Assessing individual employee risk factors for occupational asthma in primary aluminium smelting

Accelerated lung function decline in an aluminium manufacturing industry cohort exposed to PM2.5: an application of the parametric g-formula

OBJECTIVE

Occupational dust exposure has been associated with accelerated lung function decline, which in turn is associated with overall morbidity and mortality. In the current study, we assess potential benefits on lung function of hypothetical interventions that would reduce occupational exposure to fine particulate matter (PM2.5) while adjusting for the healthy worker survivor effect.

METHODS

Analyses were performed in a cohort of 6485 hourly male workers in an aluminium manufacturing company in the USA, followed between 1996 and 2013. We used the parametric g-formula to assess lung function decline over time under hypothetical interventions while also addressing time-varying confounding by underlying health status, using a composite risk score based on health insurance claims.

RESULTS

A counterfactual scenario envisioning a limit on exposure equivalent to the 10th percentile of the observed exposure distribution of 0.05 mg/m3 was associated with an improvement in forced expiratory volume in one second (FEV1) equivalent to 37.6 mL (95% CI 13.6 to 61.6) after 10 years of follow-up when compared with the observed. Assuming a linear decrease and (from NHANES reference values), a 20 mL decrease per year for a 1.8 m-tall man as they age, this 37.6 mL FEV1 loss over 10 years associated with observed exposure would translate to approximately a 19% increase to the already expected loss per year from age alone.

CONCLUSIONS

Our results indicate that occupational PM2.5 exposure in the aluminium industry accelerates lung function decline over age. Reduction in exposure may mitigate accelerated loss of lung function over time in the industry.

Pulmonary fluorosis: a review

The increased industrialization and improvised human lifestyle lead to a surge in environmental pollution nowadays. Even the chemicals which are known as prophylactic agents were currently liable to be toxic. One among them is inorganic fluoride whose wider application in numerous processes makes it as an inevitable environmental contaminant and industrial pollutant. Although the systemic toxicity of fluoride has been extensively studied, still there is lacuna in the field of pulmonary fluoride toxicity. Hence, we have focused on the molecular mechanism of action of fluoride compounds on pulmonary system. A study of literatures that focused on the potential physiological and toxicological consequences of fluoride on pulmonary system was carried out. The goal of this review is to present an overview of the research carried out till date on the molecular aspects of fluoride exposure with emphasis on pulmonary system and their possible mechanisms.

Inflammation in induced sputum after aluminium oxide exposure: an experimental chamber study

INTRODUCTION

Workers in aluminium production are exposed to a complex mixture of particles and gases potentially harmful to the airways, among them aluminium oxide (Al2O3). With the use of an exposure chamber, we aimed to examine the effects of short-term controlled exposure to Al2O3 on lung function and inflammatory markers in healthy volunteers.

METHODS

15 men (age 19-31) were exposed in random order to clean air or Al2O3 particles (3.8-4.0 mg/m(3)) for 2 h including 30 min exercise (stationary bike, 75 W). The permissible exposure level (PEL) for Al2O3 by Occupational Safety and Health Administration, USA, is 5 mg/m(3) time weighted average (TWA). Sham and particle exposures were separated by at least 2 weeks. Spirometry was carried out, and induced sputum and blood samples were collected 48 h before and 4 and 24 h after exposure.

RESULTS

Levels of sputum neutrophils (mean (±SEM)) was increased 24 h post-Al2O3 vs pre-Al2O3 exposure (43% (4) vs 31% (4), p=0.01) and the protein level of interleukin (IL)-8 had a 4.8 (0.9)-fold change increase 24 h after exposure (p<0.01). Following Al2O3 exposure, gene signatures in sputum were significantly increased related to several pathways.

CONCLUSIONS

The present study suggests that controlled exposure to Al2O3 particles at levels below PEL (TWA) induces airway inflammation in healthy humans marked by elevated neutrophils and elevated IL-8. In addition, increased expression of genes associated with several biological processes was observed in sputum. Interestingly, inhaled Al2O3-induced effects were localised to the airways and not systemic.

