Occupational exposure to metal compounds and lung cancer. Results from a multi-center case-control study in Central/Eastern Europe and UK

Update of the risk assessment of inorganic arsenic in food

The European Commission asked EFSA to update its 2009 risk assessment on arsenic in food carrying out a hazard assessment of inorganic arsenic (iAs) and using the revised exposure assessment issued by EFSA in 2021. Epidemiological studies show that the chronic intake of iAs via diet and/or drinking water is associated with increased risk of several adverse outcomes including cancers of the skin, bladder and lung. The CONTAM Panel used the benchmark dose lower confidence limit based on a benchmark response (BMR) of 5% (relative increase of the background incidence after adjustment for confounders, BMDL05) of 0.06 μg iAs/kg bw per day obtained from a study on skin cancer as a Reference Point (RP). Inorganic As is a genotoxic carcinogen with additional epigenetic effects and the CONTAM Panel applied a margin of exposure (MOE) approach for the risk characterisation. In adults, the MOEs are low (range between 2 and 0.4 for mean consumers and between 0.9 and 0.2 at the 95th percentile exposure, respectively) and as such raise a health concern despite the uncertainties.

Interaction between Occupational and Non-Occupational Arsenic Exposure and Tobacco Smoke on Lung Cancerogenesis: A Systematic Review

Although a higher lung cancer risk has been already associated with arsenic exposure, the contribution of arsenic and its compounds to the carcinogenic effects of other agents, such as tobacco smoke, is not well characterized. This systematic review examined the relationship between occupational and non-occupational arsenic exposure and tobacco smoking on lung cancer risk using papers published from 2010 to 2022. Two databases, PUBMED and Scifinder, were used for the searches. Among the sixteen human studies included, four were about occupational exposure, and the others were about arsenic in drinking water. Furthermore, only three case-control studies and two cohort studies evaluated an additive or multiplicative interaction. The interaction between arsenic exposure and tobacco smoke seems to be negligible at low arsenic concentrations (<100 μg/L), while there is a synergistic effect at higher concentrations. Finally, it is not yet possible to assess whether a linear no-threshold (LNT) model for lung cancer risk can be applied to the co-exposure to arsenic and tobacco smoke. Although the methodological quality of the included studies is good, these findings suggest that rigorous and accurate prospective studies on this topic are highly needed.

Real-world PM2.5 exposure induces pathological injury and DNA damage associated with miRNAs and DNA methylation alteration in rat lungs

Fine particulate matter (PM_2.5) has been demonstrated to threaten public health and increase lung cancer risk. DNA damage is involved in the pathogenesis of lung cancer. However, the mechanisms of epigenetic modification of lung DNA damage are still unclear. This study developed a real-world air PM_2.5 inhalation system and exposed rats for 1 and 2 months, respectively, and investigated rat lungs pathological changes, inflammation, oxidative stress, and DNA damage effects. OGG1 and MTH1 expression was measured, along with their DNA methylation status and related miRNAs expression. The results showed that PM_2.5 exposure led to pathological injury, influenced levels of inflammatory cytokines and oxidative stress factors in rat lungs. Of note, 2-month PM_2.5 exposure aggravated pathological injury. Besides, PM_2.5 significantly elevated OGG1 expression and suppressed MTH1 expression, which was correlated to oxidative stress and partially mediated by reducing OGG1 DNA methylation status and increasing miRNAs expression related to MTH1 in DNA damage with increases of γ-H2AX, 8-OHdG and GADD153. PM_2.5 also activated c-fos and c-jun levels and inactivated PTEN levels in rat lungs. These suggested that epigenetic modification was probably a potential mechanism by which PM_2.5-induced genotoxicity in rat lungs.

Air-polluted environmental heavy metal exposure increase lung cancer incidence and mortality: A population-based longitudinal cohort study

BACKGROUND

An increased risk of lung cancer has been observed due to exposure to certain environmental heavy metals. This study elucidated the role of air-polluted heavy metals in the development of lung cancer.

METHODS

A longitudinal cohort study involving the general population was conducted to compare heavy metal content among lung cancer patients. The urine concentrations of heavy metals were measured. Questionnaire surveys were designed to collect exposure-related demographic and lifestyle data of the study subjects.

RESULTS

Participants residing near the petrochemical industrial area with higher air Cd concentration had relatively higher urinary concentration of Cd. After adjusting for sociodemographic and behavioral factors, tobacco smoking and air pollution remained as potential sources of Cd exposure. An increased prevalence of lung cancer was observed in the highly polluted zone. The risk of lung cancer incidence increased 1.25-fold for each 1 μg/g-creatinine increase in urine Cd level. Patients with lung cancer had significantly higher urinary Cd concentrations. Lung cancer patients with higher urinary Cd level had significantly poor survival (urine Cd level ≥ 1.58 vs <1.58 μg/g-creatinine; survival, medium, 192.0 vs 342.5 days, p < 0.001). At the longitudinal follow-up, participants with higher urinary Cd level had a higher risk of lung cancer incidence (urine Cd level ≥ 1.58 vs <1.58 μg/g-creatinine: 3.91% v.s. 0.87%, hazard ratio: 4.65, p < 0.001).

