Bone lead associations with blood lead, kidney function and blood pressure among US, lead-exposed workers in a surveillance programme

Fucoxanthin alleviates the cytotoxic effects of cadmium and lead on a human osteoblast cell line

OBJECTIVE

Cadmium (Cd) and lead (Pb) are non-biodegradable heavy metals (HMs) that persistently contaminate ecosystems and accumulate in bones, where they exert harmful effects. This study aimed to investigate the protective effect of fucoxanthin (FX) against the chemical toxicity induced by Cd and Pb in human bone osteoblasts in vitro, using various biochemical and molecular assays.

METHODS

The effect of metals and FX on osteoblasts viability was assayed by MTT, then the effect of Pb, Cd, and FX on the cells' mitochondrial parameters was studied via assays for ATP, mitochondrial membrane potential (MMP), mitochondrial complexes, and lactate production. Also, the effect of metals on oxidative stress was assessed by reactive oxygen species, lipid peroxidation and antioxidant enzymes assays. Also the effect of FX and metals on apoptosis caspases and related genes was assessed.

RESULTS

When Cd and Pb were added to human osteoblast cultures at concentrations ranging from 1-20 μM for 72 h, they significantly reduced osteoblast viability in a time and concentration-dependent manner. The cytotoxic effect of Cd on osteoblasts was greater than that of Pb, with estimated EC50 of 8 and 12 μM, respectively, after 72 h of exposure. FX (10 and 20 μM) alleviated the cytotoxicity of the metals. Bioenergetics assays, including ATP, MMP, and mitochondrial complexes I and III activities, revealed that HMs at 1 and 10 μM concentrations inhibited cellular bioenergetics after 72 h of exposure. Cd and Pb also increased lipid peroxidation and reactive oxygen species while reducing catalase and superoxide dismutase antioxidant activities and oxidative stress-related genes. This was accompanied by increased caspases -3, -8, and - 9 and Bax/bCl-2 ratio. Co-treatment with FX (10 and 20 μM) mitigated the disruption of bioenergetics, oxidative damage, and apoptosis induced by the metals, showing a concentration-dependent pattern to varying extents.

CONCLUSION

These findings strongly support the role of FX in managing toxicities induced by environmental pollutants in bones and in addressing bone diseases associated with molecular bases of oxidative stress, apoptosis, and bioenergetic disruption.

Vitamin D Alleviates Heavy Metal-Induced Cytotoxic Effects on Human Bone Osteoblasts Via the Induction of Bioenergetic Disruption, Oxidative Stress, and Apoptosis

Cadmium (Cd) and lead (Pb) are heavy metals (HMs) that persistently contaminate the ecosystem, and bioaccumulation in bones is a health concern. We used biochemical and molecular assays to assess the cytoprotective effect of vitamin D (VD) on Cd- and Pd-induced chemical toxicity of human bone osteoblasts in vitro. Exposing Cd and Pb to human osteoblast cultures at concentrations of 0.1-1000 µM for 24-72 h significantly reduced osteoblast viability in an exposure time- and concentration-dependent manner. The cytotoxic effect of Cd on osteoblasts was more severe than Pb's, with 72-h exposure estimated half maximal effective concentration (EC50) of 8 and 12 µM, respectively, and VD (1 and 10 nM) alleviated cytotoxicity. Bioenergetics assays of ATP, mitochondrial membrane potential, and mitochondrial complex I and III activity showed that both Cd and Pb (1 and 10 µM) inhibited cellular bioenergetics after 72-h exposure. Cd and Pb increased lipid peroxidation and reactive oxygen species with reduced catalase/superoxide dismutase antioxidant activities and increased activity of caspases -3, -8, and -9. Co-treatment with VD (1 and 10 nM) counteracted bioenergetic disruption, oxidative damage, and apoptosis in a concentration-dependent manner. These findings suggest that VD is effective in managing the toxic effects of environmental pollutants and in treating bone diseases characterized by oxidative stress, apoptosis, and bioenergetic disruption.