Pre-employment examinations for preventing injury, disease and sick leave in workers

BACKGROUND

Many employers and other stakeholders believe that health examinations of job applicants prevent occupational diseases and sickness absence. This is an update of the original Cochrane review (Mahmud 2010).

OBJECTIVES

To evaluate the effectiveness of pre-employment examinations of job applicants in preventing occupational injury, disease and sick leave compared to no intervention or alternative interventions.

SEARCH METHODS

We searched CENTRAL (the Cochrane Library), MEDLINE, EMBASE, CINAHL, PsycINFO and PEDro (up to 31 March 2015). We did not impose any restrictions on date, language or publication type.

SELECTION CRITERIA

We included randomised controlled trials (RCTs), controlled before-after (CBA) studies, and interrupted time-series (ITS) studies of health examinations to prevent occupational diseases and injuries in job applicants in comparison to no intervention or alternative interventions.

DATA COLLECTION AND ANALYSIS

All five review authors independently selected studies from the updated search for inclusion. We retrieved two new studies with the updated search from 1 April 2008 to 31 March 2015, resulting in a total of eleven studies.

MAIN RESULTS

We included two RCTs, seven CBA studies and two ITS studies. Nine studies with 7820 participants evaluated the screening process of pre-employment examinations as a whole, and two studies with 2164 participants evaluated the measures to mitigate the risks found following the screening process. The studies were too heterogeneous for statistical pooling of results. We rated the quality of the evidence for all outcomes as very low quality. The two new CBA studies both used historical controls and both had a high risk of bias.Of those studies that evaluated the screening process, there is very low quality evidence based on one RCT that a general examination for light duty work may not reduce the risk for sick leave (mean difference (MD) -0.09, 95% confidence interval (CI) -0.47 to 0.29). For army recruits, there is very low quality evidence based on one CBA study that there is a positive effect on fitness for duty after 12 months follow-up (odds ratio (OR) 0.40, 95% CI 0.19 to 0.85).We found inconsistent evidence of an effect of job-focused pre-employment examinations on the risk of musculoskeletal injuries in comparison with general or no pre-employment examination based on one RCT with high risk of bias, and four CBA studies. There is very low quality evidence based on one ITS study that incorporation of a bronchial challenge test may decrease occupational asthma (trend change -2.6, 95% CI -3.6 to -1.5) compared to a general pre-employment examination with lung function tests.Pre-employment examinations may also result in a rejection of the applicant for the new job. In six studies, the rates of rejecting job applicants increased because of the studied examinations , on average, from 2% to 35%, but not in one study.There is very low quality evidence based on two CBA studies that risk mitigation among applicants considered not fit for work at the pre-employment examination may result in a similar risk of work-related musculoskeletal injury during follow-up compared to workers considered fit for work at the health examination.

AUTHORS' CONCLUSIONS

There is very low quality evidence that a general examination for light duty work may not reduce the risk for sick leave, but may have a positive effect on fitness for duty for army recruits after 12 months follow-up.There is inconsistent evidence of an effect of job-focused pre-employment examinations on the risk of musculoskeletal injuries in comparison with general or no pre-employment examination. There is very low quality evidence that incorporation of a bronchial challenge test may decrease occupational asthma compared to a general pre-employment examination with lung function tests. Pre-employment examinations may result in an increase of rejecting job applicants in six out of seven studies. Risk mitigation based on the result of pre-employment examinations may be effective in reducing an increased risk for occupational injuries based on very low quality evidence. This evidence supports the current policy to restrict pre-employment examinations to only job-specific examinations. Better quality evaluation studies on pre-employment examinations are necessary, including the evaluation of the benefits of risk mitigation, given the effect on health and on the financial situation for those employees who do not pass the pre-employment examination.

