Onset of pulmonary Epstein-Barr virus-positive diffuse large B-cell lymphoma in a patient with silicosis.

How Epstein-Barr virus (EBV)-positive diffuse large B-cell lymphoma (DLBCL) occasionally occurs following chronic inflammation remains to be elucidated. The case of a 57-year-old man who developed pulmonary EBV-positive DLBCL from underlying silicosis lesions is presented. Immunohistochemical examination of the resected silicosis lesions showed predominant helper T cells and M1/M2 macrophages, with a lack of B cells, regulatory T cells, and resident memory T cells. Two years later, EBV-positive DLBCL emerged unexpectedly from the silicosis. The imbalance of the immune cells in the microenvironment, at least in part, may help explain how chronic inflammation contributes to EBV-positive DLBCL.

Dynamic analysis of peripheral blood TCR ß-chain CDR3 repertoire in occupational medicamentosa-like dermatitis due to trichloroethylene.

Previously, we had cross-sectionally explored the characteristics of T cell receptor (TCR) repertoires from occupational medicamentosa-like dermatitis due to trichloroethylene (OMDT) patients, now we further analyzed the dynamic features of OMDT TCR repertoires. Peripheral blood TCR ß-chain complementarity-determining region 3 (CDR3) genes were detected with the high throughput sequencing in 24 OMDT cases in their acute, chronic and recovery stages, respectively, and in 24 trichloroethylene-exposed healthy controls. The TCR repertoire diversity, TRBV/TRBD/TRBJ gene usage and combination, frequencies of CDR3 nucleotide (nt) and amino acid (aa) sequences in the cases in different stages and in the controls were analyzed. TRBV6-4 and TRBV7-9 frequencies significantly differed between the cases and controls (both P < 6.1 × 10-4). TRBV6-4 combination with TRBJ2-1, TRBJ2-2, TRBJ2-3, and TRBJ2-6, and TRBV7-9 combination with TRBJ2-1 were associated with the stage by OMDT severity (all P < 0.001). Ten CDR3-nt and 7 CDR3-aa sequences in TRBV7-9-TRBJ2-1 combination and 1 CDR3-nt and 1 CDR3-aa sequences in TRBV6-4-TRBJ2-1 combination were identified as associated with the severity of OMDT (all P < 0.001). We revealed further how TCR repertoires vary with the severity in the development of OMDT, and severity-related TCRs may provide important therapeutic targets for OMDT in clinical practice.

Non-occupational and occupational factors associated with specific SARS-CoV-2 antibodies among hospital workers - A multicentre cross-sectional study.

OBJECTIVES: Protecting healthcare workers (HCWs) from coronavirus disease-19 (COVID-19) is critical to preserve the functioning of healthcare systems. We therefore assessed seroprevalence and identified risk factors for severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) seropositivity in this population. METHODS: Between 22 June 22 and 15 August 2020, HCWs from institutions in northern/eastern Switzerland were screened for SARS-CoV-2 antibodies. We recorded baseline characteristics, non-occupational and occupational risk factors. We used pairwise tests of associations and multivariable logistic regression to identify factors associated with seropositivity. RESULTS: Among 4664 HCWs from 23 healthcare facilities, 139 (3%) were seropositive. Non-occupational exposures independently associated with seropositivity were contact with a COVID-19-positive household (adjusted OR 59, 95% CI 33-106), stay in a COVID-19 hotspot (aOR 2.3, 95% CI 1.2-4.2) and male sex (aOR 1.9, 95% CI 1.1-3.1). Blood group 0 vs. non-0 (aOR 0.5, 95% CI 0.3-0.8), active smoking (aOR 0.4, 95% CI 0.2-0.7), living with children <12 years (aOR 0.3, 95% CI 0.2-0.6) and being a physician (aOR 0.2, 95% CI 0.1-0.5) were associated with decreased risk. Other occupational risk factors were close contact to COVID-19 patients (aOR 2.7, 95% CI 1.4-5.4), exposure to COVID-19-positive co-workers (aOR 1.9, 95% CI 1.1-2.9), poor knowledge of standard hygiene precautions (aOR 1.9, 95% CI 1.2-2.9) and frequent visits to the hospital canteen (aOR 2.3, 95% CI 1.4-3.8). DISCUSSION: Living with COVID-19-positive households showed the strongest association with SARS-CoV-2 seropositivity. We identified several potentially modifiable work-related risk factors, which might allow mitigation of the COVID-19 risk among HCWs. The lower risk among those living with children, even after correction for multiple confounders, is remarkable and merits further study.

