Blood Lead, Systemic Inflammation, and Blood Pressure: Exploring Associations and Mediation Effects in Workers Exposed to Lead

Inflammation in Metal-Induced Neurological Disorders and Neurodegenerative Diseases

Essential metals play critical roles in maintaining human health as they participate in various physiological activities. Nonetheless, both excessive accumulation and deficiency of these metals may result in neurotoxicity secondary to neuroinflammation and the activation of microglia and astrocytes. Activation of these cells can promote the release of pro-inflammatory cytokines. It is well known that neuroinflammation plays a critical role in metal-induced neurotoxicity as well as the development of neurological disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Initially seen as a defense mechanism, persistent inflammatory responses are now considered harmful. Astrocytes and microglia are key regulators of neuroinflammation in the central nervous system, and their excessive activation may induce sustained neuroinflammation. Therefore, in this review, we aim to emphasize the important role and molecular mechanisms underlying metal-induced neurotoxicity. Our objective is to raise the awareness on metal-induced neuroinflammation in neurological disorders. However, it is not only just neuroinflammation that different metals could induce; they can also cause harm to the nervous system through oxidative stress, apoptosis, and autophagy, to name a few. The primary pathophysiological mechanism by which these metals induce neurological disorders remains to be determined. In addition, given the various pathways through which individuals are exposed to metals, it is necessary to also consider the effects of co-exposure to multiple metals on neurological disorders.

Blood Lead Mediates the Relationship between Biological Aging and Hypertension: Based on the NHANES Database

Hypertension remains a major global public health crisis due to various contributing factors, such as age and environmental exposures. This study delves into exploring the intricate association between biological aging, blood lead levels, and hypertension, along with examining the mediating role of blood lead levels in the relationship between biological aging and hypertension. We analyzed data from two cycles of the NHANES, encompassing 4473 individuals aged 18 years and older. Our findings indicate that biological aging potentially escalates the risk of hypertension and the incidences of systolic blood pressure (SBP) and diastolic blood pressure (DBP) abnormalities. Utilizing weighted quantile sum (WQS) and quantile g-computation (QGC) model analyses, we observed that exposure to heavy metal mixtures, particularly lead, may elevate the likelihood of hypertension, SBP, and DBP abnormalities. Further mediation analysis revealed that lead significantly mediated the relationship between biological aging and hypertension and between biological aging and SBP abnormalities, accounting for 64% (95% CI, 49% to 89%) and 64% (95% CI, 44% to 88%) of the effects, respectively. These outcomes emphasize the criticality of implementing environmental health measures.

Identification of potential food sources affecting blood lead levels and their health hazards (CVD, respiratory diseases, cancer)

Environmental lead exposure is a well-known and significant public health concern. In areas with low lead exposure, comprehensive and detailed research and validation are needed to eliminate the adverse effects of environmental lead exposure. This study aims to understand the possible food pathways of environmental lead exposure by exploring the contribution of food to blood lead and the mediating effect of blood lead in the occurrence of diseases. Similarly, as lead is a heavy metal pollutant with good research foundation, fine analysis of lead in this period can also be a reference for other unknown pollutants. In this cross-sectional study of 1162 peoples, the data are taken from National Health and Nutrition Examination Survey (NANHES) 2015-2016, we grouped the population according to the median blood lead level (0.038 μmol/L) to screen the variables adjusted by the model. we grouped foods by code and used a generalized additive mixed model (GAMM) to study their relationship with blood lead levels, a correlation has been found between egg mixtures (p = 0.007) and legumes (p = 0.041) consumption and blood lead levels. We analyzed how metabolic status, exercise, and macronutrient intake modulate the impact of certain foods on blood lead levels to infer its possible process. To verify whether adverse effects are caused by lead, we explored the mediating effect of blood lead on the relationship between food intake and disease [cardiovascular diseases (CVD), respiratory diseases, cancer], however, no statistically significant mediating effect was found. Overall, environmental lead exposure through food still affects blood lead levels, but it has not led to adverse outcomes in blood, respiratory system, or cancers Under conditions where lead exposure levels were equivalent to those in the study (blood lead levels， mean = 0.052 μmol/L, standard deviation = 0.048 μmol/L, median = 0.038 μmol/L, min = 0.002 μmol/L, max = 0.904 μmol/L, skewness = 6.543, kurtosis = 89.391).

The Relationships Between Blood Pb Levels and Blood Pressure Among Lead-Exposed Workers in China: A Repeated-Measure Study

OBJECTIVES

To explore the differences in the increase of systolic blood pressure (SBP) and diastolic blood pressure (DBP) in 3 consecutive years among lead (Pb) workers.