Speciation of fluoride in workroom air during primary production of aluminium

Exposure to fluorides (F(-)) and particulate matter (PM) was assessed by personal sampling with use of Respicon® sampler in Prebake and Søderberg pot rooms in seven aluminium smelters. The inhalable PM mass was dominated by the extra-thoracic aerosol sub-fraction, which contributed with around 70% for both Prebake and Søderberg pot room workers. Quantitative and qualitative differences in exposure were found between pot room workers in smelters using these two technologies. Prebake pot room workers were exposed to 1.4 to 1.7 times higher PM concentrations than Søderberg pot room workers, depending on aerosol sub-fraction. Prebake pot room workers were also exposed to 2.5 to 2.9 higher air concentrations of water-soluble F(-) (FWS(-)) and 2.8 to 5.3 higher air concentrations of non water-soluble F(-) (FAS(-)) than Søderberg pot room workers, depending on aerosol sub-fraction. However, exposure to hydrogen fluoride (HF) was 1.3 times higher among Søderberg pot room workers. The relative amount of FWS(-), however, was higher among Søderberg pot room workers, while the relative amount of particulate F(-) (sum of FWS(-) and FAS(-)) was higher among Prebake pot room workers (6.5 vs. 3.9%). Exposure to the same PM concentration yielded higher FWS(-) and FAS(-) air concentrations among Prebake compared to Søderberg pot room workers.

Respiratory disorders in aluminum smelter workers

Objectives:

Summarizing the knowledge status, including the morphology, possible etiological factors, and clinical expression of aluminum potroom asthma and chronic obstructive pulmonary disease related to aluminum potroom exposure.

Methods:

A review of the literature from the last two decades as it appears in PubMed.

Results:

There is substantial evidence for the existence of potroom asthma, although the incidence seems to decline over the last 10 years. Increased mortality from chronic obstructive pulmonary disease and longitudinal decline in forced expiratory volume in the first second of expiration has been shown in aluminum potroom workers. Morphological manifestations in bronchial biopsies and the inflammatory markers NO and eosinophils in airway tissue and blood are consistent with asthma in general. The causative agent(s) is (are) not known.

Conclusions:

Reduction of exposure and cessation of smoking seem to be the major preventive measures to avoid respiratory disorders in the aluminum industry.

Intersampler field comparison of Respicon(R), IOM, and closed-face 25-mm personal aerosol samplers during primary production of aluminium

Intersampler field comparison of Respicon(®), 25-mm closed-face 'total dust' cassette (CFC), and IOM inhalable aerosol sampler was conducted in pot rooms at seven aluminium smelters. The aerosol mass and water-soluble fluoride were selected as airborne contaminants for the comparisons. The aerosol masses of 889 sample pairs of IOM and Respicon(®) inhalable aerosol sub-fraction, 165 of IOM and 25-mm CFC, and 194 of CFC and Respicon(®) thoracic aerosol sub-fraction were compared. The number of sample pairs for the comparison of water-soluble fluoride was 906, 170, and 195, respectively. The geometric mean aerosol mass collected with the inhalable Respicon(®) was 2.91 mg m(-3) compared with 3.38 mg m(-3) with the IOM. The overall ratio between IOM and Respicon(®) inhalable sub-fraction was 1.16 [95% confidence interval (CI) = 1.11-1.21] for aerosol mass and 1.13 (95% CI = 1.08-1.18) for water-soluble fluoride. The results indicate that Respicon(®) undersampled the aerosol mass and water-soluble fluoride in the inhalable sub-fraction compared with the IOM. The results indicated undersampling of the Respicon(®) at mass concentrations higher than 1.35 mg m(-3) and oversampling at lower mass concentrations. The overall ratio between aerosol mass collected with IOM and CFC was 4.19 (95% CI = 3.79-4.64) and 1.61 (95% CI = 1.51-1.72) for water-soluble fluoride. Thus, for this industry, a correction factor of 4.2 is suggested for the conversion of CFC to inhalable aerosol masses and a conversion factor of 1.6 for water-soluble fluoride if wall deposits in the CFC are included. CFC and thoracic Respicon(®) collected similar aerosol masses (ratio = 1.04; 95% CI = 0.97-1.12), whereas the ratio was 1.19 (95% CI = 1.11-1.28) for water-soluble fluoride. The variability of the exposure is substantial; thus, large data sets are required in sampler performance field comparisons.

