Tuberculosis and silica exposure in South African gold miners

Prevalence of pulmonary tuberculosis among casual labourers working in selected road construction sites in central Uganda

INTRODUCTION

Workers with occupational exposure to respirable silica dust, such as casual labourers at road construction sites (RCSs), are known to be at high risk of developing pulmonary tuberculosis (TB). There is limited literature about the burden of PTB among this subpopulation with high occupational exposure to silica dust at road construction sites. We aimed to determine the prevalence of PTB among casual labourers working at road construction sites in central Uganda.

METHODS

We enrolled 297 participants via consecutive sampling in a cross-sectional study between September 1st and September 30th, 2022, at four road construction sites in four districts in central Uganda. A structured questionnaire was administered, and the PTB patients were identified by using GeneXpert and/or computer-aided detection for TB (CAD4TB). The data were analysed with STATA version 17.0. Descriptive statistics adjusted for clustering were used to summarize the data, and the relationships between PTB and independent variables were assessed by using a mixed effects modified Poisson regression model to estimate the adjusted prevalence ratios.

RESULTS

Most participants were males (95.6% [284/297]), and the median age was 29 years (interquartile range [IQR]: 25-33). The prevalence of PTB among casual labourers was 2.4% (95% CI: 1.9, 2.8). Not being vaccinated with BCG (3.45, 95% CI: 1.02, 11.61), alcohol use (2.70, 95% CI: 1.52, 4.80) and staying in shared rooms (8.13, 95% CI: 4.37, 15.12) were positively associated with having PTB.

CONCLUSION

There is a high prevalence of PTB among casual labourers working at road construction sites in central Uganda. Individuals who had never been vaccinated with BCG, alcohol users and those staying in shared rooms were at an increased risk of having PTB. We recommend routine screening of casual labourers at road construction sites to optimize active TB case finding.

Risk of Silico-Tuberculosis in Miners: A Systematic Review and Meta-Analysis

Context

Tuberculosis (TB) and Silicosis are public health problems with high morbidity and mortality. They also exist as comorbidities and are highly prevalent among mine workers.

Aims

This study aims to estimate the risk of TB in miners with silicosis than in miners not having silicosis.

Methods and Material

This systematic review was conducted by literature search using PubMed, and EMBASE for studies published from 1st Jan 2017 till 20th July 2022. From the data obtained using relevant keywords for the search, a total of 345 articles were selected for screening after applying our inclusion-exclusion criteria and removing duplicates. PRISMA guidelines were followed. items JBI critical appraisal checklist for cross-sectional studies was used for assessment of the risk of bias. The odds ratio was used to estimate the strength of the association.

Results

After extensive screening, four studies have met our selection criteria. The meta-analysis of those studies revealed that the prevalence of TB in miners with silicosis is 27.11% while the prevalence of TB in miners with non-silicosis is 16.75%. The estimated pooled odds ratio (fixed effect model) is 1.34 (95% CI 1.01 - 1.76).

Conclusions

The present study reveals that there is an increased risk of TB in miners with Silicosis. Newer initiatives must be taken to prevent TB in miners.

Silicosis as a predictor of tuberculosis mortality and treatment failure and need for incorporation in differentiated TB care models in India

BACKGROUND

Differentiated tuberculosis (TB) care is an approach to improve treatment outcomes by tailoring TB management to the particular needs of patient groups based on their risk profile and comorbidities. In silicosis-prone areas, the coexistence of TB and silicosis may exacerbate treatment outcomes. The objective of the study was to determine predictors of TB-related mortality, treatment failure, and loss to follow-up in a silicosis-prone region of western India.

METHODS

A retrospective cohort was conducted among 2748 people with TB registered between January 2006 and February 2022 in Khambhat, a silicosis-prone block in western India. Death, treatment failure, and loss to follow up were the outcome variables. The significant predictors of each outcome variable were determined using multivariable logistic regression and reported as adjusted odds ratios (aOR) with 95% confidence intervals (CIs).

RESULTS

In the cohort of 2,748 people with TB, 5% presented with silicosis, 11% succumbed to the disease, 5% were lost to follow-up during treatment, and 2% encountered treatment failure upon completion of therapy. On multivariable logistic regression, concomitant silicosis [aOR 2.3 (95% CI 1.5-3.5)], advancing age [aOR 1.03 (95% CI 1.02-1.04)], male gender [aOR 1.4 (95% 1.1-1.9)], human immunodeficiency virus (HIV) positive [aOR 2.2 (95% 1.02-4.6)], and previous TB treatment [aOR 1.5 (95% CI 1.1-1.9)] significantly predicted mortality among people with TB. Concomitant silicosis [aOR 3 (95% CI 1.4-6.5)], previous TB treatment [aOR 3 (95% CI 2-6)], and multi-drug resistant TB [aOR 18 (95% CI 8-41)] were the significant predictors of treatment failure on adjusted analysis. Advancing age [aOR 1.012 (1.001-1.023)], diabetes [aOR 0.6 (0.4-0.8)], and multi-drug resistance [aOR 6 (95% CI 3-12)] significantly predicted loss to follow-up after adjusting for confounders.

CONCLUSIONS

Controlling silicosis might decrease TB mortality and treatment failure in silicosis-prone regions. The coexistence of HIV and silicosis may point to an increase in TB deaths in silicosis-prone areas. Silicosis should now be acknowledged as a major comorbidity of TB and should be included as one of the key risk factors in the differentiated TB care approach. Primary care physicians should have a high clinical suspicion for silicosis among individuals diagnosed with TB in silicosis-prone blocks.

Elimination of tuberculosis requires prior control of silicosis including sub-radiological silicosis

India is committed to the elimination of tuberculosis by 2025. But its achievement appears to be difficult as India has a huge burden of silicosis as well as sub-radiological silicosis, which was never given its required attention. Silicotic subjects are highly vulnerable to pulmonary tuberculosis due to the progressive decline of lung immunity. A study among vulnerable glass factory workers in Firozabad, Uttar Pradesh, revealed that silicotic workers were 7.5 times more at risk of pulmonary tuberculosis compared to non-silicotic subjects. Since India has a huge burden of silicosis and sub-radiological silicosis, the elimination of tuberculosis needs prior attention on silicosis. This article may be viewed as an eye-opener for understanding the necessity of dual control of both silicosis as well as tuberculosis by integrating both together.

Mycobacterium tuberculosis Infection among 1,659 Silicosis Patients in Zhejiang Province, China

Silicosis is a well-established risk factor for Mycobacterium tuberculosis infection. This study aimed to estimate the burden and risk factors of M. tuberculosis infection. Silicosis patients from Zhejiang Province were screened for M. tuberculosis by sputum culture, chest radiographs, whole-blood gamma interferon (IFN-γ) release assay (QuantiFERON-TB Gold In-Tube [QFT-GIT]), and tuberculin skin test (TST). Potential risk factors for M. tuberculosis were identified. Data for 1,659 patients were obtained from 1,684 participants. Of these, 1,656 (99.8%) were men, and the average age was 58 (54 to 63) years. The prevalence of active tuberculosis (ATB) was 6,340/100,000 (6.34%) people; the proportion of patients with latent tuberculosis infection (LTBI) was 50.6%. Age (odds ratio [OR] = 1.059, 95% confidence interval [CI] = 1.020 to 1.099, P = 0.003), being underweight (OR = 2.320, 95% CI = 1.057 to 5.089, P = 0.036), and having a history of exposure to TB patients (OR = 4.329, 95% CI = 1.992 to 9.434, P < 0.001) were associated with ATB; BCG vaccination could reduce ATB risk in silicosis patients (OR = 0.541, 95% CI = 0.307 to 0.954, P = 0.034). Among patients without ATB, the QFT-GIT positivity rate was 40.5%, which was affected by silicosis severity, while that of TST was 57.2%. BCG vaccination was an independent factor for LTBI risk reduction (OR = 0.612, 95% CI = 0.468 to 0.801, P < 0.001). The quantitative results of QFT-GIT decreased with silicosis stage (H = 6.037; P = 0.048). In conclusion, M. tuberculosis prevalence was high in silicosis patients. BCG vaccination reduced the risk of both ATB and LTBI in silicosis patients. IMPORTANCE This study evaluated the prevalence of Mycobacterium tuberculosis infection in silicosis patients in mainland China and identified the potential risk factors for both active tuberculosis (ATB) and latent tuberculosis infection (LTBI). We believe that our study makes a significant contribution to the literature because we demonstrated that M. tuberculosis prevalence was high among silicosis patients. BCG vaccination was an independent factor that reduced the risk of M. tuberculosis infection in patients with silicosis. Furthermore, we show that the prevalence of LTBI in patients with silicosis may have been underestimated by immunological detection methods. This study can help to identify targeted subgroups prioritized for M. tuberculosis control and to reduce the risk of disease development.

