Altered partition of t cell subsets in the peripheral blood of healthy workers exposed to flour dust

Occupational exposure to organic compounds can induce obvious immunological disorders or more subtle modifications. We investigated peripheral blood lymphocyte subsets in 34 bakers and 82 millers exposed to wheat flour dust, and 51 salt factory workers. Significantly decreased levels of CD4 +, CD8 +, CD57 + and CD8 + /57 + cells were noted in mill workers, and of CD57+ cells in bakers. CD29 + and CD4 + /CD29 + cells were significantly lower in millers, CD4 + /CD45RA + cells higher in all exposed workers. The lower numbers of positive cells noted in millers appeared associated to significantly higher (p<0.001) levels of CD29 and CD45RA expression as measured by fluorescence intensity. These data are opposite to those previously reported in asthmatic workers exposed to flour dust. Since the individuals tested here were clinically healthy, the alterations of T-cell subsets observed could be interpreted as a successful attempt at immunoregulation maintaining homeostasis.     

Nasal symptoms and indices of nasal inflammation in flour-dust-exposed bakers

To analyze whether indices of nasal airway inflammation in bakers were related to nasal symptoms and exposure to airborne flour dust. Methods: A cross-sectional study was performed in 12 currently flour-exposed bakers. They were examined by nasal lavage (NAL), visual inspection, a test of mucociliary clearance, and nasal peak expiratory flow (nasal PEF). NAL fluid was analyzed according to the inflammatory markers eosinophil cationic protein (ECP), indicating eosinophilic activity; myeloperoxidase (MPO), indicating active neutrophils; hyaluronic acid (HA) from active fibroblasts; tryptase, indicating activation of mast cells; and albumin, indicating plasma exudation. The bakers were also questioned about respiratory symptoms and working history. Their current and cumulative exposure to inhalable flour dust was estimated after exposure measurements and information about earlier work tasks. Office workers (n = 16) without occupational exposure to dust or any other known nasal irritant or sensitizer served as controls. Results: Personal inhalable dust measurements among the bakers working as dough makers or bread formers ranged from 1.0 to 3.8 mg/m³. Of the 12 bakers, 10 reported at least 1 nasal symptom (crusts, blockage, or a runny nose), a proportion significantly greater than that of the controls (P = 0.009). Bakers with nasal symptoms had higher concentrations of markers of inflammation in their NALs as compared with nonsymptomatic bakers. The difference was significant for MPO (P = 0.02) and HA (P = 0.04) in relation to a runny nose. Tryptase was detected in only one NAL of the bakers. There was a positive correlation between the cumulative dose of inhalable flour dust and concentrations of MPO and HA in NAL. Two bakers were sensitized to wheat; they had the highest NAL concentrations of inflammatory markers. Conclusions: Our results indicate that flour dust exposure in bakers at levels below the current occupational exposure limit causes nasal mucosal inflammation, which, in turn, is related to nasal symptoms. We propose that the inflammation may be nonallergic, characterized by activation of neutrophils and fibroblasts. Received: 16 September 1997 / Accepted: 16 May 1998     

Nasal air sampling for measuring inhaled wheat allergen in bakeries with and without facemask use

OBJECTIVE: Occupational asthma caused by flour is common in bakers. We applied novel intranasal air samplers (INAS) to assess wheat allergen exposure and evaluate respiratory protection in bakeries. METHODS: Two models of INAS (INAS-M1 and INAS-M2) were compared with simultaneous personal air sampling of inhalable dust, both with and without facemasks. Wheat allergen levels were measured using a sensitive sandwich enzyme immunoassay. Allergenic particles were immunostained for microscopic visualization. RESULTS: Personal air sampling correlated well with INAS-M1 (r = 0.89) and INAS-M2 (r = 0.75). INAS-M2 collected particles more effectively than INAS-M1. Facemasks reduced inhalation of wheat allergen by 96% and 93% measured using INAS-M1 and INAS-M2, respectively. CONCLUSIONS: Nasal air sampling can complement personal air sampling to measure short-term exposure and evaluate respiratory protection. To prevent baker's asthma, facemasks may be an effective solution in addition to improving workplaces.     