How aluminum, an intracellular ROS generator promotes hepatic and neurological diseases: the metabolic tale

Metal pollutants are a global health risk due to their ability to contribute to a variety of diseases. Aluminum (Al), a ubiquitous environmental contaminant is implicated in anemia, osteomalacia, hepatic disorder, and neurological disorder. In this review, we outline how this intracellular generator of reactive oxygen species (ROS) triggers a metabolic shift towards lipogenesis in astrocytes and hepatocytes. This Al-evoked phenomenon is coupled to diminished mitochondrial activity, anerobiosis, and the channeling of α-ketoacids towards anti-oxidant defense. The resulting metabolic reconfiguration leads to fat accumulation and a reduction in ATP synthesis, characteristics that are common to numerous medical disorders. Hence, the ability of Al toxicity to create an oxidative environment promotes dysfunctional metabolic processes in astrocytes and hepatocytes. These molecular events triggered by Al-induced ROS production are the potential mediators of brain and liver disorders.

Regular exercise training attenuates pulmonary inflammatory responses to inhaled alumina refinery dust in mice

Exposure to alumina dust has been recently associated with impaired lung mechanics and inflammation. We aimed at evaluating if moderate exercise training prevents these outcomes. Twenty-three female BALB/c mice (25-30g) were randomly divided in two main groups: control (C) and exercise (E), which were submitted, or not, to 15min of swimming, 5 days/week during 4 weeks. Then, the animals were exposed for 1h to either saline solution (CS or ES) or to a suspension of 8mg/m(3) of alumina dust (CA or EA). Twenty-four hours later pulmonary mechanics was determined by the end-inflation occlusion method. Left lungs were prepared for histology and right lungs for TGF-β determination. Static elastance increased after alumina dust exposure independently of swimming. In CA group the viscoelastic component of elastance, the viscoelastic/inhomogeneous pressure, the polymorphonuclear amount, the fraction area of alveolar collapse and TGF-β increased. Thus, exercise training may mitigate the pro-inflammatory response to inhaled aluminum refinery dust.

Is pre-employment health screening by questionnaire effective?

BACKGROUND

Following a job offer, many employers require the chosen candidate to undergo health screening by questionnaire before the applicant commences work. Despite their widespread use, the effectiveness of such questionnaires remains uncertain.

AIMS

To systematically review the evidence for the effectiveness of pre-employment health questionnaires in predicting health and employment outcomes.

METHODS

We used a sensitive search strategy to search electronic databases from 1985 to September 2009. The search included dissertations for Membership of the UK Faculty of Occupational Medicine (MFOM). The authors independently selected abstracts and papers for critical appraisal and inclusion in the review using methods based on guidelines produced by the National Health Service Centre for Reviews and Dissemination, University of York.

RESULTS

Five hundred and three abstracts were identified; nine papers and two MFOM dissertations were critically appraised. Seven papers and two MFOM dissertations were included in the final review. Six studies explored pre-employment predictors of respiratory symptoms, one explored predictors of back pain in nurses, and two dissertations explored work outcomes including sickness absence and ill-health retirement. No papers addressing mental health outcomes met our inclusion criteria. Included studies either failed to identify pre-employment predictors of health and work outcomes or found very weak predictors.

CONCLUSIONS

Pre-employment health screening (PEHS) by questionnaire has a low predictive value in detecting future adverse health and occupational outcomes. Where PEHS takes place, the health standards required and criteria for rejection of applicants should be based on a full risk assessment of the prospective post.

Occupational asthma in the aluminum smelters of Australia and New Zealand: 1991-2006

OBJECTIVE

To examine the incidence of occupational asthma in the seven aluminum smelters of Australia and New Zealand from 1991 to 2006.

METHODS

Incidence and exposure data were collected by survey from the smelters prospectively during the study period.

RESULTS

The incidence of occupational asthma across all smelters combined was highest in 1992 at 9.46/1,000/year, declining to 0.36/1,000/year in 2006; a 96.2% reduction. The incidence of occupational asthma was correlated with geometric mean total fluoride concentration, measured as personal samples from employees undertaking anode changing (r(s)  = 0.497, P < 0.001).

CONCLUSIONS

The control of exposures, respiratory protection and pre-placement medical assessments undertaken during the study period seem to have contributed to the substantial decline in occupational asthma incidence.

Pre-employment examinations for preventing occupational injury and disease in workers

BACKGROUND

Many employers and other stakeholders believe that health examinations of job applicants prevent occupational diseases and sickness absence.

