Relationship of blood and bone lead to menopause and bone mineral density among middle-age women in Mexico City

A State-of-the-Science Review on Metal Biomarkers

PURPOSE OF REVIEW

Biomarkers are commonly used in epidemiological studies to assess metals and metalloid exposure and estimate internal dose, as they integrate multiple sources and routes of exposure. Researchers are increasingly using multi-metal panels and innovative statistical methods to understand how exposure to real-world metal mixtures affects human health. Metals have both common and unique sources and routes of exposure, as well as biotransformation and elimination pathways. The development of multi-element analytical technology allows researchers to examine a broad spectrum of metals in their studies; however, their interpretation is complex as they can reflect different windows of exposure and several biomarkers have critical limitations. This review elaborates on more than 500 scientific publications to discuss major sources of exposure, biotransformation and elimination, and biomarkers of exposure and internal dose for 12 metals/metalloids, including 8 non-essential elements (arsenic, barium, cadmium, lead, mercury, nickel, tin, uranium) and 4 essential elements (manganese, molybdenum, selenium, and zinc) commonly used in multi-element analyses.

RECENT FINDINGS

We conclude that not all metal biomarkers are adequate measures of exposure and that understanding the metabolic biotransformation and elimination of metals is key to metal biomarker interpretation. For example, whole blood is a good biomarker of exposure to arsenic, cadmium, lead, mercury, and tin, but it is not a good indicator for barium, nickel, and uranium. For some essential metals, the interpretation of whole blood biomarkers is unclear. Urine is the most commonly used biomarker of exposure across metals but it should not be used to assess lead exposure. Essential metals such as zinc and manganese are tightly regulated by homeostatic processes; thus, elevated levels in urine may reflect body loss and metabolic processes rather than excess exposure. Total urinary arsenic may reflect exposure to both organic and inorganic arsenic, thus, arsenic speciation and adjustment for arsebonetaine are needed in populations with dietary seafood consumption. Hair and nails primarily reflect exposure to organic mercury, except in populations exposed to high levels of inorganic mercury such as in occupational and environmental settings. When selecting biomarkers, it is also critical to consider the exposure window of interest. Most populations are chronically exposed to metals in the low-to-moderate range, yet many biomarkers reflect recent exposures. Toenails are emerging biomarkers in this regard. They are reliable biomarkers of long-term exposure for arsenic, mercury, manganese, and selenium. However, more research is needed to understand the role of nails as a biomarker of exposure to other metals. Similarly, teeth are increasingly used to assess lifelong exposures to several essential and non-essential metals such as lead, including during the prenatal window. As metals epidemiology moves towards embracing a multi-metal/mixtures approach and expanding metal panels to include less commonly studied metals, it is important for researchers to have a strong knowledge base about the metal biomarkers included in their research. This review aims to aid metals researchers in their analysis planning, facilitate sound analytical decision-making, as well as appropriate understanding and interpretation of results.

Concentration of Selected Macronutrients and Toxic Elements in the Blood in Relation to Pain Severity and Hydrogen Magnetic Resonance Spectroscopy in People with Osteoarthritis of the Spine

Macronutrients and toxic elements may play an important role in the pathogenesis of osteoarthritis of the spine. The objective of this study was to evaluate the relationship between the concentrations of Ca, Mg, Pb, Cd and Hg in blood with the results of hydrogen magnetic resonance spectroscopy and the severity of pain. Patients with osteoarthritis of the spine (n = 90) and control subjects (n = 40) were studied. The concentrations of mineral components in blood were determined by atomic absorption spectrometry (ASA). Spinal pain severity was assessed using the Visual Analog Scale (VAS). Hydrogen magnetic resonance spectroscopy (¹H-MRS) was used to determine the fat/water ratio in the bodies of L1, L5 and the L4/5 intervertebral disc. The median concentration of Mg in the serum of subjects with spinal degenerative disease was significantly lower (p < 0.001) than that in healthy subjects. The median concentration of Cd in the blood of subjects with osteoarthritis of the spine was significantly higher (p < 0.05) than that in the control group. Significantly lower (p < 0.05) median molar ratios of Ca to Cd and Pb as well as Mg to Pb and Cd were observed among patients with osteoarthritis of the spine. Significant differences (p < 0.05) were observed in the value of the fat/water ratio in selected spinal structures, depending on normal or abnormal serum Ca and Mg concentrations. The study showed some abnormal macronutrient concentrations, as well as disturbed ratios of beneficial elements to toxic elements in the blood of people with osteoarthritis of the spine.