Chronic and acute respiratory effects among grain mill workers

Exposure to flour dust may induce chronic respiratory manifestations as well as acute ventilatory effects. We compared the prevalence of respiratory symptoms, ventilatory impairment, and variations in pulmonary function over the workshift in a group of mill workers exposed to wheat flour and in referent workers. One hundred and forty-two men exposed to flour in a mill and 37 referent workers were included in this study. Each subject completed a standardized questionnaire. Pulmonary function tests were performed before and after the workshift. The assessment of environmental exposure to flour showed high concentrations during some jobs with a high percentage of inhalable particles and a low concentration of respirable particles. The exposed workers had a significantly higher prevalence of usual cough and usual phlegm than the referents. The prevalence of asthma, based on the questionnaire, was similar. Before the workshift, the exposed workers had significantly lower mean lung function values for peak flow rate and forced expiratory flow rate at 75% of the vital capacity than the referents. After the workshift, all the lung function values showed a slight decrease, significant for forced vital capacity and forced expiratory volume during 1 s in both groups. Among the exposed workers, the asthmatic subjects had a significantly higher decrease across the shift than the nonasthmatic workers. This result is probably linked to bronchial hyperreactivity. Among nonasthmatic subjects, the decrease was larger in nonexposed workers than in exposed workers. A higher prevalence of respiratory symptoms and lower pulmonary function values were observed among mill workers by comparison with referents. Moreover, the data suggest that asthmatic status and the time of spirometric measurements need to be taken into account in epidemiological studies on exposure to airborne allergens. In addition, the study does not exclude a healthy worker effect with selection of dust-resistant subjects or better identification of asthmatic subjects among the workers exposed to an allergenic substance than among the nonexposed workers.     

Health surveillance in milling, baking and other food manufacturing operations--five years' experience.

The objective of this study was to describe the incidence of allergic respiratory disease and its outcome in terms of symptoms and jobs, across different flour-using industries. It uses the findings of a health surveillance programme in a large food organization over a five-year period. The population under surveillance consisted of 3,450 employees with exposure to ingredient dusts, of whom 400 were in flour milling, 1,650 in bread baking, 550 in cake baking and 850 in other flour-using operations. A total of 66 employees with either asthma or rhinitis symptoms attributable to sensitization to allergens in the workplace were identified. The majority of these (48/66) had become symptomatic prior to the commencement of the health surveillance programme in 1993. The incidence rates (per million employees per year) for those who developed symptoms between 1993 and 1997 were 550 for flour milling, 1,940 for bread baking, 0 for cake baking and 235 for other flour-using operations. The agent believed to be responsible for symptoms was most commonly grain dust in flour millers and fungal amylase in bread bakers. Wheat flour appeared to have a weaker sensitizing potential than these other two substances. In terms of outcome, at follow-up 18% of symptomatically sensitized employees had left the company. Two of the ex-employees retired through ill health due to occupational asthma. Of those still in employment, 63% described an improvement in symptoms, 32% were unchanged and 4% were worse than when first diagnosed. Over half the cases still in employment were continuing to work in the same job as at the time of diagnosis.     

Lung function and immunological changes in poultry breeders

Summary The results of the study of 61 persons occupationally exposed to the inhalation of dust from waste materials in chicken breeding are presented. The subjects were divided into three groups: 1. females in permanent exposure, 2. males in permanent exposure, 3. males in intermittent exposure. The following examinations were performed: case histories with special reference to symptoms of allergic alveolitis and/or chronic nonspecific lung disease, testing of skin hypersensitivity to allergens prepared from material collected in working places, blood analysis for the precipitins against chicken dropping and cock serum, testing of ventilatory lung function including measurements of residual volume, and testing of lung diffusion capacity. A very high prevalence of positive early and late skin reaction was found with no large differences between different groups of subjects. The highest percentage of precipitins was found in permanently exposed women. FVC, FEV₁ and MEF 25% values were significantly lower than predicted normal values. A statistically significant increase of the residual volume was recorded in all subjects in permanent exposure. Lung diffusion capacity in all the subjects was normal. The prevalence of acute respiratory symptoms indicative of allergic alveolitis was significantly higher in subjects in permanent than in those in intermittent exposure.     

