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PubMed2005

Water uptake on mineral dust and soot: a fundamental view of the hydrophilicity of atmospheric particles?

The interaction of water vapour with mineral dust and soot surfaces has been studied in the temperature range 203 K < T < 298 K using a Knudsen cell reactor. For the uptake of water on mineral dust an initial uptake coefficient of gamma(ini) = (6.3 +/- 0.7) x 10(-2) independent of temperature has been determined. In contrast the desorption rate has been found to be strongly temperature dependent with desorption rate constants decreasing from 1 x 10(-3) at 265 K to 1 x 10(-4) at 223 K. In addition, relatively high surface coverages have been determined from which an adsorption enthalpy of -40 kJ mol(-1) is inferred. For the uptake of water on soot the initial uptake coefficient has been found to be independent of temperature with a value of gamma(ini) = (4.7 +/- 0.2) x 10(-2), similar to the case of mineral dust. However, the corresponding desorption rate constants have been found to be three orders of magnitude larger than for mineral dust. Consistent with this finding, low surface coverages with an adsorption enthalpy of -27 kJ mol(-1) have been derived. A comparison of the uptake kinetics and adsorption enthalpies of water on mineral dust and soot leads to the conclusion that water is much stronger interacting with mineral dust than with soot. In terms of a hydrophilicity concept the results suggest, that mineral dust may be regarded as hydrophilic whereas soot is hydrophobic and that fundamental kinetic and thermochemical quantities may be related to that concept.

Adsorption↗
PubMed2006

Real-time PCR detection of toxigenic Fusarium in airborne and settled grain dust and associations with trichothecene mycotoxins.

Inhalation of immunomodulating mycotoxins produced by Fusarium spp. that are commonly found in grain dust may imply health risks for grain farmers. Airborne Fusarium and mycotoxin exposure levels are mainly unknown due to difficulties in identifying Fusarium and mycotoxins in personal aerosol samples. We used a novel real-time PCR method to quantify the fungal trichodiene synthase gene (tri5) and DNA specific to F. langsethiae and F. avenaceum in airborne and settled grain dust, determined the personal inhalant exposure level to toxigenic Fusarium during various activities, and evaluated whether quantitative measurements of Fusarium-DNA could predict trichothecene levels in grain dust. Airborne Fusarium-DNA was detected in personal samples even from short tasks (10-60 min). The median Fusarium-DNA level was significantly higher in settled than in airborne grain dust (p < 0.001), and only the F. langsethiae-DNA levels correlated significantly in settled and airborne dust (r(s) = 0.20, p = 0.003). Both F. langsethiae-DNA and tri5-DNA were associated with HT-2 and T-2 toxins (r(s) = 0.24-0.71, p < 0.05 to p < 00.01) in settled dust, and could thus be suitable as indicators for HT-2 and T-2. The median personal inhalant exposure to specific toxigenic Fusarium spp. was less than 1 genome m(-3), but the exposure ranged from 0-10(5) genomes m(-3). This study is the first to apply real-time PCR on personal samples of inhalable grain dust for the quantification of tri5 and species-specific Fusarium-DNA, which may have potential for risk assessments of inhaled trichothecenes.

Air Microbiology↗
PubMed1998

Indoor factors associated with concentrations of house dust mite allergen, Der p 1, in a random sample of houses in Norwich, UK.