Omega-3 Polyunsaturated Fatty Acid Intervention Against Established Autoimmunity in a Murine Model of Toxicant-Triggered Lupus.

Workplace exposure to respirable crystalline silica dust (cSiO2) has been etiologically linked to the development of lupus and other human autoimmune diseases. Lupus triggering can be recapitulated in female NZBWF1 mice by four weekly intranasal instillations with 1 mg cSiO2. This elicits inflammatory/autoimmune gene expression and ectopic lymphoid structure (ELS) development in the lung within 1 week, ultimately driving early onset of systemic autoimmunity and glomerulonephritis. Intriguingly, dietary supplementation with docosahexaenoic acid (DHA), an ω-3 polyunsaturated fatty acid (PUFA) found in fish oil, beginning 2 week prior to cSiO2 challenge, prevented inflammation and autoimmune flaring in this novel model. However, it is not yet known how ω-3 PUFA intervention influences established autoimmunity in this murine model of toxicant-triggered lupus. Here we tested the hypothesis that DHA intervention after cSiO2-initiated intrapulmonary autoimmunity will suppress lupus progression in the NZBWF1 mouse. Six-week old NZWBF1 female mice were fed purified isocaloric diet for 2 weeks and then intranasally instilled with 1 mg cSiO2 or saline vehicle weekly for 4 consecutive weeks. One week after the final instillation, which marks onset of ELS formation, mice were fed diets supplemented with 0, 4, or 10 g/kg DHA. One cohort of mice (n = 8/group) was terminated 13 weeks after the last cSiO2 instillation and assessed for autoimmune hallmarks. A second cohort of mice (n = 8/group) remained on experimental diets and was monitored for proteinuria and moribund criteria to ascertain progression of glomerulonephritis and survival, respectively. DHA consumption dose-dependently increased ω-3 PUFA content in the plasma, lung, and kidney at the expense of the ω-6 PUFA arachidonic acid. Dietary intervention with high but not low DHA after cSiO2 treatment suppressed or delayed: (i) recruitment of T cells and B cells to the lung, (ii) development of pulmonary ELS, (iii) elevation of a wide spectrum of plasma autoantibodies associated with lupus and other autoimmune diseases, (iv) initiation and progression of glomerulonephritis, and (v) onset of the moribund state. Taken together, these preclinical findings suggest that DHA supplementation at a human caloric equivalent of 5 g/d was an effective therapeutic regimen for slowing progression of established autoimmunity triggered by the environmental toxicant cSiO2.

Respiratory sensitization to insect allergens: Species, components and clinical symptoms.

Airborne insect particles have been identified as an important cause of respiratory allergies, including allergic asthma and rhinitis. In the literature, the significance of respiratory exposure to insect particles as a cause of occupational allergy has been well-documented. Indeed, many cases of occupational allergy have been reported including allergy to the larvae of flies and moths in anglers and occupationally exposed workers, to grain pests in bakers or other workers handling grains, and to crickets and/or locusts in researchers and workers in aquaculture companies. Furthermore, the prevalence of sensitization to insect allergens is considerably high among patients with asthma and/or rhinitis who are not occupationally exposed to insects, suggesting the clinical relevance of exposure to insects in indoor and outdoor environmental non-occupational settings. Exposure to cockroaches, a well-studied indoor insect, is associated with cockroach sensitization and the development and exacerbation of asthma. Booklice, another common indoor insect, were recently identified as a significant sensitizer of asthmatic patients in Japan and India, and potentially of asthma patients living in warm and humid climates around the world. Lip b 1 was identified as an allergenic protein contributing to the species-specific sensitization to booklice. Moths are considered a significant seasonal outdoor allergen and their allergens are considered to have the highest sensitization rate among Japanese patients. However, other than cockroaches, allergenic insect proteins contributing to sensitization have not been fully characterized to date.

Occupational IgE-mediated psyllium allergy in contemporary gluten-free and vegan baking: A case of allergic rhinitis.