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.     

Exposures and mortality among chrysotile asbestos workers. Part II: mortality

A retrospective cohort mortality study was conducted among a cohort of 1,261 white males employed one or more months in chrysotile asbestos textile operations and followed between 1940 and 1975. Statistically significant excess mortality was observed for all causes combined (standardized mortality ratio [SMR] = 150), lung cancer (SMR = 135), diseases of the circulatory system (SMR = 125), nonmalignant respiratory diseases (SMR = 294), and accidents (SMR = 134). Using estimated fiber exposure levels in conjunction with detailed worker job histories, exposure-response relationships were investigated. Strong exposure-response relationships for lung cancer and asbestos related non-malignant respiratory diseases were observed. Compared with data for chrysotile miners and millers, chrysotile textile workers were found to experience significantly greater lung cancer mortality at lower lifetime cumulative exposure levels. Factors such as differences in airborne fiber characteristics may partially account for the large differences in exposure response between textile workers and miners and millers.     

Pulmonary function impairment and airway allergy among workers in traditional bakeries

Objectives

To assess the effect of exposure to flour dust on pulmonary function tests, prevalence of symptoms (respiratory, allergic/irritating) and parameters of allergic sensitization in terms of skin prick test, and bronchial hyper-responsiveness.

Material and Methods

43 bakers (with at least 2 years of occupational exposure) working at different bakeries in Ismailia city, Egypt; and 64 control subjects of comparable socio demographic characteristics were compared. All participants were subjected to an interview questionnaire, clinical chest examination, skin prick test, bronchial hyper-responsiveness test and measurements of pulmonary function parameters.

Results

All respiratory and allergic symptoms were more prevalent among bakers compared to the control group, with the highest odds ratio for allergic symptoms (OR = 6.9; p < 0.0001) and dyspnea (OR = 6.3; p = 0.0004). Bakers had a higher percentage of SPT positive results with statistically significant difference between the two groups (p < 0.0001). Bakers had lower observed values compared to the control group with statistically significant difference for FVC, FEV₁/FVC ratio, FEF_75%, and FEF_25–75% parameters.

Conclusion

The present study suggested that occupational exposure to flour dust may affect respiratory irritation and sensitization, and reduce the pulmonary function tests such as FVC, FEV₁, and FEV₁/FVC ratio and FEF_25–75%.     

Problems in diagnosing occupational allergy to flour: results of allergologic screening in apprentice bakers

Baker's respiratory allergy is reported as one of the most common forms of occupational allergy in many countries. At the first stage of a three-year study of risk factors of occupational allergy we investigated the symptoms reported, and the results of skin prick tests (SPT) to common and flour allergens in 461 current apprentice bakers from three different regions of Poland before starting occupational exposure. The occurrence of cough was reported by 14 subjects (3%), dyspnoea by 4 (0.87%), rhinitis by 18 (3.9%), conjunctivitis by 12 (2.6%) and skin symptoms by 12 subjects (2.6%). Generally, 48 subjects (10.41%) reported at least one symptom, which might suggest the existence of allergic disease. Positive SPT to at least one allergen was found in 99 subjects (21.5%), including 82 subjects (17.78%) with positive SPT to common allergens, 13 subjects (2.81%) to flour allergens and 4 subjects (0.88%) sensitised only to Dermatophagoides farinae. The statistical analysis revealed significant correlation between positive SPT to common allergens and reported rhinitis and conjunctivitis, and between positive SPT to occupational allergens and reported dyspnoea. Moreover, a significant correlation between positive SPT to D. pteronyssinus and D. farinae was found. In our opinion, the results of SPT should be very carefully examined, when diagnosing occupational allergy, as in some apprentice bakers positive results of SPT to flour allergens are found before vocational training. In all apprentice bakers, SPT to common and occupational allergens should be performed before starting occupational exposure. It would ensure the exclusion of subjects already sensitised to occupational allergens. Positive SPT to Dermatophagoides farinae has a very limited value in recognising baker's allergy.     