BACKGROUND: Studies of house dust mite allergen concentrations suggest large variations both within and between homes. It is likely that different household characteristics influence allergen levels in different locations within the house. OBJECTIVES: To investigate household characteristics associated with higher concentrations of house dust mite allergen in a random sample of houses. METHODS: Information on indoor environment was obtained from 158 adults aged 20-44. Dust samples were collected from their living room floor, bedroom floor and mattress. Concentrations of Der p 1, the major allergen from the house dust mite Dermatophagoides pteronyssinus, were measured by monoclonal antibody immunoassay. Associations between mite allergen concentrations and household characteristics were examined using censored-normal regression models. Factors that were related to Der p 1 (P </= 0.2) in univariate analyses were included in multivariable regression models. RESULTS: Der p 1 was not detected in any location in 10 (6.3%) houses. Geometric mean concentrations of Der p 1 were 1.9 microg/g in living room floor dust, 1.7 microg/g in bedroom floor dust and 2.0 microg/g in mattress dust. Approximately 25% of living room floor and mattress, and over 30% of bedroom floor samples had Der p 1 concentrations greater than 10 microg/g. Household characteristics associated with Der p 1 concentrations in both living room and bedroom were floor level, extractor fan in the kitchen, and age of carpet. Living room Der p 1 concentrations were also associated with gas oven/hob, window condensation, open fires, vacuum cleaner type, smokers in the house and age of house. Bedroom Der p 1 concentrations were also associated with use of blankets and wash temperature of bedding. Mattress Der p 1 concentrations were associated with window condensation, concrete bedroom floor and age of mattress. CONCLUSION: Different household characteristics were associated with high Der p 1 concentrations in different parts of the house. These findings are relevant to design of allergen avoidance regimes or formulation of policy recommendations for reduction of disease associated with allergen exposure.

Adult↗
PubMed2001

Pets and vermin are associated with high endotoxin levels in house dust.

BACKGROUND: Previous studies have shown that the risk for allergic sensitization is lower in children who grew up on farms and in young adults who were exposed to dogs in early childhood. A higher microbial exposure in general and in particular to endotoxin in early childhood might contribute to this lower risk of atopy. OBJECTIVE: We examined whether the presence of pets or vermin in the home is associated with higher endotoxin concentrations in settled house dust. METHODS: House dust was sampled in a standardized manner on the living room floors of 454 homes of German children aged 5-10 years (participation rate 61%). Endotoxin was assessed with a quantitative kinetic chromogenic Limulus Amebocyte Lysate (LAL) method. Associations between endotoxin levels, pets and vermin are presented as ratios of the crude and confounder adjusted geometric means (means ratios) in the category of study vs. a reference category using multiple linear regression models. RESULTS: Endotoxin concentrations in living room floor dust sampled in homes without pets and vermin were lower (1246 ng per square meter, 1519 ng endotoxin/g dust, n = 157) than those sampled in homes with pets or vermin (2267 ng per square meter, 2200 ng endotoxin/g dust, n = 296). After adjustment for city of residence, season of dust sampling, age of the building and story of the dwelling, means ratios for endotoxin expressed per gram of dust were statistically significantly increased for dog (1.64, 95% CI 1.09-2.46), for cat (1.50, 95% CI 1.03-2.18) and for cockroach (3.01, 95% CI 1.37-6.60), whereas no major statistically significant associations were found for other pets, ants and mice. CONCLUSION: Keeping a dog or a cat in the home is consistent with higher exposure to endotoxin and might therefore contribute to the lower risk of atopy in later life.

Air Pollution, Indoor↗
PubMed2000

T-cell activation by organic dust in vitro.

Inhalation of swine dust causes intense airway inflammation with a multifold increase of inflammatory cells and lymphocyte activation as assessed by bronchoalveolar lavage. To further investigate the mechanism for lymphocyte activation the present in vitro study focuses on the lymphocyte response to swine dust in whole blood. Various concentrations of phytohaemagglutinin (PHA) (final concentrations: 3.16, 10.0, 3.16 and 100 microg ml(-1)) and swine dust (final concentrations: 10.0, 31.6, 100 and 316 microg ml(-1)) were added to heparinized whole blood from healthy donors. The blood samples were incubated in duplicate, using the homologous unstimulated blood as control, for 4, 24, 48 and 72 h in a water bath at 37 degrees C. The cells were stained with fluorochrome conjugated monoclonal antibodies. For analysis of T-cell activation CD3 was double-stained together with the activation markers CD69, CD25 and HLADR. Cell count percentages were analysed by flow cytometry. Soluble IL-2sRalpha in plasma was analysed using commercial sandwich ELISA technique. At baseline CD69, CD25 and HLA-DR were expressed in < 1%, approx 5% and < 1% of the T-cells respectively. We found a dose response relationship between swine dust exposure and the expression of all three T-cell activation markers which appeared at different time-points. Maximal expression of CD69 (8%, P<0.05) and CD25 (15%, P<0.001) was found after 24h of activation. HLA-DR was significantly expressed after 48h (8%) and maximally expressed after 72 h of activation (13%, P<0.05). The soluble IL-2sRalpha in plasma was maximally expressed after 24-48 h (1200 pg ml(1) and 1500 pg ml(-1), respectively. In conclusion, T-cells were activated by swine dust in vitro. Thus, our previous findings of T-cell activation following swine dust exposure, in vivo may be an effect of the dust either directly on T-cells or on other cells which in turn contribute to the T-cell activation.

