Urinary Excretion of Silicon in Men, Non-pregnant Women, and Pregnant Women: a Cross-sectional Study

Urinary Silicon Excretion in Relation to Lactation and Bone Mineral Density - a Longitudinal Study Post-partum

Silicon (Si) may be a mineral beneficial for bone health. Pregnancy and lactation have major impacts on maternal bone metabolism as bone minerals, including calcium (Ca), are required for growth of the foetus and for milk production. Like urinary Ca excretion, Si excretion has been reported to be high in pregnant women, but there are no data post-partum and during lactation. The aim of the present study was to investigate the urinary excretion of Si (U-Si), from the third trimester of pregnancy until 18 months post-partum, and in relation to the length of lactation, to determine if changes in U-Si are associated with changes in areal bone mineral density (aBMD). This longitudinal study included 81 pregnant women, of whom 56 completed the study. Spot urine samples were collected at the third trimester and at 0.5, 4, 12, and 18 months post-partum and were analysed for Si and Ca by ICP-OES. The aBMD was measured post-partum at lumbar spine and femoral neck by dual-energy x-ray absorptiometry. Women lactating for 4-8.9 and ≥ 9 months had significantly higher U-Si at 4 months post-partum, compared with the third trimester. No significant longitudinal differences in U-Si were found after correcting for creatinine. Changes in U-Si and in aBMD were not correlated, except at the lumbar spine from 0.5 to 12 months post-partum in the women lactating for 4-8.9 months. Taken together, our results suggest that there is a possibility that U-Si increases post-partum in women lactating for 4 months or longer, although it is not related to changes in aBMD.

Monitoring of urinary arsenic (As) and lead (Pb) among a sample of pregnant Iranian women

PURPOSE

Heavy metals, as significant toxic environmental contaminants, can cause serious adverse health outcomes on the human body even in trace concentrations. There is limited evidence on heavy metal concentrations existing in the body fluids of pregnant women. This study aims to evaluate the urinary levels of arsenic (As) and lead (Pb), as two main toxic heavy metals, among pregnant women and their lifestyle determinants.

METHODS

The study was performed in 2019-2020 in Isfahan, Iran. A number of 140 urine samples of pregnant women who were in their first pregnancy trimester were examined. Inductively coupled plasma optical emission spectrometry (ICP-OES) was applied to analyze the urinary concentrations of As and Pb. Socio-demographic data including age, pre-pregnancy body mass index (BMI), education status, and family income, as well as the use of cleaning products (cosmetic and household cleaning products), and lifestyle habits (food intake, smoking, and physical activity) were collected using a validated questionnaire.

RESULTS

The mean concentration of As and Pb were 8.14 ± 10.8 and 9.6 ± 7.1 μg/g creatinine, respectively. The mean urinary concentration of Pb indicated significant differences in the levels of cosmetic usage, second-hand smoking exposure, and the use of Copper, Aluminum, Teflon, Steel, and Enameled utensils for cooking (p-value < 0.05). Furthermore, the mean of urinary Pb concentrations at high levels of physical activity and scratched utensils using was significantly different from the other categories (p-value = 0.02). No significant differences were found between As and Pb concentration with other socio-demographic factors.

CONCLUSION

The lifestyle determinants and cosmetic products use are important predictors of urinary heavy metals in pregnant women, rather than sociodemographic characteristics. Additional research is necessary to determine long-term adverse birth outcomes of exposure to these heavy metals.

Prenatal exposure to chromium (Cr) and nickel (Ni) in a sample of Iranian pregnant women: urinary levels and associated socio-demographic and lifestyle factors

Heavy metals have been well documented to pose detrimental health effects. The current study aimed to measure the concentration of chromium (Cr) and nickel (Ni) in urinary samples of Iranian pregnant females and determine their potential correlations with different lifestyle variables. The study was conducted in 2019-2020 in Isfahan, Iran, and the urine samples were collected from 140 pregnant women. The concentrations of Cr and Ni in the urinary samples were measured by inductively coupled plasma optical emission spectrometry (ICP-OES). Data on socio-demographic characteristics, use of cleaning products, and lifestyle profiles was collected by validated questionnaires. Cr and Ni were detected in 100% of urinary samples with the mean concentration of 4.1±3.4 and 7.5±4.8 μg/g creatinine, respectively. Significant associations were found between the mean concentration of Cr and Ni with using cooking utensils made of copper, aluminum, Teflon, steel, and enameled, as well as with cosmetic use, and second-hand smoking exposure during pregnancy. The results also showed that the mean urinary Ni and Cr concentrations were significantly different among individuals who consumed seafood and canned food (p-value <0.05). Furthermore, the mean of urinary Cr and Ni concentrations at high levels of physical activity and scratched utensils used was significantly different from the other categories (p-value <0.05). According to our findings, the lifestyle determinants and cosmetic products had superiority to socio-demographic characteristics in predicting urinary heavy metals in Iranian pregnant women.