CONCLUSIONS

Accumulation of Cd could be a risk of lung cancer occurrence. High exposure to Cd may result in poor prognosis in lung cancer patients.

Analysis of targeted somatic mutations in pleomorphic carcinoma of the lung using next-generation sequencing technique

BACKGROUND

Pleomorphic carcinoma (PC) of the lung is a rare type of lung cancer with aggressive characteristics and a poor prognosis. Because it is rare, the molecular characteristics of PC remain unclear.

METHODS

A gene mutation analysis was performed using next-generation sequencing (NGS) in patients with PC of the lung who had undergone surgical resection.

RESULTS

A total of nine patients were enrolled in the study. All the patients were male and eight had a history of smoking. Eight tumors contained spindle cells and three contained giant cells. Mutations considered significant were found in eight of the nine patients: in TP53 in five patients, in MET in two patients, and in ALK, ERBB2, PIK3CA, APC, NF1, and CDKN2A in one patient each. No EGFR mutation was detected in our analysis. Co-mutations were detected in three patients: TP53 with MET and NF1, TP53 with ERBB2, and PIK3CA with CDKN2A.

CONCLUSIONS

TP53 mutations were detected most frequently in PC of the lung with NGS analysis. Different co-mutations were seen in several specimens.

KEY POINTS

Significant findings of the study This study demonstrates that mutations in the TP53 gene are frequently found and co-mutations are sometimes found in pleomorphic carcinoma of the lung using genomic profiling analysis. What this study adds Our results will help to analogize the genetic characteristics and potential target of molecular-targeted agents of pleomorphic carcinoma of the lung.

The current burden of cancer attributable to occupational exposures in Canada

Exposure to occupational carcinogens is often overlooked as a contributor to the burden of cancer. To estimate the proportion of cancer cases attributable to occupational exposure in Canada in 2011, exposure prevalence and levels of 44 carcinogens were informed by data from the Canadian carcinogen exposure surveillance project (CAREX Canada). These were used with Canadian Census (between 1961 and 2011) and Labour Force Survey (annual surveys between 1976 and 2013) data to estimate the number of workers ever exposed to occupational carcinogens. Risk estimates of the association between each carcinogen and cancer site were selected mainly from published literature reviews. Population attributable risks were estimated using Levin's equation and applied to the 2011 cancer statistics from the Canadian Cancer Registry. It is estimated that 15.5 million Canadians alive in 2011 were exposed, during at least one year between 1961 and 2001, to at least one carcinogen in the workplace. Overall, we estimated that in 2011, between 3.9% (95% CI: 3.1%-8.1%) and 4.2% (95% CI: 3.3%-8.7%) of all incident cases of cancer were due to occupational exposure, corresponding to lower and upper numbers of 7700-21,800 cases. Five of the cancer sites - mesothelioma, non-melanoma skin cancer, lung, female breast, and urinary bladder - account for a total of 7600 to 21,200 cancers attributable to occupational exposures such as solar radiation, asbestos, diesel engine exhaust, crystalline silica, and night shift work. Our study highlights cancer sites and occupational exposures that need recognition and efforts by all stakeholders to avoid preventable cancers in the future.

The crosstalk between trace elements with DNA damage response, repair, and oxidative stress in cancer

DNA damage response (DDR) is a regulatory system responsible for maintaining genome integrity and stability, which can sense and transduce DNA damage signals. The severity of damage appears to determine DDRs, which can include damage repair, cell-cycle arrest, and apoptosis. Furthermore, defective components in DNA damage and repair machinery are an underlying cause for the development and progression of various types of cancers. Increasing evidence indicates that there is an association between trace elements and DDR/repair mechanisms. In fact, trace elements seem to affect mediators of DDR. Besides, it has been revealed that oxidative stress (OS) and trace elements are associated with cancer development. In this review, we discuss the role of some critical trace elements in the risk of cancer. In addition, we provide a brief introduction on DDR and OS in cancer. Finally, we will further review the interactions between some important trace elements including selenium, zinc, chromium, cadmium, and arsenic, and DDR, and OS in cancer.

Cadmium exposure and risk of lung cancer: a meta-analysis of cohort and case-control studies among general and occupational populations

The association between cadmium exposure and risk of lung cancer is still unclear. We quantitatively reviewed the observational studies that investigated the association between cadmium exposure and lung cancer risk in both general and occupational populations published through April 2015. The final data set is comprised of three cohort studies in the general population totaling 22,551 participants (354 events) with a mean follow-up of 15 years, five occupational cohort studies including 4205 individuals (180 events) with an average follow-up of 31 years, and three occupational case-control studies including 4740 cases and 6268 controls. Comparing the highest to the lowest category of cadmium exposure, the weighted relative risk and 95% confidence interval of lung cancer in the general population was 1.42 (95% CI (0.91, 2.23)); the weighted risk estimates (95% CIs) of lung cancer in three occupational cohort studies and three case-control studies were 0.68 (95% CI (0.33, 1.41)) and 1.61 (95% CI (0.94, 2.75)), respectively. No linear association was found. When comparing participants exposed to cadmium with non-exposed based on available data, the association became statistically significant. According to findings from this meta-analysis, the possibility that cadmium exposure may increase risk of lung cancer cannot be completely ruled out in either general or occupational population.