Adult↗
PubMed2003

[Exposition and sensitisation to indoor allergens, house dust mite allergen and cat allergens].

The study examined the exposure to biological indoor air agents and their possible role for allergies and respiratory tract illnesses of children. It was conducted as a case control study (atopic vs non-atopic children) at the four surveillance public health departments in Baden-Württemberg in the winter season 1999/2000 and included 379 children of the fourth class. The concentrations of the house dust mite antigens Der F1, Der p1, and Der Gr2 as well as cat allergen Fel d1 were determined in the children's bedrooms on the ground and in the mattress. Specific IgE-antibodies against allergens from house dust, mites and cat were determined in the serum of the children. For mite allergens the following medians ( micro g/g) were estimated in floor dust: Der p1 = 0.6, Der f1 = 2.3, Gr2 = 0.1; in mattresses: Der p1 = 1.2, Der f1 = 3.4, Gr2 = 0.3. The median of Fel d1 in floor dust was 0.2 microg/g, in mattresses 0.1 microg/g. Sensitisation to dust mite allergen was found to be more prevalent than sensitisation to cat. The distribution of sensitisation among the cases and controls is different. Among the cases, more subjects were sensitised to dust mites (32.9 %) and cat (13.1 %). Among the controls, 17.1 % were sensitised to dust mites and 4.1 % to cat. The results showed no direct association between the prevalence of allergies or respiratory tract illnesses and the indoor concentrations of the allergens. Possible reasons for these findings are discussed.

Allergens↗
PubMed1990

Exposure to house-dust mite allergen (Der p I) and the development of asthma in childhood. A prospective study.

BACKGROUND AND METHODS: Children with asthma commonly have positive skin tests for inhaled allergens, and in the United Kingdom the majority of older children with asthma are sensitized to the house-dust mite. In a cohort of British children at risk for allergic disease because of family history, we investigated prospectively from 1978 to 1989 the relation between exposure to the house-dust mite allergen (Der p I) and the development of sensitization and asthma. RESULTS: Of the 67 children studied in 1989, 35 were atopic (positive skin tests), and 32 were nonatopic. Of the 17 with active asthma, 16 were atopic (P less than 0.005), all of whom were sensitized to the house-dust mite, as judged by positive skin tests and levels of specific IgE antibodies (P less than 0.001). For house-dust samples collected from the homes of 59 of the children in 1979 and from 65 homes in 1989, the geometric means for the highest Der p I exposure were, respectively, 16.1 and 16.8 micrograms per gram of sieved dust. There was a trend toward an increasing degree of sensitization at the age of 11 with greater exposure at the age of 1 (P = 0.062). All but one of the children with asthma at the age of 11 had been exposed at 1 year of age to more than 10 micrograms of Der p I per gram of dust; for this exposure, the relative risk of asthma was 4.8 (P = 0.05). The age at which the first episode of wheezing occurred was inversely related to the level of exposure at the age of 1 for all children (P = 0.015), but especially for the atopic children (r = -0.66, P = 0.001). CONCLUSIONS: In addition to genetic factors, exposure in early childhood to house-dust mite allergens is an important determinant of the subsequent development of asthma.

Age Factors↗
PubMedDate not supplied

An epidemiologic study of the respiratory effects of trona dust.