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.

Association and interactions between mixed exposure to trace elements and the prevalence of kidney stones: a study of NHANES 2017-2018

Background

The association between exposure to trace elements mixture and the prevalence of kidney stones and the interactions between elements are unclear. The aim of this study was to explore the association between exposure to trace elements mixture and the prevalence of kidney stones and the interactions between the elements.

Methods

A total of 1,244 participants (139 kidney stone formers and 1,105 non-stone former participants) in NHANES 2017-2018 were included. The exposure to trace elements was evaluated by measuring their concentration in urine samples. Three methods, Logistic regression, quantile-based g computation (qgcomp), and Bayesian kernel machine regression (BKMR), were used for analysis.

Results

According to the results from qgcomp and BKMR, a negative association was found between exposure to the 13 trace elements and the prevalence of kidney stones [OR = 0.50 (0.32, 0.78)]. Subgroup analysis revealed that Co, As, and iodine in the whole population, Co, As, and Ni in males, and Cs, iodine, and Sb in females, were most strongly associated with kidney stones. Kidney stone was found to be positively correlated with Co and negatively correlated with the other elements. Besides, there were significant interactions between Ni and Pb in the whole population, Co and iodine in males, and Pb and iodine in females.

Conclusion

There was a negative association between exposure to the mixture of 13 trace elements and the prevalence of kidney stones.

Research Recommendations for Selected IARC-Classified Agents: Impact and Lessons Learned

BACKGROUND

The International Agency for Research on Cancer (IARC) Monographs program assembles expert working groups who publish a critical review and evaluation of data on agents of interest. These comprehensive reviews provide a unique opportunity to identify research needs to address classification uncertainties. A multidisciplinary expert review and workshop held in 2009 identified research gaps and needs for 20 priority occupational chemicals, metals, dusts, and physical agents, with the goal of stimulating advances in epidemiological studies of cancer and carcinogen mechanisms. Overarching issues were also described.

OBJECTIVES

In this commentary we review the current status of the evidence for the 20 priority agents identified in 2009. We examine whether identified Research Recommendations for each agent were addressed and their potential impact on resolving classification uncertainties.

METHODS

We reviewed the IARC classifications of each of the 20 priority agents and identified major new epidemiological and human mechanistic studies published since the last evaluation. Information sources were either the published Monograph for agents that have been reevaluated or, for agents not yet reevaluated, Advisory Group reports and literature searches. Findings are described in view of recent methodological developments in Monographs evidence evaluation processes.

DISCUSSION

The majority of the 20 priority agents were reevaluated by IARC since 2009. The overall carcinogen classifications of 9 agents advanced, and new cancer sites with either "sufficient" or "limited" evidence of carcinogenicity were also identified for 9 agents. Examination of published findings revealed whether evidence gaps and Research Recommendations have been addressed and highlighted remaining uncertainties. During the past decade, new research addressed a range of the 2009 recommendations and supported updated classifications for priority agents. This supports future efforts to systematically apply findings of Monograph reviews to identify research gaps and priorities relevant to evaluation criteria established in the updated IARC Monograph Preamble. https://doi.org/10.1289/EHP12547.

The risk of dental restoration-related lead exposure on renal function

OBJECTIVE

To explore the relationship between oral restoration count, blood lead (PbB) level, and renal function as potential heavy metal releases, and the related toxicity of dental restorative materials.

METHODS

A total of 3682 participants from the National Health and Nutrition Examination Survey (January 2017 to March 2020) were included in this cross-sectional analysis. We utilized multivariable linear regression models to investigate the associations between the number of oral restorations and PbB levels or renal function. The mediating effect of PbB on renal function indicators was analyzed using the R mediation package.

