Multiple metals in children's deciduous teeth: results from a community-initiated pilot study

Toxic and essential elements in primary teeth and maternal blood during pregnancy: The Norwegian Mother, Father and Child Cohort Study (MoBa) and the MoBaTooth Biobank

BACKGROUND

Maternal exposure to toxic and essential elements can be transferred to the fetus. Deciduous tooth dentine, formed prenatally, serves as a potential biomarker for fetal exposure.

OBJECTIVE

To investigate the relationship between maternal blood Pb, Mn, Cu, Mo and Zn element concentrations and the corresponding child tooth dentine levels in mid pregnancy. A secondary objective explores the predictive value of maternal blood element concentrations for child dentine element levels for the same metals.

METHODS

Early-life element concentrations were measured in maternal whole blood from the 2nd trimester and in child tooth dentine from 94 child-mother dyads enrolled in the Norwegian Mother, Father and Child Cohort Study (MoBa), The Norwegian Environmental Biobank (NEB) and the MoBaTooth biobank. The relationship between lead (Pb), manganese (Mn), copper (Cu), molybdenum (Mo) and zinc (Zn) in maternal blood and child dentine was examined using correlations and Receiver Operating Characteristic (ROC) curves.

RESULTS

Maternal blood Pb concentration and child dentine Pb in 2nd trimester-average correlated strongly for both girls and boys (r = 0.58, p < 0.001 and r = 0.51, p < 0.001) and was able to predict child dentine Pb. Cu correlated negatively between mothers and boys (r = -0.35, p < 0.001), and with borderline significance for girls (r = -0.17, p = 0.058). For Mn, Mo and Zn the associations between maternal blood and child dentine were less clear and differed by child sex.

CONCLUSION

Our analysis confirmed a strong association between maternal blood Pb concentration and child tooth dentine Pb. These findings offer a promising biomarker of early life exposure and may help to identify consequences of maternal exposure during pregnancy.

Association of trace element levels in primary teeth and occurrence of Cleft lip and/or palate

BACKGROUND

Cleft lip and/or palate (CL/CP) are common congenital anomalies with multifactorial origins, potentially influenced by environmental factors, including multi-trace metal exposure. Primary teeth, which form in utero, offer a unique biomatrix for assessing early-life metal exposure, yet remain underexplored in CL/CP research.

OBJECTIVE

This case-control study aimed to investigate the association between multi-trace metal exposure and CL/CP occurrence by analyzing primary teeth using Inductively Coupled Plasma Mass Spectrometry (ICP-MS).

METHODS

Ethical clearance was obtained for this study, which included 30 children aged 4-12 years. Non-carious central and lateral incisors were analyzed for trace metals using ICP-MS. Demographic, socioeconomic, and nutritional data were collected via a structured proforma and environmental risk factor questionnaire.

RESULTS

A comprehensive analysis of 24 trace metals in primary teeth of CL/CP and control groups found no significant associations with 25Mg, 52Cr, 43Ca, and 56Fe, with odds ratios near 1. Lower 113 Cd concentrations were linked to CL/CP. However, the small sample size (n = 15 per group) limits conclusions on the relationship between cadmium levels and CL/CP. Maternal nutritional deficiencies (p = 0.031) and lower annual income (p = 0.001) were significantly associated with increased CL/CP prevalence, suggesting socioeconomic and dietary influences.

CONCLUSION

Exposure to 25Mg, 52Cr, 43Ca, and 56Fe showed no significant association with CL/CP risk, while lower 113 Cd levels suggested a potential link, though the small sample size limits interpretations. Further research is needed to elucidate the link between metal exposure and developmental anomalies, and to address cadmium's environmental and dietary sources to reduce CL/CP risk.

Quantified retrospective biomonitoring of fetal and infant elemental exposure using LA-ICP-MS analysis of deciduous dentin in three contrasting human cohorts

BACKGROUND

Spatial elemental analysis of deciduous tooth dentin combined with odontochronological estimates can provide an early life (in utero to ~2 years of age) history of inorganic element exposure and status.

OBJECTIVE

To demonstrate the importance of data normalization to a certified reference material to enable between-study comparisons, using populations with assumed contrasting elemental exposures.

