Association between occupational lead exposure and immunotoxicity markers: A systematic review and meta-analysis

Recent evidences suggest the role of chronic lead (Pb) exposure in altering immunological parameters. Present study aimed to systematically review existing literature and synthesize quantitative evidence on the association between chronic Pb exposure and changes in immunological markers. Observational studies reporting immunological markers such as leukocyte derivative counts (CD3⁺, CD4⁺, CD8⁺, CD45⁺, CD56⁺, lymphocyte, and total leukocyte), cytokine, Immunoglobulin (Igs), C-reactive protein (CRP) among Pb-exposed and unexposed controls were systematically searched from PubMed, Scopus and Embase digital databases from inception to January 2021. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were adhered during systematic review. Mean differences in the immunological markers between Pb-exposed and control groups were pooled using random-effects model. The heterogeneity was assessed using Cochran-Q test and I² statistic. The review included forty studies reporting immunological markers in Pb-exposed and unexposed control groups. The occupational Pb-exposed group exhibited significantly higher BLL, impaired immunological markers, characterized by a marginal lowering in lymphocyte count, lymphocyte subsets (CD3⁺, CD4⁺, CD4⁺/CD8⁺ ratio), IFN-γ and IgG levels, while CD8⁺, IgM, IgA, IgE, and cytokines (IL-4, IL-6, IL-10, and TNF-α) exhibited a trend of higher values in comparison to the control group. Further, inflammatory marker viz., total leukocyte count was significantly higher among Pb-exposed. The included studies exhibited high levels of heterogeneity. In conclusion, Occupational Pb exposure alters the immunological markers such as the circulating cytokines and leukocyte counts. However, high-quality, multicentered studies are required to strengthen present observations and further understand the Pb's role on the immune system. Prospero Registration ID: CRD42021228252.

Hematological Indices of Patients with Retained Lead Pellets in the Craniomaxillofacial Region Following Gunshot Wounds

Background:

Acute and chronic environmental lead exposures are associated with alteration of hematological parameters. It is not known whether retained lead pellets have similar effects on hematological variables to environmental exposures.

Objective:

The objective of this study is to assess the effects of retained lead pellets on hematological indices in patients that sustained gunshot injuries to the craniomaxillofacial region.

Patients and Methods:

We examined individuals with retained pellets following gunshot injuries to the craniomaxillofacial region using a prospective cohort study design in a tertiary health center, Nigeria.

Results:

A total of 54 male individuals (27 in each group) enlisted in the study. The age of the patients and control subjects ranges from 20 to 58 years, with a mean age of 40.3 years. The mean blood lead levels (BLLs) of the exposed group were lower than the unexposed (P = 0.03). There were statistically significant (P < 0.05) variations in the hematological indices between the exposed and the unexposed groups. There was a significant association (P < 0.001) between the hematological indices assessed and the BLLs, number of retained pellets, and duration of retention. No basophilic stippling was observed in the red cell morphology of the individuals.

Conclusion:

Retained lead pellets cause significant elevated BLL and associated higher hematocrit, hemoglobin concentration, and mean cell volume.