Blood lead as a cardiovascular risk factor

Contaminant Metals and Cardiovascular Health

A growing body of research has begun to link exposure to environmental contaminants, such as heavy metals, with a variety of negative health outcomes. In this paper, we sought to review the current research describing the impact of certain common contaminant metals on cardiovascular (CV) health. We reviewed ten metals: lead, barium, nickel, chromium, cadmium, arsenic, mercury, selenium, zinc, and copper. After a literature review, we briefly summarized the routes of environmental exposure, pathophysiological mechanisms, CV health impacts, and exposure prevention and/or mitigation strategies for each metal. The resulting article discloses a broad spectrum of pathological significance, from relatively benign substances with little to no described effects on CV health, such as chromium and selenium, to substances with a wide-ranging and relatively severe spectrum of CV pathologies, such as arsenic, cadmium, and lead. It is our hope that this article will provide clinicians with a practical overview of the impact of these common environmental contaminants on CV health as well as highlight areas that require further investigation to better understand how these metals impact the incidence and progression of CV diseases.

Association of low-level lead exposure with all-cause and cardiovascular disease mortality in US adults with hypertension: evidence from the National Health and Nutrition Examination Survey 2003-2010

BACKGROUND

To explore the association of low-level lead exposure with all-cause mortality and cardiovascular disease (CVD) mortality among hypertensive patients.

METHODS

This cohort study enrolled 6453 adults with hypertension from the National Health and Nutrition Examination Survey 2003-2010 and followed mortality information through December 31, 2019. The baseline population were divided into four groups based on quartiles of blood lead levels (Q1: < 1.2 μg/dL, Q2: 1.2-1.6 μg/dL, Q3: 1.7-2.4 μg/dL, Q4: 2.5-4.9 μg/dL). The correlation of blood lead levels to mortality was investigated by Kaplan-Meier survival curves, restricted cubic spline (RCS), proportional hazard regression model, and subgroup analysis.

RESULTS

During a median follow-up period of 136 (interquartile range 113, 164) months, a total of 1943 (30.1%) deaths were documented, among which 553 (28.5%) were due to CVD. Blood lead showed a linear dose-response relationship with all-cause and CVD mortality. After adequate adjusting for confounders, the risk of all-cause death rose by 23% for each unit increase in continuous variable blood lead (hazard ratio (HR): 1.23; 95% confidence interval (CI):1.16-1.30). When blood lead was a quartile group variable, participants in the Q 4 group had a 73% higher risk of death than those in the Q 1 group (HR:1.73; 95% CI: 1.43-2.10; P for trend < 0.001). The association for CVD mortality was analogous. The concordant results were achieved in the subgroup analysis.

CONCLUSION

Elevated blood lead levels were strongly associated with an increased all-cause and CVD mortality in adults with hypertension, even at the reference range of blood lead.

Association of Endocrine-Disrupting Chemicals with All-Cause and Cause-Specific Mortality in the U.S.: A Prospective Cohort Study

Wide exposure to endocrine-disrupting chemicals (EDCs) poses a great risk on human health. However, few large-scale cohort studies have comprehensively estimated the association between EDCs exposure and mortality risk. This study aimed to investigate the association of urinary EDCs exposure with mortality risk and quantify attributable mortality and economic loss. Multivariable Cox proportional hazards regression models were performed to investigate the association of 38 representative EDCs exposure with mortality risk in the National Health and Nutrition Examination Survey (NHANES). During a median follow-up of 7.7 years, 47,279 individuals were enrolled. All-cause mortality was positively associated with 1-hydroxynaphthalene, 2-hydroxynaphthalene, cadmium, antimony, cobalt, and monobenzyl phthalate. Cancer mortality was positively associated with cadmium. Cardiovascular disease (CVD) mortality was positively associated with 1-hydroxynaphthalene, 2-hydroxynaphthalene, and 2-hydroxyfluorene. Nonlinear U-shaped relationships were found between all-cause mortality and cadmium and cobalt, which was also identified between 2-hydroxyfluorene and CVD mortality. J-shaped association of cadmium exposure with cancer mortality was also determined. EDCs exposure may cause 56.52% of total deaths (1,528,500 deaths) and around 1,897 billion USD in economic costs. Exposure to certain phthalates, polycyclic aromatic hydrocarbons, phytoestrogens, or toxic metals, even at substantially low levels, is significantly associated with mortality and induces high economic costs.

Lower Extremity Peripheral Artery Disease: Contemporary Epidemiology, Management Gaps, and Future Directions: A Scientific Statement From the American Heart Association

Lower extremity peripheral artery disease (PAD) affects >230 million adults worldwide and is associated with increased risk of various adverse clinical outcomes (other cardiovascular diseases such as coronary heart disease and stroke and leg outcomes such as amputation). Despite its prevalence and clinical importance, PAD has been historically underappreciated by health care professionals and patients. This underappreciation seems multifactorial (eg, limited availability of the first-line diagnostic test, the ankle-brachial index, in clinics; incorrect perceptions that a leg vascular disease is not fatal and that the diagnosis of PAD would not necessarily change clinical practice). In the past several years, a body of evidence has indicated that these perceptions are incorrect. Several studies have consistently demonstrated that many patients with PAD are not receiving evidence-based therapies. Thus, this scientific statement provides an update for health care professionals regarding contemporary epidemiology (eg, prevalence, temporal trends, risk factors, and complications) of PAD, the present status of diagnosis (physiological tests and imaging modalities), and the major gaps in the management of PAD (eg, medications, exercise therapy, and revascularization). The statement also lists key gaps in research, clinical practice, and implementation related to PAD. Orchestrated efforts among different parties (eg, health care providers, researchers, expert organizations, and health care organizations) will be needed to increase the awareness and understanding of PAD and improve the diagnostic approaches, management, and prognosis of PAD.

Associations between Blood Lead Levels and Coronary Artery Stenosis Measured Using Coronary Computed Tomography Angiography

BACKGROUND

Lead exposure is a risk factor for increased blood pressure and cardiovascular disease, even when blood lead levels (BLLs) are within the normal range.

OBJECTIVE

This study aimed to investigate the association between BLL and coronary artery stenosis (CAS) in asymptomatic adults using 128-slice dual-source coronary computed tomography (CT) angiography.

METHODS

We analyzed medical records data from 2,193 adults (1,461 men and 732 women) who elected to complete a screening health examination, coronary CT angiography, and BLL measurement during 2011-2018 and had no history of CAS symptoms, cardiovascular disease, or occupational exposure to lead. Logistic regression models were used to estimate associations between moderate-to-severe CAS (≥25% stenosis) and a 1-μg/dL increase in blood lead, with and without adjustment for age, sex, hypertension, diabetes mellitus, dyslipidemia, body mass index, regular exercise, smoking status, and alcohol drinking.

RESULTS

BLLs ranged from 0.12 to 10.14μg/dL, with an arithmetic mean of 2.71±1.26μg/dL. The arithmetic mean was higher for men than for women (2.98±1.26μg/dL vs. 2.18±1.08μg/dL, p<0.001) and higher in the moderate-to-severe CAS group than in the no-CAS or <25% stenosis group (3.02±1.44μg/dL vs. 2.67±1.23μg/dL, p<0.001). Moderate-to-severe CAS was significantly associated with BLL before and after adjustment, with an adjusted odds ratio for a 1-μg/dL increase in BLL of 1.14 (95% CI: 1.02, 1.26), p=0.017.

CONCLUSIONS

BLL was positively associated with the prevalence of moderate-to-severe CAS in Korean adults who completed an elective screening examination for early cardiovascular disease, 94% of whom had a BLL of <5μg/dL. More efforts and a strict health policy are needed to further reduce BLLs in the general population. https://doi.org/10.1289/EHP7351.

