rather than their efficiency. It is important that the choice of a filter should be made with close reference to the situation in which it is to be used, and optimum respiratory protection should be sought, rather than maximum filtration efficiency. Special problems of filters are illustrated by some case histories, and finally the use of filters as size selectors for dust samplers is briefly described.

Prevention of new sensitizations in asthmatic children monosensitized to house dust mite by specific immunotherapy. A six-year follow-up study

BACKGROUND

Specific immunotherapy (SIT) is a recognized way of treating IgE-mediated respiratory diseases. The clinical outcome is usually better in allergic children than in adults.

OBJECTIVE

To increase our knowledge of the ability of SIT to prevent the onset of new sensitizations in monosensitized subjects, so far poorly documented.

METHODS

134 children (age range 5-8 years), who had intermittent asthma with or without rhinitis, with single sensitization to mite allergen (skin prick test and serum-specific IgE), were enrolled. SIT was proposed to all the children's parents, but was accepted by only 75 of them (SIT Group). The remaining 63 children were treated with medication only, and were considered the Control Group. Injective SIT with mite mix was administered to the SIT Group during the first three years and all patients were followed for a total of 6 years. All patients were checked for allergic sensitization(s) by skin prick test and serum-specific IgE every year until the end of the follow-up period.

RESULTS

Both groups were comparable in terms of age, sex and disease characteristics. 123 children completed the follow-up study. At the end of the study, 52 out of 69 children (75.4%) in the SIT Group showed no new sensitization, compared to 18 out of 54 children (33.3%) in the Control Group (P < 0.0002). Parietaria, Gramineae and Olea were the most common allergens responsible for the new sensitization(s).

CONCLUSIONS

According to our data, SIT may prevent the onset of new sensitizations in children with respiratory symptoms monosensitized to house dust mite (HDM).

Double-blind placebo-controlled house dust mite control measures in adult patients with atopic dermatitis

BACKGROUND

Avoidance of allergens has been shown to be of benefit in patients with atopic asthma sensitized to indoor allergens. In atopic dermatitis, there is so far little information about the effect of house dust mite elimination strategies.

OBJECTIVES

We therefore performed a randomized controlled study of house dust mite control in patients with this disease.

METHODS

Twenty adult patients with moderate to severe atopic dermatitis were included. Inclusion criteria were a positive RAST to house dust mite antigen (CAP class > 3) and a concentration of > 2 microg g(-1) of the house dust mite antigen Der p1 in the patient's mattress dust. Patients were randomized to either the active treatment group (allergen-impermeable mattress encasing, acaricide spray containing tannic acid and benzylbenzoate) or a control group (allergen-permeable encasing, spray containing water and traces of ethanol). Severity of disease was estimated every 2 months by an established score (SCORAD), and eosinophil cationic protein (ECP) in the serum was determined by enzyme-linked immunosorbent assay. Furthermore, the use of topical steroids was quantified. Patients assessed daytime pruritus and pruritus-induced sleeplessness weekly on a visual analogue scale. The study lasted 1 year.

RESULTS

At the end of the study, the active treatment group showed a statistically significant reduction in Der p1 exposure as compared with the control group. However, when comparing the change from the start to the end of the study, there was no statistically significant difference between active treatment and control groups as measured by the SCORAD score and by ECP levels in the serum. Some patients in the active treatment group reported less pruritus-induced sleeplessness, but there was no statistically significant difference between the two treatment groups.

CONCLUSIONS

For adult patients with atopic dermatitis it was shown that 1 year of house dust mite avoidance reduced the allergen exposure, but an improvement of overall disease activity was not demonstrated.

A simple method to protect patient and environment when using sandblasting for intraoral repair

Repair or correction of intraoral restorations can be an alternative to complete replacement. A simple sandblasting device is very effective in producing a microretentive surface on every restorative material. A disadvantage of the technique is the production of an aerosol contaminated with the small, abrasive aluminum-oxide particles. In this article, a simple solution is given to protect the patient and environment against this dust during intraoral reparatory procedures involving sandblasting.

