Biological indicators of exposure to total and respirable aluminium dust fractions in a primary aluminium smelter

The association between urinary aluminum and lung function among an urban adult population: A repeated-measure longitudinal study

OBJECTIVES

To investigate the cross-sectional and longitudinal associations between aluminum exposure and lung function and the risk of chronic obstructive pulmonary disease (COPD).

METHODS

The repeated-measure study was developed with 3917 adults from the Wuhan-Zhuhai cohort and they were followed-up after 3 years and 6 years. Urinary aluminum and lung function were measured at each period. Linear mixed models were used to estimate the exposure-response relationship between urinary aluminum and lung function. COX regression models were used to evaluate the association of urinary aluminum with the risk of COPD.

RESULTS

A total of 6996 observations including 2251 (32.2%) males with a mean age of 54.8 years were included. In the cross-sectional analyses, each 1-unit increase in log-transformed urinary aluminum was associated with a -33.34 mL (95% confidence interval (CI) -45.71 to -20.96) change in forced vital capacity (FVC) and a -17.89 mL (-27.80 to -7.97) change in forced expiratory volume in 1 s (FEV1). The follow-up analyses detected a negative association between urinary aluminum and the annual change of FVC (-6.73 mL/year, 95% CI -10.92 to -2.54), while the association of annual decline of FEV1 with urinary aluminum was statistically insignificant (-2.26 mL/year, -5.76 to 1.23). In the adjusted COX regression model, each 1-unit increase in log-transformed urinary aluminum was associated with a 29% increase in the incident risk of COPD (hazard ratio 1.29, 95% CI 1.04-1.62).

INCLUSION

Increased urinary aluminum was associated with lung function reduction and the increased risk of COPD in a general urban population.

Relationship between occupational aluminium exposure and histone lysine modification through methylation

BACKGROUND

Aluminium is an environmental neurotoxin to which human beings are extensively exposed. However, the molecular mechanism of aluminium toxicity remains unclear.

METHODS

The changes in cognitive function of aluminum exposed workers under long-term occupational exposure were evaluated, and the relationship between cognitive changes, plasma memory related BDNF and EGR1 protein expression, and variations of epigenetic markers H3K4me3, H3K9me2, H3K27me3 expression levels in blood was explored.

RESULTS

MMSE, DSFT, DST scores in cognitive function and the levels of plasma BDNF and EGR1 protein expression decreased with the increase of blood aluminum level. H3K4me3, H3K9me2, H3K27me3 expression levels in peripheral blood lymphocytes of aluminum exposed workers were statistically different (all P<0.05). H3K4me3, H3K9me2 and H3K27me3 expression levels in lymphocytes were correlated with blood aluminum level. BDNF, EGR1 protein level and H3K4me3, H3K9me2, H3K27me3 expression levels have different degrees of correlation. There was a linear regression relationship between plasma BDNF, H3K4me3 and H3K9me2. H3K9me2 had a greater effect on BDNF than H3K4me3. There is a linear regression relationship between EGR1, H3K4me3 and H3K27me3, and the influence of H3K4me3 on EGR1 is greater than that of H3K27me3 on EGR1.

CONCLUSION

Alummnum may regulate the expression of BDNF and EGR1 by regulating H3K4me3, H3K27me3 and H3K9me2, and affect the cognitive function of workers by affecting the expression of BDNF and EGR1.

Effects of occupational exposure to aluminium on some oxidative stress and DNA damage parameters

Aim:

The aim of this work was to investigate the relationships between aluminium levels, oxidative status and DNA damage in workers occupationally exposed to aluminium.

Subjects and methods:

This study was conducted in a secondary aluminium smelter. It included 96 male workers occupationally exposed to aluminium fume and dust compared to 96 male nonexposed individuals. Full history and clinical examination were done for all participants. Laboratory investigations in the form of serum aluminium, total antioxidant capacity (TAC), urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG) and comet assay test were performed.

Results:

Serum aluminium level ranged from 4 to 30 µg/L of median: 10 µg/L; urinary 8-OHdG ranged from 2.7 to 17.2 ng/mg creatinine of median: 7.6 ng/mg creatinine; comet tail length (CTL) ranged from 19.7 to 50.5 µm of median: 45 µm, were statistically significantly increased in the exposed group compared to nonexposed group. In exposed workers, a statistically significant positive correlations were found between serum aluminium level and urinary 8-OHdG ( r = 0.75, p < 0.001); aluminium level and CTL ( r = 0.71, p < 0.001); and urinary 8-OHdG and CTL ( r = 0.71, p < 0.001). There was a statistically significant negative correlation between serum aluminium and TAC ( r = −0.76, p < 0.001).