From properties to toxicity: Comparing microplastics to other airborne microparticles

Microplastic (MP) debris is considered as a potentially hazardous material. It is omnipresent in our environment, and evidence that MP is also abundant in the atmosphere is increasing. Consequently, the inhalation of these particles is a significant exposure route to humans. Concerns about potential effects of airborne MP on human health are rising. However, currently, there are not enough studies on the putative toxicity of airborne MP to adequately assess its impact on human health. Therefore, we examined potential drivers of airborne MP toxicity. Physicochemical properties like size, shape, ζ-potential, adsorbed molecules and pathogens, and the MP's bio-persistence have been proposed as possible drivers of MP toxicity. Since their role in MP toxicity is largely unknown, we reviewed the literature on toxicologically well-studied non-plastic airborne microparticles (asbestos, silica, soot, wood, cotton, hay). We aimed to link the observed health effects and toxicology of these microparticles to the abovementioned properties. By comparing this information with studies on the effects of airborne MP, we analyzed possible mechanisms of airborne MP toxicity. Thus, we provide a basis for a mechanistic understanding of airborne MP toxicity. This may enable the assessment of risks associated with airborne MP pollution, facilitating effective policymaking and product design.

Resistance to Mycobacterium tuberculosis infection among highly TB exposed South African gold miners

BACKGROUND

Despite high exposure to Mycobacterium tuberculosis, a small proportion of South African goldminers resist TB infection. We determined, among long-service gold miners i) the proportion who were TB uninfected and ii) epidemiological factors associated with being uninfected.

METHODS

We enrolled HIV-negative gold miners aged 33-60 years with ≥15 years' service and no history of TB or silicosis. Miners were defined as TB uninfected if i) QuantiFERON-TB Gold Plus (QFT-Plus) negative or ii) in a stricter definition, QFT-Plus-negative and zero-response on TST and as resisters if they were of Black/African ethnicity and negative on both tests. Logistic regression was used to identify epidemiological factors associated with being TB uninfected.

RESULTS

Of 307 participants with a QFT-Plus result, median age was 48 years (interquartile range [IQR] 44-53), median time working underground was 24 years (IQR 18-28), 303 (99%) were male and 91 (30%) were QFT-Plus-negative. The odds of being TB uninfected was 52% lower for unskilled workers (adjusted odds ratio [aOR] 0.48; 95% confidence interval [CI] 0.27-0.85; p = 0.013). Among 281 participants of Black/African ethnicity, 71 (25%) were QFT-Plus negative. Miners with a BMI ≥30 were less likely to be TB uninfected (OR 0.38; 95% CI 0.18-0.80). Using the stricter definition, 44.3% (136/307) of all miners were classified as either TB uninfected (35; 26%) or infected, (101; 74%) and the associations remained similar. Among Black/African miners; 123 were classified as either TB uninfected (23; 19%) or infected (100; 81%) using the stricter definition. No epidemiological factors for being TB uninfected were identified.

CONCLUSIONS

Despite high cumulative exposure, a small proportion of miners appear to be resistant to TB infection and are without distinguishing epidemiological characteristics.

Tuberculosis and Silicosis Burden in Artisanal and Small-Scale Gold Miners in a Large Occupational Health Outreach Programme in Zimbabwe

Artisanal and small-scale miners (ASMs) labour under archaic working conditions and are exposed to high levels of silica dust. Exposure to silica dust has been associated with an increased risk of tuberculosis and silicosis. ASMs are highly mobile and operate in remote areas with near absent access to health services. The main purpose of this study was to evaluate the prevalence of tuberculosis, silicosis and silico-tuberculosis among ASMs in Zimbabwe. A cross-sectional study was conducted from 1 October to 31 January 2021 on a convenient sample of 514 self-selected ASMs. We report the results from among those ASMs who attended an outreach medical facility and an occupational health clinic. Data were collected from clinical records using a precoded data proforma. Data variables included demographic (age, sex), clinical details (HIV status, GeneXpert results, outcomes of chest radiographs, history of tuberculosis) and perceived exposure to mine dust. Of the 464 miners screened for silicosis, 52 (11.2%) were diagnosed with silicosis, while 17 (4.0%) of 422 ASMs were diagnosed with tuberculosis (TB). Of the 373 ASMs tested for HIV, 90 (23.5%) were sero-positive. An HIV infection was associated with a diagnosis of silicosis. There is need for a comprehensive occupational health service package, including TB and silicosis surveillance, for ASMs in Zimbabwe. These are preliminary and limited findings, needing confirmation by more comprehensive studies.

Tuberculosis Screening in Silica-Exposed Workers : Developing a Tool for Health Care Providers

Both the Occupational Safety and Health Administration and Washington State require safety and health protections for workers exposed to respirable crystalline silica, including tuberculosis (TB) screening as part of occupational medical surveillance. We describe the creation of a TB screening tool for silica-exposed workers receiving regulated medical surveillance examinations in Washington State. The tool provides relevant clinical recommendations to assist health care providers and public health practitioners who choose to use the tool when performing such examinations. A cross-disciplinary team at the Washington State Department of Labor and Industries created the TB screening tool to help health care providers identify silica-exposed workers who should receive a comprehensive evaluation for active TB disease and workers who should or must receive testing for latent TB infection. The Washington State Adult Tuberculosis Screening Tool for Workers Exposed to Respirable Crystalline Silica benefits occupational and respiratory clinicians and public health practitioners by aiding both the individual- and population-level delivery of occupational health and TB screening services to silica-exposed workers receiving required medical surveillance examinations.

The prevalence of pulmonary tuberculosis among miners from the Karonga, Rumphi, Kasungu and Lilongwe Districts of Malawi in 2019

Introduction

Miners in sub-Saharan Africa have a greater risk of tuberculosis (TB) than any other working population in the world. In spite of the presence of large and vulnerable population of miners in Malawi, no previous study has aimed to assess the burden of TB among these miners. This study aimed to determine the prevalence of pulmonary tuberculosis (PTB) and health-seeking behaviour (HSB) in a population of miners in Malawi, and a range of associated factors. Our goal was to develop a method to identify missing cases of TB.

Methods

We conducted a cross-sectional study in the Karonga, Rumphi, Kasungu and Lilongwe districts of Malawi in 2019. We calculated frequencies, proportions, odds ratios (ORs) and their 95% confidence intervals (95% CIs), and used the chi-square test in STATA version15.1 to investigate the burden and magnitude of PTB in the mining sector. Bivariate and multivariate logistic regression models were also fitted for PTB and HSB.