Psyllium (from Plantago ovata; ispaghula) is used as a dietary supplement and is supplied in the form of husk, granules, capsules, or powder. Consumers using psyllium-containing laxatives, healthcare workers handling these, and pharmaceutical workers in laxative-manufacturing plants are known to be at risk of sensitization and subsequent rhinitis, asthma, contact urticaria, and even anaphylaxis. To our knowledge, the case we present here is the first of baker's immunoglobulin E (IgE)-mediated occupational allergy due to psyllium exposure. Our patient, a 24-year-old female baker with no previous allergies, was referred to our clinic with suspected occupational rhinitis. After 1 year of baking with cereal flour or gluten-free flour-mix, she began to suffer from rhino-conjunctival symptoms during workdays. Skin prick tests with agents from the patient's workplace revealed allergies not only to wheat and rye flours but also to psyllium, with a remarkable 10 mm wheal. Subsequently, nasal provocation tests confirmed occupational allergic rhinitis to psyllium. We also found work-related sensitization to buckwheat, which she used in gluten-free baking. Due to the increased prevalence of celiac disease and the popularity of gluten-free and vegan food, psyllium has recently become a common ingredient in baking, used as a substitute for gluten or eggs. Bakers handle allergens such as these in high concentrations and this may lie behind the emergence of respiratory and dermal symptoms. It is essential to consider new or recenlty introduced materials as possible allergens if it is suspected that a baker has work-related respiratory or allergic symptoms.

Hepatitis B virus infection and associated risk factors among medical students in eastern Ethiopia.

BACKGROUND: Hepatitis B virus (HBV) is a highly contagious pathogen that has become a severe public health problem and a major cause of morbidity and mortality, particularly in developing countries. Medical students are at high occupational risk during their training. However, no facility-based studies were found among medical students in eastern Ethiopia. Thus, this study aimed to investigate the seroprevalence of Hepatitis B Virus and associated factors among medical students in eastern Ethiopia. METHODS: A facility-based cross-sectional study was conducted among 407 randomly selected medical students from March to June 2018. A pretested and structured questionnaire was used to collect data on socio-demographic characteristics and other risk factors. A 5ml blood was collected, and the serum was analyzed for Hepatitis B surface antigen (HBsAg) using the Instant Hepatitis B surface antigen kit. Data were entered using Epidata version 3.1 and analyzed using SPSS statistical packages version 22. Outcome and explanatory variables were described using descriptive summary measures. Binary and multivariable logistic regression was conducted at 95% CI and an association at P-value < 0.05 was declared statistically significant. RESULTS: The seroprevalence of hepatitis B virus surface antigen was 11.5% (95%CI = 8.6, 14.7). Poor knowledge of universal precaution guideline (AOR = 2.58; 95% CI = [1.35-4.93]), history of needle stick injury (AOR = 2.11; 95% CI = [1.07-4.18]) and never been vaccinated for HBV (AOR = 2.34; 95% CI = [1.17-4.69]) were found statistically significantly associated with HBsAg positivity after multivariate analysis. CONCLUSION: Hepatitis B virus infection rate is high among health care trainees in eastern Ethiopia. Improvement at health care practice centers safety through training on universal precaution guidelines, and scaling up HBV vaccination is mandatory.

Exposure to additives or multigrain flour is associated with high risk of work-related allergic symptoms among bakers.

OBJECTIVES: Wheat flour exposure in bakers can elicit respiratory and skin symptoms. Scarce data are available on the prevalence of such conditions in bakers. We investigated the prevalence of work-related rhinitis, asthma-like symptoms and dermatitis in bakers according to job task and type of allergens involved. METHODS: Of the 229 traditional bakeries in Verona area who were invited to participate in a cross-sectional survey, 211 (92%) accepted; 727 employees in these bakeries answered a modified version of a questionnaire on job tasks; allergen exposure within the bakery; and work-related nasal, asthma-like and skin symptoms during 2010-2014. Determinants of work-related nasal, asthma-like or skin disorders were separately evaluated using different logistic models. RESULTS: The prevalence of work-related nasal and asthma-like symptoms was, respectively, 15.1% and 4.2% in bakery shop assistants, increasing to 25.7% and 9.5% in bakers using only wheat flour, and further to 31.8% and 13.6% in bakers using flour and additives, and then to 34.1% and 18.2% in bakers using flour with additives and multigrain (p<0.001). The risk of work-related asthma-like symptoms was more than doubled in bakers using additives without or with multigrain than in shop assistants (OR 2.3, 95% CI 1.0 to 5.5 and OR 3.4, 95% CI 1.1 to 10.8, respectively). Making bread with additives alone or with multigrain significantly increased the risk of work-related nasal symptoms in shop assistants, while the risk of skin symptoms was not significantly affected. CONCLUSIONS: Bakers using additives alone or with multigrain are at a high risk of experiencing nasal and asthma-like symptoms.