Inhalable dust exposures, tasks, and use of ventilation in small woodworking shops: a pilot study

Measures of workers' inhalable dust exposures, tasks, and ventilation use were made in five small woodworking shops prior to the start of an intervention effectiveness study aimed at lowering personal wood dust exposures. The data were used to (1) design a sampling protocol for an intervention success measure, (2) identify targets for intervention among the tasks and activities responsible for high dust levels, and (3) develop shop-level measures as tools for tailoring intervention activities. Geometric mean dust concentrations ranged from 1.6 to 9.9 mg/m3 in the five shops, with the highest levels occurring in a cabinet shop. All shops had centralized dust collection systems and workers generally used dust control on stationary tools (60-100% of the time) when it was available. Sanding with both stationary and handheld powered tools, cleaning with methods that can disperse dust (e.g., brushes, compressed air), and miscellaneous tasks were all responsible for significant personal exposures. The positive association between miscellaneous tasks and exposures probably reflects the high background levels generated by nearby processes. Sanding with both stationary tools and handheld powered tools represents the most significant influence on personal exposures in small woodworking shops. The authors conclude that pilot studies are useful tools for designing occupational health and safety intervention effectiveness studies.

House dust mite avoidance measures for perennial allergic rhinitis

BACKGROUND

In developed countries, it is estimated that 15% of the general population suffer from one or more allergic disorders, of which allergic rhinitis is the most common. Perennial rhinitis is most often due to allergy to the house dust mite. In such patients, house dust mite avoidance is logical, but there is considerable uncertainty regarding the efficacy and effectiveness of interventions designed to reduce dust mite exposure.

OBJECTIVES

To assess the benefit (and harm) of measures designed to reduce house dust mite exposure in the management of house dust mite sensitive allergic rhinitis.

SEARCH STRATEGY

We searched the Cochrane Controlled Trials Register, Central, MEDLINE and EMBASE. No restrictions on the language of publication were employed. The bibliography of each paper and other published reviews were checked for further references. We wrote to first authors of all included trials in an attempt to identify further published and unpublished trials.

SELECTION CRITERIA

Randomised controlled trial (with or without blinding), in which house dust mite control measures have been evaluated in comparison with placebo or other dust mite avoidance measures, in patients with clinician diagnosed allergic rhinitis and confirmed allergy to dust mite.

DATA COLLECTION AND ANALYSIS

Two reviewers independently checked titles and abstracts identified by the searches and full text copies of all papers of potential relevance were considered. Trials were graded for methodological quality using the Cochrane approach. Data extraction was performed in a standardised manner. Meta-analysis was neither possible, nor considered appropriate, because of the heterogeneity of the patient groups studied; a narrative overview of the results is therefore presented.

MAIN RESULTS

Four trials satisfied the inclusion criteria, all of which were small and of poor quality. Two trials investigated the efficacy of acaricides, a third investigated the role of high-efficiency particulate air (HEPA) filters, whilst a fourth investigated the efficacy of a bedroom environmental control program that comprised use of a barrier mattress cover, fortnightly washing of bed covers, removal of soft furnishings and daily cleaning. Each of the four trials showed the interventions to result in significant reductions in house dust mite load when compared with control. Trial results suggest that the interventions may be effective in reducing some rhinitis symptoms, though it is not possible to provide a reliable summary estimate about the magnitude of such symptom reduction. No serious adverse effects were reported from the interventions.

REVIEWER'S CONCLUSIONS

Trials to date have been small and of poor methodological quality making it difficult to offer any definitive recommendations on the role, if any, of house dust mite avoidance measures in the management of house dust mite sensitive perennial allergic rhinitis. The results of these studies suggest that interventions designed to reduce house dust mite exposure in patients with house dust mite allergic perennial rhinitis may be of some benefit in reducing rhinitis symptoms. Data at present is only available for acaricides, HEPA filters and a bedroom-based environmental control program; therefore, if considered appropriate, these should be the interventions of choice.