RESULTS

Based on the indicators of 3682 participants, we found that the elderly, females, and whites were fit with more oral restoration, which was accompanied by increased PbB levels and decreased renal function. Meanwhile, oral restoration count was positively associated with PbB level (β = 0.023, 95% CI: -0.020 to 0.027), renal function-related urine albumin creatinine ratio (β = 1.541, 95% CI: 0.615-2.468), serum uric acid level (β = 0.012, 95% CI: 0.007 to 0.017), and serum creatinine level, and negatively associated with estimated glomerular filtration rate (eGFR) (β = -0.804, 95% CI: -0.880 to -0.728). Furthermore, the mediation effect test confirmed that PbB played a mediating role in the relationship between restoration count and serum uric acid or eGFR, with mediation effects accounting for 98.0% and 71.0%, respectively.

CONCLUSIONS

Oral restoration negatively affects renal function. Oral restoration-related PbB level is a potential mediating factor.

The mediating role of gut microbiota in the associations of prenatal maternal combined exposure to lead and stress with neurodevelopmental deficits in young rats

Prenatal single and combined exposure to lead (Pb) and stress (Ps) impairs neurodevelopment. Prenatal single exposure to Pb or Ps affects the composition of intestinal microbiota, and bidirectional communication between gut microbiota and central nervous system has been well recognized. However, whether gut microbiota mediated the effects of prenatal Pb+Ps co-exposure on neurodevelopmental deficits remains unclear. This study established rat models with prenatal single and combined exposure to Ps and Pb. We investigated the effects of such prenatal single and combined exposure on hippocampal structures using morphological analyses, on learning/memory using the Morris-water-maze test, and on fecal microbiota using 16S rRNA sequencing. The mediating roles of gut microbiota were analyzed using the bootstrap method. The study found both single and combined exposure affected hippocampal ultra-structures and spatial learning/memory, and the most significant impairments were observed in the Pb+Ps group. Prenatal Pb+Ps co-exposure decreased fecal microbial alpha/beta-diversity. Significantly lower levels of B/F-ratio, class-Bacteroidia, order-Bacteroidales, and family-S24-7, and significantly higher levels of class-Bacilli, order-Lactobacillales, family-Lactobacillaceae, and genus-Lactobacillus were observed in the co-exposure group, compared with the controls. Increased relative abundances of genus-Helicobacter mediated the detrimental effect of prenatal Ps+Pb co-exposure on learning/memory [β (95%CI) for the total and indirect effects: - 10.70 (-19.19, -2.21) and - 4.65(-11.07, -1.85)], accounting for 43.47% of the total effect. As a result, increased relative abundances of genus-Lactobacillus alleviated the adverse effects of the co-exposure on learning/memory, and the alleviation effect accounted for 44.55% of the direct effect [β (95%CI) for the direct and indirect effects: - 0.28(-0.48, -0.08) and 0.13(0.01, 0.41)]. This study suggested that prenatal combined exposure to Pb and Ps induced more impairments in offspring gut microbiota and neurodevelopment than single exposure, and alterations in fecal microbiome may mediate the developmental neurotoxicity induced by such prenatal co-exposure.

Immigration and Blood Lead Levels Among Asian Populations in the United States: NHANES 2011-2018

OBJECTIVE

The aim of this study was to explore determinants of high BLLs among the Asian population in the United States.

METHODS

We used the US nationally representative National Health and Nutrition Examination Survey (NHANES), 2011-2018. We conducted stratified analyses to compare the BLLs of US-born and non-US-born Asians. We used adjusted linear regression to find predictors of high BLLs.

RESULTS

Among 12,563 participants in our analysis, the length of stay in the United States is a predictor of the gradual decrease in BLL among Asian immigrants ( P < 0.05). BLLs of immigrants who stayed in the United States for over 50 years were 0.36 μg/dL (95% confidence interval, 0.07 to 0.66) lower than new immigrants, but still higher than their US-born counterparts.

SIGNIFICANCE

Asian population in the US has the highest BLLs among all ethnic groups, and the exposure outside of the US among immigrants is likely the driver.