Chronic Beryllium Disease: Update on a Moving Target.

Beryllium exposure remains an ongoing occupational health concern for workers worldwide. Since the initial Occupational Safety and Health Administration (OSHA) ruling on a permissible exposure limit (PEL) for beryllium in 1971, our understanding of the risks of beryllium sensitization and chronic beryllium disease (CBD) has evolved substantially. A new OSHA ruling released in early 2017 and implemented in late 2018 reduced the PEL for beryllium, increased requirements for medical screening and monitoring, and may ultimately enhance worker protection. This review highlights advances in our understanding of the pathway from beryllium exposure to sensitization and progression to CBD that guided the development of this OSHA ruling. Screening workers exposed to beryllium and management of CBD will also be discussed. Finally, we will discuss the role of beryllium as a cause of morbidity and mortality among exposed workers in this potentially preventable occupational lung disease.

Vacunas en salud laboral: una oportunidad para prevenir e invertir en salud / Vaccines in occupational medicine: an opportunity to prevent and invest in health

La vacunación es la medida preventiva más costo-efectiva para evitar las enfermedades infecciosas inmunoprevenibles, a nivel individual y comunitario. Los riesgos biológicos laborales, deben ser manejados en un sistema de gestión del riesgo, donde la vacuna es el elemento clave de protección personal (EPP) específico cuya provisión y uso obligatorio tiene normas legislativas referidas a la entrega por el empleador, la capacitación en la prevención y el uso por el trabajador. En Chile, hay 8.364.282 trabajadores según datos de Superintendencia de Seguridad Social (SUSESO). La Ley 16.744 y sus Decretos Supremos (DS) indican las condiciones que se deben mantener en los lugares de trabajo y el derecho a saber por parte del trabajador; también existen circulares del Ministerio de Salud que incluyen situaciones y grupos especiales laborales a vacunar, pero es necesaria una normativa que oriente a trabajadores dependientes e independientes y a empleadores sobre qué vacunas colocar, en qué situaciones y a quiénes dependiendo de la actividad laboral. En este artículo, hacemos una reseña de la situación legal, de recomendaciones en otros países y enumeramos algunas vacunas que podrían implementarse en la población expuesta a riesgo.

Vaccination is the most cost-effective measure for immune-preventable infectious diseases, at individual and community level. Biological occupational hazards must be faced in a risk management system, where the vaccine is a specific key as an element of personal protection, whose provision and obligatory use has legislative norms related to the delivery by the employer, the training in the prevention and the use by the worker. Several countries count with technical guides for vaccination in the working population. In Chile in 2018, there were 8.364.282 workers according with Superintendence of Social Security. Law 16.744 and Supreme Decrees indicate the environmental conditions for workers and the right to know the risks; also, Ministry of Health has issued circulars where some working conditions need specific vaccination. Is for that reason that is necessary a regulation that guides dependent and independent workers and employers on when and which vaccines must be used depending on the labor activity. In this article, we review the legal situation, other guides in different countries and list some vaccines that could be implemented in the population at specifical risks.

Horse allergen sensitivity and respiratory symptoms among horse farm workers

Background/aim: Sensitivity and symptoms related to animal proteins have been investigated in various occupational groups. However, data from horse farm workers are limited. We aimed to determine horse allergen sensitivity in the horse farm workers, and to evaluate its relationship with respiratory symptoms and functional parameters. Materials and methods: A total of 110 subjects were enrolled in the study. The study group consisted of 80 horse farm workers. Face-to-face surveys, skin prick tests (SPT), and pulmonary function tests (PFT) were performed in the study group. Control group consisted of 30 healthy subjects. SPT and PFTs were also performed for control group. The SPT test results of the horse farm workers were compared with the SPT results provided from the medical records of 1376 subjects who admitted to the outpatient clinic with respiratory symptoms. Results: Atopy rate was significantly higher in horse farm workers than in healthy subjects (41% and 13%, respectively; P = 0.008). Horse allergen sensitivity was positive 8/80 (10%) in horse farm workers, 0/30 in healthy subjects, and 32/1376 (2%) in medical records of subjects who were admitted to the outpatient clinic with respiratory symptoms. (P = 0.07, P = 0.001, respectively). There was no statistically significant relationship between respiratory symptoms and horse allergen sensitivity in horse farm workers (P = 0.67). However, mean FEV1 ratios were lower in horse farm workers with horse allergen sensitivity than healthy subjects (88.6% ± 17.9, 103.7 ± 10, P = 0.031, respectively). Conclusion: Atopy and animal allergen sensitization were significantly higher in horse farm workers, suggesting the relationship between the intensity of specific allergen exposure and the sensitization to this specific allergen.