Determination of Blood Calcium and Lead Concentrations in Osteoporotic and Osteopenic Patients in Pakistan

Osteoporosis is the leading cause of deformity and bones fracture all over the world and has some relationship with the blood concentrations of calcium and lead. Therefore, in the current study, the blood samples of 58 control and 56 clinically diagnosed osteoporotic and osteopenic patients were taken from different hospitals in Pakistan and analyzed for calcium and lead concentrations using atomic absorption spectrometry. In female control samples, the mean calcium value was found to be 98.53 ± 4.81 μg/mL, and in male control samples, the mean blood calcium level was found to be 121.33 ± 7.27 μg/mL. In female control samples, the mean lead value was found to be 0.133 ± 0.005 μg/mL, and in male control samples, the mean lead level was found to be 0.183 ± 0.008 μg/mL. All the male and female control samples showed a mean value of calcium of 115.63 ± 5.2 μg/mL and a mean value of lead of 0.153 ± 0.007 μg/mL. In osteoporotic female patients, the decline in the mean calcium value was found to be 34.93 ± 1.9 μg/mL, and in male patients, the decrease in the mean calcium level was found to be 47.73 ± 2.5 μg/mL. The increase in the mean value of lead in osteoporotic females was 4.13 ± 0.22 μg/mL, whereas in male patients, the increase in the mean lead value was 0.95 ± 0.07 μg/mL. All the male and female patients showed a decrease in the mean value of calcium of 41.43 ± 2.2 μg/mL and an increase in the mean value of Pb of 3.63 ± 0.16 μg/mL.

Metal exposure and bone remodeling during pregnancy: Results from the PROGRESS cohort study

Pregnancy is characterized by high bone remodeling and might be a window of susceptibility to the toxic effects of metals on bone tissue. The aim of this study was to assess associations between metals in blood [lead (Pb), cadmium (Cd)and arsenic (As)] and bone remodeling during pregnancy. We studied pregnant woman from the PROGRESS Cohort (Programming Research in Obesity, Growth, and Environment and Social Stress). We measured concentrations of metals in blood and obtained measures of bone remodeling by quantitative ultrasound (QUS) at the radius in the second and third trimester of pregnancy. To account for chronic lead exposure, we measured lead in tibia and patella one-month postpartum with K-shell X-ray fluorescence. We assessed cross-sectional and longitudinal associations between multiple-metal concentrations and QUS z-scores using linear regression models and linear mixed models adjusted for potential confounders. Third trimester blood Cd concentrations were marginal associated with lower QUS z-scores [-0.16 (95% CI: -0.33, 0.007); P-Value = 0.06]. Mixed models showed that blood Cd was longitudinally and marginally associated with an average of -0.10 z-score (95% CI: -0.21, 0.002; P-Value = 0.06) over the course of pregnancy. Associations for Pb and As were all inverse however none reached significance. Additionally, bone Pb concentrations in patella, an index of cumulative exposure, were significantly associated with -0.06 z-score at radius (95% CI: -0.10, -0.01; P-Value = 0.03) during pregnancy. Pb and Cd blood levels are associated with lower QUS distal radius z-scores in pregnant women. Bone Pb concentrations in patella were negatively associated with z-score at radius showing the long-term effects of Pb on bone tissue. However, we cannot exclude the possibility of reverse causality for patella Pb and radius z-score associations. Our results support the importance of reducing women's metal exposure during pregnancy, as metals exposure during pregnancy may have consequences for bone strength later in life. The main finding of our study is the association between Cd blood levels and radius z-score during pregnancy. Bone lead in patella was also negatively associated with radius z-scores.

