Pulmonary reaction to durum wheat; a constituent of grain dust

Respiratory Diseases Associated With Organic Dust Exposure

Organic dusts are complex bioaerosol mixtures comprised of dust and par ticulate matter of organic origin. These include components from bacteria, fungi, pollen, and viruses to fragments of animals and plants commonplace to several environmental/occupational settings encompassing agriculture/farming, grain processing, waste/recycling, textile, cotton, woodworking, bird breeding, and more. Organic dust exposures are linked to development of chronic bronchitis, chronic obstructive pulmonary disease, asthma, asthma-like syndrome, byssinosis, hypersensitivity pneumonitis, and idiopathic pulmonary fibrosis. Risk factors of disease development include cumulative dust exposure, smoking, atopy, timing/duration, and nutritional factors. The immunopathogenesis predominantly involves Toll-like receptor signaling cascade, T-helper 1/T-helper 17 lymphocyte responses, neutrophil influx, and potentiation of manifestations associated with allergy. The true prevalence of airway disease directly attributed to organic dust, especially in a workplace setting, remains challenging. Diagnostic confirmation can be difficult and complicated by hesitancy from workers to seek medical care, driven by fears of potential labor-related consequence. Clinical respiratory and systemic presentations coupled with allergy testing, lung function patterns of obstructive versus restrictive disease, and radiological characteristics are typically utilized to delineate these various organic dust-associated respiratory diseases. Prevention, risk reduction, and management primarily focus on reducing exposure to the offending dust, managing symptoms, and preventing disease progression.

Respiratory Health Outcomes, Rhinitis, and Eczema in Workers from Grain Storage Facilities in Costa Rica

Objectives

To examine the associations of inhalable grain dust exposure with respiratory health outcomes, rhinitis, and eczema reported by workers from rice, wheat, and maize storage facilities.

Methods

A cross-sectional study of 136 workers (73 operators and 63 administrative staff and other workers) from eight Costa Rican grain storage facilities was conducted in 2014-2015. Full-shift personal inhalable dust samples from all workers were collected. Study participants were administered a short version of the European Community Respiratory Health Survey questionnaire to identify symptoms of asthma, chronic bronchitis, rhinitis, and eczema. Associations between grain dust exposure and health outcomes were assessed using multivariable logistic and negative binomial regression models adjusted for age, smoking history, grain type, and presence of pets or farm animals in the home.

Results

The median inhalable grain dust concentration was 2.0 (25th to 75th percentile: 0.3-7.0) mg m-3. Higher concentrations of inhalable dust were associated with increased odds of (i) asthma symptoms or medication use [adjusted Odds ratio (ORa) per 10-fold increase in dust concentration 2.7; 95% confidence interval (CI): 1.3-6.7]; (ii) a score of at least two out of five symptoms suggestive of asthma (ORa 1.2; 95% CI: 1.0-1.3); and (iii) eczema (ORa 3.6; 95% CI: 1.7-9.6). No associations of inhalable grain dust exposure with chronic bronchitis and rhinitis were observed.

Conclusions

High exposure to inhalable dust in Costa Rican grain storage facilities was associated to asthma symptoms and eczema in workers.

Mechanisms of occupational asthma

BACKGROUND

The pathogenesis and the pathologic alterations of occupational asthma are similar to those of nonoccupational asthma. Occupational asthma may therefore represent a useful model of "human asthma" to investigate mechanisms and pathophysiology of asthma in general. In an occupational setting the cause and onset of asthma may be easily identified, and the natural history may be examined in follow-up studies. The mechanisms involved in occupational asthma include genetic predisposition, immunologically mediated responses, as well as nonspecific airway inflammation. In particular, high molecular weight (eg, grain dust, flour) and some low molecular weight sensitizers (eg, acid anhydrides and platinum halide salts) have been shown to induce occupational asthma through an immunoglobulin E (IgE)-dependent mechanism, while cell-dependent immunologic mechanisms are likely to be more relevant for occupational asthma induced by other low molecular weight sensitizers (eg, toluene diisocyanate and plicatic acid contained in western red cedar). The pathology of the airway mucosa of occupational asthma is remarkably similar to the pathology of nonoccupational asthma, ie, characterized by infiltration and accumulation of eosinophils, mast cells, and activated lymphocytes along with subepithelial fibrosis. In this article, the most relevant mechanisms are discussed with particular reference to the similarities and discrepancies between occupational and nonoccupational asthma.

