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Occupational exposure and respiratory diseases

During the 20th century coal workers’ pneumoconiosis—or anthraco-silicosis—and asbestos-related diseases were the major occupational respiratory diseases among Belgian workers, both in terms of public health impact as well as public visibility. Except for asbestos-induced mesothelioma, the occurrence of these occupational diseases has been declining in recent decades, due to improved prevention but to a large extent also because many hazardous industries, such as coal mining, were closed or have moved to the global south. In Europe, this has led many to think that occupational respiratory diseases can be considered diseases ‘of the past’.

However, workplace exposures do still contribute substantially to respiratory diseases. By bridging the gaps between the clinic, the university and the workplace, we can increase our understanding and improve the prevention of adverse health effects of occupational exposure to hazardous agents. This PhD project focuses on three topics, all requiring a different research approach: (1) the search for a cause of an enigmatic disease—sarcoidosis, (2) the re-emergence of an “old” disease in a new industry—silicosis in artificial stone workers, and (3) respiratory health effects of cleaning products in domestic cleaners.

(1) Sarcoidosis is a systemic disease characterized by the formation of immune granulomas in various organs. The lungs and intrathoracic lymph nodes are the most commonly affected organs, but also the eyes, skin, liver, spleen, heart, and other organs can be involved. It is unclear what causes sarcoidosis. Several lines of evidence indicate that the disease results from an immune reaction in genetically susceptible persons upon exposure to one or several antigens. Many occupational and environmental exposures have been associated to sarcoidosis: inhaled organic dust, inorganic dust—including metals and minerals—and infectious agents—such as mycobacteria and Cutibacterium acnes. The diverse clinical manifestations and the wide range of associated exposures fuel the hypothesis that sarcoidosis has more than one cause, each of which may promote a different disease phenotype. However, the relationship between exposure and disease phenotype has barely been studied.

In a retrospective study of 238 sarcoidosis patients, we showed that different occupational and environmental exposures are associated with different organ involvements. Sarcoidosis limited to pulmonary involvement was associated with exposure to inorganic dust prior to diagnosis (odds ratio [OR] 2.11; 95% confidence interval [CI] 1.11–4.17). Patients with liver involvement had higher odds of contact with livestock (OR 3.68; 95%CI 0.91–12.7) or having jobs with close human contact (OR 4.33; 95%CI 1.57–11.3) than patients without liver involvement. Similar associations were found for splenic involvement (livestock: OR 4.94, 95%CI 1.46–16.1; close human contact: OR 3.78; 95%CI 1.47–9.46). Cardiac sarcoidosis was associated with exposure to reactive chemicals (OR 5.08; 95%CI 1.28–19.2) or livestock (OR 9.86; 95%CI 1.95–49.0). Active smokers had more ocular sarcoidosis (OR 3.26; 95%CI 1.33–7.79).

(2) In recent years, outbreaks of silicosis in artificial stone workers have been reported around the globe. Artificial stones consist of a very high percentage of crystalline silica (70-95% quartz or cristobalite) bound together with synthetic resins. They are increasingly used to make kitchen or bathroom countertops. For the workers who process the stones, the risk of silicosis is particularly high because the grinding and cutting of these stones generates high concentrations of respirable particles of crystalline silica. In Belgian artificial stone workers, silicosis has been probably underdetected. Via the clinic for occupational and environmental medicine in the University Hospitals Leuven, we initially confirmed silicosis in two referred workers from a 2-man company in the province of Antwerp, Belgium, which were the first cases reported in Belgium.

We also describe an outbreak at a company producing silica-based artificial kerbstones—that were made for hygienic wall protection in the food industry—suggesting that silica-based artificial stones might have more applications than we had previously assumed. We report on 5 workers—of whom 4 had developed definite silicosis. Annual spirometries—but no chest X-rays—had been performed since 8 to 10 years prior to diagnosis. The four men with silicosis proved to have undergone an excessively rapid FEV1 decline [between 98 (95%CI 79–116) and 221 mL/year (95%CI 214–228)], many years before their first symptoms appeared. High respirable quartz concentrations (>0.1 mg/m³) were measured during various operations, especially during dry finishing of the cured kerbstones (1.080 mg/m³).

The discovery of rapidly progressive serious lung disease in workers producing silica-based artificial kerbstones shows that the hazards of artificial stone production/processing reach beyond the kitchen/bathroom countertop industry. Increasing awareness, improving prevention and establishing workers’ health surveillance programmes—or improving the quality of existing programmes—are crucial.

(3) Professional domestic cleaners have an increased risk of asthma-like and other respiratory symptoms and conditions—which has been associated with the use of bleach, ammonia, disinfectants, and sprays. There is, however, uncertainty about which products are most hazardous. We did a questionnaire-based cross-sectional study in the Belgian service voucher sector to investigate, among professional domestic cleaners, the associations of the use of 40 types of cleaning products at work (liquids and sprays) with the occurrence of work-related eye and respiratory outcomes (eye symptoms, rhinitis, sore throat, inducible laryngeal obstruction, asthma and cough) and with chronic bronchitis. We defined “work-relatedness” as symptoms that disappear or improve on days off-work—which has been shown to be a typical clinical feature of work-related asthma and rhinitis.

Among 1,586 domestic cleaners, the total number of cleaning sprays used per week (median 12/week) was significantly associated with all studied respiratory outcomes, with odds ratios ranging from 1.016 to 1.038 per spray per week. Bleach/disinfectant-containing liquid products were associated with work-related eye symptoms (OR 1.100 per product per week; 95%CI 1.017–1.190) and asthma (OR 1.104; 95%CI 1.008–1.208); liquid ammonia with chronic bronchitis (OR 1.463; 95%CI 1.053–2.035). Using elastic net regression, we identified several specific types of products that were strongly related to respiratory outcomes, such as mould removal sprays and carpet/seat/curtain sprays. Notably, cleaners capable of choosing their own products had fewer work-related eye symptoms (OR 0.758; 95%CI 0.576–0.996), rhinitis (OR 0.746; 95%CI 0.578–0.963) or cough (OR 0.697; 95%CI 0.539–0.901), suggesting that empowering domestic cleaners to choose their products may reduce the burden of symptoms.

Date:1 Dec 2017 →  14 Feb 2022
Keywords:occupational medicine, occupational respiratory diseases, sarcoidosis
Disciplines:Occupational health and safety, Environmental health and safety
Project type:PhD project