Blood lead levels in relation to smoking and chronic obstructive pulmonary disease (COPD): a study from Korean National Health and Nutrition Examination Survey (KNHANES)

Background

Lead exposure is a resurgent environmental issue globally. Smoking can be a source of lead exposure, although the majority of lead poisonings originate from workplace exposures. However, no study has been undertaken concerning the blood lead levels based on the chronic obstructive pulmonary disease (COPD), smoking status, and other risk factors of COPD. This cross-sectional study was conducted to investigate the blood lead levels according to COPD and clinical variables associated with COPD.

Methods

Data (total number =53,829) were collected from the Korean National Health and Nutrition Examination Survey (IV in 2008 and 2009, V in 2010–2012, and VI in 2013). Multivariable linear regression analyses were performed to determine variables associated with elevated blood lead levels.

Results

Univariate regression analysis showed that male sex, older age, smoking, occupation level, income level, education level, and presence of COPD were related to higher blood lead levels, whereas the other co-morbidities including diabetes, hypertension, cerebral stroke, osteoporosis, asthma, and depression were not related (P<0.05). Multivariable regression analysis demonstrated that older age, male sex, smoking, occupation, and education level were independently associated with higher blood lead levels (P<0.05).

Conclusions

Smoking status, occupation, and education level along with old age and male sex were independently associated with higher blood lead levels; however, COPD was not after adjustment of all confounding factors.

Environmental heavy metals and cardiovascular diseases: Status and future direction

Cardiovascular disease (CVD) and environmental degradation are leading global health problems of our time. Recent studies have linked exposure to heavy metals to the risks of CVD and diabetes, particularly in populations from low- and middle-income countries, where concomitant rapid development occurs. In this review, we 1) assessed the totality, quantity, and consistency of the available epidemiological studies, linking heavy metal exposures to the risk of CVD (including stroke and coronary heart disease); 2) discussed the potential biological mechanisms underlying some tantalizing observations in humans; and 3) identified gaps in our knowledge base that must be investigated in future work. An accumulating body of evidence from both experimental and observational studies implicates exposure to heavy metals, in a dose-response manner, in the increased risk of CVD. The limitations of most existing studies include insufficient statistical power, lack of comprehensive assessment of exposure, and cross-sectional design. Given the widespread exposure to heavy metals, an urgent need has emerged to investigate these putative associations of environmental exposures, either independently or jointly, with incident CVD outcomes prospectively in well-characterized cohorts of diverse populations, and to determine potential strategies to prevent and control the impacts of heavy metal exposure on the cardiometabolic health outcomes of individuals and populations.

Blood Lead Levels and Risk of Atherosclerosis in the Carotid Artery: Results from a Swedish Cohort

BACKGROUND

Lead exposure has been associated with increased incidence of adverse clinical cardiovascular outcomes. Atherosclerosis has been suggested as one of the underlying mechanisms, and findings from experimental studies support this, but human data are scarce.

OBJECTIVES

Our objective was to determine the association between environmental lead exposure based on blood lead (B-Pb) concentrations and the prevalence of atherosclerotic plaque in the carotid artery.

METHODS

We used cross-sectional data from the Malmö Diet and Cancer Study cardiovascular cohort (MDCS-CC; recruitment in 1991-1994) covering 4,172 middle-aged men and women. B-Pb at baseline, measured by inductively coupled plasma mass spectrometry, was used as the exposure biomarker. The presence of atherosclerotic plaque in the carotid artery was determined by B-mode ultrasonography. We used logistic regression to estimate odds ratios (ORs) for prevalence of plaque in the carotid artery according to B-Pb quartiles.

RESULTS

The median B-Pb was 25μg/L (range: 1.5-258), and 36% of the cohort had any atherosclerotic plaque. After controlling for confounders and known cardiovascular risk factors, the OR for prevalence of plaque in the highest quartile (Q4) of B-Pb compared with the lowest quartile (Q1) was 1.35 (95% CI: 1.09, 1.66) in the total group, 1.58 (95% CI: 1.20, 2.08) among women, and 1.18 (95% CI: 0.83, 1.69) among men. Among women, associations were limited to those who were postmenopausal [OR for Q4 vs. Q1=1.72 (95% CI: 1.26, 2.34) vs. OR=0.96 (95% CI: 0.49, 1.89 in premenopausal women)]. Associations were weak and nonsignificant in never-smokers [OR for Q4 vs. Q1=1.14 (95% CI: 0.81, 1.61)].

DISCUSSION

Our study shows an association between B-Pb concentrations and occurrence of atherosclerotic plaque in the carotid artery, adding evidence for an underlying pro-atherogenic role of lead in cardiovascular disease. Associations appeared to be limited to postmenopausal (vs. premenopausal) women. https://doi.org/10.1289/EHP5057.

Environmental toxic metal contaminants and risk of cardiovascular disease: systematic review and meta-analysis

OBJECTIVE

To conduct a systematic review and meta-analysis of epidemiological studies investigating the association of arsenic, lead, cadmium, mercury, and copper with cardiovascular disease.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed, Embase, and Web of Science searched up to December 2017.

REVIEW METHODS

Studies reporting risk estimates for total cardiovascular disease, coronary heart disease, and stroke for levels of arsenic, lead, cadmium, mercury, or copper were included. Two investigators independently extracted information on study characteristics and outcomes in accordance with PRISMA and MOOSE guidelines. Relative risks were standardised to a common scale and pooled across studies for each marker using random effects meta-analyses.

RESULTS

The review identified 37 unique studies comprising 348 259 non-overlapping participants, with 13 033 coronary heart disease, 4205 stroke, and 15 274 cardiovascular disease outcomes in aggregate. Comparing top versus bottom thirds of baseline levels, pooled relative risks for arsenic and lead were 1.30 (95% confidence interval 1.04 to 1.63) and 1.43 (1.16 to 1.76) for cardiovascular disease, 1.23 (1.04 to 1.45) and 1.85 (1.27 to 2.69) for coronary heart disease, and 1.15 (0.92 to 1.43) and 1.63 (1.14 to 2.34) for stroke. Relative risks for cadmium and copper were 1.33 (1.09 to 1.64) and 1.81 (1.05 to 3.11) for cardiovascular disease, 1.29 (0.98 to 1.71) and 2.22 (1.31 to 3.74) for coronary heart disease, and 1.72 (1.29 to 2.28) and 1.29 (0.77 to 2.17) for stroke. Mercury had no distinctive association with cardiovascular outcomes. There was a linear dose-response relation for arsenic, lead, and cadmium with cardiovascular disease outcomes.

CONCLUSION

Exposure to arsenic, lead, cadmium, and copper is associated with an increased risk of cardiovascular disease and coronary heart disease. Mercury is not associated with cardiovascular risk. These findings reinforce the importance of environmental toxic metals in cardiovascular risk, beyond the roles of conventional behavioural risk factors.

Association between heavy metal levels and acute ischemic stroke

Background

Few studies have examined the relationship between the amounts of heavy metal and stroke incidence. The aim of this study was to explore the relationship between levels of heavy metals, including Pb, Hg, As, and Cd, in patients with acute ischemic stroke (AIS).

Methods

We selected patients with first-ever AIS onset within 1 week as our study group. Healthy controls were participants without a history of stroke or chronic disease, except hypertension. The serum levels of Pb, Hg, As, and Cd in participants in the experimental and control groups were determined. All participants received a 1-g infusion of edetate calcium disodium (EDTA). Urine specimens were collected for 24 h after EDTA infusion and measured for heavy metal levels.

Results

In total, 33 patients with AIS and 39 healthy controls were enrolled in this study. The major findings were as follows: (1) The stroke group had a significantly lower level of serum Hg (6.4 ± 4.3 μg/L vs. 9.8 ± 7.0 μg/L, P = 0.032, OR = 0.90, 95% CI = 0.81–0.99) and a lower level of urine Hg (0.7 ± 0.7 μg/L vs. 1.2 ± 0.6 μg/L, P = 0.006, OR = 0.27, 95% CI = 0.11–0.68) than the control group. (2) No significant difference in serum Pb (S-Pb), As (S-As), and Cd (S-Cd) levels and urine Pb (U-Pb), As (U-As) and Cd (U-Cd) levels was observed in either group.