Environmental exposures to lead, cadmium, and mercury and pterygium in Korean adults

Pterygium, one of the most common eye disorders, is an abnormal fibrovascular proliferation extending from the conjunctiva to the cornea. The mechanism of development in pterygium has not been fully elucidated; however, oxidative stress is suggested to be one of the major causes. Heavy metals such as lead (Pb), cadmium (Cd), and mercury (Hg) enter the human body and induce oxidative stress. However, no study has investigated the association of these heavy metals with pterygium. Therefore, this study aimed to evaluate the associations of environmental exposures to Pb, Cd, and Hg with pterygium in the Korean general adults. We analyzed data from 6,587 adults (≥ 20 years of age) who participated in the Korea National Health and Nutrition Examination Survey (KNHANES) 2008-2011. Pterygium was diagnosed as the presence of a wing-shaped fibrovascular growth. The exposures of Pb, Cd, and Hg were estimated by measuring blood concentrations. The prevalence of pterygium in this study population was 4.0% (348 subjects). After adjusting for potential confounders, the Pb level in blood was found to have a significant dose-dependent association with pterygium (p for trend = 0.001), and its highest quintile (vs. the lowest) had an odds ratio (OR) of 2.22 (95% CI: 1.30, 3.78) for pterygium. The Hg level in blood in the second quintile (vs. the lowest) had an OR of 1.64 (95% CI: 1.04, 2.59) for pterygium. In conclusion, this study suggests that environmental exposures to Pb and Hg in the Korean general adults may be related to the development of pterygium.

Potentials of orally supplemented selenium-enriched Lacticaseibacillus rhamnosus to mitigate the lead induced liver and intestinal tract injury

Lead is a metal that exists naturally in the Earth's crust and is a ubiquitous environmental contaminant. The alleviation of lead toxicity is important to keep human health under lead exposure. Biosynthesized selenium nanoparticle (SeNPs) and selenium-enriched Lactobacillus rhamnosus SHA113 (Se-LRS) were developed in this study, and their potentials in alleviating lead-induced injury to the liver and intestinal tract were evaluated in mice by oral administration for 4 weeks. As results, oral intake of lead acetate (150 mg/kg body weight per day) caused more than 50 times and 100 times lead accumulation in blood and the liver, respectively. Liver function was seriously damaged by the lead exposure, which is indicated as the significantly increased lipid accumulation in the liver, enhanced markers of liver function injury in serum, and occurrence of oxidative stress in liver tissues. Serious injury in intestinal tract was also found under lead exposure, as shown by the decrease of intestinal microbiota diversity and occurrence of oxidative stress. Except the lead content in blood and the liver were lowered by 52% and 58%, respectively, oral administration of Se-LRS protected all the other lead-induced injury markers to the normal level. By the comparison with the effects of normal L. rhamnosus SHA113 and the SeNPs isolated from Se-LRS, high protective effects of Se-LRS can be explained as the extremely high efficiency to promote lead excretion via feces by forming insoluble mixture. These findings illustrate the developed selenium-enriched L. rhamnosus can efficiently protect the liver and intestinal tract from injury by lead.

Chronic renal disease among lead-exposed workers

BACKGROUND

Very high exposure to inorganic lead causes serious kidney damage. We have studied workers with occupational exposure and data on blood lead.

METHODS

We extended follow-up for 7 more years, for a previously studied cohort of 58 307 male workers who were part of a surveillance programme in 11 different states. Mortality was assessed using the National Death Index, and end-stage renal disease (ESRD) incidence was assessed using the US Renal Data System. We conducted internal analyses via Cox regression adjusting for age, calendar time and race.