Trona (sodium sesquicarbonate) is mined from an underground deposit in Wyoming and processed for use in glass, paper, detergent, and chemical applications. Trona dust is alkaline (pH 10.5) and can have an irritant effect on respiratory airways, mucous membranes, and the skin. A study population of 142 underground miners and 88 surface workers from one facility volunteered for an epidemiologic study. Their mean age was 37.6 yr and mean duration of employment was 10.0 yr. The percentage with chronic cough and phlegm was 23%; both symptoms were more common among smokers than nonsmokers. Thirty-three percent of the workers complained of dyspnea when hurrying on level ground or walking up a slight hill. Half of the workers complained of upper respiratory tract symptoms and eye irritation. Both smokers and exsmokers had significant declines of forced expiratory volume in 1 sec (FEV1.0) with age; exsmokers also had declines with work-years when compared to a nonsmoking comparison population. Nonsmokers with personal dust measurements had a significant decline of FEV1.0 related to respirable dust exposure. A shift study of 104 workers revealed a significant fall in FEV1.0 among nonsmokers and surface workers. Significance was approached in the high dust exposure group. An increase in the mean percent predicted forced vital capacity and FEV1.0 was shown for the 125 workers who had a 5-yr follow-up of pulmonary function. There was no correlation between the shift study decrements and the longitudinal 5-yr follow-up. Industrial hygiene dust sampling found elevated levels of total dust but lower respirable dust, with no detectable free silica.

Bicarbonates↗
PubMedDate not supplied

Symptoms and pulmonary function in western red cedar workers related to duration of employment and dust exposure.

Measurements of total dust concentration were made in a western red cedar sawmill that employed 701 workers. Both area sampling and personal sampling of total dust were done over an 8-hr shift corresponding to job descriptions and locations to assign each worker an exposure level. A total of 652 (93%) of the workers completed a respiratory-occupational questionnaire and performed spirometry, of whom 334 were assigned an exposure level. Dust exposure ranged from undetectable to 6.0 mg/m3 with a median exposure level of 0.2 mg/m3. Only 10% of the workers with an assigned exposure level were exposed to more than 1.0 mg/m3. Work-related asthma, defined as symptoms of asthma which improved on days off work, was reported by 52 workers (8.0%) and was more prevalent after 10 or more yr of employment. Chronic cough, dyspnea, persistent wheeze, and physician-diagnosed asthma were unrelated to either work duration or exposure. Levels of forced vital capacity (FVC) and forced expiratory volume in 1 sec (FEV1.0) were lower with dust concentrations greater than 2.0 mg/m3, controlling for age and smoking; maximum mid-expiratory flow rate (FEF25-75%) and FEV1.0/FVC were unrelated to dust exposure concentration. Work-related symptoms of eye irritation were seen more commonly with exposure to dust concentrations of 3.0 mg/m3 or more. It is concluded that symptoms of work-related asthma in red cedar workers are more common after 10 yr of exposure, and that levels of pulmonary function are lower with higher wood dust exposures.

Adult↗
PubMed2001

The performance of personal inhalable dust samplers in wood-products industry facilities.

Recent guidelines for particulate matter and aerosol measurements in the workplace describe sampling criteria for three progressively finer particle-size-selective fractions: inhalable, thoracic, and respirable. For substances like wood dust, for which health concerns usually center on particles that enter and deposit within the nasal passages, the inhalable fraction, which by definition includes particles ranging from 0 to 100 microm in diameter, is of greatest interest. There are a variety of commercially available personal samplers that can be used to measure inhalable dust in the workplace. At this time, however, most of these samplers have received only limited field testing in wood-products facility workplaces. This study compared the performance of three different personal inhalable dust samplers and a personal total dust sampler in several different wood-products industry facilities. Specifically, the study provided information on sampler precision and the relationship between results obtained with the various personal samplers. The personal samplers that were evaluated were the Institute of Occupational Medicine (IOM), the conical inhalable (CIS), and the multi-orifice (7-Hole) inhalable dust samplers and the closed-face filter cassette (CFFC) total dust sampler. Study results suggest that the CIS and CFFC may be more precise than the IOM and 7-hole samplers. Results also indicate that the relative performance of the inhalable samplers as compared to the total dust sampler may vary as a function of particle size distribution in the workplace.

Dust↗
PubMedDate not supplied

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.

Dust↗
PubMedDate not supplied

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.