Particle and metal exposure in Parisian subway: Relationship between exposure biomarkers in air, exhaled breath condensate, and urine

Subway particulate toxicity results from in vitro and in vivo studies diverge and call for applied human research on outcomes from chronic exposures and potential exposure biomarkers. We aimed to (1) quantify airborne particulate matter (PM) concentrations (mass and number) and metal concentrations in exhaled breath condensate (EBC), urine, and PM; (2) investigate their associations (EBC vs. PM vs. urine); and (3) assess the relevance of EBC in biomonitoring. Nine subway workers in three jobs: station agents, locomotive operators and security guards were monitored during their 6-h shifts over two consecutive weeks. Six-hour weighed average mass concentrations expressed as PM10, PM2.5 and their metal concentrations were determined. Urine and EBC samples were collected pre- and post-shift. Ultrafine particle (UFP) number concentrations were quantified in PM and EBC samples. Metal concentrations in urine and EBC were standardized by creatinine and EBC volume, respectively, and log-transformed. Associations were investigated using Pearson correlation and linear mixed regression models, with participant's ID as random effect. PM concentrations were below occupational exposure limits (OEL) and varied significantly between jobs. Locomotive operators had the highest exposure (189 and 137 μg/m³ for PM10 and PM2.5, respectively), while station agents had the highest UFP exposure (1.97 × 10⁴ particles/cm³). Five metals (Al, Fe, Zn, Cu, and Mn) in PM2.5 and three (Al, Fe, and Zn) in PM10 were above the limit of quantification (LOQ). Fe, Cu, Al and Zn were the most abundant by mass fraction in PM. In EBC, the metal concentrations in decreasing order were: Zn > Cu > Ni > Ba > Mn. Security guards had the highest EBC metal concentrations, and in particular Zn and Cu. Urinary metal concentrations in decreasing order were: Si > Zn > Mo > Ti > Cu > Ba ≈ Ni > Co. All urinary metal concentrations from the subway workers were similar to concentrations found in the general population. A statistically significant relationship was found for ultrafine particle number concentrations in PM and in EBC. Zn and Cu concentrations in post-shift EBC were associated with Zn and Cu concentrations in PM10 and with post-shift urinary Zn and Cu concentrations. Therefore, EBC appears a relevant matrix for assessing exposure to UFP in human biomonitoring when inhalation is a primary route of exposure. We found different temporal variation patterns between particle and metal exposures in three matrices (PM, urine, EBC) quantified daily over two full weeks in subway workers. These patterns might be related to metal oxidation, particulates' solubility and size as well as their lung absorption capabilities, which need to be further explored in toxicological research. Further research should also focus on understanding possible influences of low chronic exposures to subway particulates on health in larger cohorts.

Inhibitory effects of orthosilicic acid on osteoclastogenesis in RANKL-stimulated RAW264.7 cells

Numerous studies have reported on the positive effects of silicon (Si) on bone metabolism, particularly on the stimulatory effects of Si on osteoblast cells and on bone formation. Inhibitory effects of Si on osteoclast formation and bone resorption have also been demonstrated in vitro and are suggested to be mediated indirectly via stromal and osteoblast cells. Direct effects of Si on osteoclasts have been less studied and mostly using soluble Si, but no characterisation of the Si treatment solutions are provided. The aims of the present study were to (a) further investigate the direct inhibitory effects of Si on osteoclastogenesis in RANKL-stimulated RAW264.7 cells, (b) determine at what stage during osteoclastogenesis Si acts upon, and (c) determine if these effects can be attributed to the biologically relevant soluble orthosilicic acid specie. Our results demonstrate that silicon, at 50 μg/ml (or 1.8 mM), does not affect cell viability but directly inhibits the formation of TRAP+ multinucleated cells and the expression of osteoclast phenotypic genes in RAW264.7 cells. The inhibitory effect of Si was clearly associated with the early stages (first 24 hr) of osteoclastogenesis. Moreover, these effects can be attributed to the soluble orthosilicic acid specie.

Monitoring of urinary phthalate metabolites among pregnant women in Isfahan, Iran: the PERSIAN birth cohort

Recently, increasing evidences have shown that the exposure to phthalates can adversely affect health status of pregnant women and their newborns. However, only a limited number of studies have investigated the concentrations of these compounds in the body fluids of pregnant women. In the present study, we aimed to evaluate the concentrations of phthalate metabolites in urinary samples of pregnant women in correlation with the population characteristics and different lifestyle factors. The study was conducted in 2018-2019 and urinary samples were taken from 121 pregnant women during their first pregnancy trimester who lived in Isfahan, Iran. The concentrations of monobutyl phthalate (MBP), mono-benzyl phthalate (MBzP), mono-2-ethylhexyl phthalate (MEHP), and mono (2-ethyl-5hydroxyhexyl) phthalate (MEHHP) metabolites in urinary samples were determined by gas chromatography mass spectrometry (GC/MS). The socio-demographic profile of the participants (maternal education, age, family income, pre-pregnancy BMI), their lifestyle information (smoking habit, food pattern, and physical activity), cleaning products use data (cosmetic and household cleaning products) were collected by the use of PERSIAN birth cohort questionnaire. MBzP, MBP, MEHP, and MEHHP were detected in 100% of participated pregnant women with the mean concentration of 342.5 ± 193.8, 308.5 ± 229.4, 126.5 ± 118.3, and 866.5 ± 307.6 μg/g creatinine, respectively. Significant correlations were observed between the mean concentration of urinary phthalate metabolites with the following variables: using plastic packaging (for bread, lemon juice, pickle, leftover, and water), lower physical activity, passive smoking exposure during pregnancy (p value<0.05). Furthermore, the pre-pregnancy BMI (r = 0.27, r = 0.3, r = 0.26, and r = 0.26), use of the household cleaning products (r = 0.2, r = 0.22, r = 0.3, and r = 0.26), utilize of the cosmetic products (r = 0.46, r = 0.48, r = 0.49, and r = 0.54), and passive smoking status (r = 0.5, r = 0.44, r = 0.44, and r = 0.26) directly correlated with the urinary concentrations of MBP, MBzP, MEHP, and MEHHP, respectively. No significant association was seen between the concentration of urinary phthalate metabolites with the maternal education level and family income. According to our findings, higher amounts of phthalate metabolites were detected in urinary samples of pregnant women who were passive smokers, or had higher pre-pregnancy BMI and lower physical activity, as well as those women who used higher amounts of cosmetic and household cleaning products, or used plastic packaging for food and non-food products.