RESULTS

The cohort was followed for a median of 18 years and had 524 cases of ESRD and 6527 deaths. Average maximum blood lead was 26 µg/dL; the mean year of first blood lead test was 1997. No trends by lead level were seen overall or when restricting to those with 15+ years follow-up. Among non-Caucasians with >15 years of follow-up, there was a positive but inconsistent trend (Rate ratios (RRs) 1.00, 2.10, 1.33, 2.20 and 2.76 for maximum blood lead categories of <20 µg/dL, 20-29 µg/dL, 30 to <40 µg/dL, 40 to ≤50 µg/dL and >50 µg/dL, respectively (p for linear trend 0.26). Those with >15 years of follow-up and birth year <1941 showed a positive trend with increased blood lead (RRs 1.00, 1.14, 1.18, 1.46, 1.66, p trend=0.26).

CONCLUSIONS

We found no association between higher lead exposure and ESRD. There were positive but not statistically significant trends of increased risk for non-Caucasians with >15 years of follow-up and for older men with >15 years of follow-up.

The heavy metals lead and cadmium are cytotoxic to human bone osteoblasts via induction of redox stress

The heavy metals (HMs) lead and cadmium are persistent environmental pollutants capable of inducing ill-health in exposed individuals. One of the primary sites of accumulation and potential damage from HMs is bone, and we therefore examined the acute effects of lead and cadmium on human bone osteoblasts in vitro over a concentration range of 0.1 μM to 1mM, and for 3, 6, 12, 24, and 48 hour exposures. Incubation of osteoblasts with either lead or cadmium reduced cell viability in a concentrations and exposure durations dependent manner, as measured using MTT and LDH assays. Cytotoxicity was significant from 0.1 μM concentrations after 48 hour exposures. Both HMs damaged cellular bioenergetics with reductions of ATP production, mitochondrial complex activities, and aerobic respiration. There was a concomitant elevation of reactive oxygen species, with induction of redox stress measured as increased lipid peroxidation, and depleted cellular redox defense systems via reduced superoxide dismutase and catalase activity and cellular glutathione levels. Both HMs induced nuclear activation of Nrf2, presumably to increase transcription of antioxidant responsive genes to combat oxidative stress. Incubation of osteoblasts with HMs also compromised the secretion of procollagen type 1, osteocalcin, and alkaline phosphatase. Pre-incubation of osteoblasts with reduced glutathione prior to challenge with HMs lessened the cytotoxicity of the HMs, indicative that antioxidants may be a beneficial treatment adjunct in cases of acute lead or cadmium poisoning.

Nephrotoxic metals of cadmium, lead, mercury and arsenic and the odds of kidney stones in adults: An exposure-response analysis of NHANES 2007-2016

BACKGROUND

Nephrotoxic metals of arsenic, cadmium, lead and mercury exposures are common environmental pollutants. The associations between arsenic, cadmium, lead and mercury exposures and the risk of kidney stones are unclear.

OBJECTIVE

To explore the associations between biomarkers of arsenic, cadmium, lead and mercury exposures and the odds of kidney stones.

METHODS

Adult participants (≥20 years) from the 2007-2016 NHANES were included. Restricted cubic splines were adopted.

RESULTS

The odds ratio (95% confidence interval) of kidney stones increased with increasing blood cadmium and reached the maximum at 1.00 μg/L [1.38 (1.02-1.88) overall, 1.62 (1.11-2.32) for women and 1.53 (1.06-2.22) for non-Hispanic white]. The odds of kidney stones increased with increasing urinary cadmium and reached the maximum at 1.50 μg/L [2.56 (1.17-5.59) overall, 5.57 (1.88-16.49) for women, 4.31 (1.75-10.63) for obese individuals and 3.75 (1.60-8.78) for non-Hispanic white]. The odds of kidney stones increased with increasing total urinary arsenic and urinary dimethylarsinic acid in women, and reached the maximum of 1.69 (1.08-2.67) at 40 μg/L and 1.71 (1.07-2.72) at 10.00 μg/L, respectively. Inverse associations were found between the odds of kidney stones and blood lead within 5.00 μg/dL [0.64 (0.46-0.90) overall, 0.53 (0.33-0.84) for men and 0.58 (0.37-0.92) for non-Hispanic white], methyl mercury within 3.00 μg/L [non-obese individuals: 0.71 (0.51-0.99)] and urinary arsenous acid within 1.20 μg/L [individuals other than non-Hispanic white: 0.63 (0.41-0.95)]. No association was found with other biomarkers.