Results

Of the 2400 miners approached, we were able to interview 2013 (84%). Of these, 1435 (71%) were males, 1438 (71%) had known HIV status and 272 (14%) had PTB. Multivariate analysis showed that the miners performing informal mining were 50% more likely to develop PTB compared with those in formal mining (adjusted odds ratio [AOR]=1.50, 95% CI: 1.10–2.05, P=0.01). A total of 459 (23% of 2013) miners had presumptive TB. Of these, 120 (26%) sought health care; 80% sought health care at health facilities. Multivariate analysis also showed that miners who experienced night sweats were less likely to seek health care compared with those without night sweats (AOR=0.52, 95% CI: 0.30–0.90, P=0.02).

Conclusion

The prevalence of PTB was higher among miners than in the general population. Consequently, targeted TB screening programmes for miners may represent a suitable strategy to adopt if we are to end TB by 2030. Poor health-seeking behaviours among miners is worrisome and further qualitative research is necessary to understand the barriers to accessing health care in these settings.

The association between silica exposure, silicosis and tuberculosis: a systematic review and meta-analysis

BACKGROUND

While the association between occupational inhalation of silica dust and pulmonary tuberculosis has been known for over a century, there has never been a published systematic review, particularly of experience in the current era of less severe silicosis and treatable tuberculosis. We undertook a systematic review of the evidence for the association between (1) silicosis and pulmonary tuberculosis, and (2) silica exposure and pulmonary tuberculosis controlling for silicosis, and their respective exposure-response gradients.

METHODS

We searched PUBMED and EMBASE, and selected studies according to a priori inclusion criteria. We extracted, summarised and pooled the results of published case-control and cohort studies of silica exposure and/or silicosis and incident active tuberculosis. Study quality was assessed on the Newcastle-Ottawa Scale. Where meta-analysis was possible, effect estimates were pooled using inverse-variance weighted random-effects models. Otherwise narrative and graphic synthesis was undertaken. Confidence regarding overall effect estimates was assessed using the GRADE schema.

RESULTS

Nine studies met the inclusion criteria. Meta-analysis of eight studies of silicosis and tuberculosis yielded a pooled relative risk of 4.01 (95% confidence interval (CI) 2.88, 5.58). Exposure-response gradients were strong with a low silicosis severity threshold for increased risk. Our GRADE assessment was high confidence in a strong association. Meta-analysis of five studies of silica exposure controlling for or excluding silicosis yielded a pooled relative risk of 1.92 (95% CI 1.36, 2.73). Exposure-response gradients were observable in individual studies but not finely stratified enough to infer an exposure threshold. Our GRADE assessment was low confidence in the estimated effect owing to inconsistency and use of proxies for silica exposure.

CONCLUSIONS

The evidence is robust for a strongly elevated risk of tuberculosis with radiological silicosis, with a low disease severity threshold. The effect estimate is more uncertain for silica exposure without radiological silicosis. Research is needed, particularly cohort studies measuring silica exposure in different settings, to characterise the effect more accurately as well as the silica exposure threshold that could be used to prevent excess tuberculosis risk.

Silicosis, progressive massive fibrosis and silico-tuberculosis among workers with occupational exposure to silica dusts in sandstone mines of Rajasthan state: An urgent need for initiating national silicosis control programme in India

Context:

Silicosis is a progressive, irreversible and incurable respiratory morbidity and often becomes a cause for pre-mature mortality among occupationally silica dust-exposed workers in India and similar countries. It has a dual problem of associated silico-tuberculosis as a co-morbidity. The present study was done to assess the respiratory morbidity caused by silicosis in sandstone mine of Rajasthan, India.

Methods:

The chest X-rays of 529 subjects having history of employment in stone mines with respiratory morbidity were subjected for this study and evaluated in accordance with ILO Classification 2000. The X-rays were classified into various categories of silicosis and progressive massive fibrosis (PMF) in relation to years of work in stone mines.

Results:

Out of 529 chest radiographs evaluated, 275 (52%) showed radiological evidence of silicosis. Of them, 40 (7.5%) subjects showed large opacities suggestive of progressive massive fibrosis. Both silicosis and progressive massive fibrosis were associated with increasing duration of work in stone mines. Sixty-one (12.4%) subjects with silicosis also had associated pulmonary tuberculosis, termed as silico-tuberculosis.

Conclusion:

The present study showed a high prevalence of silicosis, progressive massive fibrosis and silico-tuberculosis among stone mine workers. It appears that that unless silicosis is controlled, elimination of tuberculosis is far from reality in the country. Hence, states and central authorities must work together towards control of both silicosis as well as silico-tuberculosis. Similarly, there is an urgent need of initiation of national silicosis control programme, similar to existing national tuberculosis control programme, considering the huge burden of silicosis in India

Mini-review: Silico-tuberculosis

Silicosis continues to be a serious health issue in many countries and its elimination by 2030 (a target set by WHO and the International Labour Organization in 1995) is virtually impossible. The risk to develop pulmonary tuberculosis for silicosis patients is higher than for non-silicosis people, and there is also an increased risk of both pulmonary and extrapulmonary tuberculosis in individuals exposed to silica. HIV coinfection adds further to the risk, and in some countries, such as South Africa, miners living with HIV are a considerable number. The diagnosis of active tuberculosis superimposed on silicosis is often problematic, especially in initial phases, and chest X-ray and smear examination are particularly important for the diagnosis of pulmonary tuberculosis. Treatment is difficult; directly observed therapy is recommended, a duration of at least eight months is probably needed, drug reactions are frequent and the risk of relapse higher than in non-silicosis patients. TB prevention in silicosis patients is essential and include active surveillance of the workers, periodic chest X-rays, tuberculin skin test or interferon-gamma releasing assay testing, and, importantly, adoption of measures to reduce the exposure to silica dust. Chemoprophylaxis is possible with different regimens and needs to be expanded around the world, but efficacy is unfortunately limited. Silico-tuberculosis is still a challenging health problem in many countries and deserves attention worldwide.

Pulmonary Tuberculosis among Stone Miners of India vis-à-vis Silica Exposure

Background:

Tuberculosis is one of the biggest public health concerns in India with a prevalence of 195 cases per 100000. Silica is cytotoxic to macrophage which is primary defense mechanism to tubercular bacilli and, hence, exposure to silica dust increases risk for TB. Silica exposed persons are at 2.8 to 39 times greater risk of affected by pulmonary tuberculosis in comparison to healthy subjects.

Methodology:

A cross-sectional epidemiological study was conducted among 935 workers in sandstone mining. Full-size posteroanterior view (PA) chest X-ray in full inspiration was evaluated and evidence of tuberculosis was noted. Fourier transform infrared spectrophotometer was used for determining the free silica in 23 dust samples.

Results:

6.4% X-rays showed evidence of TB and silica dust concentration was 0.11 to 0.16 mg/m³. The TB cases significantly increased from 2% to 6% to 12.7% as the work exposure increased from <10 years to 11–20 years to >20 years respectively. 8.5% of the TB cases were seen among the workers having more than 10 years of work exposure. The odds ratio (95% CI) for work exposure more than 10 years to less than 10 years was 4.53 (1.92–10.65).

Conclusion:

Reduction of silica particles from work environment can significantly reduce the number of TB cases and hence wet drilling should be practiced and personal protective equipment should be regularly used.

Can the South African Milestones for Reducing Exposure to Respirable Crystalline Silica and Silicosis be Achieved and Reliably Monitored?