Etiology and pathogenesis of airway disease in children and adults from rural communities

Asthma is the most common chronic disease of childhood and affects nearly 5 million children. The prevalence and severity of childhood asthma have continued to increase over the past decade despite major advances in the recognition and treatment of this condition. A comparison of urban and rural children suggests that the etiology of airway disease is multifactorial and that unique exposures and genetic factors contribute to the development of asthma in both settings. The most important environmental exposure that distinguishes the rural environment and is known to cause asthma is the organic dusts. However, animal-derived proteins, common allergens, and low concentrations of irritants also contribute to the development of airway disease in children and adults living in rural communities. A fundamental unanswered question regarding asthma is why only a minority of children who wheeze at an early age develop persistent airway disease that continues throughout their life. Although genetic factors are important in the development of asthma, recurrent airway inflammation, presumably mediated by environmental exposures, may result in persistent airway hyperresponsiveness and the development of chronic airway disease. Increasing evidence indicates that control of the acute inflammatory response substantially improves airflow and reduces chronic airway remodeling. Reducing exposure to agricultural dusts and treatment with anti-inflammatory medication is indicated in most cases of childhood asthma. In addition, children with asthma from rural (in comparison to urban) America face multiple barriers that adversely affect their health e.g., more poverty, geographic barriers to health care, less health insurance, and poorer access to health care providers. These unique problems must be considered in developing interventions that effectively reduce the morbidity and mortality of asthma in children from rural communities.

Oilseed rape allergy presented as occupational asthma in the grain industry

BACKGROUND

There have been several reports on respiratory allergic symptoms induced by pollen of oilseed rape. To the best of our knowledge, this is the first report dealing with oilseed rape dust mainly composed of seeds, as an occupational allergen in the grain industry. In this paper, we present a case of occupational asthma caused by oilseed rape dust from the Animal Feed Industry, which proved to be induced by an IgE-mediated reaction.

METHODS AND RESULTS

The patient displayed positive responses to Dermatophagoides farinae as well as oilseed rape dust extract. The bronchoprovocation test showed an early asthmatic response to oilseed rape dust extract. Serum specific IgE antibody to oilseed rape antigen was detected by enzyme-linked immunosorbent assay (ELISA). ELISA inhibition test showed significant inhibitions with addition of oilseed rape antigen. In order to further identify the allergenic components of extract, sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblot analysis were performed. Fourteen IgE-binding components ranging from 10 to 160kDa were detected within the oilseed rape extract.

CONCLUSION

These results suggest that the inhalation of oilseed rape dust, not pollen, can cause IgE mediated bronchoconstriction in an exposed worker of the grain industry.

Neutrophilic respiratory tract inflammation and peripheral blood neutrophilia after grain sorghum dust extract challenge

STUDY OBJECTIVE

To determine if inhalation of grain sorghum dust in the laboratory would cause neutrophilic upper and lower respiratory tract inflammation in human volunteers, as well as systemic signs of illness.

DESIGN

Prospective.

SETTING

University of Nebraska Medical Center.

PARTICIPANTS

Thirty normal volunteers.

INTERVENTIONS

Inhalation challenge with 20 mL of a nebulized solution of filter-sterilized grain sorghum dust extract (GSDE). One group received prednisone, 20 mg for 2 days, prior to the challenge.

MEASUREMENTS AND RESULTS

Bronchoscopy with bronchoalveolar lavage (BAL) was performed 24 h after challenge, with samples collected as bronchial and alveolar fractions. Findings included visible signs of airways inflammation, quantified as the bronchitis index. The percentage of bronchial neutrophils was significantly increased in those challenged with GSDE vs the control solution, Hanks' balanced salt solution (40.3 +/- 4.5% vs 14.3 +/- 5.1%, p < or = .01). Similar findings were seen in the alveolar fraction. Pretreatment with corticosteroids did not prevent the rise in neutrophils recovered by BAL. Peripheral blood neutrophils were also increased in volunteers challenged with the grain dust extract. To explain the increase in peripheral blood neutrophil counts, the capacity of the peripheral blood neutrophils to migrate in chemotaxis experiments was examined. The results demonstrate an increase in peripheral blood neutrophils and an increase in chemotactic responsiveness.

