Pneumococcal pneumonia on the job: Uncovering the past story of occupational exposure to metal fumes and dust

Issue 3-The occupational burden of respiratory diseases, an update

INTRODUCTION AND AIMS

Workplace exposures are widely known to cause specific occupational diseases such as silicosis and asbestosis, but they also can contribute substantially to causation of common respiratory diseases. In 2019, the American Thoracic Society (ATS) and the European Respiratory Society (ERS) published a joint statement on the occupational burden of respiratory diseases. Our aim on this narrative review is to summarise the most recent evidence published after the ATS/ERS statement as well as to provide information on traditional occupational lung diseases that can be useful for clinicians and researchers.

RESULTS

Newer publications confirm the findings of the ATS/ERS statement on the role of workplace exposure in contributing to the aetiology of the respiratory diseases considered in this review (asthma, COPD, chronic bronchitis, idiopathic pulmonary fibrosis, hypersensitivity pneumonitis, infectious pneumonia). Except for COPD, chronic bronchitis and infectious pneumonia, the number of publications in the last 5 years for the other diseases is limited. For traditional occupational lung diseases such as silicosis and asbestosis, there are old as well as novel sources of exposure and their burden continues to be relevant, especially in developing countries.

CONCLUSIONS

Occupational exposure remains an important risk factor for airways and interstitial lung diseases, causing occupational lung diseases and contributing substantially in the aetiology of common respiratory diseases. This information is critical for public health professionals formulating effective preventive strategies but also for clinicians in patient care. Effective action requires shared knowledge among clinicians, researchers, public health professionals, and policy makers.

Occupationally Relevant Zinc- and Copper-Containing Metal Fumes Inhibit Human THP-1 Macrophage TNF and IL-6 Responses to Bacterial Stimuli

Metal workers have an increased risk of severe lobar pneumonia due to exposure to metal fume particles, which lead to recent pneumococcal vaccination recommendations. To investigate the effects of metal fume-derived zinc oxide (ZnO) and copper oxide (CuO) particles on airway immune responses, human THP-1-derived macrophages are exposed in vitro to the bacterial pathogen-associated molecular patterns (PAMPs) lipopolysaccharide (LPS), lipoteichoic Acid (LTA), or peptidoglycan (PGN), together with particle suspensions. Particles are generated through metal inert gas (MIG) soldering. Spectrometric and microscopic analysis confirms CuO and ZnO as main components. Macrophage IL-6 and TNF mRNAs are quantified by qPCR and secreted protein levels by electrochemiluminescent multi-spot assay. A dose-dependent increase in macrophage TNF and IL-6 mRNA (4 h) and protein (24 h) levels following exposure to PAMPs is significantly inhibited by 2 µg mL-1 CuO/ZnO particles (n = 5). Additionally, CuO/ZnO particles significantly inhibit TNF protein expression in unstimulated macrophages, while IL-6 protein levels are unaffected (n = 5). The presented in vitro immunotoxicity approach may extend existing new approach methodology (NAM) elements for chemical risk assessment and possibly exposure limit evaluation refinements. These findings implicate that CuO/ZnO particles suppress macrophage proinflammatory responses to PAMPs, potentially compromising lung immunity, underlining current vaccine recommendations and efforts for preventive occupational health guidelines.

Vaccinating Welders against Pneumococcus: Evidence from a Systematic Review and Meta-Analysis

Workers occupationally exposed to welding dusts and fumes have been suspected to be at increased risk of invasive pneumococcal disease (IPD). Since the 2010s, the United Kingdom Department of Health and the German Ständige Impfkommission (STIKO) actively recommend welders undergo immunization with the 23-valent polysaccharide (PPV23) pneumococcal vaccine, but this recommendation has not been extensively shared by international health authorities. The present meta-analysis was therefore designed to collect available evidence on the occurrence of pneumococcal infection and IPD among welders and workers exposed to welding fumes, in order to ascertain the effective base of evidence for this recommendation. PubMed, Embase and MedRxiv databases were searched without a timeframe restriction for the occurrence of pneumococcal infections and IPD among welders and workers exposed to metal dusts, and articles meeting the inclusion criteria were included in a random-effect meta-analysis model. From 854 entries, 14 articles (1.6%) underwent quantitative analysis, including eight retrospective studies (publication range: 1980-2010), and six reports of professional clusters in shipbuilding (range: 2017-2020). Welders had an increased likelihood of developing IPD compared with non-welders (odds ratio 2.59, 95% CI 2.00-3.35, I2 = 0%, p = 0.58), and an increased likelihood of dying from IPD (standardized mortality ratio (SMR) 2.42, 95% CI 1.96-2.99, I2 = 0%, p = 0.58). Serotype typing was available for 72 cases, 60.3% of which were represented by serotype 4, followed by 12F (19.2%) and serotype 8 (8.2%). Although the available data derive from a limited number of studies, available results suggest that pneumococcal vaccination should be recommended for workers exposed to welding fumes, and vaccination strategies should consider the delivery of recombinant formulates in order to combine the direct protection against serotypes of occupational interest with the mucosal immunization, reducing the circulation of the pathogen in occupational settings characterized by close interpersonal contact.