Silicosis and other respirable crystalline silica-associated diseases, most notably tuberculosis, have long been substantial causes of morbidity and mortality in South Africa. For the mining and non-mining industries, silicosis elimination programmes have been developed with milestones regarding reduction of levels of exposure to respirable crystalline silica (RCS) and targets regarding the date of eradication. The present paper explores the feasibility of achieving these targets by investigating the evidence that levels of exposure and silicosis incidence rates have declined by an appraisal of the methods for data collection and reporting. In the mining industry the silicosis elimination programme is supported by the development and advocacy of leading practices to reduce the exposure. RCS exposure data are routinely collected according to a Code of Practice (CoP) and the results are reported to the Mine Health and Safety Inspectorate. As the CoP and the actual workplace practices have been demonstrated to have some flaws, there is some concern about the accuracy of the actual exposure data and the data interpretation. The annually reported levels of exposure suggest a decline, however, the actual levels of RCS as well as the number of exposed workers, were not reported over the last few years. With regard to the silicosis incidence rates, a steady decline of new cases is reported. However, there is a risk of under-diagnosis and- reporting especially in former miners. In the non-mining industries, a systematic baseline of RCS exposure levels and silicosis incidence is lacking. The reporting by industries on assigning of the workforce to exposure categories seems to be fragmented and incomplete. Consequently, any evidence of progress toward achieving the silicosis elimination target cannot be documented. Both the silicosis elimination target and the exposure milestone are aspirational but are unlikely to be achieved. Nevertheless, the formal mining industry may get close. Exposure control interventions, especially in the non-mining industries, should be developed and implemented and pragmatic methods need to be put in place to identify sources of new silicosis cases for targeted intervention.

Environmental Silica Dust Exposure and Pulmonary Tuberculosis in Johannesburg, South Africa

Background: Occupational crystalline silica dust exposure is associated with an elevated risk of pulmonary tuberculosis (PTB). However, there is less evidence for an association with environmental silica dust exposure. Methods: A cross-sectional study of 310 participants was conducted in an exposed community living within 2 km of gold mine tailings and an unexposed population residing more than 10 km from the nearest gold mine tailing. Chest radiographs (n = 178) were read for PTB, past or current, by three readers. Results: Past or current PTB was radiologically identified in 14.4% (95%CI 9.2–21.8) in the exposed and 7.5% (95%CI 2.8–18.7) in the unexposed groups. Multivariate logistic regression models suggested that PTB prevalence was independently associated with exposure to second-hand smoke (OR = 8.13, 95%CI 1.16–57.22), a lower body mass index (OR = 0.88, 95%CI 0.80–0.98), previous diagnosis and treatment of PTB (OR = 8.98, 95%CI 1.98–40.34), and exposure to dust in the workplace from sand, construction, and/or mining industries (OR = 10.2, 95%CI 2.10–50.11). Conclusion: We found no association between PTB and environmental exposure to gold mine tailing dust. However, workplace silica dust exposure is a significant risk factor for PTB in South Africa, and PTB patients of working age should be screened for silica exposure.

Active tuberculosis case finding in India - The way forward

Community based active case finding (ACF) for tuberculosis (TB) has seen resurrection in the current armamentarium of many TB managers in their fight toward eliminating TB. This article explores the accuracy and approximate cost of various ACF algorithms currently in vogue in India or those which could be useful, while inputting the sensitivity and specificity of screening and diagnostic tools as estimated from recently conducted community based surveys. This analysis informs that ACF may be prioritized to higher prevalence settings and the diagnostic algorithm for specific setting may be chosen taking into account the expected prevalence, estimated accuracy of the algorithm and resource availability. Further, chest X-ray cannot be used alone as a diagnostic tool and can be relied upon for this purpose when at least one of the three sputum specimen is smear positive. Accuracy of Xpert MTB/RIF as a diagnostic tool in community situations needs to be investigated further. The review brings out significant proportions of initial default and default during treatment among cases detected through ACF thus emphasizing the need for heightened efforts toward preventing the same. The article rounds off emphasizing priority to addressing barriers to speedy scale up of more sensitive diagnostic tools for health center based case finding including in private sector and ACF in high risk clinical groups for early and efficient case detection. It concludes by putting forth certain research areas that would strengthen future efforts.

Those Who Don't Return: Improving Efforts to Address Tuberculosis Among Former Miners in Southern Africa

Despite increasing awareness regarding the role of oscillating migration in the mining industry as a major driving force in the spread of tuberculosis (TB) throughout southern Africa, very little work has focused on the historical and contextual factors which may contribute to former migrant miners' present-day risk of TB. Most research regarding migration-related and occupational influences on TB has been done on current miners still employed by the mining industry. Through both a historical and contemporary lens, this paper explores and elucidates the need to address the TB epidemic among former migrant mine workers and provides considerations to improve current interventions among this critical population.

Hearing function of gold miners with and without a history of tuberculosis treatment: a retrospective data review

Introduction

South Africa has a high prevalence of co-existing tuberculosis and HIV. As ototoxicity linked to the treatments for these conditions occurs with concomitant exposure to other ear toxins such as hazardous noise exposure, it is important to investigate the combination impact of these toxins. Limited published evidence exists on the co-occurrence of these conditions within this population.

Objectives

The objective of this study was to compare the hearing function of gold miners with (treatment group) and without (non-treatment group) the history of tuberculosis treatment, in order to determine which group had increased risk of noise induced hearing loss. Furthermore, possible influence of age and HIV in these two groups was examined.

Methods

A retrospective record review of 102 miners’ audiological records, divided into two groups, was conducted, with data analyzed both qualitatively and quantitatively.

Results

Findings suggest that gold miners with a history of tuberculosis treatment have worse hearing thresholds in the high frequencies when compared to those without this history; with evidence of a noise induced hearing loss notch at 6000 Hz in both groups. Pearson's correlations showed values between 0 and 0.3 (0 and −0.3) which are indicative of a weak positive (negative) correlation between HIV and hearing loss, as well as between hearing loss and age in this population.

Conclusions

Current findings highlight the importance of strategic hearing conservation programs, including ototoxicity monitoring, and the possible use of oto-protective/chemo-protective agents in this population.

Occupational Lung Diseases: Underreported Diagnosis in Radiological Practice

Underreporting of occupational lung diseases is a widespread problem in clinical practice. In Europe there is not a common regulation even for the recognition of occupational cancers. Furthermore epidemiologic data on occupational interstitial lung diseases, in general, is limited by no standardized diagnostic criteria, varied physician awareness and training, limitations inherent to the various data sources, and the long latency period. Therefore, to optimize the management of the patient with occupational pathology, the collaboration and skills of the multidisciplinary at the service of the patient, play a fundamental role. In particular, radiologists should give substance to a clinical suspicion on an anamnestic basis and at the same time should recognize patterns of illness that can lead to the emergence of stories of misunderstood exposures. This article aims to provide an overview of the main occupational lung diseases with attention to diagnostic possibilities of the different imaging techniques. The issue of the radiological error is investigated, providing tools to minimize it in the daily practice.

Oxidative potential (OP) and mineralogy of iron ore particulate matter at the Gol-E-Gohar Mining and Industrial Facility (Iran)

Concentrations of total suspended particulate matter, particulate matter with aerodynamic diameter <2.5 μm (PM_2.5), particulate matter <10 μm (PM₁₀), and fallout dust were measured at the Iranian Gol-E-Gohar Mining and Industrial Facility. Samples were characterized in terms of mineralogy, morphology, and oxidative potential. Results show that indoor samples exceeded the 24-h PM_2.5 and PM₁₀ mass concentration limits (35 and 150 µg m^-3, respectively) set by the US National Ambient Air Quality Standards. Calcite, magnetite, tremolite, pyrite, talc, and clay minerals such as kaolinite, vermiculite, and illite are the major phases of the iron ore PM. Accessory minerals are quartz, dolomite, hematite, actinolite, biotite, albite, nimite, laumontite, diopside, and muscovite. The scanning electron microscope structure of fibrous-elongated minerals revealed individual fibers in the range of 1.5 nm to 71.65 µm in length and 0.2 nm to 3.7 µm in diameter. The presence of minerals related to respiratory diseases, such as talc, crystalline silica, and needle-shaped minerals like amphibole asbestos (tremolite and actinolite), strongly suggests the need for detailed health-based studies in the region. The particulate samples show low to medium oxidative potential per unit of mass, in relation to an urban road side control, being more reactive with ascorbate than with glutathione or urate. However, the PM oxidative potential per volume of air is exceptionally high, confirming that the workers are exposed to a considerable oxidative environment. PM released by iron ore mining and processing activities should be considered a potential health risk to the mine workers and nearby employees, and strategies to combat the issue are suggested.