Conclusion:

Occupational exposure to aluminium in secondary aluminium smelters was related to the induction of oxidative stress and DNA damage. This may promote the development of adverse health hazards in the exposed workers

Study of potential transfer of aluminum to the brain via the olfactory pathway

Many employees in the aluminum industry are exposed to a range of aluminum compounds by inhalation, and the presence of ultrafine particles in the workplace has become a concern to occupational health professionals. Some metal salts and metal oxides have been shown to enter the brain through the olfactory route, bypassing the blood-brain barrier, but few studies have examined whether aluminum compounds also use this pathway. In this context, we sought to determine whether aluminum was found in rat olfactory bulbs and whether its transfer depended on physicochemical characteristics such as solubility and granulometry. Aluminum salts (chloride and fluoride) and various nanometric aluminum oxides (13nm, 20nm and 40-50nm) were administered to rats by intranasal instillation through one nostril (10μg Al/30μL for 10days). Olfactory bulbs (ipsilateral and contralateral relative to instilled nostril) were harvested and the aluminum content was determined by graphite furnace atomic absorption spectrometry after tissue mineralization. Some transfer of aluminum salts to the central nervous system via the olfactory route was observed, with the more soluble aluminum chloride being transferred at higher levels than aluminum fluoride. No cerebral translocation of any of the aluminas studied was detected.

Role of environmental contaminants in the etiology of Alzheimer's disease: a review

Alzheimer's dis ease (AD) is a leading cause of mortality in the developed world with 70% risk attributable to genetics. The remaining 30% of AD risk is hypothesized to include environmental factors and human lifestyle patterns. Environmental factors possibly include inorganic and organic hazards, exposure to toxic metals (aluminium, copper), pesticides (organochlorine and organophosphate insecticides), industrial chemicals (flame retardants) and air pollutants (particulate matter). Long term exposures to these environmental contaminants together with bioaccumulation over an individual's life-time are speculated to induce neuroinflammation and neuropathology paving the way for developing AD. Epidemiologic associations between environmental contaminant exposures and AD are still limited. However, many in vitro and animal studies have identified toxic effects of environmental contaminants at the cellular level, revealing alterations of pathways and metabolisms associated with AD that warrant further investigations. This review provides an overview of in vitro, animal and epidemiological studies on the etiology of AD, highlighting available data supportive of the long hypothesized link between toxic environmental exposures and development of AD pathology.

Occupational exposure to aluminum and its amyloidogenic link with cognitive functions

As many other metals, aluminum is a widely recognized neurotoxicant and its link with neurodegenerative disorders has been the subject of scientific debate. One proposal focuses on amyloid β deposition (amyloidogenesis) as the key player in triggering neuronal dysfunction the so-called amyloid cascade hypothesis. We undertook this study first to investigate the cognition status of workers exposed to Al dust in an Al factory in Southern Cairo, second, to evaluate serum amyloid precursor protein (APP) and cathepsin D (CD) enzyme activity to study the possible role of Al in amyloidogenesis, and finally to explore the relation between these potential biomarkers and cognitive functions. The study was conducted on 54 exposed workers and 51 matched controls. They were subjected to questionnaire, neurological examination and a cognitive test battery, Addenbrooke's Cognitive Examination - Revised (ACE-R). Serum Al, APP and CD enzyme activity were measured. A significant increase of serum Al was found in the exposed workers with an associated increase in serum APP and decrement in CD activity. The exposed workers displayed poor performance on the ACE-R test. No significant correlation was detected between ACE-R test total score and either APP or CD activity. We concluded that occupational exposure to Al is associated with cognitive impairment. The effect of occupational Al exposure on the serum levels of APP and CD activity may be regarded as a possible mechanism of Al in amyloidogenesis. However, our findings do not support the utility of serum APP and CD activity as screening markers for early or preclinical cognitive impairment.

Impact of aluminum exposure on lung

Aluminum (Al) metal is considered one of the most benign industrial metals. Although the harmful effects of Al on respiratory health have been denied by some studies, others reported its noxious effect on the lung through spirometric measurements. This work aimed at studying the effect of Al fumes on pulmonary functions of occupationally exposed workers. It investigated the possible relationship between inhalation exposure to Al fumes and levels of C-reactive protein (CRP) and alpha-1-antitrypsin (A1AT). The study participants comprised a group of 56 male Al workers with a mean duration of occupational exposure of 10.1 ± 9.5 years and 52 male participants who were not exposed to Al fumes as the control group. All participants filled a questionnaire, underwent full clinical examination and their spirometric pulmonary functions were measured. Blood samples were collected for the determination of serum CRP and A1AT and urine samples for measuring Al. Results revealed that urinary Al (UAl) was significantly higher in Al workers compared with controls (p < 0.05). However, spirometric measures showed no significant difference between the exposed group and the controls. A1AT was significantly lowered in Al workers compared with the controls (p < 0.000). Serum CRP was positive in only two (3.6%) of the exposed workers. Smokers of both groups (exposed and controls) showed significantly higher UAl and lower A1AT compared with nonsmokers. There was only significant negative correlation between the duration of exposure and A1AT (p < 0.05). There was a positive significant correlation between smoking index (SI) and UAl. There was also significant negative correlation between SI and some of the pulmonary function tests namely the percentage of predicted forced vital capacity, forced expiratory volume in the first second and peak expiratory flow in the exposed group. Those correlations point to the importance of the combined effect of smoking and Al exposure on the impairment of lung functions. The study recommends the determination of CRP and A1AT in Al-exposed workers. It is expected that those parameters may undergo changes before reduction in pulmonary functions takes place.