CONCLUSIONS

Several biomarkers of arsenic, cadmium, lead and mercury exposures were associated with the odds of kidney stones in adults.

Lead exposure and mortality among U.S. workers in a surveillance program: Results from 10 additional years of follow-up

BACKGROUND

A cohort of male lead-exposed workers with past blood lead levels, previously followed for mortality over 12 years, has now been followed for an additional 10 years. This has doubled the number of deaths and allowed for examination of mortality outcomes across a wide range of blood lead levels.

OBJECTIVE

Evaluate association between lead exposure and 16 causes of death.

METHODS

The cohort included male workers from 11 U.S. states enrolled in a U.S. lead surveillance program. Maximum blood lead level for each worker was abstracted from surveillance records. Mortality was assessed using the National Death Index. We conducted internal analyses via Cox regression adjusting for age, calendar time, and race. External analyses compared cohort mortality rates with those of the U.S.

POPULATION

Blood lead categories were defined as 0-<5, 5-<25, 25-<40, and ≥40 μg/dL with the two lower categories combined for outcomes with <5 deaths in the 0-<5 group.

RESULTS

The cohort (n = 58,368) was followed for a median of 19 years and experienced 6,527 deaths. Average maximum blood lead was 25.9 μg/dL and mean year of first blood lead test was 1997. Strong associations were found between blood lead level with larynx and lung cancer mortality. For these outcomes, hazard ratios and 95% confidence intervals across blood lead categories were 1.0 (ref), 1.1 (0.4-3.2), 3.4 (1.3-9.1) for larynx and 1.0 (ref), 1.6 (1.0-2.5), 2.0 (1.3-3.1), 2.9 (1.9-4.5) for lung (trend p-values = 0.08 and < 0.01, respectively). Positive significant trends were also seen for mortality from brain cancer, chronic obstructive pulmonary disease, ischemic heart disease, and non-hodgkin's lymphoma. Findings suggested associations with chronic renal disease and rectal cancer mortality, although trends were not statistically significant.

CONCLUSIONS

The additional follow up confirmed previous relationships between lead and mortality and also detected new associations.

Cancer incidence among workers with blood lead measurements in two countries

OBJECTIVE

Study carcinogenicity of inorganic lead, classified as 'probably carcinogenic' to humans by the International Agency for Research on Cancer (brain, lung, kidney and stomach).

METHODS

We conducted internal and external analyses for cancer incidence in two cohorts of 29 874 lead-exposed workers with past blood lead data (Finland, n=20 752, Great Britain=9122), with 6790 incident cancers. Exposure was maximum measured blood lead.

RESULTS

The combined cohort had a median maximum blood lead of 29 μg/dL, a mean first blood lead test of 1977, and was 87% male. Significant (p<0.05) positive trends, using the log of maximum blood lead, were found for brain cancer (malignant), Hodgkin's lymphoma, lung cancer and rectal cancer, while a significant negative trend was found for melanoma. Borderline significant positive trends (0.05≤p≤0.10) were found for oesophageal cancer, meningioma and combined malignant/benign brain cancer. Categorical analyses reflected these trends. Significant interactions by country were found for lung, brain and oesophageal cancer, with Finland showing strong positive trends, and Great Britain showing modest or no trends. Larynx cancer in Finland also showed a positive trend (p=0.05). External analyses for high exposure workers (maximum blood lead >40 μg/dL) showed a significant excess for lung cancer in both countries combined, and significant excesses in Finland for brain and lung cancer. The Great Britain data were limited by small numbers for some cancers, and limited variation in exposure.

CONCLUSIONS

We found strong positive incidence trends with increasing blood lead level, for several outcomes in internal analysis. Two of these, lung and brain cancer, were sites of a priori interest.