Respiratory protection as a function of respirator fitting characteristics and fit-test accuracy

The fitting characteristics of particulate respirators are no longer assessed in the National Institute for Occupational Safety and Health respirator certification program. It is important for respirator program administrators to understand the implications of that change and the additional burden it may impose. To address that issue, a typical respirator fit-testing program is analyzed using a mathematical model that describes the effectiveness of a fit-testing program as a function of the fitting characteristics of the respirator and the accuracy of the fittesting method. The model is used to estimate (1) the respirator assignment error, the percentage of respirator wearers mistakenly assigned an ill-fitting respirator; (2) the number of fit-test trials necessary to qualify a group of workers for respirator use; and (3) the number of workers who will fail the fit-test with any candidate respirator model and thereby fail to qualify for respirator use. Using data from previous studies, the model predicts respirator assignment errors ranging from 0 to 20%, depending on the fitting characteristics of the respirator models selected and the fit-testing method used. This analysis indicates that when respirators do not necessarily have good fitting characteristics, respirator program administrators should exercise increased care in the selection of respirator models and increased care in fit-testing. Also presented are ways to assess the fitting characteristics of candidate respirator models by monitoring the first-time fit-testing results. The model demonstrates that significant public health and economic benefits can result when only respirators having good fitting characteristics are purchased and respirators are assigned to workers using highly accurate fit-testing methods.

Dust in pig buildings

It is well documented in the international scientific literature that airborne dust in pig houses can cause serious health problems for humans as well as for animals. Extensive research has been carried out in different countries during the last few decades to improve the scientific understanding of air quality issues related to intensive animal production. Research and review papers were presented at the international symposium on Dust Control in Animal Production Facilities, held in Denmark in 1999. Different techniques have been used in order to reduce dust burdens in pig confinement buildings, but up to date only the procedure of spraying oil or a mixture of oil and water has contributed to reducing the indoor dust concentrations significantly. This article summarizes the current level of understanding of dust issues in intensive animal production buildings, mainly on the basis of papers presented at the above-mentioned symposium.

Dust levels and control methods in poultry houses

This article summarizes information from the papers and posters presented at the international symposium on "Dust Control in Animal Production Facilities", held in Aarhus (Denmark) on 30 May-2 June 1999. Dust concentrations in poultry houses vary from 0.02 to 81.33 mg/m3 for inhalable dust and from 0.01 to 6.5 mg/m3 for respirable dust. Houses with caged laying hens showed the lowest dust concentrations, i.e., less than 2 mg/m3, while the dust concentrations in the other housing systems, e.g., perchery and aviary systems, were often four to five times higher. Other factors affecting the dust concentrations are animal category, animal activity, bedding materials and season. The most important sources of dust seem to be the animals and their excrements. Further studies on the effects of housing systems on dust sources and their compounds are desired for development of a healthier working environment in poultry production facilities. Adjustment of the relative humidity (RH) of the air in a broiler house to 75% will have an effect on inhalable dust, but not on respirable dust. A slight immediate effect on the respirable dust was observed after fogging with pure water or water with rapeseed oil. In an aviary system, a 50 to 65% reduction of the inhalable dust concentration was found after spraying water with 10% of oil and pure water, respectively. To obtain a higher dust reducing efficiency, improvement of techniques for application of droplets onto dust sources will be desired.

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.

[Atopic dermatitis and domestic animals]

Several arguments are raised attributing to aeroallergens an important role in atopic dermatitis. The aeroallergens that penetrate the epidermis could be fixed by IgE on the Langerhans cells and then induce a cellular mediator reaction comparable to that of allergic contact eczema. Patch tests have been developed to evaluate the role of aeroallergens (dust mites, animal dander, etc.). Preventive anti-dust mites measures in the home of atopic patients are recommended. Eviction of domestic animals (cat, dog, etc.) or avoidance measures for animal dander in the home can produce improvement in atopic dermatitis. Oral specific immunotherapy is being validated as a treatment for this disease.

Effect of house dust mite avoidance measures in children with atopic dermatitis

BACKGROUND

House dust mite allergens are associated with atopic dermatitis (AD).

OBJECTIVES

The aim of our study was to verify if house dust mite allergen avoidance measures can improve the clinical manifestations of AD in children.

