Heavy Metals in Human Lung Tissue: Sources, Concentrations, and Health Implications – A Systematic Review

Heavy metals, including chromium (Cr), cadmium (Cd), lead (Pb), nickel (Ni), and arsenic (As), are pervasive environmental pollutants that accumulate in human lung tissue through inhalation from sources such as smoking, industrial emissions, and ambient air pollution. This systematic review synthesizes evidence on metal concentrations in lung tissues across diverse human populations and their associations with respiratory diseases. To systematically review and synthesize data from studies conducted between 1975 and 2025 on the concentrations of heavy metals in human lung tissues, their sources of exposure, and associated health implications. Adhering to PRISMA guidelines, a comprehensive search was conducted across databases including PubMed, Scopus, Web of Science, and Embase, utilizing keywords related to heavy metals and lung tissue. Inclusion criteria encompassed human studies reporting quantifiable metal concentrations and health outcomes. Two independent reviewers screened titles, abstracts, and full texts, with data extracted on population characteristics, metal concentrations, key findings, and study quality. From an initial pool of 1,256 records, 39 studies were included after excluding duplicates, animal studies, and those not meeting quality thresholds (32 human epidemiological/autopsy studies and 7 in vitro studies using human cell lines). Elevated levels of Cd and Pb were strongly associated with smoking and impaired lung function, including chronic obstructive pulmonary disease (COPD) with a pooled odds ratio from meta-analysis of 2.85 (95% CI: 1.34–6.10) for Cd (highest vs. lowest exposure quartile) and 1.73 (95% CI: 1.37–2.18) for Pb. Chromium and Ni exhibited significant correlations with occupational exposures and inflammatory responses. Combined metal exposures demonstrated amplified health risks.
The accumulation of heavy metals in lung tissue contributes significantly to respiratory morbidity. Mitigation strategies, including regulatory measures and smoking cessation initiatives, are imperative. Further longitudinal research on the effects of mixed-metal exposures is warranted.

Heavy metals, Lung tissue, Concentrations, Respiratory diseases, Systematic review

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