The effects of heavy metals and their interactions with polycyclic aromatic hydrocarbons on the oxidative stress among coke-oven workers

Heavy metals and polycyclic aromatic hydrocarbons (PAHs) are predominate toxic constituents of particulate air pollution that may be related to the increased risk of cardiopulmonary events. We aim to investigate the effects of the toxic heavy metals (arsenic, As; cadmium, Cd; chromium, Cr; nickel, Ni; and lead, Pb), and their interactions with PAHs on oxidative stress among coke-oven workers. A total of 1333 male workers were recruited in this study. We determined their urinary levels of As, Cd, Cr, Ni, Pb, twelve PAH metabolites, 8-hydroxydeoxyguanosine (8-OHdG), and 8-iso-prostaglandin-F2α (8-iso-PGF2α). Multivariate linear regression models were used to analyze the effects of these metals and their interactions with PAHs on 8-OHdG and 8-iso-PGF2α levels. It was found that only urinary As and Ni showed marginal or significant positive linear dose-dependent effects on 8-OHdG in this study population, especially among smokers (β=0.103, P=0.073 and β=0.110, P=0.002, respectively). After stratifying all participants by the quartiles of ΣOH-PAH, all five metals showed linear association with 8-OHdG in the highest quartile subgroup (Q4) of ΣOH-PAHs. However, these five urinary metals showed significantly consistent linear associations with 8-iso-PGF2α in all subjects and each stratum. Urinary ΣOH-PAHs can significant modify the effects of heavy metals on oxidative stress, while co-exposure to both high levels of ΣOH-PAHs and heavy metals render the workers with highest 8-OHdG and 8-iso-PGF2α (all P(interaction)≤0.005). This study showed evidence on the interaction effects of heavy metals and PAHs on increasing the oxidative stress, and these results warrant further investigation in more longitudinal studies.

An expert-based job exposure matrix for large scale epidemiologic studies of primary hip and knee osteoarthritis: the Lower Body JEM

BACKGROUND

When conducting large scale epidemiologic studies, it is a challenge to obtain quantitative exposure estimates, which do not rely on self-report where estimates may be influenced by symptoms and knowledge of disease status. In this study we developed a job exposure matrix (JEM) for use in population studies of the work-relatedness of hip and knee osteoarthritis.

METHODS

Based on all 2227 occupational titles in the Danish version of the International Standard Classification of Occupations (D-ISCO 88), we constructed 121 job groups comprising occupational titles with expected homogeneous exposure patterns in addition to a minimally exposed job group, which was not included in the JEM. The job groups were allocated the mean value of five experts' ratings of daily duration (hours/day) of standing/walking, kneeling/squatting, and whole-body vibration as well as total load lifted (kg/day), and frequency of lifting loads weighing ≥20 kg (times/day). Weighted kappa statistics were used to evaluate inter-rater agreement on rankings of the job groups for four of these exposures (whole-body vibration could not be evaluated due to few exposed job groups). Two external experts checked the face validity of the rankings of the mean values.

RESULTS

A JEM was constructed and English ISCO codes were provided where possible. The experts' ratings showed fair to moderate agreement with respect to rankings of the job groups (mean weighted kappa values between 0.36 and 0.49). The external experts agreed on 586 of the 605 rankings.

CONCLUSION

The Lower Body JEM based on experts' ratings was established. Experts agreed on rankings of the job groups, and rankings based on mean values were in accordance with the opinion of external experts.

Heavy Metal Content in Thoracic Tissue Samples from Patients with and without NSCLC

Objectives. Environmental factors expose an individual to heavy metals that may stimulate cancer growth preclinically including non-small cell lung cancer (NSCLC) cells. Here, we examine the prevalence of four heavy metals present in postsurgical tissues from individuals with and without NSCLC. Materials and Methods. Thoracic tissue samples from two separate sample sets were analyzed for cadmium (Cd), arsenic (As), mercury (Hg), and lead (Pb) content. Results. In the first sample set, there was no significant measurable amount of Pb and Hg found in either NSCLC tissue or nonmalignant lung tissue samples. Cd was the most prevalent heavy metal and As was present in moderate amounts. In the second sample set, Cd was measurable across all tissue types taken from 28 NSCLC patients and significantly higher Cd was measurable in noncancer benign lung (n = 9). In the NSCLC samples, As was measurable in moderate amounts, while Hg and Pb amounts were negligible. Conclusion. Cd and As are present in lung tissues for patients with NSCLC. With existing preclinical evidence of their tumorigenecity, it is plausible that Cd and/or As may have an impact on NSCLC development. Additional studies examining the prevalence and association between smokers and nonsmokers are suggested.