Aerosols↗
PubMed1983

Preliminary study of mycoflora and mycotoxins in grain dust from New Orleans area grain elevators.

Dust particles arising from disintegration of grain during handling and shipping may be inhaled by exposed barge and elevator workers. Since the normal grain mycoflora usually contain mycotoxin-producing fungi, these toxins could be natural contaminants of grain dust. Known mycoflora of commercial grain include species of Penicillium, Aspergillus, and Fusarium-fungi that may produce ochratoxins, aflatoxins and zearalenone. A procedure was developed to extract simultaneously these toxins from grain dust. Initial extraction with methylene chloride and water was followed by specific cleanup procedures for each toxin and then by thin layer chromatographic quantitation. In 50-g samples the lowest level of detection for zearalenone was 50 ng of zearalenone/g of dust, for ochratoxin, 10 ng/g and for aflatoxin, 5 ng/g. Dust samples were collected at various locations in two grain elevators and their associated transfer facilities in the New Orleans area. Large amounts of dust that had settled upon floors, machinery and ledges were tested, as well as that which had been collected by dust control systems. Samples were analyzed for aflatoxins, ochratoxin A, and zearalenone. None of the 15 samples contained any detectable amount of aflatoxins or ochratoxin A, but 10 of the 15 samples contained zearalenone at levels from 25 to 100 ng/g.

Dust↗
PubMed1992

The use of tracer gases to determine dust dispersion patterns and ventilation parameters in a mineral processing plant.

A study was conducted in a fluorspar milling plant to assess the effectiveness of tracer gases as a reliable supplement to conventional air-monitoring and ventilation measurements. In the course of this study, a tracer gas was used as a surrogate substance to analyze the direction and the rate of spread of contaminants from various potential dust production points in the plant. Time-weighted average and continuous mineral dust concentrations were measured in several areas of the plant; these results were compared and correlated with steady-state tracer gas concentrations in the mill. Time-weighted average dust concentrations varied between 0.18 and 0.57 mg/m3 for total dust and 0.04 and 0.20 mg/m3 for quartz respirable dust, depending on the location. Correlation of these values with steady-state tracer gas concentrations yielded linear relationships with correlation coefficients (R2) of 0.95 and 0.87, respectively, for total and quartz dust. Results from this study, therefore, indicate that tracer gases may help model the spread of airborne respirable dust from point sources. These tracer gas releases also allowed the simultaneous quantitative determination of air residence times and contaminant clearance times from the building. Hence, tracer gases will help industrial hygienists obtain useful data with respect to building ventilation.

Air Pollutants, Occupational↗
PubMed1995

Variability of particle size-specific fractions of personal coal mine dust exposures.

This study estimated the ratio of the tracheo-bronchial dust fraction to the fraction collected by a respirable dust sampler for a variety of job classifications found in conventional, continuous, and longwall coal mining sections. The ratios could then be applied in epidemiologic studies to existing respirable dust measurements to estimate thoracic mass concentrations for evaluation of the relative importance of the respirable and thoracic dust fractions to obstructive lung disease. Data collected include particle size distributions from four U.S. underground coal mines using eight-stage personal cascade impactors. A total of 180 samples were examined by mine, occupation and occupations grouped by proximity to the mine face, and by mining technology. Several fractions--that collected by the 10-mm nylon cyclone, the American Conference of Governmental Industrial Hygienists respirable and thoracic particulate mass fractions, and the estimated alveolar and tracheo-bronchial deposition fractions--were estimated. These were not significantly different when grouped by occupation, by proximity of work to the mine face, or by the type of mining technology in use. Distributions from one mine varied from the others, perhaps because it used diesel equipment in the haulage ways, which contributed to the fine aerosol fractions. Results suggest that although the tracheo-bronchial dust fraction may contribute to the development of obstructive lung disease, occupation-specific tracheo-bronchial dust fractions are not likely to produce stronger exposure-response estimates than the historically collected respirable dust concentrations.

Bronchi↗
PubMed2005

Fungal types and concentrations from settled dust in normal residences.