Analysis of the effects of mesoporous silica particles SBA-15 and SBA-16 in Streptococcus pneumoniae transformation process

Streptococcus pneumoniae are natural competent bacteria which requires the presence of a pheromone-like molecule to do the transformation process. This study verified the influence of mesoporous silica (SBA-15 and SBA-16) on the transformation process in S. pneumoniae using a donor DNA obtained from a mutant strain of this microorganism (Sp360∆luxS). The results showed that mesoporous silica SBA-15 and SBA-16 particles doubled the transformation ratio frequency compared with negative control (without nanoparticles) in using SBA-15 (ratio 1.81 ± 0.04) and SBA-16 (ratio 2.18 ± 0.22). We demonstrated the how mesoporous silica nanoparticles were able to increase the pneumococcus transformations, which could possibly lead to the acquisition of virulence factor genes and resistance of antibiotics.

Modificação do perfil da silicose na mineração subterrânea de ouro em Minas Gerais

Resumo Introdução: Minas Gerais é o estado brasileiro com maior registro de casos de silicose, sendo grande parte proveniente de casuísticas acumuladas das minerações de ouro. Objetivos: descrever e analisar temporalmente a ocorrência de silicose na mineração de ouro identificando fatores ocupacionais relacionados. Métodos: estudo transversal com 1.020 ex-mineiros da região de Nova Lima/MG, avaliados entre 1995 e 2011. Resultados: o diagnóstico de silicose foi confirmado em 19,7% dos avaliados. Nenhum caso da doença foi identificado em indivíduos que trabalharam apenas na superfície. A prevalência no grupo que trabalhou até 5 anos no subterrâneo foi de 3,8% e no grupo com mais de 20 anos de trabalho nesse local foi de 44,2%. Os admitidos para trabalho subterrâneo até 1950 apresentaram prevalência de 57,9%. Entre os admitidos após 1990, não houve registro de casos. Conclusão: verificou-se uma queda expressiva na ocorrência de silicose no período analisado. Uma vez que a doença é sabidamente dose-dependente, é esperado que a diminuição dos níveis de exposição, obtido pelas melhorias dos ambientes ocupacionais, tenha refletido nestes resultados. É fundamental que tais medidas continuem a ser adotadas na mineração e em outros ramos de atividade visando reduzir a ocorrência da doença.

Four decades of pulmonary tuberculosis in deceased South African miners: trends and determinants

OBJECTIVE

We investigated trends and determinants of pulmonary tuberculosis (PTB) in deceased South African miners.

METHODS

Statutory autopsies are performed on miners for occupational lung disease compensation, irrespective of cause of death. Data were extracted from the PATHAUT (Pathology Automation System) autopsy database. PTB trends were analysed and explanatory variables (year of autopsy, age at death, gold employment duration, silicosis and HIV) were evaluated using binary logistic regression modelling. Analyses were stratified by population group because of racial differences in socioeconomic status, employment patterns and access to facilities for autopsies. The analyses were segmented to represent the pre-HIV (1975-1989), rapid HIV spread (1990-2004) and antiretroviral therapy (2005-2014) periods.

RESULTS

The proportions of men with PTB at autopsy increased from 4.62% in 1975 to 27.18% in 2014 in black miners, and from 2.07% to 5.19% in white miners, with peaks in 2007 (43.12% and 9.51%, respectively). The magnitude and significance of adjusted ORs of determinants differed by population group and calendar period. PTB was largely associated with silicosis, increasing gold employment duration and year of autopsy (a surrogate for unmeasured confounders, such as unknown HIV status and tuberculosis transmission).

CONCLUSIONS

Changes in PTB time trends and determinants reflect the complex social and political environment in which mining occurs. Silica dust reduction remains a key intervention for tuberculosis reduction, together with tuberculosis and HIV treatment and management. The autopsy data provide reliable information to monitor progress towards the achievement of industry and national targets to reduce tuberculosis.

Combined effect of silica dust exposure and cigarette smoking on total and cause-specific mortality in iron miners: a cohort study

BACKGROUND

Both cigarette smoking and long-term exposure to crystalline silica dust were reported to be associated with increased mortality. However, the combined effect of both factors has not been well evaluated.

METHODS

We investigated a retro-prospective cohort of 7,665 workers from one Chinese iron mine with a median follow-up of 42.8 years. Cumulative silica exposure was estimated for each worker by linking work histories with a job-exposure matrix. Cigarette smoking information was collected through face-to-face questionnaires. Hazard ratios (HRs) for total and cause-specific mortality due to silica exposure and smoking were estimated using Cox proportional hazards models.

RESULTS

A total of 2,814 deaths occurred during 315,772.9 person-years of follow-up. Significantly elevated mortality from all causes, cardiovascular disease, non-malignant respiratory disease and lung cancer was observed among silica-exposed workers, while elevated mortality from non-malignant respiratory disease and lung cancer was observed among smokers. Combined exposure to silica dust and cigarette smoking elevated the proportion of mortality and accounted for 21.2, 76.0, 35.7 and 81.4% of all causes, non-malignant respiratory disease, cardiovascular disease, and lung cancer, respectively. Significant additive joint effects of silica exposure and cigarette smoking on mortality from lung cancer (HR 1.893, 95% CI 0.628 to 3.441) and pneumoconiosis (6.457, 0.725 to 39.114), together with a significant multiplicative joint effect from all causes (1.002, 1.000 to 1.004) were observed.

CONCLUSIONS

The present findings indicated that silica exposure in combination with cigarette smoking accounted for a fraction of extra deaths in our cohort. Our research showed the urgent need for smoking cessation and silica control among iron miners.

Influence of quartz exposure on lung cancer types in cases of lymph node-only silicosis and lung silicosis in German uranium miners

Inhaled crystalline quartz is a carcinogen. Analyses show differences in the distribution of lung cancer types depending on the status of silicosis. Using 2,524 lung tumor cases from the WISMUT autopsy repository database, silicosis was differentiated into cases without silicosis in lung parenchyma and its lymph nodes, with lymph node-only silicosis, or with lung silicosis including lymph node silicosis. The proportions of adenocarcinoma, squamous cell carcinoma, and small-cell lung carcinoma mortality for increasing quartz exposures were estimated in a multinomial logistic regression model. The relative proportions of the lung cancer subtypes in lymph node-only silicosis were more similar to lung silicosis than without any silicosis. The results support the hypothesis that quartz-related carcinogenesis in case of lymph node-only silicosis is more similar to that in lung silicosis than in without silicosis.

Comparison of digital and film chest radiography for detection and medical surveillance of silicosis in a setting with a high burden of tuberculosis

BACKGROUND

Continuing use of analog film and digital chest radiography for screening and surveillance for pneumoconiosis and tuberculosis in lower and middle income countries raises questions of equivalence of disease detection. This study compared analog to digital images for intra-rater agreement across formats and prevalence of changes related to silicosis and tuberculosis among South African gold miners using the International Labour Organization classification system.