Long-Term Accumulation of Metals in the Skeleton as Related to Osteoporotic Derangements

The concentrations of metals in the environment are still not within the recommended limits as set by the regulatory authorities in various countries because of human activities. They can enter the food chain and bioaccumulate in soft and hard tissues/organs, often with a long half-life of the metal in the body. Metal exposure has a negative impact on bone health and may result in osteoporosis and increased fracture risk depending on concentration and duration of metal exposure and metal species. Bones are a long-term repository for lead and some other metals, and may approximately contain 90% of the total body burden in birds and mammals. The present review focuses on the most common metals found in contaminated areas (mercury, cadmium, lead, nickel, chromium, iron, and aluminum) and their effects on bone tissue, considering the possibility of the long-term bone accumulation, and also some differences that might exist between different age groups in the whole population.

Relationship between personal-sampled air lead and blood lead in low-lead-exposure workers in Japan to apply multiple regression models determining permissible air lead concentration

OBJECTIVES

We investigated the relationship between lead in air (Pb-A) measured by personal sampling and blood lead (Pb-B) in workers with relatively low lead exposure to estimate the permissible air concentration of lead corresponding to the biological tolerance value of Pb-B of 15 µg/dL.

METHODS

We collected air samples at a lead-acid battery factory in Japan by personal sampling devices attached to 32 workers (19 males and 13 females) and measured Pb-A by a graphite furnace atomic absorption spectrophotometer in 2017-2020. In addition, we collected information on age, smoking habits, Pb-B, and urinary δ-aminolevulinic acid from the records of medical examinations for lead poisoning. Samples were collected two times from four workers, resulting in 36 data sets.

RESULTS

Before analyses, we excluded four inappropriate data sets. The levels of Pb-A in the factory and Pb-B in the workers were almost under the current permissible limits. Multiple regression models showed significant correlations between Pb-B and Pb-A, and sex, and borderline significance between Pb-B and age. Based on them, we calculated Pb-A corresponding to Pb-B 15 μg/dL, and obtained similar values to the current occupational exposure limit (OEL) of 30 μg/m3 , with slight variation between sex and age.

CONCLUSION

These results validate OEL, although supplementary conditions in terms of sex and age may be necessary.

Menopause and lead body burden among US women aged 45-55, NHANES 1999-2010

BACKGROUND

Environmental factors in menopause have received limited attention. Lead is a known reproductive toxicant associated with delayed puberty in girls that may also affect menopause.

METHODS

The odds of menopause among US women aged 45-55 were estimated in the National Health and Nutrition Examination Survey, 1999-2010, in relation to quartiles of blood lead. Women still menstruating (n=2158) were compared to women with natural menopause (n=1063). Logistic regression models included age, race/ethnicity, current hormone use, poverty, smoking and where available, bone density or bone alkaline phosphatase.

RESULTS

Lead levels (ug/dL) were higher in menopausal women, geometric mean (standard error)=1.71 (0.04) vs. 1.23 (0.02). Adjusted odds of menopause and 95% confidence intervals for lead quartiles (lowest quartile referent) were 1.7 (1.0-2.8), 2.1 (1.2-3.6), and 4.2 (2.5-7.0) respectively. Results adjusting for bone markers were generally similar but had less precision.

CONCLUSIONS

Blood lead was associated with natural menopause in US women even after adjustment for bone turnover. This raises concern that lead exposure, even at low levels, may shorten women's reproductive lifespan.