Symptoms and immunoglobulin development in hospital staff exposed to a SARS-CoV-2 outbreak.

BACKGROUND: Worldwide, the number of SARS-CoV-2 infections is increasing. Serological immunoglobulin tests may help to better understand the development of immune mechanisms against SARS-CoV-2 in COVID-19 cases and exposed but asymptomatic individuals. The aim of this study was to investigate exposure to SARS-CoV-2, symptoms, and antibody responses in a large sample of healthcare workers following a COVID-19 outbreak. METHODS: A COVID-19 outbreak among staff members of a major German children's and women's hospital was followed by massive RT-PCR SARS-CoV-2 tests and provided the opportunity to study symptoms, chains of infection, and SARS-CoV-2-specific antibody responses (IgG and IgA) by ELISA. Study participants were classified as COVID-19 cases, and persons with close, moderate, or no exposure to SARS-CoV-2 in the clinical setting, respectively. RESULTS: Out of 201 study participants, 31 were COVID-19 cases. While most study participants experienced many symptoms indicative for SARS-CoV-2 infection, anosmia and coughing were remarkably more frequent in COVID-19 cases. Approximately 80% of COVID-19 cases developed some specific antibody response (IgA and IgG) approximately 3 weeks after onset of symptoms. Subjects in the non-COVID-19 groups had also elevated IgG (1.8%) and IgA values (7.6%) irrespective of contact history with cases. CONCLUSION: We found that a significant number of diseased did not develop relevant antibody responses three weeks after symptom onset. Our data also suggest that exposure to COVID-19 positive co-workers in a hospital setting is not leading to the development of measurable immune responses in a significant proportion of asymptomatic contact persons.

Venom allergy and knowledge about anaphylaxis among beekeepers and their families.

BACKGROUND: Beekeepers and their families are at an increased risk of life-threatening anaphylaxis due to recurrent bee-sting exposures. OBJECTIVE: The aim of this study is to evaluate the demographic features, previous history of anaphylaxis among beekeepers and their family members, and their knowledge about the symptoms and management of anaphylaxis. METHODS: A standardized questionnaire was administered to beekeepers during the 6th International Beekeeping and Pine Honey Congress held in 2018, in Mugla, Turkey. Additionally, food-service staff from restaurants were surveyed as an occupational control group about their knowledge about anaphylaxis. RESULTS: Sixty-nine beekeepers (82.6% male, mean age 48.4±12.0 years) and 52 restaurant staff (46.2% male, mean age 40.5±10.0 years) completed the questionnaire. Awareness of the terms 'anaphylaxis' and 'epinephrine auto-injector' among the beekeepers were 55.1% and 30.4% and among the restaurant staff were 23.1% and 3.8%, respectively. Of the beekeepers, 74% were able to identify the potential symptoms of anaphylaxis among the given choices; 2.9% and 5.8% reported anaphylaxis related to bee-stings in themselves and in their family members, respectively. None of the restaurant staff had experienced or encountered anaphylaxis before but 3.8% of their family members had anaphylaxis and those reactions were induced by drugs. CONCLUSION: It is essential that implementation of focused training programs about anaphylaxis symptoms and signs as well as practical instructions of when and how to use an epinephrine auto-injector will decrease preventable morbidities and mortalities due to bee-stings in this selected high-risk population of beekeepers and their family members, as well as other fieldworkers under risk.

Diagnostic approach to occupational rhinitis: the role of nasal provocation tests.