OBJECTIVES

To evaluate the effectiveness of pre-employment examinations of job applicants in preventing occupational injury, disease and sickness absence compared to no intervention or alternative interventions.

SEARCH STRATEGY

We searched CENTRAL (The Cochrane Library), MEDLINE, EMBASE, CINAHL, PsycINFO and PEDro (to December 2009) not restricted by date, language or publication type.

SELECTION CRITERIA

We included randomised controlled trials (RCTs), controlled before-after studies (CBA), and interrupted time-series (ITS) of health examinations to prevent occupational diseases and injuries in job applicants.

DATA COLLECTION AND ANALYSIS

Four review authors (NM, ML, JV, ES) independently selected studies, extracted data, and determined study quality. The studies were too heterogeneous for statistical pooling of results.

MAIN RESULTS

We included two RCTs, five CBA studies and two ITS. Seven studies with 5872 participants evaluated the screening process of pre-employment examinations and two studies with 2164 participants evaluated the measures to mitigate the risks found following the screening process.Of those studies that evaluated the screening process, one study found that a general examination did not reduce sick leave (Mean Difference -0.1 95% CI -0.5 to 0.3) but another study found that a more task focused examination did (MD -36 95% CI -68.3 to -3.8). One study found that incorporation of a bronchial challenge test decreased occupational asthma (trend change -2.6 95% CI -3.6 to -1.5). Three studies that included functional capacity evaluation found contradictory effects on injury rates and number of medical visits. The rates of rejecting job applicants varied from 2% to 35%.Neither of the two studies that evaluated risk mitigation found an increased injury rate after training or work accommodations had been implemented.We rated the evidence for all outcomes as very low quality.

AUTHORS' CONCLUSIONS

There is very low quality evidence that pre-employment examinations that are specific to certain jobs or health problems could reduce occupational disease, injury, or sickness absence. This supports the current policy to restrict pre-employment examinations to job-specific examinations. More studies are needed that take into account the harms of rejecting job applicants.

Respiratory and ocular symptoms in workers exposed to potassium aluminium-tetrafluoride soldering flux

BACKGROUND

Exposure to aluminium compounds, such as fluorides in gaseous and particulate form, places people who work in potrooms at risk for respiratory symptoms. Workers in potrooms, however, also are exposed to a number of other air contaminants. In this study, we present the first report of a dose-response relationship after exposure to potassium aluminium tetrafluoride (KAlF(4)) and the influence of smoking and atopy.

MATERIALS

All workers (308) from an industrial plant that used KAlF as soldering flux were invited to participate in the study. In all, 289 workers participated and 118 employees not exposed to chemicals in their professional work served as an unexposed group.

METHODS

In the first step, all subjects answered a questionnaire concerning respiratory symptoms and work history, and participated in a lung function examination. In a second step, all workers who reported work-related complaints from lower respiratory airways were invited to participate in medical examination, methacholine test, screening test of respiratory allergy, and skin prick test against KAlF(4).

RESULTS

The exposed subjects had more symptoms than the unexposed group; dry cough odds ratio (OR): 5.17 (confidence interval 1.79-15.0), stuffy nose: 2.3 (1.25-4.22), nose bleeding: 10.7 (3.26-35.3) and ocular symptoms 5.01 (1.92-13.1) except for chest tightening and wheezing, and shortness of breath. The symptoms appeared in a dose response-like manner although the ORs between high and low exposed were significant for only chest tightening and wheezing, 2.62 (1.30-5.26) and stuffy nose 2.1 (1.22-3.66). Smokers and atopics did not report more frequent work-related symptoms. Smokers were significantly less hyperreactive than non-smokers, indicating a healthy-worker effect. No one showed a positive skin prick test against KAlF(4).

CONCLUSION

In spite of exposure levels of KAlF(4 )well below the new Swedish threshold limit, value frequent respiratory and ocular symptoms were reported. No evidence of IgE mediated allergy was found.