Bone mineral density and blood metals in premenopausal women

Exposure to metals, specifically cadmium, lead, and mercury, is widespread and is associated with reduced bone mineral density (BMD) in older populations, but the associations among premenopausal women are unclear. Therefore, we evaluated the relationship between these metals in blood and BMD (whole body, total hip, lumbar spine, and non-dominant wrist) quantified by dual energy X-ray absorptiometry in 248 premenopausal women, aged 18-44. Participants were of normal body mass index (mean BMI 24.1), young (mean age 27.4), 60% were white, 20% non-Hispanic black, 15% Asian, and 6% other race group, and were from the Buffalo, New York region. The median (interquartile range) level of cadmium was 0.30 μg/l (0.19-0.43), of lead was 0.86 μg/dl (0.68-1.20), and of mercury was 1.10 μg/l (0.58-2.00). BMD was treated both as a continuous variable in linear regression and dichotomized at the 10th percentile for logistic regression analyses. Mercury was associated with reduced odds of decreased lumbar spine BMD (0.66, 95% confidence interval: 0.44, 0.99), but overall, metals at environmentally relevant levels of exposure were not associated with reduced BMD in this population of healthy, reproductive-aged women. Further research is needed to determine if the blood levels of cadmium, lead, and mercury in this population are sufficiently low that there is no substantive impact on bone, or if effects on bone can be expected only at older ages.

Blood lead and cadmium levels in a six hospital employee population. PESA study, 2009

INTRODUCTION

Exposure to lead and cadmium is a public health problem due to the broad exposure to these toxic substances among the general population. The objective of this study is to determine blood lead and cadmium concentrations in a working population drawn from six university hospitals in Madrid, Getafe, Cartagena, Santiago de Compostela, Santander and Palma de Mallorca (Spain) and to identify associated factors.

MATERIALS AND METHODS

951 individuals participated in the study and were administered the standardized PESA® questionnaire regarding exposure to lead and cadmium. The blood lead and cadmium concentrations were measured by electrothermal atomization atomic absorption spectrometry with Zeeman background correction in Perkin-Elmer spectrometers, guaranteeing the transferability of the results.

RESULTS

The median overall blood lead concentration was: 1.6 μg/dL (IQR: 0.9-2.7) and that of cadmium was: 0.21 μg/L (IQR: 0.10-0.50). There were significant differences in lead levels between men (2 μg/dL) and women (1.5 μg/dL), postmenopausal (2.6 μg/dL) and premenopausal women (1.1 μg/dL), and between participants who cooked in earthenware (2.1 μg/dL) and those who did not (1.5 μg/dL). The median of cadmium in women (0.24 μg/L) was higher than in men (0.11 μg/L) and was also higher in subjects who smoked (0.70 μg/L) than in non-smokers (0.13 μg/L).

CONCLUSIONS

A reduction in blood lead and cadmium levels was observed with respect to previous studies carried out in Spain. Nevertheless, the results suggest there are certain factors which increase risk such as age, gender, menopause, age of housing, cooking in lead-glazed earthenware and exposure to cigarette smoke.

Association between bone turnover, micronutrient intake, and blood lead levels in pre- and postmenopausal women, NHANES 1999-2002

BACKGROUND

Blood lead levels (BLLs) have been shown to increase during periods of high bone turnover such as pregnancy and menopause.

OBJECTIVES

We examined the associations between bone turnover and micronutrient intake with BLLs in women 20-85 years of age (n = 2,671) participating in the National Health and Nutrition Examination Survey, 1999-2002.

METHODS

Serum bone-specific alkaline phosphatase (BAP) and urinary cross-linked N-telopeptides (NTx) were measured as markers of bone formation and resorption, respectively. Lead was quantified in whole blood. The association between tertiles of BAP and NTx, and BLLs was examined using linear regression with natural log transformed BLLs as the dependent variable and interpreted as the percent difference in geometric mean BLLs.