Respiratory-Function Changes in Textile Workers Exposed to Synthetic Fibers

The prevalence of respiratory symptoms and acute and chronic changes in ventilatory function were studied in three groups of textile workers: 68 workers with exposure to synthetic fibers only, 30 with previous exposure to cotton, and 77 with previous exposure to hemp. The prevalence of dyspnea, grade 3 or 4, was significantly lower (P < .0 1 ) in workers with a history of exposure to synthetic fibers only than in those previously exposed to hemp or cotton. No case of byssinosis was found in any of the workers studied. Values in ventilatoryfunction tests (FEV_1.0, FVC and MEF 50%) were significantly reduced during the work shift on Monday and Thursday. The Monday MEF 50% preshift values were significantly lower than expected in all three groups of workers. A comparison of the 1963–1973 data on the 77 workers previously exposed to hemp showed a lower prevalence of most chronic respiratory symptoms and smaller acute FEV_1.0and FVC reductions when they worked with synthetic fibers (1973) than when they were exposed to hemp (1963).     

Exposure-response relations for self reported asthma and rhinitis in bakers

OBJECTIVES—To explore relations between two estimates of exposure to inhalable flour dust, and the incidence rates (IRs) of asthma and rhinitis in bakers.
METHODS—This was a retrospective cohort study among 2923 bakers. A posted questionnaire registered the disease and work history. For every year, each baker was assigned an estimate of the exposure concentration to inhalable flour dust derived from reported job-tasks and dust measurements. Exposure at onset of disease was expressed as current dust exposure concentration, and as cumulative dose of exposure to dust. A multiple Poisson regression analysis assessed the impacts of the exposure estimates on the IRs of asthma and rhinitis.
RESULTS—IRs of asthma and rhinitis increased by dust concentration at onset of disease. The IR of asthma for the bakers with highest exposure (dough makers) was 7.3/1000 person-years in men and 6.5 in women and for rhinitis 43.4 and 38.5, respectively. There was a significant association between the dust concentration at onset of disease and the risk for asthma or rhinitis, but not of the cumulative exposure.
CONCLUSION—The risk of asthma seemed to be increased at inhalable dust concentrations 3 mg/m³ (dough making or bread forming), whereas the risk of rhinitis was increased at all concentrations 1 mg/m³, indicating an increased risk in all bakery job-tasks. The risks seemed to be less dependent on the cumulative exposure dust than the inhalable dust concentrations.


Keywords: bakers; exposure-response relations; flour dust     

Exposure-response relations for work related respiratory symptoms and sensitisation in a cohort exposed to alpha-amylase

Methods: A prospective cohort study among 300 bakers and millers was followed up for a maximum of seven years. Exposure to α-amylase was estimated by air measurements and questionnaires and classified into three categories. Symptoms were recorded with a self-administered questionnaire and skin sensitisation assessed using skin prick test (SPT). Results: There were 36 new cases of chest symptoms, 86 of eyes/nose symptoms, and 24 of a positive SPT to α-amylase. There were exposure-response relations for chest and eyes/nose symptoms and for sensitisation, and a significantly increased prevalence ratio for chest symptoms in the highest exposure category. Conclusion: A reduction in α-amylase exposure is likely to reduce the risk for respiratory morbidity in bakery workers.     