CONCLUSIONS

Inhalation challenge with a grain dust extract causes respiratory tract inflammation and a peripheral blood neutrophilia. One reason for this may be an increase in activated peripheral blood neutrophils.

Characterization of health effects of grain dust exposures

Grain dust has a long history of association with disease, and its effects on various organs have been reported for many years. Inflammatory diseases of the eyes, nose, and skin may be caused by both direct irritation and immune-based reactions. The lung and airways frequently suffer adverse effects. Asthma is well documented as being a result of exposure. Several studies show increased incidences of respiratory symptoms and of reduced pulmonary function in grain workers. Grain dust should be regarded as a dust with toxic properties, not just a nuisance dust.

Demonstration of inflammatory cell population changes in rat lungs in response to intratracheal instillation of spring wheat dust using lung enzymatic digestion and centrifugal elutriation

The inhalation of grain dust by grain workers is responsible for a large number of pulmonary pathophysiologies. These problems may be acute or chronic and may be mediated by the chronic activation of the immune system. Constant inflammatory states in the lung may eventually lead to tissue damage and respiratory deficit. This study was designed to measure the changes in the relative number of inflammatory cells in peripheral blood, bronchoalveolar spaces, and lung interstitium that occur in response to intratracheally instilled airborne spring wheat dust in rats. It was found that 6 h after instillation with dust, neutrophils were present in greater numbers in the blood and bronchoalveolar spaces than in lung interstitium. After 24 h, there appeared to be a larger number of neutrophils in the lung interstitium in dust-instilled animals than in saline-instilled controls. These results indicate that intratracheal instillation of grain dust initiates an acute inflammatory reaction, and that there is an initial influx of neutrophils into the air spaces of the lung followed by transit of these cells into the lung interstitium.

Atopy, non-allergic bronchial reactivity, and past history as determinants of work related symptoms in seasonal grain handlers

One hundred and five young subjects with little or no previous exposure to grain dust were studied before and after a seven week period of grain handling work to determine if there was an association between symptoms experienced at work and pre-employment respiratory symptoms, allergy skin test responses, and non-allergic bronchial reactivity. The incidence of work related symptoms was cough 18%, wheeze 13%, and dyspnoea 14%. The results showed that pre-employment history of respiratory symptoms, positive allergy skin test responses, and a high level of non-allergic bronchial reactivity were significantly associated with these symptoms. These measurements may be useful to predict symptoms associated with exposure to grain dust in new employees and the results suggest that these work related symptoms may be due to allergen induced asthma.

Baker's asthma. Clinical and immunological studies

Seven bakers with respiratory symptoms were evaluated by skin tests, RAST assay for specific IgE antibodies to rye and wheat, inhalation challenge with methacholine for the determination of non-specific bronchial reactivity, and bronchoprovocation with rye and wheat extracts for the determination of antigen-specific bronchial reactivity. An immediate asthmatic response to antigen challenge was observed in four subjects and all of them had a high level of flour-specific IgE antibodies. The serum RAST values provided a more accurate predictive value than the degree of cutaneous sensitivity determined by skin testing with respect to the bronchial response to antigenic challenge. Among those who reacted positively to antigenic bronchoprovocation, a much lower antigen dose was required to elicit a positive reaction if the subject also had an increased degree of non-specific bronchial reactivity. An elevated RAST value was not found in thirty-eight asymptomatic bakers or in ten asthmatics who had no occupational exposure to flour. Thus, baker's asthma appears to be a form of allergic asthma to cereal flours mediated by specific IgE antibodies. Both the level of serum IgE antibodies and the degree of non-specific bronchial reactivity are important factors which may influence a baker's bronchial response upon inhalation of cereal flours.