Smoking and occupational asthma

Cigarette smoking is a known risk factor for many chronic illnesses such as coronary heart and chronic obstructive pulmonary diseases. Smoking is often described as a risk factor for occupational asthma even though its effect on the development of asthma is still under debate and the links between smoking and occupational asthma, occupational rhinitis or occupational sensitization are elusive, controversial and contradictory. This review describes these relationships in a wide range of occupations, from laboratory, farm, brewery and hospital workers, to bakers, printers, cleaners, fish processors and others as observed in cross-sectional, cohort, and case-control studies published over the past thirty-five years i.e. from 1970 to 2005. Surprisingly, the data show there is little to support the view that the risk of occupational asthma is increased in workers who are smokers. However, evidence emerges of an increased risk of occupational sensitization in smoking workers exposed to several high and low molecular weight agents. This in-depth review confirms the relationship between smoking and occupational asthma is complex and contradictory. It deserves more attention and further studies, which need to be conducted without being influenced by selection bias or by the justifiable prejudice against smoking.

Incidence of asthma among aluminum workers

Exposures to respiratory irritants encountered in aluminum smelters in Europe, Australia, and New Zealand have been suggested as the cause of "potroom asthma." However, there remains disagreement in North America regarding the existence of this entity. This study was designed to assess whether asthma occurs excessively among potroom workers and if so, delineate dose-response relationships for possible causal risk factors. The asthma incidence ratio between potroom and nonpotroom workers after adjusting for smoking was 1.40. Although bivariate analyses showed a relationship between asthma incidence and exposure to total fluoride, gaseous fluoride, particulate fluoride, sulfur dioxide, and smoking, only the effects of gaseous fluoride (relative risk [RR] = 5.1) and smoking (RR = 7.7) remained significant in a multivariate model. Potroom asthma appears to occur at the studied U.S. aluminum smelters at doses within regulatory guidelines.

Serum Clara Cell Protein as an Indicator of Pulmonary Impairment in Occupational Exposure at Aluminum Foundry

OBJECTIVES

Although some of the exposures in aluminum (Al) smelting have been well characterized, and respiratory disorders in aluminum production workers are well known, the relationship between internal aluminum loads and appropriate lung biomarkers have not been elucidated. The aim of our work was to carry out a comprehensive investigation in workers employed in the Aluminum Foundry Casting Department with special reference to currently existing hygiene standards, known as threshold limit values (TLV) based on aluminum effects on the respiratory system. The measurement of serum anti-inflammatory Clara cell protein (CC16) was employed as a peripheral marker of the lung epithelium function.

MATERIALS AND METHODS

A group of 50 casting smelters, 5 locksmiths, 11 sawyers and auxiliary workers exposed to dust containing 14% of aluminum, and a group of 42 controls were examined. Respiratory function tests were performed and forced volume capacity (FVC), forced expiratory volume in 1 s (FEV1), forced expiratory volume in the first percent (FEV1%), forced expiratory flows in 50% VC (FEV50), and markers of foundry workers' exposure and body burden, Al concentration in the breathing zone, blood and urine, biomarkers of the effects of exposure, concentration of CC16 and hyaluronic acid (HA) in serum were determined in all examined workers. Additional measurements comprised determinations of serum iron (Fe) levels, myeloperoxidase (MPO), eosinophil cationic protein (ECP), immunoglobulin E (IgE), glutathione S-transferase (GST), and superoxide dismutase (SOD) activity in erythrocytes.

RESULTS

The group of casting smelters was characterized by the highest levels of aluminum in urine (Al-U) (43.7 microg L(-1)), high levels of MPO, ECP and IgE, high SOD activity, low CC16 levels, and low activity of GST. Lower Al-U excretion was observed in locksmiths (35.2 microg L(-1)) and sawyers (21.7 microg L(-1)). Serum CC16 proved to be the most sensitive biomarker, showing high inverse relationship with serum Al (Al-S) concentrations in casting smelters (p = 0.006).

CONCLUSIONS

The study showed that in conditions of occupational exposure, dusts containing Al2O3 < 1 mg m(-3) cause changes in the respiratory system and biomarkers in serum, especially in CC16, connected with altered functioning of this system. Changes in concentrations of the examined biomarkers and also in respiratory parameters of the study subjects were observed when Al-U concentration was > 40 microg L (-1).