METHODS

We used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of dentin to derive a history of elemental composition from three distinct cohort studies: a present day rural cohort, (the New Hampshire Birth Cohort Study (NHBCS; N = 154)), an historical cohort from an urban area (1958-1970), (the St. Louis Baby Tooth Study (SLBT; N = 78)), and a present-day Nigerian cohort established to study maternal HIV transmission (Dental caries and its association with Oral Microbiomes and HIV in young children-Nigeria (DOMHaIN; N = 31)).

RESULTS

We report Li, Al, Mn, Cu, Zn, Sr, Ba and Pb concentrations (µg/g) and qualitatively examine As, Cd and Hg across all three cohorts. Rates of detection were highest, both overall and for each cohort individually, for Zn, Sr, Ba and Li. Zinc was detected in 100% of samples and was stably present in teeth at a concentration range of 64 - 86 µg/g. Mercury, As and Cd detection rates were the lowest, and had high variability within individual ablated spots. We found the highest concentrations of Pb in the pre- and postnatal dentin of the SLBT cohort, consistent with the prevalent use of Pb as an additive to gasoline prior to 1975. The characteristic decline in Mn after the second trimester was observed in all cohorts.

IMPACT

Spatially resolved elemental analysis of deciduous teeth combined with methods for estimating crown formation times can be used to reconstruct an early-life history of elemental exposure inaccessible via other biomarkers. Quantification of data into absolute values using an external standard reference material has not been conducted since 2012, preventing comparison between studies, a common and highly informative component of epidemiology. We demonstrate, with three contrasting populations, that absolute quantification produces data with the lowest variability, compares well with available data and recommends that future tooth biomarker studies report data in this way.

Brief communication: New method for measuring nitrogen isotopes in tooth dentine at high temporal resolution

OBJECTIVES

Nitrogen isotopes (δ15N) are widely used to study human nursing and weaning ages. Conventional methods involve sampling 1-mm thick sections of tooth dentine-producing an averaging effect that integrates months of formation. We introduce a novel protocol for measuring δ15N by multicollector secondary ion mass spectrometry (SIMS).

MATERIALS AND METHODS

We sampled dentine δ15N on a weekly to monthly basis along the developmental axis in two first molars of healthy children from Australia and New Zealand (n = 217 measurements). Nitrogen isotope ratios were determined from measurements of CN- secondary molecular ions in ~35 μm spots. By relating spot position to enamel formation, we identified prenatal dentine, as well as sampling ages over more than 3 years. We also created calcium-normalized barium and strontium maps with laser ablation-inductively coupled plasma-mass spectrometry.

RESULTS

We found rapid postnatal δ15N increases of ~2‰-3‰, during which time the children were exclusively breastfed, followed by declines as the breastfeeding frequency decreased. After weaning, δ15N values remained stable for several months, coinciding with diets that did not include meat or cow's milk; values then varied by ~2‰ starting in the third year of life. Barium did not show an immediate postnatal increase, rising after a few months until ~1-1.5 years of age, and falling until or shortly after the cessation of suckling. Initial strontium trends varied but both individuals peaked months after weaning.

DISCUSSION

Developmentally informed SIMS measurements of δ15N minimize time averaging and can be precisely related to an individual's early dietary history.

Deciduous teeth from the New Hampshire birth cohort study: Early life environmental and dietary predictors of dentin elements

BACKGROUND

Sparse research exists on predictors of element concentrations measured in deciduous teeth.

OBJECTIVE

To estimate associations between maternal/child characteristics, elements measured in home tap water during pregnancy and element concentrations in the dentin of shed deciduous teeth.

METHODS

Our analysis included 152 pregnant person-infant dyads followed from the second trimester through the end of the first postnatal year from the New Hampshire Birth Cohort Study. During pregnancy and early infancy, we collected dietary and sociodemographic information via surveys, measured elements in home tap water, and later collected naturally exfoliated teeth from child participants. We measured longitudinal deposition of elements in dentin using LA-ICP-MS. Multivariable linear mixed models were used to estimate associations between predictors and dentin element concentrations.

RESULTS

We measured 12 elements in dentin including those previously reported (Ba, Mn, Pb, Sr, Zn) and less frequently reported (Al, As, Cd, Cu, Hg, Li, and W). A doubling of Pb or Sr concentrations in water was associated with higher dentin Pb or Sr respectively in prenatally formed [9% (95%CI: 3%, 15%); 3% (1%, 6%)] and postnatally formed [10% (2%, 19%); 6% (2%, 10%)] dentin. Formula feeding from birth to 6 weeks or 6 weeks to 4 months was associated with higher element concentrations in postnatal dentin within the given time period as compared to exclusive human milk feeding: Sr: 6 weeks: 61% (36%, 90%) and 4 months: 85% (54%, 121%); Ba: 6 weeks: 35% (3.3%, 77%) and 4 months: 42% (10%, 83%); and Li: 6 weeks: 61% (33%, 95%) and 4 months: 58% (31%, 90%).