METHODS

Forty-one children (mean age 3.9 years) affected by AD associated with high total and/or specific IgE serum levels ('extrinsic' AD) were recruited. Clinical evaluation was performed utilizing the Severity Scoring of AD (SCORAD) index; dust was sampled from the children's beds and tested using an enzyme-linked immunosorbent assay. The study was planned in two parts. In the first part, a placebo-controlled trial of 2 months duration, mite allergen avoidance measures (encasing mattresses and pillows; a weekly hot wash of bedding; frequent vacuum cleaning of living room and bedroom; soft toys and carpets regularly cleaned or removed; no pets allowed) were recommended to group A patients, but not to group B. In the second part of the study, environmental avoidance measures were recommended to initial control group B patients also. One year after the start of the study the amounts of mite allergen in the home and clinical score of AD were measured in both groups.

RESULTS

At the end of the first part of the study, significant decreases in major allergens of Dermatophagoides pteronyssinus (Der p1) and D. farinae (Der f1) load (from 393 to 94 ng m-2) and concentration (from 1.84 to 0.73 microg g-1 of dust) in children's beds were observed in treatment group A. At the same time, in this group the mean SCORAD index improved significantly (from 33 to 26; P = 0.022). After 12 months, when all patients had used allergen avoidance measures, Der p1 + Der f1 load, concentration and clinical score had improved, reaching similar values in both groups.

CONCLUSIONS

Simple mite allergen avoidance measures should be recommended to families with children affected by extrinsic AD in order to control the clinical manifestations and prevent mite sensitization.

[Occurrence of allergens on hospital premises]

The occurrence of allergens from the house-dust mites Der p 1, Der f 1 and Der m, and from dogs (Can f 1) and cats (Fel d 1) was assessed in Viborg Hospital. Three hundred samples collected in a standardized manner were analysed for allergens by ELISA technique. In only one dust sample was the total occurrence of mite allergens marginally above the sensitization threshold level of 2,000 ng mite allergens/g dust. For Fel d 1 a threshold level for sensitization or symptoms of 8,000 ng Fel d 1/g dust has been proposed; none of the dust samples contained this concentration. A low occurrence of Can f 1 was found. One dust sample contained 8,902 ng Can f 1, while the remainder exhibited lower concentrations. Efficient cleaning and adequate ventilation can reduce allergens in public buildings, but it is impossible to remove all allergens from upholstered furniture. Avoidance of such furniture in wards and outpatient departments which receive allergic patients might be considered.

Assessment of vacuum cleaners and vacuum cleaner bags recommended for allergic subjects

BACKGROUND

High-quality vacuum cleaners and vacuum cleaner bags are often recommended to allergic patients as a means of reducing indoor allergen exposure. A number of vacuum cleaners on the market today claim to capture 99.9% of particles 0.3 microm or larger entering the vacuum cleaner, and many vacuum cleaner bags are now being sold as microfiltration bags.

OBJECTIVE

The purpose of this study was to compare the allergen-trapping abilities of vacuum cleaners and to use a new technique for testing vacuum cleaner bags that are recommended for allergic patients.

METHODS

Vacuum cleaners were tested in an 18-m(3) laboratory room permeated with dust containing high levels of cat allergen by using techniques previously described. Air was sampled with parallel filters in conjunction with a particle counter. The filters were assayed by ELISA for cat allergen (Fel d 1). Vacuum cleaner bags were tested by using a modified dust trap to pull sieved house dust containing a known amount of Fel d 1 across the material used for the bag. Allergen passing through the bag was trapped on a filter covering the exit of the trap and analyzed for Fel d 1.

RESULTS

In general, vacuum cleaners designed for allergic patients leaked lower amounts of allergen (<0.5-4.04 ng/m(3)) than that found in our previous studies (<0.5-100 ng/m(3)). Single-layer vacuum cleaner bags performed poorly (1250-2640 ng recovered) compared with most of the 2- and 3-layer microfiltration bags (0.53-2450 ng recovered). The range of allergen recovered from the 2-layer bags (0.93-2450 ng recovered) highlighted the variability found between manufacturers.

CONCLUSION

The results suggest that although allergen leakage has been reduced, there is still room for improvement. A method of testing allergen leakage by using Fel d 1 should be applied to vacuum cleaners and bags recommended for allergic patients.