METHODS

Four hundred forty-eight Pb workers were enrolled in this repeated-measure study. Blood Pb, SBP, and DBP were measured in 2015 to 2017. Repeated measure of analysis of variance was used to compare the differences in the increase of SBP and DBP.

RESULTS

The mean SBP values were 124.0/125.5/126.9 mm Hg, and the mean DBP values were 75.4/77.4/77.8 mm Hg from 2015 to 2017. The differences in the increase of SBP and DBP were 2.94/2.42 mm Hg during the 3-year period. The average annual increase of SBP or DBP showed an upward trend in different Pb dose groups ( F = 4.904, P = 0.002; F = 3.612, P = 0.013).

CONCLUSIONS

Lead exposure caused average annual increases in SBP and DBP with 0.98 and 0.81 mm Hg, which provided basic data for health surveillance.

The association of lead exposure with blood pressure and hypertension: a mediation analyses of estimated glomerular filtration rate

The link between lead and blood pressure was debatable, and whether it was mediated by renal function was unknown. The purpose was to investigate the relationship between blood lead concentrations and blood pressure and hypertension, as well as the mediating role of estimated glomerular filtration rate (eGFR) in this relationship. Participants aged 18 were recruited from the National Health and Nutrition Examination Survey (1999-2014) and provided with lead and blood pressure data. Multivariate linear and logistic regression, stratification, interaction tests, and a restricted cubic spline curve were used to assess the association of blood lead with systolic/diastolic blood pressure (SBP/DBP) and hypertension, and mediation effect analysis was used to investigate the role of eGFR in this relationship. A total of 20,073 subjects were enrolled, and among them, 9837 (49.01%) were male and 7800 (38.86%) were hypertensive patients. Multivariate linear and logistic regression analysis showed that blood lead levels were significantly associated with SBP (β = 3.14, 95%CI: 2.03, 4.25; P < 0.001), DBP (β = 3.50, 95%CI: 2.69, 4.30; P < 0.001), and hypertension (OR = 1.29, 95%CI: 1.09, 1.52; P = 0.0026). In comparison to the lowest blood lead quartile, the highest lead group was significantly associated with SBP (= 2.55, 95%CI: 1.66, 3.44; P = 0.0001), DBP (= 2.60, 95%CI: 1.95, 3.24; P = 0.0001), and hypertension (OR = 1.26, 95%CI: 1.10, 1.45; P = 0.0007). Mediation analysis showed that the proportion of blood lead mediated for SBP, DBP, and hypertension was 3.56% (95%CI: 0.42%, 7.96%; P = 0.0320), 6.21% (95%CI: 4.02%, 9.32%; P < 0.0001), and 17.39% (95%CI: 9.34%, 42.71%; P < 0.0001), respectively. Adjusted restricted cubic spline curves presented a non-linear correlation of blood lead levels with DBP (P-non-linearity < 0.001), linear with SBP (P-non-linearity = 0.203), and hypertension (P-non-linearity = 0.763). Our findings demonstrated that blood lead levels were non-linear with DBP, but linear with SBP and hypertension, and this relationship was mediated by eGFR.

Co-exposure to priority-controlled metals mixture and blood pressure in Chinese children from two panel studies

Metals may affect adversely cardiovascular system, but epidemiological evidence on the associations of priority-controlled metals including antimony (Sb), arsenic (As), cadmium, lead, and thallium with children's blood pressure (BP) was scarce and inconsistent. We conducted two panel studies with 3 surveys across 3 seasons among 144 and 142 children aged 4-12 years in Guangzhou and Weinan, respectively. During each seasonal survey, urine samples were collected for 4 consecutive days and BP was measured on the 4th day. We obtained 786 BP values and urinary metals measurements at least once within 4 days, while 773, 596, 612, and 754 urinary metals measurements were effective on the health examination day (Lag 0), and the 1^st, 2^nd, and 3^rd day preceding BP measurement (Lag 1, lag 2 and lag 3), respectively. We used linear mixed-effect models, generalized estimating equations and multiple informant models to assess the associations of individual metal at each lag day and accumulated lag day (4 days averaged, lag 0-3) with BP and hypertension, and Bayesian Kernel Machine Regression to evaluate the relations of metals mixture at lag 0-3 and BP outcomes. We found Sb was positively and consistently related to systolic BP (SBP), mean arterial pressure (MAP), and odds of having hypertension within 4 days, which were the strongest at lag 0 and declined over time. And such relationships at lag 0-3 showed in a dose-response manner. Meanwhile, Sb was the only contributor to the relations of mixture with SBP, MAP, and odds of having hypertension. Also, synergistic interaction between Sb and As was significant. In addition, modification effect of passive smoking status on the association of Sb and SBP was more evident in passive smokers. Accordingly, urinary Sb was consistently and dose-responsively associated with increased BP and hypertension, of which Sb was the major contributor among children.