RESULTS

In adjusted analyses, mean BLLs among postmenopausal women in the upper tertiles of NTx and BAP were 34% [95% confidence interval (CI), 23%-45%] and 30% (95% CI, 17%-43%) higher than BLLs among women in the lowest tertiles of NTx and BAP, respectively. These associations were weaker, but remained statistically significant, among premenopausal women (NTx: 10%; 95% CI, 0.60%-19%; BAP: 14%; 95% CI, 6%-22%). Within tertiles of NTx and BAP, calcium intake above the Dietary Reference Intake (DRI), compared with below the DRI, was associated with lower mean BLLs among postmenopausal women but not premenopausal women, although most of the associations were not statistically significant. We observed similar associations for vitamin D supplement use.

CONCLUSIONS

Bone resorption and bone formation were associated with a significant increase in BLLs among pre- and postmenopausal women.

Bone lead and endogenous exposure in an environmentally exposed elderly population: the normative aging study

OBJECTIVE

The objective of this study is to investigate the mobilization of lead from bone to blood (endogenous exposure) in a large epidemiologic population.

METHODS

Study subjects were 776 participants in the Normative Aging Study. The subjects had their tibia lead, patella lead, blood lead, and urinary N-telopeptide (NTx) levels measured 1 to 4 times from 1991 to 2002. Regression models were estimated to quantify the association between tibia and patella lead and blood lead. We studied nonlinearity of the association, and explored possible factors that may modify it, including age and NTx levels.

RESULTS AND CONCLUSIONS

There is significant association between bone lead and blood lead, and the association is nonlinear. The nonlinear associations between blood lead and bone lead are not significantly modified by age and NTx.

Childhood lead poisoning: conservative estimates of the social and economic benefits of lead hazard control

BACKGROUND

This study is a cost-benefit analysis that quantifies the social and economic benefits to household lead paint hazard control compared with the investments needed to minimize exposure to these hazards.

OBJECTIVES

This research updates estimates of elevated blood lead levels among a cohort of children < or = 6 years of age and compiles recent research to determine a range of the costs of lead paint hazard control ($1-$11 billion) and the benefits of reduction attributed to each cohort for health care ($11-$53 billion), lifetime earnings ($165-$233 billion), tax revenue ($25-$35 billion), special education ($30-$146 million), attention deficit-hyperactivity disorder ($267 million), and the direct costs of crime ($1.7 billion).

RESULTS

Each dollar invested in lead paint hazard control results in a return of $17-$221 or a net savings of $181-269 billion.

CONCLUSIONS

There are substantial returns to investing in lead hazard control, particularly targeted at early intervention in communities most likely at risk. Given the high societal costs of inaction, lead hazard control appears to be well worth the price.

Relationship of blood lead levels to incident nonspine fractures and falls in older women: the study of osteoporotic fractures

Lead is stored in the skeleton and can serve as an endogenous source for many years. Lead may influence the risk of fracture, through direct effects on bone strength or indirectly by disturbing neuromuscular function and increasing the risk of falls. The objective of this analysis is to test the hypothesis that women with higher blood lead levels experience higher rates of falls and fracture. This was a prospective cohort study of 533 women 65-87 yr of age enrolled in the Study of Osteoporotic Fractures at two U.S. research centers (Baltimore, MD; Monongahela Valley, PA) from 1986 to 1988. Blood lead levels (in microg/dl) were measured in 1990-1991 by atomic absorption spectrophotometry and classified as "low" (<or=3; lower 15th percentile, referent); "medium" (4-7); or "high" (>or=8; upper 15th percentile). Total hip BMD was measured by DXA twice, 3.55 yr apart. Information on falls was collected every 4 mo for 4 yr. Incident nonspine fractures were identified and confirmed over 10 yr. Cox proportional hazards models were used to estimate the hazard ratio (HR) and 95% CI of fracture. Generalized estimating equations were used to calculate the incident rate ratio of falls (95% CI). The mean blood lead level was 5.3 +/- 2.3 (SD) microg/dl (range, 1-21 microg/dl). Baseline BMD was 7% lower in total hip and 5% lower in femoral neck in the highest compared with lowest blood lead group (p < 0.02). Hip bone loss tended to be greater in the high lead group, but differences were not significant. In multivariable adjusted models, women with high blood lead levels had an increased risk of nonspine fracture (HR = 2.50; 95% CI = 1.25, 5.03; p trend = 0.016) and higher risk of falls (incident rate ratio = 1.62; 95% CI = 1.07, 2.45; p trend = 0.014) compared with women with lowest lead level. Blood lead levels are associated with an increased risk of falls and fractures, extending the negative health consequences of lead to include osteoporotic fractures.