Conclusions

Our study found low levels of serum and urine Hg in first-ever patients with AIS, providing new evidence of dysregulated heavy metals in patients with AIS.

Electronic supplementary material

The online version of this article (10.1186/s12929-018-0446-0) contains supplementary material, which is available to authorized users.

ADC, Camargo AEI, Urbano MR, Mesas AE, Paoliello MMB. Association between blood lead and blood pressure: a population-based study in Brazilian adults

BACKGROUND

Environmental lead exposure among adults may increase blood pressure and elevate the risk of hypertension. The availability of data on blood lead levels (BLL) in adult Brazilian population is scarce and population-based studies are important for screening the population exposure and also to evaluate associations with adverse health effects. The goal of this study was to examine the association of BLL with blood pressure and hypertension in a population-based study in a city in Southern Brazil.

METHODS

A total of 948 adults, aged 40 years or older, were randomly selected. Information on socioeconomic, dietary, lifestyle and occupational background was obtained by orally administered household interviews. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured according to the guidelines VI Brazilian Guidelines on Hypertension. BLL were measured by inductively coupled plasma mass spectrometry technique. Multiple linear and logistic regression models were performed to evaluate associations of BLL with SBP and DBP, and with the chance of hypertension and of elevated SBP and DBP.

RESULTS

The geometric mean of BLL was 1.97 μg/dL (95%CI:1.90-2.04 μg/dL). After multivariable adjustment, participants in the quartile 4 of blood lead presented 0.06 mm/Hg (95%CI, 0.04-0.09) average difference in DBP comparing with those in quartile 1. Participants in the 90th percentile of blood lead distribution had 0.07 mmHg (95% CI, 0.03 to 0.11) higher DBP compared with those participants in the 10th percentile of blood lead. The adjusted OR for hypertension was 2.54 (95% CI, 1.17-5.53), comparing the highest to the lowest blood lead quartiles. Compared with participants in the 10th percentile of blood lead, participants in the 90th percentile presented higher OR for hypertension (OR: 2.77; 95% CI, 1.41 to 5.46).

CONCLUSION

At low concentrations, BLL were positively associated with DBP and with the odds for hypertension in adults aged 40 or older. It is important to enforce lead exposure monitoring and the enactment of regulatory laws to prevent lead contamination in urban settings.

Association of Blood Pressure with Exposure to Lead and Cadmium: Analysis of Data from the 2008-2013 Korean National Health and Nutrition Examination Survey

We examined the association of blood pressure with blood levels of cadmium, lead, and their combination in a representative sample of adults from South Korea (Korean National Health and Nutrition Examination Survey, 2008-2013). This cross-sectional study enrolled subjects who were at least 19 years-old, completed a health examination survey, and had blood measurements of lead and cadmium. We estimated the adjusted mean differences in diastolic and systolic blood pressure associated with doubling of blood lead and cadmium by regression of blood pressure against log₂-transformed blood metals and their tertiles after covariate adjustment. Adjusted odds ratios for hypertension and prehypertension were calculated for log₂-transformed blood levels of lead and cadmium and their tertiles. In the general population of Korea, blood lead level was associated with increased BP and risk of hypertension. Blood cadmium levels had a stronger association with elevated blood pressure and risk of hypertension than blood lead levels, and these associations remained significant after statistical adjustment for blood lead. The combination of blood lead and cadmium was more strongly associated with elevated blood pressure than exposure to each individual metal. In females, there was a stronger relationship between blood pressure and blood levels of these metals by analyzing interaction model. After adjustment for confounding factors, there were significant associations of blood pressure with the level of blood lead, cadmium, and their combination in adults from South Korea.

Clinical manifestations of lead workers of Mangalore, India

Objective: To correlate blood lead levels and clinical manifestations. Participants: Battery workers and painters (occupationally exposed to lead in and around Mangalore, India) and occupationally unexposed controls. Main outcome measures: We measured the blood lead levels by anodic stripping voltammetry, and a clinical examination was carried out on all participants. Results: There was a statistically significant difference between the lead-exposed group and controls with respect to clinical manifestations. The prominent findings among the lead-exposed group were fatigue, abdominal colic, abdominal discomfort, backache, muscular exhaustability, myalgia and paresthesia, at a blood lead level ranging from 0.4 to 116.6 μg/dL. Conclusions: Such a study on battery workers and painters has not been reported in India. Several attempts have been made over the years to relate blood lead levels to adverse health effects. It was not possible to determine a precise blood lead level below which symptoms never occur or a blood lead level at which symptoms are always reported. Toxicology and Industrial Health 2006; 22: 405-413.

Serum Levels of Trace Elements in Patients with Testicular Cancers

INTRODUCTION

Trace elements are primary components of biological structures; however, they can be toxic when their concentrations are higher than those needed for biological functions.

MATERIALS AND METHODS

In the present study serum levels of trace elements were measured in 30 patients (mean age was 26.9±11.2 years) newly diagnosed with germ cell testicular cancer and 32 healthy volunteers (mean age: 27.4±10.8) by using furnace atomic absorption spectrophotometer. Serum samples were stored at-20ºC until assays.

RESULTS

In patients with germ cell testicular cancer, the diagnosis was seminoma in 15, mix germ cell tumor in 7, embryonal carcinoma in 4, yolk sac tumor in 2 and teratoma in 2 patients. There was stage I testicular tumor in 19 patients (63.3%) while stage II in 6 patients (20.0%), stage IIIA in 4 patients (13.3%) and stage IIIC in one patient (3.4%). It was found that serum Co, Cu, Mg and Pb levels were increased (p<0.05), whereas Fe, Mn, and Zn levels were decreased in patients with testicular cancer (p<0.05).

CONCLUSIONS

These alterations may be important in the pathogenesis of testicular cancers; however, further prospective studies are needed to identify the relationship between testicular cancer and trace elements.

Blood Lead Levels and Cause-Specific Mortality of Inorganic Lead-Exposed Workers in South Korea

The objective of this study was to identify the association of blood lead level (BLL) with mortality in inorganic lead-exposed workers of South Korea. A cohort was compiled comprising 81,067 inorganic lead exposed workers working between January 1, 2000, and December 31, 2004. This cohort was merged with the Korean National Statistical Office to follow-up for mortality between 2000 and 2008. After adjusting for age and other carcinogenic metal exposure, all-cause mortality (Relative risk [RR] 1.36, 95% confidence interval [CI] 1.03-1.79), digestive disease (RR 3.23, 95% CI 1.33-7.86), and intentional self-harm (RR 2.92, 95% CI 1.07-7.81) were statistically significantly higher in males with BLL >20 μg/dl than of those with BLL ≤10μg/dl. The RR of males with BLL of 10-20 μg/dl was statistically higher than of those with BLL ≤10μg/dl in infection (RR 3.73. 95% CI, 1.06-13.06). The RRs of females with 10-20 μg/dl BLL was statistically significantly greater than those with BLL <10μg/dl in all-cause mortality (RR 1.93, 95% CI 1.16-3.20) and colon and rectal cancer (RR 13.42, 95% CI 1.21-149.4). The RRs of females with BLL 10-20 μg/dl (RR 10.45, 95% CI 1.74-62.93) and BLL ≥20 μg/dl (RR 12.68, 95% CI 1.69-147.86) was statistically significantly increased in bronchus and lung cancer. The increased suicide of males with ≥20 μg/dl BLLs, which might be caused by major depression, might be associated with higher lead exposure. Also, increased bronchus and lung cancer mortality in female workers with higher BLL might be related to lead exposure considering low smoking rate in females. The kinds of BLL-associated mortality differed by gender.

Study for Promotion of Health in Recycling Lead - Rationale and design

BACKGROUND

The level at which low-level lead exposure produces subclinical adverse health effects in adults remains to be established.