PURPOSE OF REVIEW: The diagnosis of occupational rhinitis is a challenge. Underdiagnosis is substantial as the clinical presentation is nonspecific and often no occupational history is taken. Detection of occupational rhinitis can be improved by including screening questions on occupational exposure in the assessment of every patient with adult-onset rhinitis. RECENT FINDINGS: Case reports, case series and epidemiological studies continuously demonstrate new sensitizers and irritants capable of inducing allergic or nonallergic (irritant-induced) occupational rhinitis. Recent reviews have focused on the value of immunological tests with specific IgE, skin prick tests or basophil activation tests in demonstrating sensitization to occupational agents. Nasal provocation tests (NPT) can establish a definite diagnosis of allergic occupational rhinitis. Several NPT guidelines have been published, however, focusing exclusively on standardized high-molecular weight allergens. When performing NPT with nonstandardized agents -- like most occupational sensitizers -- adapted protocols are needed. SUMMARY: We provide pragmatic guidance to clinicians taking care of rhinitis patients on how to diagnose occupational rhinitis, based on recent insights from the literature. We focus on the challenges in the diagnostic work-up, on how to identify suspected causes, and on the role of NPT.

Current state of occupational latex allergy.

PURPOSE OF REVIEW: During the 1980s, natural rubber latex (NRL) emerged as a major cause of occupational allergy and asthma, especially in healthcare workers using powdered NRL gloves. Increased recognition of NRL allergies and transfer of research findings into prevention strategies resulted into an almost elimination of this health problem. Here, the current knowledge on allergens, their use in diagnostics, prevalence data of occupational NRL allergy and the status of prevention strategy are summarized. RECENT FINDINGS: While the current studies conducted in high-income countries show that prevention measures have reduced NRL allergy, this does not yet apply worldwide. For latex allergy diagnosis, it is important that recombinant allergens as reliable tools are available, because in several European countries and the United States, NRL skin prick test extracts and powdered latex gloves for bronchial challenge test are no longer commercially available, leading to a deficit in diagnostic tools. Due to the fact that latex is suitable with good properties as a raw material for gloves, alternatives with significantly lower protein content and without cross-reactive structures to latex proteins are sought. SUMMARY: Awareness of the sensitization risk associated with the use of latex gloves should still be present in all occupational settings.

Update on exhaled breath condensate analyses in occupational disease.

PURPOSE OF REVIEW: The present work represents an update of the review published in this journal by Corradi et al., regarding the use of exhaled breath condensate (EBC) to investigate occupational lung diseases. RECENT FINDINGS: The relevant literature was searched in the Medline database, assessed through PubMed using key terms such as 'breath AND condensate AND occupational'. Eleven pertinent publications were retrieved between January 2018 and October 2019. One article only was related to occupational allergy, and the conclusion is that EBC hydrogen peroxide is not an useful marker in laboratory animal allergy. The biomarkers of exposure most often assessed with EBC are metals. However, it is controversial whether this approach has any advantage over the conventional environmental monitoring. The biomarkers of effect studied by the majority of investigations were those related to oxidative stress. They appear consistently elevated upon occupational exposures to various agents, including welding fumes, crystalline silica, nanomaterials and chemicals. SUMMARY: Although EBC represent a suitable tool to sample airway lining fluid in a noninvasive manner, it remains a niche approach to the investigation of occupational diseases. The confounding influence of EBC dilution should be better addressed in the expression of the results.

Occupational exposure to organic dusts and risk of developing rheumatoid arthritis: findings from a Swedish population-based case-control study.

Objectives: We estimated the association between occupational exposures to five different organic dusts: wood, animal, paper, textile and flour dust and the risk of developing rheumatoid arthritis (RA). Methods: This population-based case-control study analysed 12 582 incident cases and 129 335 controls. Participants were identified from national public authority and quality registers. Census data on occupations were collected 1960-2010 and we estimated the exposure to organic dust with the help of job-exposure matrices. We used logistic regression to assess the OR of seropositive or seronegative RA. Estimates were adjusted for the matching variables (sex, county, age and index year), education and occupational silica exposure. Results: Exposure to animal dust was associated with an increased risk of RA among both men and women. The OR was 1.2 (95% CI=1.1 to 1.4) for seropositive RA and 1.3 (95% CI=1.1 to 1.5) for seronegative RA among ever exposed participants compared with unexposed. The risk increased with duration of exposure for seropositive RA, and participants who had been exposed in five or more censuses had an OR of 1.6 (95% CI=1.1 to 2.2, p for trend=0.003). Exposure to textile dust also generated a significant dose-response relationship for seropositive RA (p for trend=0.014). We detected no association between exposure to wood, paper or flour dust and risk of RA. Conclusions: Overall, exposure to animal dust and textile dust was associated with an increased risk of developing RA. These observations give further support to the notion that airborne exposures are involved in the aetiology of RA.