Lead exposure and spine bone mineral density

OBJECTIVE

The purpose of this study was to assess changes in spine BMD over time in relation to changes in bone and blood lead levels and baseline risk factors among female former smelter workers in Bunker Hill, Idaho.

METHODS

Spine BMD was measured using Norland XR-26 X-Ray bone densitometer. Cd109 K XRF system was used to estimate tibia bone lead content. Blood lead levels were analyzed using graphite furnace atomic absorption with Zeeman effect background correction. Information about risk factors was obtained through a questionnaire.

RESULTS

In the final backward stepwise multivariate regression model after controlling for baseline BMD, baseline blood lead measured in 1994 and time since menopause; spine bone density in 2000 decreased with increasing blood lead levels in 2000 in all these women, especially if they worked in a technical job (miner) most of the time at the smelter.

CONCLUSIONS

Blood lead may adversely affect bone mineral density.

Cadmium-induced effects on bone in a population-based study of women

High cadmium exposure is known to cause bone damage, but the association between low-level cadmium exposure and osteoporosis remains to be clarified. Using a population-based women's health survey in southern Sweden [Women's Health in the Lund Area (WHILA) ] with no known historical cadmium contamination, we investigated cadmium-related effects on bone in 820 women (53-64 years of age) . We measured cadmium in blood and urine and lead in blood, an array of markers of bone metabolism, and forearm bone mineral density (BMD) . Associations were evaluated in multiple linear regression analysis including information on the possible confounders or effect modifiers: weight, menopausal status, use of hormone replacement therapy, age at menarche, alcohol consumption, smoking history, and physical activity. Median urinary cadmium was 0.52 microg/L adjusted to density (0.67 microg/g creatinine) . After multivariate adjustment, BMD, parathyroid hormone, and urinary deoxypyridinoline (U-DPD) were adversely associated with concentrations of urinary cadmium (p < 0.05) in all subjects. These associations persisted in the group of never-smokers, which had the lowest cadmium exposure (mainly dietary) . For U-DPD, there was a significant interaction between cadmium and menopause (p = 0.022) . Our results suggest negative effects of low-level cadmium exposure on bone, possibly exerted via increased bone resorption, which seemed to be intensified after menopause. Based on the prevalence of osteoporosis and the low level of exposure, the observed effects, although slight, should be considered as early signals of potentially more adverse health effects. Key words: biochemical bone markers, bone mineral density, cadmium, lead, osteoporosis, women.

Prospective study of blood and tibia lead in women undergoing surgical menopause

Despite the dramatic decline in environmental lead exposure in the United States during the past couple of decades, concern has been expressed regarding mobilization during menopause of existing lead stored in bone. To investigate whether bone lead concentrations decrease and blood lead levels increase, we conducted a prospective study of 91 women who were scheduled to undergo a bilateral oophorectomy for a benign condition at Mount Sinai Hospital in New York City during October 1994 through April 1999. We excluded women who were younger than 30 years of age or who were postmenopausal at the time of the surgery. We observed a small but significant increase in median blood lead levels between the baseline visit and the 6-month visit (0.4 microg/dL, p<0.0001), particularly for women who were not on estrogen replacement therapy (0.7 microg/dL, p=0.008). No significant change was observed in blood lead values between 6 and 18 months postsurgery, nor was there evidence of significant changes in tibia lead concentrations during the follow-up period. These findings do not point to substantial mobilization of lead from cortical bone during menopause.

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.