METHODS

The Study for Promotion of Health in Recycling Lead (SPHERL) will enroll 500 newly hired workers, whose blood lead during 2 years of follow-up is expected to increase from levels less than 2 μg/dl, as currently observed in the US population, to 20-30 μg/dl. The main outcome variables to be studied are (i) blood pressure (BP) analyzed as a continuous or categorical variable, both cross-sectionally and longitudinally, and using conventional and ambulatory BP measurement; (ii) indexes of glomerular and tubular renal function, (iii) heart rate variability analyzed in the frequency domain as measure of autonomous sympathetic modulation, (iv) peripheral nerve conductivity velocity, (v) neurocognitive performance, and (vi) quality of life. Expected outcomes. Assuming a 10-fold increase in blood lead, SPHERL will have sufficient statistical power to detect over 2 years a steepening of the age-related rise in systolic BP from 1 to 5 mmHg and a doubling of the age-related decline in the estimated glomerular filtration rate from 3.5 to 7.0 ml/min/1.73 m(2). The longitudinal design of our study complies with the temporality principle of the Bradford-Hill criteria for assessing possible causality between outcomes and exposure. SPHERL will attempt to resolve the apparent contradiction between general population studies showing associations between adverse health effects and low lead exposure with blood lead levels below 5 μg/dl and studies conducted in occupational cohorts indicating that adverse effects of lead exposure occur at much higher blood lead levels.

Susceptibility to particle health effects, miRNA and exosomes: rationale and study protocol of the SPHERE study

BACKGROUND

Despite epidemiological findings showing increased air pollution related cardiovascular diseases (CVD), the knowledge of the involved molecular mechanisms remains moderate or weak. Particulate matter (PM) produces a local strong inflammatory reaction in the pulmonary environment but there is no final evidence that PM physically enters and deposits in blood vessels. Extracellular vesicles (EVs) and their miRNA cargo might be the ideal candidate to mediate the effects of PM, since they could be potentially produced by the respiratory system, reach the systemic circulation and lead to the development of cardiovascular effects.The SPHERE ("Susceptibility to Particle Health Effects, miRNAs and Exosomes") project was granted by ERC-2011-StG 282413, to examine possible molecular mechanisms underlying the effects of PM exposure in relation to health outcomes.

METHODS/DESIGN

The study population will include 2000 overweight (25 < BMI < 30 kg/cm2) or obese (BMI ≥ 30 kg/cm2) subjects presenting at the Center for Obesity and Work (Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy).Each subject donates blood, urine and hair samples. Extensive epidemiological and clinical data are collected. Exposure to PM is assigned to each subject using both daily PM10 concentration series from air quality monitors and pollutant levels estimated by the FARM (Flexible air Quality Regional Model) modelling system and elaborated by the Regional Environmental Protection Agency.The recruitment period started in September 2010 and will continue until 2015. At December 31, 2013 we recruited 1250 subjects, of whom 87% lived in the province of Milan.Primary study outcomes include cardiometabolic and respiratory health effects. The main molecular mechanism we are investigating focuses on EV-associated microRNAs.

DISCUSSION

SPHERE is the first large study aimed to explore EVs as a novel potential mechanism of how air pollution exposure acts in a highly susceptible population. The rigorous study design, the availability of banked biological samples and the potential to integrate epidemiological, clinical and molecular data will also furnish a powerful base for investigating different complementary molecular mechanisms. Our findings, if confirmed, could lead to the identification of potentially reversible alterations that might be considered as possible targets for new diagnostic and therapeutic interventions.

Loss of Integrity: Impairment of the Blood-brain Barrier in Heavy Metal-associated Ischemic Stroke

Although stroke is one of the leading causes of death and disability worldwide, preventive or therapeutic options are still limited. Therefore, a better understanding of the pathophysiological characteristics of this life-threatening disease is urgently needed. The incidence and prevalence of ischemic stroke are increased by exposure to certain types of xenobiotics, including heavy metals, suggesting the possible toxicological contribution of these compounds to the onset or aggravation of stroke. Among the potential targets, we have focused on alterations to cerebral endothelial cells (CECs), which play important roles in maintaining the functional integrity of brain tissue.

Serum levels of trace elements and heavy metals in patients with acute hemorrhagic stroke

Trace elements are essential components of biological structures, but alternatively, they can be toxic at concentrations beyond those necessary for their biological functions. Changes in the concentration of essential trace elements and heavy metals may affect acute hemorrhagic stroke. The aim of this study was to measure serum levels of essential trace elements [iron (Fe), zinc (Zn), manganese (Mn), copper (Cu), and magnesium (Mg)] and heavy metals [cobalt (Co), cadmium (Cd), and lead (Pb)] in patients with acute hemorrhagic stroke. Twenty-six patients with acute hemorrhagic stroke and 29 healthy controls were enrolled. Atomic absorption spectrophotometry (UNICAM-929) was used to measure serum Fe, Cu, Pb, Cd, Zn, Co, Mn and Mg concentrations. Serum Cd, Pb and Fe levels were significantly higher in patients with acute hemorrhagic stroke than controls (p < 0.001), while serum Cu, Zn, Mg and Mn levels were significantly lower (all p < 0.001). However, there was no significant difference between the groups with respect to serum Co levels (p > 0.05). We first demonstrate increased Cd, Pb, and Fe levels; and decreased Cu, Zn, Mg, and Mn levels in patients with acute hemorrhagic stroke. These findings may have diagnostic and prognostic value for acute hemorrhagic stroke. Further studies are required to elucidate the roles of trace elements and heavy metals in patients with acute hemorrhagic stroke.

The Influence of Arsenic, Lead, and Mercury on the Development of Cardiovascular Diseases

As a group, cardiovascular disease (CVD) is the leading cause of death worldwide. It killed twice as many people as infectious and parasitic disease and three times as many people as all forms of cancer. There are other crucial risk factors next to the major risk factors identified by the Framingham Heart Study. In the last few years, detailed studies showed the correlation between environmental pollution and the development of CVD. The question, which environmental toxin is particularly harmful, is answered by CERCLA Priority List of Hazardous Substances with the following toxins: arsenic, lead, and mercury. The effect of these potential toxic metals on the development of cardiovascular diseases includes pathomechanisms as the accumulation of free radicals, damage of endothelial nitric oxide synthase, lipid peroxidation, and endocrine influences. This leads to the damage of vascular endothelium, atherosclerosis, high blood pressure, and an increased mortality from cardiovascular diseases. The cardiovascular effects of arsenic, lead, and mercury exposure and its impact on cardiovascular mortality need to be included in the diagnosis and the treatment of CVD.

Association of environmental toxic elements in biological samples of myocardial infarction patients at different stages

The exposure of toxic elements may directly or indirectly associate with different pathogenesis of heart diseases. In the present study, the association of arsenic (As), cadmium (Cd), cobalt (Co), lead (Pb), and nickel (Ni) in biological samples (whole blood and urine) and mortality from myocardial infarction (MI) patients at first, second, and third heart attacks was carried out. Both biological samples of 130 MI patients (77 male and 53 female), with ages ranging from 45 to 60 years, and 61 healthy persons (33 male and 28 female) of the same age group were collected. The elements in biological samples were assessed by electrothermal atomic absorption spectrophotometer, prior to microwave-assisted acid digestion. The validity of methodology was checked by the biological certified reference materials. During this study, 78% of 32 patients aged above 50 years, registered after third MI attack, died. In these subjects, the levels of As, Cd, Co, Ni, and Pb in blood samples were higher in MI patients as compared with referents (p < 0.05), while increased by 11.7%, 12.2%, 5.55%, and 7.2%, respectively, in the blood samples of those patients who tolerated the third MI attack (p = 0.12). The high level of understudied toxic elements may play a role in the mortality of MI patients.

Acute lead exposure increases arterial pressure: role of the renin-angiotensin system

Background

Chronic lead exposure causes hypertension and cardiovascular disease. Our purpose was to evaluate the effects of acute exposure to lead on arterial pressure and elucidate the early mechanisms involved in the development of lead-induced hypertension.