Respiratory symptoms and ventilatory performance in workers exposed to grain and grain based food dusts

A health surveillance study of male grain food manufacturingworkers used a respiratory health questionnaire and spirometryto assess the prevalence of work-related respiratory symptomsand impaired ventilatory performance. The prevalence of cough,breathlessness, wheeze and chest tightness was between 8–13%but was 20% for rhinitis. Rhinitis was the most common symptomwith 37% of those reporting rhinitis describing this as work-related.A case-control analysis of workers reporting rhinitis did notidentify any specific occupational activities associated withincreased risk of rhinitis. Smoking habit and all respiratorysymptoms apart from rhinitis had a significant effect upon ventilatoryperformance. Occupational exposure to raw grains, flour, ingredientsand finished food was categorized as high, medium or low ineither continuous or intermediate patterns. Multiple regressionanalysis confirmed the effects of height, age and smoking uponventilatory performance. However, occupational exposure to grain,flour, food ingredients and cooked food dusts had no effectupon ventilatory performance. It is concluded that smoking habitis the major determinant of respiratory symptoms and impairedventilatory function. The excess complaints of rhinitis warrantfurther study but it would appear that the current occupationalexposure limits for grain, flour, food ingredients and cookedfood dusts are adequate to protect workers against impairmentof ventilatory performance.     

Respiratory symptoms and sensitization in bread and cake bakers

This purpose of this study was to examine the relationship betweenexposure to wheat flour, soya flour and fungal amylase and thedevelopment of work-related symptoms and sensitization in breadand cake bakery employees who have regular exposure to thesesubstances. The study populations consisted of 394 bread bakeryworkers and 77 cake bakery workers whose normal jobs involvedthe sieving, weighing and mixing of ingredients. The groupswere interviewed with the aim of identifying the prevalence,nature and pattern of any work-related respiratory symptoms.They were also skin-prick tested against the common bakery sensitizingagents, i.e., wheat flour, soya flour, rice flour and fungalamylase. The results of personal sampling for sieving, weighingand mixing operations at the bakeries from which the study groupswere taken were collated in order to determine typical exposuresto total inhalable dust from the ingredients, expressed as 8hour time-weighted average exposures. Data from the health surveillanceand collated dust measurements were compared with the aim ofestablishing an exposure-response relationship for sensitization.The prevalence of work-related symptoms in bread bakery andcake bakery ingredient handlers was 20.4% and 10.4% respectively.However, in a large proportion of those reporting symptoms inconnection with work, the symptoms were intermittent and ofshort duration. It is considered that the aetiology of suchsymptoms is likely to be due to a non-specific irritant effectof high total dust levels, rather than allergy. None of thecake bakers and only 3.1% of the bread bakers had symptoms whichwere thought to be due to allergy to baking ingredients. Usingskin-prick testing as a marker of sensitization, the prevalenceof positive tests to wheat flour was 6% for the bread bakersand 3% for the cake bakers. Comparable prevalences for soyaflour were 7% and 1 % respectively. However, the prevalenceof positive skin-prick tests to fungal amylase was 16% amongstthe bread baking group with only a single employee (1 %) inthe cake baking group having a positive test. Furthermore, thisemployee had previously worked in a bread bakery. The differencein rates of sensitization to wheat flour between the bread andcake bakers is not statistically significant, whereas the differencefor soya flour is at the borderline of statistical significance(p=0.045). In contrast, the difference in fungal amylase sensitizationis significant at the 0.1% level. For both bread and cake bakers,the 8 hour time-weighted average exposures for each of the activitiesshowed a wide variation with mixing having the lowest averageexposure and sieving the highest. Out of the allergens studiedin this investigation, fungal amylase is the principal sensitizerin large scale bread bakeries, with the main source of exposurebeing the handling of bread improvers. In contrast, the riskof sensitization to wheat flour is low in both bread and cakebakeries. The absence of positive skin-prick tests in the subgroupof cake bakery employees who regularly handle fungal-amylase-containingflour suggests that their levels of exposure are below the thresholdfor sensitization to amylase.     

Wheat flour sensitisation and airways disease in urban bakers.