Analysis of settled dust collected from carpeting and furnishings is occasionally used by investigators to determine whether an environment contains unusual fungi. Little information is available concerning the types and concentrations of culturable fungi present on textile surfaces in normal residential settings not affected by unusual mold reservoirs, such as from fungal growth sites within the built environment. This study presents the results of the collection and analysis of surface dust from 26 residential environments that were prescreened by interview, physical inspection, and air sampling to limit the surface dust collection to structures in which there was no history of water intrusion, flooding, plumbing leaks, signs of mold growth, or evidence of unusual airborne fungal spore types or concentrations. In those structures found to have no history or indications of water events or unusual fungi, surface dust was vacuumed from prescribed horizontal areas on carpet and textile-covered furnishings. These samples were then subjected to fungal culture, from which viable colonies were enumerated and identified. Based on the study results, it does not appear reasonable that the frequently quoted total fungi concentration exceeding 10(5) CFU/g is definitive evidence that a residential surface is contaminated with unusual amounts of culturable fungi. Collocated samples collected from eight side-by-side carpets sections revealed poor reproducibility. While settled dust sampling may be appropriate for determining the fungal status of a localized area, or as a gross screening tool, using settled dust results alone to establish the presence of unusual fungal types or concentrations within a structure appears to be inappropriate, and using settled dust results with other investigative methods, such as visual observations and air sampling, requires cautious interpretation.

Air Pollution, Indoor↗
PubMed2006

Dust in the underground railway tunnels of an Italian town.

This article assesses hazards associated with exposure to dust in tunnels and platforms of the A and B lines of Rome's underground railway and provides an informed opinion on the risks to workers and the travelling public of exposure to tunnel dust. The study focused on the analysis and measurement of dust granulometric classes PM10, respirable fraction, respirable combustible dust, and the organic, metallic, siliceous, and fibrous components. Comparing the measurement values from the tunnels and platforms with those found at the entrances to the underground railway stations, it emerges that dust concentration in the tunnels and platforms is three times higher, with a maximum PM10 value of 479 microg/m3. Averaged over 24 hours, in relation to the above ground levels, drivers and station staff are exposed to an additional value of 11 microg/m3 and 10 microg/m3, respectively. If commuters were to remain in the trains or on the station platforms, the 24-hour average exposure would increase by 3 microg/m3. Iron and silica were the major components found in the dust. The use of silica sand in the emergency braking system of the carriages is capable of causing a dispersion of quartz in the air in percentages varying from 5% to 14%. Methods are suggested in this article for the reduction of dust dispersion.

Air Pollutants↗
PubMed2003

Exposure to inhalable flour dust in Canadian flour mills.

In 1999, the American Conference of Governmental Industrial Hygienists (ACGIH(R)) proposed a Threshold Limit Value (TLV(R)) of 0.5 mg/m(3) for flour dust with a sensitization notation. The Labour Program of the Department of Human Resources Development Canada (HRDC), following notice of the intention to set a TLV, conducted a study of the levels of exposure to flour dust in flour mills across Canada to verify existing conditions, as well as to decide whether to adopt the proposed TLV or reference some other value. As part of the study, a relationship between flour dust concentrations obtained by using Institute of Occupational Medicine (IOM) samplers and closed-face 37-mm cassettes was examined and the literature on the health effects of exposure to flour dust was reviewed. A total of 104 millers, packers, sweepers, bakery mix operators, and others (mixed tasks) from 14 flour mills were sampled over an 8-hour work shift using IOM samplers. The results indicate that 101 employees (97.1%) were exposed to levels exceeding 0.5 mg/m(3), 66 employees (67.3%) to levels exceeding 5 mg/m(3), and 44 employees (42.3%) to levels exceeding 10 mg/m(3). For comparison purposes, flour dust measurements were also taken in a highly automated flour mill using state-of-the-art technology. The results suggest that even with the most up-to-date technology and proper cleaning operations in place, the flour milling industry may not be able to reduce the flour dust levels to below the TLV of 0.5 mg/m(3). According to the measurements of inhalable and total dust concentrations, the IOM sampler appears to be a more efficient collector of inhalable airborne particles up to 100 microm than the closed-face 37-mm cassette.

Air Pollutants, Occupational↗