Methodology/Principal Findings

Wistar rats were treated with lead acetate (i.v. bolus dose of 320 µg/Kg), and systolic arterial pressure, diastolic arterial pressure and heart rate were measured during 120 min. An increase in arterial pressure was found, and potential roles of the renin-angiotensin system, Na⁺,K⁺-ATPase and the autonomic reflexes in this change in the increase of arterial pressure found were evaluated. In anesthetized rats, lead exposure: 1) produced blood lead levels of 37±1.7 µg/dL, which is below the reference blood concentration (60 µg/dL); 2) increased systolic arterial pressure (Ct: 109±3 mmHg vs Pb: 120±4 mmHg); 3) increased ACE activity (27% compared to Ct) and Na⁺,K⁺-ATPase activity (125% compared to Ct); and 4) did not change the protein expression of the α1-subunit of Na⁺,K⁺-ATPase, AT₁ and AT₂. Pre-treatment with an AT₁ receptor blocker (losartan, 10 mg/Kg) or an ACE inhibitor (enalapril, 5 mg/Kg) blocked the lead-induced increase of arterial pressure. However, a ganglionic blockade (hexamethonium, 20 mg/Kg) did not prevent lead's hypertensive effect.

Conclusion

Acute exposure to lead below the reference blood concentration increases systolic arterial pressure by increasing angiotensin II levels due to ACE activation. These findings offer further evidence that acute exposure to lead can trigger early mechanisms of hypertension development and might be an environmental risk factor for cardiovascular disease.

A prospective study of bone lead concentration and death from all causes, cardiovascular diseases, and cancer in the Department of Veterans Affairs Normative Aging Study

BACKGROUND

Blood lead concentration has been associated with mortality from different causes in several studies. Many effects of lead exposure that might increase risk of death are likely to result from cumulative exposure, for which bone lead is a better biomarker than blood lead. The association between bone lead levels and mortality has not been explored.

METHODS AND RESULTS

We prospectively assessed the association between both blood lead and bone lead, analyzed with the use of K-shell x-ray fluorescence, and mortality among 868 men in the Normative Aging Study. We identified 241 deaths over an average of 8.9 (SD=3.9) years of follow-up. We calculated adjusted hazard ratios and 95% confidence intervals using Cox proportional hazards. Compared with the lowest tertile of patella bone lead, the fully adjusted hazard ratios in the highest tertile for all-cause and cardiovascular mortality (n=137 deaths) were 2.52 (95% confidence interval, 1.17 to 5.41) and 5.63 (95% confidence interval, 1.73 to 18.3), respectively. The age-, smoking-, and race-adjusted hazard ratio for ischemic heart disease mortality (n=62 deaths) in the highest tertile was 8.37 (95% confidence interval, 1.29 to 54.4). Results were similar for tibia lead. Bone lead was not associated with cancer, and blood lead was not associated with any mortality category.

CONCLUSIONS

We found bone lead to be associated with all-cause and cardiovascular mortality in an environmentally exposed population with low blood lead levels. This study suggests that cumulative lead exposure from prior decades of high environmental exposures continues to significantly affect risk of death despite recent declines in environmental lead exposure.

Association of high body lead store with severe intracranial carotid atherosclerosis

OBJECTIVE

Lead is involved in the pathogenesis of atherosclerosis and hypertensive disease and may be related to cerebrovascular disease. We studied the association of body lead level with stroke subtypes and severity of cerebral atherosclerosis in order to identify the significance of lead exposure to cerebrovascular disease.

METHODS

From April, 2002 to March, 2005, we studied the lead level in all patients receiving digital subtraction angiography. Diameter stenosis at extracranial carotid, intracranial carotid and vertebrobasilar system was calculated according to the NASCET criteria. A blood sample and a mobilization test of 72-h urine sample were collected for lead measurement.

RESULTS

In a total of 213 subjects, 19 were free of stroke (blood lead level=4.62+/-2.41 microg/dL, body lead store=39.04+/-20.91 microg) and 194 were stroke patients (4.89+/-2.75 microg/dL, 45.13+/-29.8 microg; all stroke vs. non-stroke, P>0.05). In the 153 subjects with atherosclerotic origin, body lead store but not blood lead level in the intracranial carotid system was significantly higher in > or =50% group than <50% group (blood lead: 5.61+/-3.02 microg/dL vs. 4.80+/-2.50 microg/dL, Student's t-test, P=0.129; body lead store: 51.7+/-27.0 microg vs. 41.9+/-23.5 microg, Student's t-test, P=0.038, multivariate logistic regression, odds ratio=1.02, 95% CI: 1.00-1.03, P=0.043). However, there was no significant association between lead level and stenotic severity in extracranial and vertebrobasilar systems (P>0.05).

CONCLUSION

Our study demonstrated that long-term lead exposure as measured by body lead store might carry a potential risk of intracranial carotid atherosclerosis.

The non-cancer mortality experience of male workers at British Nuclear Fuels plc, 1946-2005

BACKGROUND

Recent studies of the Hiroshima and Nagasaki A-bomb survivors, together with some (but not all) cohorts exposed occupationally or medically to ionizing radiation, have found an increasing trend in mortality from non-malignant disease with increasing radiation dose. The aim of this study was to establish whether such a trend could be found in a large cohort of employees in the UK nuclear industry.

METHODS

The cohort comprised 64 937 individuals ever employed at the study sites between 1946 and 2002, followed up to 2005; radiation exposures as measured by personal dosimeters ('film badges') were available for 42 426 individuals classified as 'radiation workers'. Poisson regression models were used to investigate the relationship between excess mortality rates and cumulative radiation exposure, using both relative and additive risk models.

RESULTS

The cohort shows a pronounced 'healthy worker' effect. Overall, socio-economic status as indicated by employment status has a greater influence on mortality than does radiation exposure status. For male radiation workers, there is an apparent dose response for mortality from circulatory system disease [P < 0.001, ERR = 0.65 (90% CI 0.36-0.98) Sv(-1)]. However there is evidence for inhomogeneity in the apparent dose response (P = 0.016), arising principally at cumulative doses in excess of 300 mSv, when the four categories of employment and radiation exposure status are examined separately.

CONCLUSIONS

We have found evidence for an association between mortality from non-cancer causes of death, particularly circulatory system disease, and external exposure to ionizing radiation in this cohort. However, the tentative nature of biological mechanisms that might explain such an effect at low chronic doses and the above inhomogeneities in apparent dose-response, mean that the results of our analysis are not consistent with any simple causal interpretation. Further work is required to explain these inhomogeneities, and on the possible role of factors associated with socio-economic status and shift working, before any further conclusions can be drawn.

Clinical evidence for lead-induced inhibition of nitric oxide formation

Lead exposure has been associated with increased cardiovascular risk, which may result, at least in part, from lead-induced increases in oxidative stress and depressed nitric oxide (NO) availability. However, no previous clinical study has examined whether lead exposure is associated with significant effects on biomarkers of NO activity (plasma nitrites, nitrates, and cyclic guanosine 3',5'-monophosphate; cGMP). We investigated whether there is an association between the circulating concentrations of nitrites, nitrates, and cGMP and the concentrations of lead in whole blood (B-Pb) or plasma (P-Pb) from 62 lead-exposed subjects (30 men and 32 women). P-Pb was determined by inductively coupled plasma mass spectrometry and B-Pb by graphite furnace atomic absorption spectrometry. Plasma nitrite and nitrate concentrations were measured using an ozone-based chemiluminescence assay. Plasma cGMP concentrations were measured using a commercial enzyme immunoassay. We found a negative correlation between plasma nitrite and B-Pb concentrations (r = -0.358; P = 0.004), and between plasma nitrite and P-Pb concentrations (r = -0.264; P = 0.038), thus suggesting increased inhibition of NO formation with increasing B-Pb or P-Pb concentrations. However, no significant correlations were found between plasma nitrate or cGMP and B-Pb or P-Pb concentrations (all P > 0.05). These findings suggest a significant inhibitory effect of lead exposure on NO formation and provide clinical evidence for a biological mechanism possibly involved the association between lead exposure and increased cardiovascular risk.

