Effects of environmental and occupational lead toxicity and its association with iron metabolism.

BACKGROUND: Discrepancies are present in the findings from clinical trials evaluating a physiological role of iron status in the lead-exposed population. OBJECTIVE: The purpose of this article was to summarize the current understanding of cellular mechanisms of lead toxicity and present a comprehensive review of existing clinical trials related to associations of lead poisoning and iron status. Although an association of iron metabolism pathways that are affected by lead intoxication has been studied, there are still aspects that remain to be elucidated. The existence of additional Pb uptake pathways besides DMT1 transporter-mediated is postulated to non-specifically regulate lead absorption. METHODS: Authors performed a systematic search of PubMed, EMBASE® and Web of Science databases to identify studies that reported an association between health risks of non-organic lead that are associated with iron status markers as possible effect modifier. RESULTS: There were 58 studies that met the pre-defined inclusion criteria for the systematic review. There is a strong body of evidence supporting the hypothesis that alleviated blood lead level can be correlated with a reduced body iron store and increasing the risk of anemia. This association is of a high significance in cases of a young adolescent, weaker in groups of older children and often without a statistical significance in adults. DISCUSSION: Discrepancies in the observations may result from different specificities of lead absorption pathways in children and adults, as well as the power of the statistical tests in varying population sizes. It may be assumed that the extent of iron deficits coupled together with source, timing, and severity of lead exposure, significantly influence the correlation between these factors. Some of the intervention programs of counteracting lead poisoning by iron supplementation proved to be effective and may be a promising prevention strategy for the exposed population.

Relationship between lead absorption and iron status and its association with oxidative stress markers in lead-exposed workers.

BACKGROUND: The emission of lead (Pb) occurring during the extraction, processing and industrial applications of this element remains a significant environmental risk factor. The absorbability of lead in humans is strongly associated with the general health status of exposed individuals. Existing mineral deficiencies are considered being a predisposition to an increased Pb uptake. Both, iron deficiency and lead poisoning are the major causative factors responsible for the prevalence of anemia within the vulnerable population, especially in children. Although some of the intervention programs of counteracting lead poisoning by iron supplementation proved to be effective in the Pb-exposed population, the exact mechanisms of this interaction still require further studies. The objective of the presented study was to examine the association of iron level on oxidative stress measures and its effects on the severity of lead toxicity in the exposed population. METHODS: The analyzed population consisted of 270 male workers from the lead-zinc smelter. The studied population was divided into two sub-groups based on the serum iron concentration: low iron level group (L-Fe; Fe < median value) and high iron level group (H-Fe; Fe > median value). Measured traits comprised of blood lead (PbB), serum Fe and zinc protoporphyrin (ZPP) levels as well as a blood count and oxidative stress markers. RESULTS: No significant correlation between serum iron concentration and PbB in the tested cohort was found. On the contrary, the analysis of ZPP levels (long-term marker related to a hematologic toxic effect of Pb) within the subgroups differing in serum Fe level shown that ZPP was 12.3 % lower (p = 0.043) in subjects classified within the H-Fe group. A positive correlation of serum Fe and total antioxidant capacity (TAC) was found (R = 0.1999). The conducted 3-D PCA analysis showed that individuals classified within the H-Fe group were characterized by the co-occurrence of higher Fe levels, lower ZPP, and higher TAC value. CONCLUSION: These results support the existing evidence providing that maintaining the optimal status of Fe may play a significant role in preventing the lead poisoning and alleviating harmful effects of Pb on the oxidative balance in humans.