METHODS

Miners with diverse radiological presentations of silicosis and tuberculosis were recruited. Digital and film chest images on each subject were classified by four expert readers.

RESULTS

Readings of film and soft copy digital images showed no significant differences in prevalence of tuberculosis or silicosis, and intra-rater agreement across formats was fair to good. Hard copy images yielded higher prevalences.

CONCLUSION

Film and digital soft copy images show consistent prevalence of findings, and generally fair to good intra-rater agreement for findings related to silicosis and tuberculosis.

Environmental dust inhalation in the European badger (Meles meles): Systemic distribution of silica-laden macrophages, pathological changes, and association with Mycobacterium bovis infection status

Chronic inhalation of crystalline silica and silicates may lead to severe lung disease in humans, termed silicosis. The disease is an occupational health concern in miners and related professions worldwide. Silicosis is also a strong risk factor for tuberculosis in humans. Due to its subterranean lifestyle, the European badger (Meles meles) is continuously exposed to environmental dust, while this species is also susceptible to tuberculosis, caused by Mycobacterium bovis. To date, a thorough investigation of mineral dust retention and its possible implication as a risk factor for mycobacterial infection in badgers has not been performed. The aims of this retrospective histological study were (1) to describe the systemic tissue distribution of silica-laden macrophages (SLMs) in badgers; (2) to compare the amount of SLMs in tissues of badgers of differing M. bovis infection status, pulmonary SLM burden and age; and (3) to assess whether inflammation was associated with SLMs. We assessed lung, lymph nodes, liver and spleen of 60 wild-caught badgers of known M. bovis infection status for the presence of SLMs using polarizing light microscopy. SLMs were consistently present within the lungs and were widely distributed throughout the lymphatic system. No inflammatory reaction to SLMs, as occurs in human silicosis, was observed in any tissue. Distribution and amount of SLMs were similar between M. bovis positive and negative badgers, and we were not able to show an association between the amount of SLMs and M. bovis infection status. The amount of SLMs within intra- and extrathoracic lymph nodes was positively associated with the amount of pulmonary SLMs, and with age. This is the first report of substantial and systemic tissue retention of mineral dust particles in a mammalian species lacking associated chronic inflammation (i.e. silicosis). We further highlight different pathogenetic mechanisms underlying silicosis and benign SLM accumulations following siliceous dust inhalation.

Determinants of respirable quartz exposure in farming

The objectives of this article are to quantify personal respirable quartz exposure on sandy, sandy loam, and clay soil farms and to identify exposure determinants. The methods applied included observing and examining the variables soil type, commodity farmed, activity, process, quartz % in respirable dust, and weather variables. Multiple linear regression was used to identify determinants of respirable quartz concentration and logistic regression was applied to identify determinants of respirable quartz concentration > 50 µg.m^-3 (a commonly used reference value of over-exposure). The highest quartz concentration was 626 µg.m^-3 and 30%, 22%, and 31% of measurements were > 50 µg.m^-3 for sandy, sandy loam, and clay soil farms, respectively. In general, the commodities livestock farming and cereal grains as well as the activity cereal planter operator, decreased humidity on the day of measurement, the mechanical processes, and quartz % in respirable dust (in a confounding way) were associated with higher respirable quartz concentrations (p ≤ 0.10) as well as season (p = 0.14). Variables associated with quartz levels above 50 µg.m^-3 were cereal planter operator, increased quartz % in respirable dust, decreased humidity on day of measurement, and increased respirable dust concentration. Cereal planter operator (Multivariate Odds Ratio (OR) 4.56, 95% CI: 1.79-8.89) and levels of quartz % > 10 µg.m^-3 (Multivariate OR 6.01, 95% CI: 3.52-9.71 if quartz % > 10 but ≤ 20 µg.m^-3, and Multivariate OR 5.32, 95% CI: 2.56-8.34 if quartz % > 20 µg.m^-3) were clear determinants of quartz over-exposure. It can therefore be concluded that over-exposure to quartz in farming is possible. Joint influences of more farming characteristics and weather variables should be included, together with soil type in future farming exposure assessments.

Concurrence of Tuberculosis and Other Major Diseases

The chronic respiratory disease of tuberculosis (TB) has become one of the most significant infectious diseases because of its high mortality. It also results in serious social and economic problems that challenge global public health. Anti-TB treatment has achieved satisfactory results; however, concurrence with other diseases such as diabetes, silicosis, malnutrition, or immunosuppressive therapy can significantly interfere with the treatment of TB. Though irregular treatment is the overriding cause of treatment failure, drug-resistant TB or severe TB and complications are also significant factors. Respiratory tract infection and respiratory failure are the leading cause of death for TB.

The risk of pulmonary tuberculosis in underground copper miners in Zambia exposed to respirable silica: a cross-sectional study

Background

Pulmonary tuberculosis (PTB) among underground miners exposed to silica remains a global problem. Although well described in gold and coal mining, risk in other mining entities are not as well documented. This study aims to determine dust-related dose response risk for PTB among underground miners exposed to silica dust in Zambia's copper mines.

Methods

A cross sectional study of in-service miners (n = 357) was conducted at Occupational Health and Safety Institute (OHSI), Zambia. A systematic review of medical data over a 5-year period from assessments conducted by doctors at OHSI and statutory silica exposure data (n = 16678) from the Mine Safety Department (MSD) were analysed. Lifetime cumulative exposure metrics were calculated. Multivariate logistic regression analysis was used to determine the association between PTB and lifetime exposure to silica, while adjusting for various confounders.

Results

The median respirable silica dust level was 0.3 mg/m³ (range 0.1–1.3). The overall prevalence of PTB was 9.5 % (n = 34). High cumulative respirable silica dust category showed a statistically significant association with PTB (OR = 6.4 (95 % CI 1. 8–23)) and a significant trend of increasing disease prevalence with increasing cumulative respirable silica dust categories was observed (p_trend < 0.01). Smoking showed a statistically significant association with PTB with OR = 4.3 (95 % CI 1.9–9.9).

Conclusions

Our results demonstrate the association of increased risk for certified active TB with cumulative respirable dust in a dose related manner among this sample of copper miners. There is need to intensify dust control measures and incorporate anti-smoking interventions into TB prevention and control programmes in the mines.

[Silicotuberculosis]

OBJECTIVE

Tuberculosis is a serious and common complication of silicosis. The aim of this study is to describe the epidemiological, clinical, radiological and progressive aspects of this pathological entity.

PATIENTS AND METHODS

The study concerns 23 cases of silicotuberculosis which were collected at the service of respiratory diseases at CHU Ibn Rochd of Casablanca, Morocco during 12years (2003-2015).

RESULTS

All patients were men. They were 7 diggers, 5 rock crushers, 7 miners and 4 masons. The mean duration of silica exposure was 11years. The symptomatology was dominated by dyspnea and persistent bronchial syndrome. Imagery showed tumor-like opacities in all cases, associated with mediastinal calcified lymphadenopathy in 9 cases, with micronodules in 8 cases and an excavated opacity in 2 cases. The diagnosis of tuberculosis was confirmed by isolation of the Koch's bacillus in sputum in 13% of cases in the bronchial aspirate in 52% and culture in sputum post-bronchoscopy in 13%. The bronchial biopsies confirmed the diagnosis in 2 cases. Tuberculosis had complicated silicosis 9years on average after the cessation of exposure to silica in 65% of cases. The antituberculous treatment was started in all patients with good clinical outcome in 22 cases. We had deplored a case of death by acute respiratory failure.

CONCLUSION

Silicosis increases the risk of tuberculosis, hence the importance of TB screening in all patients with silicosis.