Lead levels and ischemic heart disease in a prospective study of middle-aged and elderly men: the VA Normative Aging Study

BACKGROUND

Lead exposure has been associated with higher blood pressure, hypertension, electrocardiogram abnormalities, and increased mortality from circulatory causes.

OBJECTIVE

We assessed the association between bone lead-a more accurate biomarker of chronic lead exposure than blood lead-and risk for future ischemic heart disease (IHD).

METHODS

In a prospective cohort study (VA Normative Aging Study), 837 men who underwent blood or bone lead measurements at baseline were followed-up for an ischemic heart disease event between 1 September 1991 and 31 December 2001. IHD was defined as either a diagnosis of myocardial infarction or angina pectoris that was confirmed by a cardiologist. Events of fatal myocardial infarction were assessed from death certificates.

RESULTS

An IHD event occurred in 83 cases (70 nonfatal and 13 fatal). The mean blood, tibia, and patella lead levels were higher in IHD cases than in noncases. In multivariate Cox-proportional hazards models, one standard deviation increase in blood lead level was associated with a 1.27 (95% confidence interval, 1.01-1.59) fold greater risk for ischemic heart disease. Similarly, a one standard deviation increase in patella and tibia lead levels was associated with greater risk for IHD (hazard ratio for patella lead = 1.29; 95% confidence interval, 1.02-1.62).

CONCLUSIONS

Men with increased blood and bone lead levels were at increased risk for future IHD. Although the pathogenesis of IHD is multifactorial, lead exposure may be one of the risk factors.

Lead exposure and cardiovascular disease--a systematic review

OBJECTIVE

This systematic review evaluates the evidence on the association between lead exposure and cardiovascular end points in human populations.

METHODS

We reviewed all observational studies from database searches and citations regarding lead and cardiovascular end points.

RESULTS

A positive association of lead exposure with blood pressure has been identified in numerous studies in different settings, including prospective studies and in relatively homogeneous socioeconomic status groups. Several studies have identified a dose-response relationship. Although the magnitude of this association is modest, it may be underestimated by measurement error. The hypertensive effects of lead have been confirmed in experimental models. Beyond hypertension, studies in general populations have identified a positive association of lead exposure with clinical cardiovascular outcomes (cardiovascular, coronary heart disease, and stroke mortality; and peripheral arterial disease), but the number of studies is small. In some studies these associations were observed at blood lead levels < 5 microg/dL.

CONCLUSIONS

We conclude that the evidence is sufficient to infer a causal relationship of lead exposure with hypertension. We conclude that the evidence is suggestive but not sufficient to infer a causal relationship of lead exposure with clinical cardiovascular outcomes. There is also suggestive but insufficient evidence to infer a causal relationship of lead exposure with heart rate variability. PUBLIC HEALTH IMPLICATIONS: These findings have immediate public health implications. Current occupational safety standards for blood lead must be lowered and a criterion for screening elevated lead exposure needs to be established in adults. Risk assessment and economic analyses of lead exposure impact must include the cardiovascular effects of lead. Finally, regulatory and public health interventions must be developed and implemented to further prevent and reduce lead exposure.

Blood lead levels and death from all causes, cardiovascular disease, and cancer: results from the NHANES III mortality study

BACKGROUND

Analyses of mortality data for participants examined in 1976-1980 in the second National Health and Nutrition Examination Survey (NHANES II) suggested an increased risk of mortality at blood lead levels > 20 microg/dL. Blood lead levels have decreased markedly since the late 1970s. In NHANES III, conducted during 1988-1994, few adults had levels > 20 microg/dL.

OBJECTIVE

Our objective in this study was to determine the risk of mortality in relation to lower blood lead levels observed for adult participants of NHANES III.

METHODS

We analyzed mortality information for 9,757 participants who had a blood lead measurement and who were > or = 40 years of age at the baseline examination. Using blood lead levels categorized as < 5, 5 to < 10, and > or = 10 microg/dL, we determined the relative risk of mortality from all causes, cancer, and cardiovascular disease through Cox proportional hazard regression analysis.

RESULTS

Using blood lead levels < 5 microg/dL as the referent, we determined that the relative risk of mortality from all causes was 1.24 [95% confidence interval (CI), 1.05-1.48] for those with blood levels of 5-9 microg/dL and 1.59 (95% CI, 1.28-1.98) for those with blood levels > or = 10 microg/dL (p for trend < 0.001). The magnitude of risk was similar for deaths due to cardiovascular disease and cancer, and tests for trend were statistically significant (p < 0.01) for both causes of death.

CONCLUSION

In a nationally representative sample of the U.S. population, blood lead levels as low as 5-9 mug/dL were associated with an increased risk of death from all causes, cardiovascular disease, and cancer.

Matrix Metalloproteinase-9 Activity in Plasma Correlates with Plasma and Whole Blood Lead Concentrations

Matrix metalloproteinases (MMPs) are enzymes involved in the degradation of the extracellular matrix. MMP-2 and MMP-9 have been implicated in a variety of pathological conditions including cardiovascular and neoplastic diseases, and recent studies have shown that circulating concentrations of MMP-9 may be a marker helping in the diagnosis and prognosis of cardiovascular and neoplastic diseases. We investigated whether there is an association between plasma MMP-2 and MMP-9 activities and the concentrations of lead in whole blood (blood Pb) or plasma (plasma Pb) from 40 lead-exposed persons (22 men and 18 women). Plasma Pb was determined by inductively coupled plasma mass spectrometry (ICP-MS) and blood Pb by graphite furnace atomic absorption spectrometry (GF-AAS). Plasma MMP-2 and MMP-9 activities were measured by gelatin zymography. We found a significant correlation between pro-MMP-9 activity in plasma and blood Pb (r=0.454; P=0.003), and between pro-MMP-9 activity in plasma and plasma Pb (r=0.312; P=0.049). No significant correlations were found between blood Pb or plasma Pb and plasma MMP-2. The association between pro-MMP-9 activity in plasma and both blood Pb and plasma Pb concentrations suggests a mechanism through which low lead exposure may increase the susceptibility to cardiovascular and neoplastic diseases. A causal relationship, however, remains to be proved.

Confounding of the relation between homocysteine and peripheral arterial disease by lead, cadmium, and renal function

Homocysteine levels are associated with peripheral arterial disease (PAD) in observational studies. Lead and cadmium are risk factors for PAD that affect thiol metabolism, and they may partly explain the association of homocysteine with PAD. To evaluate the roles of lead and cadmium exposure in confounding the association between homocysteine and PAD, the authors performed a cross-sectional study among 4,447 persons aged > or = 40 years who participated in the 1999-2002 National Health and Nutrition Examination Survey (NHANES). PAD was defined as an ankle-brachial blood pressure index less than 0.90 in at least one leg. After adjustment for sociodemographic variables, the odds ratio for PAD in the highest quintile of homocysteine compared with the lowest was 1.92 (p(trend) = 0.004). Adjusting for blood lead and cadmium levels reduced this odds ratio to 1.37 (p(trend) = 0.13), and further adjusting for estimated glomerular filtration rate and smoking reduced it to 0.89 (p(trend) = 0.87). Adjustment for other risk factors did not affect this association. In the general population, the association of homocysteine level with PAD can be completely explained by confounding due to smoking, increased blood lead and cadmium levels, and impaired renal function. The association of lead and cadmium with PAD risk deserves further investigation.