A total of 176 bakers and 24 subjects employed as bread slicers and wrappers were studied to examine the effect of occupational category on respiratory symptoms, ventilatory capacity, non-specific bronchial reactivity, and prick skin test responses to wheat and common allergens. Bakers had a greater prevalence of attacks of wheeze and dyspnoea and more frequently considered that work affected their chests than did slicers and wrappers. Bakers with a history of asthma with onset since starting work in a bakery had a greater prevalence of chronic cough and sputum, increased bronchial reactivity, and positive prick skin test responses to wheat and common allergens than other bakers. There was a significant association between the frequency of positive prick skin tests to wheat and common allergens, suggesting that prior atopy facilitates sensitisation to cereal antigens. The frequency of positive prick skin responses to common allergens, however, declined with increasing baking duration whereas the frequency of positive skin responses to wheat increased with increasing baking duration, suggesting that subjects who were sensitised to common allergens were leaving the industry whereas subjects who stayed in the industry increased their risk of developing sensitisation to wheat. Oven handlers had a greater prevalence of attacks of wheeze and dyspnoea and more frequently considered that work affected their chests than either dough makers or general bakers. They also had a greater prevalence of positive prick skin test responses to wheat than dough makers or general bakers. Oven handlers also had a lower mean standardised casual FEV1 than either general bakers or dough makers. Thus oven handlers appear to have a greater risk of developing respiratory allergy and airflow obstruction than bakers in other occupational categories.     

Allergic airway disease in Italian bakers and pastry makers.

A survey was carried out on respiratory symptoms and skin prick test response to common allergens (atopy), storage mites, and occupational allergens among 226 bakers and pastry makers from 105 small businesses in northern Italy. Atopy was present in 54 workers (23.4%); 40 workers (17.7%) were skin positive to at least one storage mite, 27 (11.9%) to wheat flour and 17 (7.5%) to alpha-amylase. Work related asthma was reported by 11 (4.9%) workers and rhinoconjunctivitis by 31 (17.7%); 22 workers (10.2%) complained of chronic bronchitis. The distribution of skin prick test results among bakers and among 119 white collar workers did not indicate (by logistic analysis) an increased risk for bakers to skin sensitisation to common allergens, storage mite, or to a group of five flours. Sensitisation to wheat flour, on the other hand, was present only among exposed workers. Skin sensitisation to occupational allergens was significantly associated with atopy (p < 0.001), smoking habit (p = 0.015), and work seniority (p = 0.027). The risk of work related symptoms was associated with sensitisation to wheat or alpha-amylase, and with atopy, but not with sensitisation to storage mites, work seniority, or smoking habit. The results of the study indicate that there is still a significant risk of allergic respiratory disease among Italian bakers. Not only wheat allergens, but also alpha-amylase must be considered as causative agents, although sensitisation to storage mites is not important in the occupational allergic response. Atopy must be regarded as an important predisposing factor for skin sensitisation to occupational allergens and for the onset of symptoms at work. The data confirm that for effective prevention, greater care should be taken not only in limiting environmental exposure, but also in identifying susceptible people.     

Exposure assessment in occupational epidemiology: measuring present exposures with an example of a study of occupational asthma

The aim of the present paper is to present a comprehensive review of the issues involved in exposure assessment for occupational epidemiology studies and to provide an example. Exposure assessment for occupational epidemiology studies is becoming more quantitatively refined. This paper discusses important issues that need to be taken into account for exposure assessment, with particular reference to occupational asthma. It discusses issues such as survey design, data collection, the effect of measurement error and data interpretation. It presents recently developed methodology to evaluate exposure variability and its effect on the attenuation of risk estimates. It also presents methodology to control for such variability. It uses examples from a recent cohort study of flour millers and bakers. This example shows various characteristics of exposure and demonstrates that various measures of exposure, such as peak and full-shift exposure measurements, are regularly correlated, which has consequences for the analyses of exposure-response relationships. This paper stresses the importance of the recognition and evaluation of exposure variability and its effect on risk estimates and shows that with different exposure grouping schemes, different health risk estimates can be obtained. Quantitative exposure assessment is generally difficult, time-consuming and expensive and many issues need to be taken into account, but it can be rewarding and has become an absolute necessity for many occupational epidemiology studies. Evaluation of components of exposure variance is absolutely necessary. Exposure variability could lead to serious attenuation of risk estimates. Received: 3 July 1996 / Accepted: 2 April 1997