Acute Exposure to Crystalline Silica Reduces Macrophage Activation in Response to Bacterial Lipoproteins

Numerous studies have examined the relationship between alveolar macrophages (AMs) and crystalline silica (SiO2) using in vitro and in vivo immunotoxicity models; however, exactly how exposure to SiO2 alters the functionality of AM and the potential consequences for immunity to respiratory pathogens remains largely unknown. Because recognition and clearance of inhaled particulates and microbes are largely mediated by pattern recognition receptors (PRRs) on the surface of AM, we hypothesized that exposure to SiO2 limits the ability of AM to respond to bacterial challenge by altering PRR expression. Alveolar and bone marrow-derived macrophages downregulate TLR2 expression following acute SiO2 exposure (e.g., 4 h). Interestingly, these responses were dependent on interactions between SiO2 and the class A scavenger receptor CD204, but not MARCO. Furthermore, SiO2 exposure decreased uptake of fluorescently labeled Pam2CSK4 and Pam3CSK4, resulting in reduced secretion of IL-1β, but not IL-6. Collectively, our data suggest that SiO2 exposure alters AM phenotype, which in turn affects their ability to uptake and respond to bacterial lipoproteins.

Silico-tuberculosis and associated risk factors in central province of Iran

INTRODUCTION

Co-existence of silicosis and tuberculosis is known as silico-tuberculosis. This article review the frequency of silicosis and tuberculosis in workers who exposed to silica and evaluate influencing factors that may increase the risk of silico-tuberculosis.

METHODS

An analytical cross-sectional study was performed in silica exposed workers in central province of Iran during 2011-2012. Sampling method was un-randomized and considering all workers who at least 6 months exposed to silica. The study was done via questionnaire, clinical examination, spirometry, chest x-ray and tuberculosis investigations.

RESULTS

A total of 3,121 workers were included in the study, the mean age of participants was 43.1±12.4 years, and mean employment duration 14.9±6.8 years. Prevalence of TB in silica-exposed workers without silicosis was 172 cases per 100 000 people and prevalence in silicosis cases was 917 cases per 100 000 people. Incidence of TB in silica-exposed workers without silicosis was 69 cases per 100,000 people and incidence in silicosis cases was 459 cases per 100,000 people. The frequency of LTBI/TB was higher in age over thirty years old (P=0.02), in workers with employment duration over 10 years (P=0.004), in workers with exposure duration over 5 years (P=0.03) and smokers with over 5 pack-years (P=0.01).

CONCLUSION

Exposure to silica causes a renewed multiplication of bacilli in the healing TB lesions. Prevalence of pulmonary tuberculosis in Silicosis is more common when compared to prevalence in general population, hence all should use prophylactic measures Intensification of work place.

Co-existence of tuberculous meningitis and pulmonary tuberculosis in a denim sandblaster

Silicosis is a well-known occupational lung disease that was discovered by the ancient Greeks and Romans. In 2001, it has emerged again in an unexpected occupation: denim sandblasting. Exposure to crystalline silica, with or without clinical disease, is one of the most important predisposing factors for the development of tuberculosis; however, there has been no previous report of tuberculosis among cases of silicosis due to denim sandblasting. Herein, we report the first case of a denim sandblaster with silicosis who developed both pulmonary tuberculosis and tuberculous meningitis.

Evaluation of ¹⁸F-fluorodeoxyglucose uptake in enlarged mediastinal lymph nodes in patients with lung cancer

Accurate lymph nodal staging of lung cancer is critical for determining the treatment options. With the help of (18)F-fluorodeoxyglucose positron emission tomography/computer tomography ((18)F-FDG-PET/CT), the clinician can rule out/in the regional lymph nodes positive for metastasis in the patients with lung cancer in a majority of cases. However, a small proportion of cases with false positivity of metastasis have been reported. Transbronchial needle aspirations and mediastinoscopic biopsies are still necessary to determine whether enlarged hypermetabolic mediastinal lymph nodes are positive for lung cancer metastasis. Here we report three intricate cases showing hypermetabolic activity in the mediastinal lymph nodes in the patients with pathologically diagnosed lung cancer on PET/CT. The first patient had squamous cell carcinoma in the left upper lobe of the lung with surrounding necrotizing granulomas and concurrent with silicosis and granulomatous inflammation in the lymph nodes; the second presented with symptoms of viral pneumonia, which was pathologically diagnosed as a lung adenocarcinoma, stage IA, concurrent with sarcoidosis involving the lymph nodes; the last case was diagnosed as squamous cell carcinoma in the right upper lobe of the lung, but lymph nodes showed reactive hyperplasia. These cases suggest that some cases are so complex that avid (18)F-FDG uptake in the mediastinal lymph nodes in the patients with pathologically diagnosed lung cancer should be carefully analyzed based on individual patients' clinical background.

Perturbation of pulmonary immune functions by carbon nanotubes and susceptibility to microbial infection

Occupational and environmental pulmonary exposure to carbon nanotubes (CNT) is considered to be a health risk with a very low threshold of tolerance as determined by the United States Center for Disease Control. Immortalized airway epithelial cells exposed to CNTs show a diverse range of effects including reduced viability, impaired proliferation, and elevated reactive oxygen species generation. Additionally, CNTs inhibit internalization of targets in multiple macrophage cell lines. Mice and rats exposed to CNTs often develop pulmonary granulomas and fibrosis. Furthermore, CNTs have immunomodulatory properties in these animal models. CNTs themselves are proinflammatory and can exacerbate the allergic response. However, CNTs may also be immunosuppressive, both locally and systemically. Studies that examined the relationship of CNT exposure prior to pulmonary infection have reached different conclusions. In some cases, pre-exposure either had no effect or enhanced clearance of infections while other studies showed CNTs inhibited clearance. Interestingly, most studies exploring this relationship use pathogens which are not considered primary pulmonary pathogens. Moreover, harmony across studies is difficult as different types of CNTs have dissimilar biological effects. We used Pseudomonas aeruginosa as model pathogen to study how helical multi-walled carbon nanotubes (HCNTs) affected internalization and clearance of the pulmonary pathogen. The results showed that, although HCNTs can inhibit internalization through multiple processes, bacterial clearance was not altered, which was attributed to an enhanced inflammatory response caused by pre-exposure to HCNTs. We compare and contrast our findings in relation to other studies to gauge the modulation of pulmonary immune response by CNTs.

Aspiring to zero tuberculosis deaths among southern Africa's miners: is there a way forward?

Tuberculosis notification rates among South African miners range from 4,000 to 7,000 per 100,000 people. These rates far exceed national tuberculosis notification rates for the general population. Tuberculosis mortality also surpasses deaths caused by mining accidents. These extraordinarily high rates of disease are unambiguously linked to a series of contributing factors, including exposure to silica dust, HIV infection, and poor working and living conditions. We argue that the only way to stop the transmission of this airborne disease is to treat the mine and its living quarters as one should any other congregate setting with individuals who have high rates of infection with drug-susceptible and drug-resistant strains of tuberculosis. This means implementing interventions that have been demonstrated to stop the spread of tuberculosis over the last 60 years: immediate treatment of active tuberculosis, concurrent treatment of latent tuberculosis disease to reduce the burden of active cases, and appropriate management of patients infected with HIV. Because tuberculosis is also a social disease, biomedical interventions must be coupled with improved living and working conditions. Achieving zero deaths from tuberculosis in the mines is possible if a clear commitment is made to a strategy that recognizes and ameliorates the biological and social antecedents to this epidemic.

Frequent detection of latent tuberculosis infection among aged underground hard coal miners in the absence of recent tuberculosis exposure

Background

Miners are at particular risk for tuberculosis (TB) infection due to exposure to silica dust and silicosis. The objectives of the present observational cohort study were to determine the prevalence of latent TB infection (LTBI) among aged German underground hard coal miners with silicosis or chronic obstructive pulmonary disease (COPD) using two commercial interferon-gamma release assays (IGRAs) and to compare their performance with respect to predictors of test positivity.