Environmental lead level and pregnancy-induced hypertension

Previous studies have suggested that environmental lead exposure increases the risk of hypertension in the general population. In this article, the authors used the 1998 linked birth/infant death database of the United States to examine the association between environmental lead level and the occurrence of pregnancy-induced hypertension (PIH). Yearly summaries of environmental lead levels were abstracted from the US Environmental Protection Agency's air pollution databases, and linked with birth/infant death records by state codes. Generalized estimating equations (GEEs) were used to evaluate the odds ratios of PIH associated with environmental lead measured at ecological levels, with adjustment for maternal age, race, education level, marital status, parity, and adequacy of prenatal care measured at individual levels, stratified by maternal cigarette smoking. A total of 2,994,072 women pregnant in 1998 were included in this study. With the first quartile of lead level as the reference group, the odds ratio for PIH among all study subjects in the second quartile of seasonal average lead level at conception was 1.07 (95% CI: 1.05-1.08), and odds ratios in the third and fourth quartiles were 1.22 (95% CI: 1.20-1.25) and 1.16 (95% CI: 1.15-1.18), respectively. The odds ratios for the second, third, and fourth quartiles of seasonal average lead level at birth were 1.07 (95% CI: 1.05-1.09), 1.21 (95% CI: 1.19-1.23), and 1.15 (95% CI: 1.13-1.17), respectively. The risk of PIH increased by 4% per 0.05 microg/m3 increase in seasonal average lead level at conception and birth, in both smokers and nonsmokers. These results suggest that higher environmental lead levels increase the risk of PIH.

eNOS genotype-dependent correlation between whole blood lead and plasma nitric oxide products concentrations

Experimental data indicate that lead exposure decreases nitric oxide (NO) availability. However, no previous study has examined whether lead exposure affects plasma nitrite/nitrate (NO(x)) concentrations in humans. In addition, the T(-786)C polymorphism affects endothelial NO synthase (eNOS) expression and endogenous NO release. Here, we investigated whether there is an association between the circulating concentrations of NO(x) and the concentrations of lead in whole blood (B-Pb) and in plasma (P-Pb) from lead-exposed subjects. In addition, we also evaluated whether eNOS genotype for the T(-786)C polymorphism affects NO(x) concentrations in lead-exposed subjects. We studied 104 subjects exposed to lead who were non-smokers, 18-60 years of age, and not alcohol consumers. Genomic DNA was isolated from blood samples and genotypes for the T(-786)C polymorphism were determined by PCR and restriction fragment length digestion. Circulating NO(x) was determined by chemiluminescence. B-Pb and P-Pb were determined by inductively coupled plasma mass spectrometry and by graphite furnace atomic absorption spectrometry, respectively. No significant correlations were found between NO(x) and B-Pb and P-Pb measured in the 104 subjects (all P > 0.05). However, while no significant correlation was found in subjects with TT genotype, a negative correlation was found between plasma NO(x) and B-Pb (r = 0.230, P = 0.048) and P-Pb (r = 0.194, P = 0.110) in subjects from TC + CC genotypes group. Our study shows a negative correlation between plasma NO(x) concentrations and B-Pb in carriers of the "C" allele, thus suggesting a possible mechanism possibly involved in lead exposure-induced increase in the susceptibility to cardiovascular diseases.

The change of beta-adrenergic system after cessation of lead exposure

For understanding a reversible or irreversible harm of beta-adrenergic system in lead induced cardiovascular disease (hypertension), We set up animal model to estimate the change of blood pressure and sympathetic nervous system after lead exposure withdrawn in the study. We address three topics in this study: (a) the relationship between withdrawal time of lead exposure and beta-adrenergic receptor, plasma catecholamine level, blood pressure, and lead level in heart, aorta, and kidney in lead-induced hypertensive rats after lead exposure stopped; (b) the relationship between blood pressure and beta-adrenergic receptor in heart, aorta, and kidney; (c) the estimation of relationship between lead withdrawn and the variation of beta-adrenergic system. Wistar rats were chronically fed with 2% lead acetate (experimental group) and water (control group) for 2 months. The rats were divided into 8 groups by withdrawal time of lead exposure stopped. Plasma catecholamine level was measured by high-performance liquid chromatography. Radioligand binding assay was measured by a method that fulfilled strict criteria of beta-adrenergic receptor using the ligand [125I]iodocyanopindolol. The levels of lead were determined by electrothermal atomic absorption spectrometry. The results showed that a close relation between reduced lead level and the plasma catecholamine level decreased, aorta beta-adrenergic receptor increased, kidney beta-adrenergic receptor diminished, heart beta-adrenergic receptor increased, and blood pressure dropped after lead exposure withdrawn. The study on the regulation of beta-adrenergic system in lead-induced hypertension after lead withdrawn might also provide insight about the nature of this disease state.

Metals in urine and peripheral arterial disease

Exposure to metals may promote atherosclerosis. Blood cadmium and lead were associated with peripheral arterial disease (PAD) in the 1999-2000 National Health and Nutrition Examination Survey (NHANES). In the present study we evaluated the association between urinary levels of cadmium, lead, barium, cobalt, cesium, molybdenum, antimony, thallium, and tungsten with PAD in a cross-sectional analysis of 790 participants > or =40 years of age in NHANES 1999-2000. PAD was defined as a blood pressure ankle brachial index < 0.9 in at least one leg. Metals were measured in casual (spot) urine specimens by inductively coupled plasma-mass spectrometry. After multivariable adjustment, subjects with PAD had 36% higher levels of cadmium in urine and 49% higher levels of tungsten compared with noncases. The adjusted odds ratio for PAD comparing the 75th to the 25th percentile of the cadmium distribution was 3.05 [95% confidence interval (CI), 0.97 to 9.58]; that for tungsten was 2.25 (95% CI, 0.97 to 5.24). PAD risk increased sharply at low levels of antimony and remained elevated beyond 0.1 microg/L. PAD was not associated with other metals. In conclusion, urinary cadmium, tungsten, and possibly antimony were associated with PAD in a representative sample of the U.S. population. For cadmium, these results strengthen previous findings using blood cadmium as a biomarker, and they support its role in atherosclerosis. For tungsten and antimony, these results need to be interpreted cautiously in the context of an exploratory analysis but deserve further study. Other metals in urine were not associated with PAD at the levels found in the general population.

Blood lead is a predictor of homocysteine levels in a population-based study of older adults

Lead and homocysteine are both associated with cardiovascular disease and cognitive dysfunction. We evaluated the relations among blood lead, tibia lead, and homocysteine levels by cross-sectional analysis of data among subjects in the Baltimore Memory Study, a longitudinal study of 1,140 randomly selected residents in Baltimore, Maryland, who were 50-70 years of age. Tibia lead was measured by (superscript)109(/superscript)Cd K-shell X-ray fluorescence. The subject population had a mean +/- SD age of 59.3 +/- 5.9 years and was 66.0% female, 53.9% white, and 41.4% black or African American. Mean +/- SD blood lead, tibia lead, and homocysteine levels were 3.5 +/- 2.4 microg/dL, 18.9 +/- 12.5 microg/g, and 10.0 +/- 4.1 micromol/L, respectively. In unadjusted analysis, blood lead and homocysteine were moderately correlated (Pearson's r = 0.27, p < 0.01). After adjustment for age, sex, race/ethnicity, educational level, tobacco and alcohol consumption, and body mass index using multiple linear regression, results revealed that homocysteine levels increased 0.35 micromol/L per 1.0 microg/dL increase in blood lead (p < 0.01). The relations of blood lead with homocysteine levels did not differ in subgroups distinguished by age, sex, or race/ethnicity. Tibia lead was modestly correlated with blood lead (Pearson's r = 0.12, p < 0.01) but was not associated with homocysteine levels. To our knowledge, these are the first data to reveal an association between blood lead and homocysteine. These results suggest that homocysteine could be a mechanism that underlies the effects of lead on the cardiovascular and central nervous systems, possibly offering new targets for intervention to prevent the long-term consequences of lead exposure.

Lead-induced hypertension: role of oxidative stress

Chronic, low-level lead exposure causes hypertension in both animals and humans. The pathogenesis of lead-induced hypertension is multifactorial, including such diverse mechanisms as: inactivation of endogenous nitric oxide and downregulation of soluble guanylate cyclase by reactive oxygen species (ROS), leading to a functional deficiency in nitric oxide; heightened sympathetic activity and plasma norepinephrine together with depressed vascular and elevated renal beta-adrenergic receptor density; elevated plasma angiotensin-converting enzyme (ACE) activity, plasma renin activity (PRA), angiotensin II (Ang-II), and aldosterone levels; increased kininase I and kininase II activities; lead-induced inhibition of vascular smooth muscle Na(+)-K+ ATPase, leading to a rise in cellular Na+ and, hence, Ca2+; and a possible rise in endothelin and thromboxane generation. In this article, we present an overview of the epidemiology and proposed underlying mechanisms of lead-induced hypertension.