SIGNIFICANCE

These findings offer insights into predictors of dentin elements and potential confounders in exposure-health outcome relationships during critical developmental periods.

Permanent and decidua dentition as chronological biomarkers of heavy metal contamination: A review of the forensic literature

STATEMENT OF PROBLEM

Contamination with heavy metals (HM) has great environmental consequences in the environment due to lack of biodegradation, in addition, accumulation in living beings causes defects in tissues and organs, deteriorating their function and inducing a wide spectrum of diseases. Human biomonitoring consists of the periodic measurement of a certain chemical substance or metabolite in a particular population, using matrices that can be acute or chronic. Teeth are chronic matrices that have great characteristics of resistance and chronological storage of information. This review aims to identify the mechanisms, spatial location, and affinity of HM within teeth, along with understanding its applicability as a chronological record matrix in the face of HM contamination.

MATERIAL AND METHODS

A systematic search review was performed using the PubMed/Medline, Web of Science, and Scopus metasearch engines, and the terms "teeth" OR "dental" OR "tooth" AND "heavy metals" were intersected. Complete articles are included in Spanish, English and Portuguese without time restrictions, involving studies in humans or in vitro; Letters to the editor, editorials and those that did not refer to information on the incorporation and relationship of HM with the teeth were excluded.

RESULTS

837 published articles were detected, 91 were adjusted to the search objective, and 6 were manually included. Teeth are structures with a great capacity for information retention in the face of HM contamination due to low physiological turnover and their long processes of marked formations by developmental biorhythm milestones such as the neonatal line (temporal reference indicator). The contamination mechanisms inside the tooth are linked to the affinity of hydroxyapatite for HM; this incorporation can be in the soft matrix during the apposition phase or as part of the chemical exchanges between hydroxyapatite and the elements of the environment.

CONCLUSION

The teeth present unique characteristics of great resistance and affinity for HM, as well as a chronological biomarker for human biomonitoring, so they can be used as means of expertise or evidence to confirm or rule out a fact of environmental characteristics in the legal field.

Manganese in residential drinking water from a community-initiated case study in Massachusetts

BACKGROUND

Manganese (Mn) is a metal commonly found in drinking water, but the level that is safe for consumption is unknown. In the United States (U.S.), Mn is not regulated in drinking water and data on water Mn concentrations are temporally and spatially sparse.

OBJECTIVE

Examine temporal and spatial variability of Mn concentrations in repeated tap water samples in a case study of Holliston, Massachusetts (MA), U.S., where drinking water is pumped from shallow aquifers that are vulnerable to Mn contamination.

METHODS

We collected 79 residential tap water samples from 21 households between September 2018 and December 2019. Mn concentrations were measured using inductively coupled plasma mass spectrometry. We calculated descriptive statistics and percent of samples exceeding aesthetic (secondary maximum containment level; SMCL) and lifetime health advisory (LHA) guidelines of 50 µg/L and 300 µg/L, respectively. We compared these concentrations to concurrent and historic water Mn concentrations from publicly available data across MA.

RESULTS

The median Mn concentration in Holliston residential tap water was 2.3 µg/L and levels were highly variable (range: 0.03-5,301.8 µg/L). Mn concentrations exceeded the SMCL and LHA in 14% and 12% of samples, respectively. Based on publicly available data across MA from 1994-2022, median Mn concentration was 17.0 µg/L (N = 37,210; range: 1-159,000 µg/L). On average 40% of samples each year exceeded the SMCL and 9% exceeded the LHA. Samples from publicly available data were not evenly distributed between MA towns or across sampling years.

IMPACT STATEMENT

This study is one of the first to examine Mn concentrations in drinking water both spatially and temporally in the U.S. Findings suggest that concentrations of Mn in drinking water frequently exceed current guidelines and occur at concentrations shown to be associated with adverse health outcomes, especially for vulnerable and susceptible subpopulations like children. Future studies that comprehensively examine exposure to Mn in drinking water and its associations with children's health are needed to protect public health.