Methods

Between October 2008 and June 2010, miners were consecutively recruited when routinely attending pneumoconiosis clinics for an expert opinion. Both IGRAs, the QuantiFERON®-TB Gold In-Tube (QFT) and the T-SPOT®.TB (T-SPOT), were performed at baseline. A standardized clinical interview was conducted at baseline and at follow-up. The cohort was prospectively followed regarding the development of active TB for at least two years after inclusion of the last study subject. Independent predictors of IGRA positivity were calculated using logistic regression.

Results

Among 118 subjects (mean age 75 years), none reported recent exposure to TB. Overall, the QFT and the T-SPOT yielded similarly high rates of positive results (QFT: 46.6%; 95% confidence interval 37.6–55.6%; T-SPOT: 61.0%; 95% confidence interval 52.2–69.8%). Positive results were independently predicted by age ≥80 years and foreign country of birth for both IGRAs. In addition, radiological evidence of prior healed TB increased the chance of a positive QFT result fivefold. While 28 subjects were lost to follow-up, no cases of active TB occurred among 90 subjects during an average follow-up of >2 years.

Conclusions

Considering the high prevalence of LTBI, the absence of recent TB exposure, and the currently low TB incidence in Germany, our study provides evidence for the persistence of specific interferon-gamma responses even decades after putative exposure. However, the clinical value of current IGRAs among our study population, although probably limited, remains uncertain.

Delayed development of pulmonary hemorrhage in a patient with positive circulating anti-neutrophil cytoplasmic antibody: a clinical dilemma

Detection of circulating anti-neutrophil cytoplasmic antibody (ANCA) provides a powerful clue in the diagnosis of vasculitis, but the clinical interpretation of the results is difficult in some cases. Here, we describe the case of a 65-year-old man who underwent hemodialysis due to focal segmental glomerulosclerosis and abruptly developed hemoptysis 14 years after a renal biopsy. At the time of the biopsy, computed tomography (CT) showed interstitial shadows in the lungs and pleural thickening, indicating pneumoconiosis that was accompanied by tuberculosis. Circulating myeloperoxidase-ANCA (10.5–32.5 U/ml) was subsequently noted, but the significance of this observation was unclear due to the preexisting disorders in the lungs and kidneys. Potent immunosuppressive therapies were avoided because of the pulmonary lesions and decreased renal function. There were few changes noted on follow-up CT, but infiltrative shadows emerged in the bilateral lungs, consistent with hemoptysis. The hemorrhagic shadows completely disappeared shortly after initiation of steroid therapy, with normalization of the serum ANCA level. Herein, we report this case, with an emphasis on the clinical dilemma faced in deciding the appropriate treatment. The findings in the case provide deep insights into clinical management of ANCA-positive patients.

Correlation between Silica Exposure and Risk of Tuberculosis in Lorestan Province of Iran

BACKGROUND

Tuberculosis is considered a prevalent and hazardous disease in developing countries. Recognition and control of TB risk factors are of special significance. This study sought to determine the frequency of occupational silica exposure in TB patients residing in Lorestan Province.

MATERIALS AND METHODS

This cross-sectional study was conducted in 2012. List of registered TB patients was obtained from the Infectious Disease Control Center of Lorestan Province. Data were collected from 871 TB patients through interview and filling out a checklist. Also, 429 subjects presenting to Health Centers of Lorestan Province with respiratory complaints suspicious of TB (which was ruled out) were entered the study as the control group for comparison of frequency of silica occupational exposure. Understudy subjects based on the degree of silica exposure were categorized into 4 groups of no exposure, mild exposure, moderate exposure and severe exposure and compared in terms of frequency of TB incidence.

RESULTS

Frequency of silica exposure was significantly higher in TB patients compared to controls (P < 0.001, OR: 3.39, 95%CI = 2.63-4.36). Additionally, frequency of TB was greater in patients with probable silicosis and silica exposed subjects compared to those with no history of silica exposure (P < 0.05). Logistic regression analysis revealed significant associations between moderate and severe silica exposure and TB frequency. Significant correlations were also detected between age, work experience, level of education, male gender and cigarette smoking with TB frequency (P < 0.05).

CONCLUSION

The study results revealed that silica exposure was prevalent among TB patients and frequency of TB increased by increased intensity of silica exposure, older age, higher work experience, lower level of education, male gender and cigarette smoking. Provided that our study results are confirmed by prospective studies, TB screening is recommended for workers with occupational silica exposure particularly those with higher work experience.

A century of miners' compensation in South Africa

The year 2011 marked the centenary of compensation legislation for miners' lung disease in South Africa. This commentary aims to demonstrate that the current compensation system does not serve its intended beneficiaries, particularly the large population of former gold miners affected by high rates of silicosis and tuberculosis. The system has a complex legislative history, reflecting contending political, and economic forces, and characterized by racial discrimination. The financial basis of the system is currently in crisis owing to historical underfunding and failure to take into account the mounting burden of disease among black former miners. The real value of compensation awards fell sharply between 1973 and 1993, only partly recovering in recent years. Barriers to claiming benefits, particularly by black former miners who know little about the process, have been extensively documented. Integration of miners' compensation into general workers' compensation has been mooted since the 1980s but has stalled, owing to the high cost of closing the gap between the mostly inferior financial benefits under the mining legislation and those available under workers' compensation legislation. A recent constitutional court decision has opened the way for unprecedented civil litigation against the gold mining industry for silicosis, adding to the pressure for reform. A number of changes are called for: harmonization of financial benefits with retention of certain of the special arrangements for miner claims, a regional cross-border system of medical examination points for former miners, education of miners about the system, and some degree of privatization of claims processing.

Silicosis

Silicosis is a fibrotic lung disease caused by inhalation of free crystalline silicon dioxide or silica. Occupational exposure to respirable crystalline silica dust particles occurs in many industries. Phagocytosis of crystalline silica in the lung causes lysosomal damage, activating the NALP3 inflammasome and triggering the inflammatory cascade with subsequent fibrosis. Impairment of lung function increases with disease progression, even after the patient is no longer exposed. Diagnosis of silicosis needs carefully documented records of occupational exposure and radiological features, with exclusion of other competing diagnoses. Mycobacterial diseases, airway obstruction, and lung cancer are associated with silica dust exposure. As yet, no curative treatment exists, but comprehensive management strategies help to improve quality of life and slow deterioration. Further efforts are needed for recognition and control of silica hazards, especially in developing countries.

Checklist model to improve work practices in small-scale demolition operations with silica dust exposures

A systematic approach was developed to review, revise and adapt existing exposure control guidance used in developed countries for use in developing countries. One-page employee and multiple-page supervisor guidance sheets were adapted from existing documents using a logic framework and workers were trained to use the information to improve work practices. Interactive, hands-on training was delivered to 26 workers at five small-scale demolition projects in Maputo City, Mozambique, and evaluated. A pre-and-post walkthrough survey used by trained observers documented work practice changes. Worker feedback indicated that the training was effective and useful. Workers acquired knowledge (84% increase, p < 0.01) and applied the work practice guidance. The difference of proportions between use of work practice components before and after the intervention was statistically significant (p < 0.05). Changes in work practices following training included preplanning, use of wet methods and natural ventilation and end-of-task review. Respirable dust measurements indicated a reduction in exposure following training. Consistency in observer ratings and observations support the reliability and validity of the instruments. This approach demonstrated the short-term benefit of training in changing work practices; follow-up is required to determine the long-term impact on changes in work practices, and to evaluate the need for refresher training.