Lead, Cadmium, Smoking, and Increased Risk of Peripheral Arterial Disease

BACKGROUND

Lead and cadmium exposure may promote atherosclerosis, although the cardiovascular effects of chronic low-dose exposure are largely unknown. The objective of the present study was to evaluate the association between blood levels of lead and cadmium and peripheral arterial disease.

METHODS AND RESULTS

We analyzed data from 2125 participants who were > or =40 years of age in the 1999 to 2000 National Health and Nutrition Examination Survey (NHANES). Peripheral arterial disease was defined as an ankle brachial index <0.9 in at least 1 leg. Lead and cadmium levels were measured by atomic absorption spectrometry. After adjustment for demographic and cardiovascular risk factors, the ORs of peripheral arterial disease comparing quartiles 2 to 4 of lead with the lowest quartile were 1.63 (95% CI, 0.51 to 5.15), 1.92 (95% CI, 0.62 to 9.47), and 2.88 (95% CI, 0.87 to 9.47), respectively (P for trend=0.02). The corresponding ORs for cadmium were 1.07 (95% CI, 0.44 to 2.60), 1.30 (95% CI, 0.69 to 2.44), and 2.82 (95% CI, 1.36 to 5.85), respectively (P for trend=0.01). The OR of peripheral arterial disease for current smokers compared with never smokers was 4.13. Adjustment for lead reduced this OR to 3.38, and adjustment for cadmium reduced it to 1.84.

CONCLUSIONS

Blood lead and cadmium, at levels well below current safety standards, were associated with an increased prevalence of peripheral arterial disease in the general US population. Cadmium may partially mediate the effect of smoking on peripheral arterial disease.

Effects of lead on the human erythrocyte membrane and molecular models

Lead has no biological function; however, low, and particularly, high levels of exposure have a number of negative consequences for human health. Despite the number of reports about lead toxicity, very little information has been obtained regarding its effects on cell membranes. For this reason, the structural effects of lead on the human erythrocyte membranes were investigated. This aim was attained by making lead ions interact with intact erythrocytes, isolated unsealed erythrocyte membranes (IUM) and molecular models. The latter consisted of bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representing phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane. The results, obtained by electron microscopy, fluorescence spectroscopy and X-ray diffraction, indicated that (a) lead particles adhered to the external and internal surfaces of the human erythrocyte membrane; (b) lead ions disturbed the lamellar organization of IUM and DMPC large unilamellar vesicles (LUV) and (c) induced considerable molecular disorder in both lipid multilayers, the effects being much more pronounced in DMPC.

Deaths related to lead poisoning in the United States, 1979-1998

This study was conducted to describe trends in US lead poisoning-related deaths between 1979 and 1998. The predictive value of relevant ICD-9 codes was also evaluated. Multiple cause-of-death files were searched for records containing relevant ICD-9 codes, and underlying causes and demographic characteristics were assessed. For 1979-1988, death certificates were reviewed; lead source information was abstracted and accuracy of coding was determined. An estimated 200 lead poisoning-related deaths occurred from 1979 to 1998. Most were among males (74%), Blacks (67%), adults of age >/=45 years (76%), and Southerners (70%). The death rate was significantly lower in more recent years. An alcohol-related code was a contributing cause for 28% of adults. Only three of nine ICD-9 codes for lead poisoning were highly predictive of lead poisoning-related deaths. In conclusion, lead poisoning-related death rates have dropped dramatically since earlier decades and are continuing to decline. However, the findings imply that moonshine ingestion remains a source of high-dose lead exposure in adults.

The longitudinal association of lead with blood pressure

BACKGROUND

Several investigators have reported an association of blood lead or bone lead with increased blood pressure and hypertension, but questions remain concerning whether these effects are acute or chronic in nature.

METHODS

In this longitudinal study, we evaluated the relation of lead, measured in blood and tibia, to changes in blood pressure between 1994 and 1998. We studied 496 current and former employees of a chemical-manufacturing facility in the eastern United States who had previous occupational exposure to inorganic and organic lead. Cohort members who provided three or four blood pressure measurements during the study were included.

RESULTS

Mean age at baseline was 55.8 years with a mean of 18 years since last occupational exposure to lead. Blood lead at baseline averaged 4.6 microg/dL (standard deviation [SD] = 2.6) or 0.22 micromole/Liter (SD = 0.13). Tibia lead at year three averaged 14.7-microg/gm (SD = 9.4) bone mineral. Change in systolic blood pressure during the study was associated with lead dose, with an average annual increase of 0.64 mmHg (standard error [SE] = 0.25), 0.73 mmHg (SE = 0.26), and 0.61 mmHg (SE = 0.27) for every standard deviation increase in blood lead at baseline, tibia lead at year three, or peak past tibia lead, respectively.

CONCLUSIONS

The results support an etiologic role for lead in the elevation of systolic blood pressure among adult males and are consistent with both acute and chronic modes of action.

Association between bone lead concentration and blood pressure among young adults

BACKGROUND

Occupational and environmental exposure to lead has been examined for its effect on blood pressure (BP) in adults with varying results. The present analyses assessed the association between bone lead concentration and BP in early adult life in persons exposed during childhood.

METHODS

Study participants included young adult members of two cohorts with different past histories of lead exposure. Lead exposure was assessed using noninvasive K-X-ray fluorescence spectroscopy to quantify bone lead concentration, an index of long-term lead exposure superior to current blood lead concentration. Systolic and diastolic BP measurements were obtained using conventional clinical methods. Multiple linear regression models were constructed to allow for control of covariates of BP identified a priori.

RESULTS

Analyses were performed on 508 participants. While controlling for potential confounders, systolic BP was 4.3 mm Hg greater among members of the highest of four bone lead concentration groups (> 10 microg Pb/g bone) when compared with the lowest bone lead concentration group (< 1 microg Pb/g bone; P = 0.004), and diastolic BP was 2.8 mm Hg greater among members of the highest bone lead concentration group when compared with the lowest bone lead concentration group (P = 0.03).

CONCLUSIONS

These results suggest that substantial lead exposure during childhood can increase BP during young adulthood.

Excitatory action of lead on rat sympathetic preganglionic neurons in vitro and in vivo

Lead exposure elicited an increase in blood pressure and was considered to be a cardiovascular risk factor. The involvements of sympathetic nervous system and circulating catecholamines have been implicated in lead-induced hypertension. This study examined the effects of PbCl(2) on sympathetic preganglionic neurons (SPNs) in vitro and in vivo. In vitro electrophysiological study showed that superfusion of a low concentration (5 microM) of PbCl(2), which had no effects on membrane potential and spontaneous discharge rate, enhanced excitatory postsynaptic potentials (EPSPs) in some of the SPNs examined but inhibited inhibitory postsynaptic potentials (IPSPs) in other SPNs tested. A higher concentration (50 microM) of PbCl(2) inhibited both EPSPs and IPSPs in all SPNs examined. In vivo study showed that intrathecal injection of PbCl(2) (10 and 100 nmol) via an implanted cannula to the T7-T9 segments of urethane-anesthetized rats increased both the heart rate and mean arterial pressure. The pressor and tachycardic responses of intrathecal PbCl(2) (100 nmol) were attenuated by pretreatment with intravenous administration of hexamethonium (10 mg/kg) or intrathecal AP-5 (DL-2-amino-5-phosphonovaleric acid, 100 nmol), but were not significantly antagonized by prior intrathecal administration of CNQX (6-cyano-7-nitroquinoxaline-2,3-dione, 100 nmol). Taken together, these results demonstrated that lead may exert a stimulatory effect on SPNs, which may result from the enhancement of EPSPs and inhibition of IPSPs by low concentrations of lead.