Early-life manganese exposure during multiple developmental periods and adolescent verbal learning and memory

BACKGROUND

Manganese (Mn) is both an essential and toxic metal, and associations with neurodevelopment depend on exposure timing. Prospective data examining early life Mn with adolescent cognition are sparse.

METHODS

We enrolled 140 Italian adolescents (10-14 years old) from the Public Health Impact of Metals Exposure study. Mn in deciduous teeth was measured using laser ablation-mass spectrometry to represent prenatal, postnatal and early childhood exposure. The California Verbal Learning Test for Children (CVLT-C) was administered to assess adolescent verbal learning and memory. Multivariable regression models estimated changes in CVLT-C scores and the odds of making an error per doubling in dentine Mn in each exposure period. Multiple informant models tested for differences in associations across exposure periods.

RESULTS

A doubling in prenatal dentine Mn levels was associated with lower odds of making an intrusion error (OR = 0.23 [95% CI: 0.09, 0.61]). This beneficial association was not observed in other exposure periods. A doubling in childhood Mn was beneficially associated with short delay free recall: (ß = 0.47 [95% CI: -0.02, 0.97]), which was stronger in males (ß = 0.94 [95% CI: 0.05, 1.82]). Associations were null in the postnatal period.

CONCLUSION

Exposure timing is critical for understanding Mn-associated changes in cognitive function.

The Influence of Environmental Exposure to Heavy Metals on the Occurrence of Selected Elements in the Maxillary Bone

The elemental composition of the body's calcified tissues may reflect the environmental exposure of the population to heavy metals. The aim of the study was to assess whether the elemental composition of the maxillary bone from individuals belonging to a given population reflects the environmental exposure of this population to lead and cadmium. The research material consisted of cortical bone from the anterolateral walls of the maxilla collected from 126 patients during Caldwell-Luc maxillary sinus surgery on residents of two cities differing in terms of the lead and cadmium pollution of the natural environment. The content levels of lead, cadmium, iron, manganese, chromium, copper, and iron were determined by using atomic absorption spectrophotometry. The content levels of lead and cadmium in the samples of the maxillary bones of residents of Bielsko-Biala were 3.26 ± 2.42 µg/g and 0.74 ± 0.38 µg/g, respectively, whereas in the samples from the residents of Katowice, they were 7.66 ± 2.79 µg/g and 1.12 ± 0.08 µg/g, respectively. It was found that the lead and cadmium levels in the maxillary bone corresponded to the environmental exposure to these heavy metals in the place of residence, which was proven here via the example of the residents of two cities with different concentrations of these heavy metals in the air over long time periods. Additionally, higher content levels of essential metals such as manganese, chromium, copper, and iron are characteristic of the maxillary bone samples of residents of the area that is more polluted with heavy metals.

Use of zinc deposited in deciduous teeth as a retrospective measurement of dietary zinc exposure during early development

Purpose

We proposed that zinc (Zn) deposition in deciduous teeth would be a timed record of exposure to this essential micronutrient over very early life. We tested this hypothesis by gathering information on the maternal and child's diet during pregnancy and early infancy and measuring mineral deposition in the dentine at points during deciduous tooth development.

Methods

We developed a short food frequency questionnaire (S-FFQ) to record consumption of food containing Zn during pregnancy and over the first year of life of the child in an Indonesian population. Zn, Sr and Ca were measured by laser ablation ICP-MS in a series of points across the developmental timeline in deciduous teeth extracted from 18 children undergoing the process as part of dental treatment whose mothers completed the SFFQ. Mothers and children were classified into either high Zn or low Zn groups according to calculated daily Zn intake.

Results

The Zn/Sr ratio in dentine deposited over late pregnancy and 0-3 months post-partum was higher (p < 0.001, 2-way ANOVA; p < 0.05 by Holm-Sidak post hoc test) in the teeth of children of mothers classified as high Zn consumers (n = 10) than in children of mothers classified as low Zn consumers (n = 8).

Conclusion

The S-FFQ was validated internally as adequately accurate to measure zinc intake retrospectively during pregnancy and post-partum (∼7 years prior) by virtue of the correlation with measurements of zinc in deciduous teeth. The ratio of Zn/Sr in deciduous teeth appears to be a biomarker of exposure to zinc nutrition during early development and offers promise for use as a record of prior exposure along a timeline for research studies and, potentially, to identify individuals at heightened risk of detrimental impacts of poor early life zinc nutrition on health in later life and to implement preventative interventions.