Evaluation of occupational exposure in a slide bearings factory on the basis of urine and blood sample analyses

The impact of a slide bearings factory on its workers was examined. Urine and blood samples were collected from 42 workers and six people employed in the offices in the same factory (control group). Concentrations of Al, Cu, Pb and Zn in blood and urine samples were measured twice (before and after chelation therapy) by ICP-MS technique using standard addition method. The essential differences in concentrations of elements for workers and control group were evaluated using non-parametric Mann-Whitney U-test. Significant differences between workers and control group were found for Pb in blood and Al in urine samples. The study was also undertaken to indicate correlation between blood and urine element content, workers' ages, their period of work and work section. It was also found that intravenous administration of 1 g of calcium-disodium versanate significantly increased urinary excretion of Pb and Zn, but not Al.

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).

Spirometric function in non-smoking workers exposed to aluminum

BACKGROUND

Exposure to aluminum (Al) causes the onset of respiratory disorders. This study is aimed at providing further information on how occupational exposure to Al affects the respiratory apparatus in healthy non-smokers, with particular attention to respiratory function.

METHODS

A group of 50 male shipyard workers who were exposed to Al underwent medical examination, standard chest X-rays and spirometry in accordance with the C.E.C.A. protocol. The data were compared with those of a homogeneous group of controls, all with blood aluminum (AlB) levels below 7.5 ng/ml. Statistical analysis was performed on the following spirometric parameters: vital capacity (VC), forced vital capacity (FVC), maximum forced expiratory volume in 1 s (FEV1), and mean forced expiratory flow during mid-half of FVC (FEF(25-75%)). Environmental Al levels were also measured at the various workstations.

RESULTS

Fifty male workers with an average age 31.82 +/- 5.05 years, occupational exposure of 11.81 +/- 3.71 years, presented with average AlB levels of 32.64 +/- 8.69 ng/ml. Environmental monitoring displayed Al levels higher than TLV TWA for all the workstations studied. None of the sample displayed significant pathological conditions. Statistical comparison of the spirometric parameters showed a decrease in the examined values in exposed workers. This decrease was found to be directly proportional to the AlB level.

CONCLUSION

The authors conclude that Al affects respiratory function and that limit values should be reassessed.

Identification of aluminium fractions in serum using the techniques of high performance liquid chromatography, ultrafiltration and Zeeman atomic absorption spectrometry

In order to ascertain the distribution of aluminium in normal and occupationally exposed sera, size-exclusion chromatography using two fractionation techniques was applied: gel filtration (Sephadex G-100 SF) and HPLC (TSK G4000 SW). For each of the techniques, protein profiles obtained for control and exposed sera did not differ and aluminium was found to be associated with the same fractions. Ultrafiltration of sera using Centricon concentrators having a nominal cut-off of M(r) = 10,000 confirmed the presence of high molecular mass and ultrafiltrable low molecular mass aluminium complexes in serum. Absolute quantitation and relative distribution of aluminium in the aforementioned complexes in original and spiked sera were determined using Zeeman atomic absorption spectrometry. It was found that the relative distribution of aluminium between high molecular mass and low molecular mass fractions was 79.1% and 19.6% in controls, compared to 91.3% and 8.7% in exposed sera, which is highly significant for both high molecular mass (p < 0.026) and low molecular mass (p < 0.004). After spiking both control and exposed sera with 400 micrograms/l of Al, the distribution changed. The percentage of the aluminium bound to high molecular mass increased from 79.1% to 98.9% for controls, and from 91.3% to 98.4% for exposed sera, confirming the affinity of high molecular mass proteins, especially transferrin for aluminium. On the other hand, the percentage of aluminium bound to low molecular mass decreased after spiking to 1.12% for controls and to 1.6% for exposed sera. These differences were not statistically significant. This suggests that at high concentrations of total aluminium in serum, the percentage of the aluminium bound to the low molecular mass is lower but the absolute quantity of aluminium circulating as the low molecular mass complex is increased. This low molecular mass aluminium complex is thought to play an important role in intracellular accumulation of aluminium.