Occupational risks associated with severe COVID-19 disease and SARS-CoV-2 infection - a Swedish national case-control study conducted from October 2020 to December 2021

OBJECTIVE

This study aimed to investigate whether workplace factors and occupations are associated with SARS-CoV-2 infection or severe COVID-19 in the later waves of the pandemic.

METHODS

We studied 552 562 cases with a positive test for SARS-CoV-2 in the Swedish registry of communicable diseases, and 5985 cases with severe COVID-19 based on hospital admissions from October 2020 to December 2021. Four population controls were assigned the index dates of their corresponding cases. We linked job histories to job-exposure matrices to assess the odds for different transmission dimensions and different occupations. We used adjusted conditional logistic analyses to estimate odds ratios (OR) for severe COVID-19 and SARS-CoV-2 with 95% confidence intervals (CI).

RESULTS

The highest OR for severe COVID-19 were for: regular contact with infected patients, (OR 1.37, 95% CI 1.23-1.54), close physical proximity (OR 1.47, 95% CI 1.34-1.61), and high exposure to diseases or infections (OR 1.72, 95% CI 1.52-1.96). Mostly working outside had lower OR (OR 0.77, 95% CI 0.57-1.06). The odds for SARS-CoV-2 when mostly working outside were similar (OR 0.83, 95% CI 0.80-0.86). The occupation with the highest OR for severe COVID-19 (compared with low-exposure occupations) was certified specialist physician (OR 2.05, 95% CI 1.31-3.21) among women and bus and tram drivers (OR 2.04, 95% CI 1.49-2.79) among men.

CONCLUSIONS

Contact with infected patients, close proximity and crowded workplaces increase the risks for severe COVID-19 and SARS-CoV-2 infection. Outdoor work is associated with decreased odds for SARS-CoV-2 infection and severe COVID-19.

Temporal risk assessment - 20th century Pb emissions to air and exposure via inhalation in the Swedish glass district

The objective of the present study was to assess historical emissions of Pb to air around a number of glassworks sites in southeastern Sweden, and the possible implications for human exposure. To do so, a four-step method was applied. First, emissions of Pb to air around 10 glassworks were modelled for the 20th century. Second, an assessment of the resulting exposure was made for a number of scenarios. Third, the number of people potentially exposed at different times was estimated, and fourth, measurements of "current" Pb concentrations in PM₁₀ material from four sites were conducted in 2019. The results show that the highest emissions, and exposures, occurred from 1970 to1980. It coincides with the time period when the highest number of people resided in the villages. At this time, the average Pb concentration in air around the six largest factories was about 2.4 μg Pb/m³, i.e. 16 times the present US national ambient air quality standard (NAAQS) of 0.15 μg Pb/m³. By year 2000 the modelled average concentration had dropped to 0.05 μg Pb/m³, a level that is normal for urban regions today. The PM₁₀ measurements from 2019 indicate a further decline, now with a mean value of about 0.02 μg Pb/m³. Over the entire study period, inhalation hazard quotients (HQs) exceeded the dietary HQ by many orders of magnitude, indicating that inhalation has been the most prevalent exposure pathway in the past. At present, both pathways are judged to be associated with low exposures. Even if only roughly approximated, a picture of the historical exposure can increase our understanding of the connection between exposure and disease, and can be valuable when risks are to be communicated to residents near contaminated areas.

Transmission factors and exposure to infections at work and invasive pneumococcal disease

BACKGROUND

Working in close contacts with coworkers or the general public may be associated with transmission of invasive pneumococcal disease (IPD). We investigated whether crowded workplaces, sharing surfaces, and exposure to infections were factors associated with IPD.

METHODS

We studied 3,968 cases of IPD, and selected six controls for each case from the Swedish population registry with each control being assigned the index date of their corresponding case. We linked job histories to job-exposure matrices to assess different transmission dimensions of pneumococci, as well as occupational exposure to fumes. We used adjusted conditional logistic analyses to estimate the odds ratios (ORs) for IPD with 95% confidence intervals (95% CI).

RESULTS

ORs for IPD for the different transmission dimensions were increased moderately but were statistically significant. Compared to home-working or working alone, the highest odds was for Working mostly outside, or partly inside (OR 1.19, 95% CI 1.04-1.38). Estimates were higher in men for all dimensions, compared to women. The odds for IPD for Working mostly outside, or partly inside were 1.33 (95% CI 1.13-1.56) and 0.79 (95% CI 0.55-1.14) for men and women, respectively. Higher odds were seen for all transmission dimensions among those exposed to fumes, although CIs included unity. Contact with ill or infected patients did not increase the odds for IPD.

CONCLUSION

IPD was associated with working in close contact with coworkers or the general public, and with outside work, especially for men. Contact with infected patients or persons was not associated with IPD.