Bioconcentration of lipophilic organochlorines in ovine dentine

How does the early life environment influence the oral microbiome and determine oral health outcomes in childhood?

The first 1000 days of life, from conception to 2 years, are a critical window for the influence of environmental exposures on the assembly of the oral microbiome, which is the precursor to dental caries (decay), one of the most prevalent microbially induced disorders worldwide. While it is known that the human microbiome is susceptible to environmental exposures, there is limited understanding of the impact of prenatal and early childhood exposures on the oral microbiome trajectory and oral health. A barrier has been the lack of technology to directly measure the foetal "exposome", which includes nutritional and toxic exposures crossing the placenta. Another barrier has been the lack of statistical methods to account for the high dimensional data generated by-omic assays. Through identifying which early life exposures influence the oral microbiome and modify oral health, these findings can be translated into interventions to reduce dental decay prevalence.

Minimally Invasive Biospecimen Collection for Exposome Research in Children's Health

PURPOSE OF REVIEW

The advent of low-volume biosampling and novel biomarker matrices offers non- or minimally invasive approaches to sampling in children. These new technologies, combined with advancements in mass spectrometry that provide high sensitivity, robust measurements of low-concentration exposures, facilitate the application of untargeted metabolomics in children's exposome research. Here, we review emerging sampling technologies for alternative biomatrices-dried capillary blood, interstitial fluid, saliva, teeth, and hair-and highlight recent applications of these samplers to drive discovery in population-based exposure research.

RECENT FINDINGS

Biosampling and biomarker technologies demonstrate potential to directly measure exposures during key developmental time periods. While saliva is the most traditional of the reported biomatrices, each technology has key advantages and disadvantages. For example, hair and teeth provide retrospective analysis of past exposures, and dried capillary blood provides quantitative measurements of systemic exposures that can be more readily compared with traditional venous blood measurements. Importantly, all technologies can or have the potential to be used at home, increasing the convenience and parental support for children's biosampling. This review describes emerging sample collection technologies that hold promise for children's exposome studies. While applications in metabolomics are still limited, these novel matrices are poised to facilitate longitudinal exposome studies to discover key exposures and windows of susceptibility affecting children's health.

The tooth exposome in children's health research

PURPOSE OF REVIEW

The exposome concept proposes a comprehensive assessment of environmental exposures from the prenatal period onwards. However, determining exposure timing, especially over the prenatal period, is a major challenge in environmental epidemiologic studies.

RECENT FINDINGS

For decades, teeth have been used to estimate long-term cumulative exposure to metals. Recently developed high-dimensional analytical methods, which combine sophisticated histological and chemical analysis to precisely sample tooth layers that correspond to specific life stages, have the potential to reconstruct the exposome in the second and third trimesters of prenatal development and during early childhood.

SUMMARY

A retrospective temporal exposomic approach that precisely measures exposure intensity 'and timing' during prenatal and early childhood development would substantially aid epidemiologic investigations, particularly case-control studies of rare health outcomes.

Tooth matrix analysis for biomonitoring of organic chemical exposure: Current status, challenges, and opportunities

Epidemiological evidence supports associations between prenatal exposure to environmental organic chemicals and childhood health impairments. Unlike the common choice of biological matrices such as urine and blood that can be limited by short half-lives for some chemicals, teeth provide a stable repository for chemicals with half-life in the order of decades. Given the potential of the tooth bio-matrix to study long-term exposures to environmental organic chemicals in human biomonitoring programs, it is important to be aware of possible pitfalls and potential opportunities to improve on the current analytical method for tooth organics analysis. We critically review previous results of studies of this topic. The major drawbacks and challenges in currently practiced concepts and analytical methods in utilizing tooth bio-matrix are (i) no consideration of external (from outer surface) or internal contamination (from micro-odontoblast processes), (ii) the misleading assumption that whole ground teeth represent prenatal exposures (latest formed dentine is lipid rich and therefore would absorb and accumulate more organic chemicals), (iii) reverse causality in exposure assessment due to whole ground teeth, and (iv) teeth are a precious bio-matrix and grinding them raises ethical concerns about appropriate use of a very limited resource in exposure biology and epidemiology studies. These can be overcome by addressing the important limitations and possible improvements with the analytical approach associated at each of the following steps: (i) tooth sample preparation to retain exposure timing, (ii) organics extraction and pre-concentration to detect ultra-trace levels of analytes, (iii) chromatography separation, (iv) mass spectrometric detection to detect multi-class organics simultaneously, and (v) method validation, especially to exclude chance findings. To highlight the proposed improvements we present findings from a pilot study that utilizes tooth matrix biomarkers to obtain trimester-specific exposure information for a range of organic chemicals.

Distribution of organochlorine pollutants in ovine dental tissues and bone

The distribution of selected lipophilic organochlorine pollutants, including two pairs of tetra- and hexa-chlorobiphenyl isomers (PCB-54, -80, -155, -169) and organochlorine pesticides [hexachlorobenzene (HCB) and 1,1-bis(4-chlorophenyl)-2,2-dichloroethene (4,4'-DDE)], in ovine dental pulp, dentine, enamel and mandibular bone was examined. Sheeps were given a single dose of individual organochlorine (1-4μmol/kg) in olive oil by intramuscular injection and sacrificed 2 months later. Organochlorine residues were determined by gas chromatography. The highest levels of organochlorines were found in bone. The lipid adjusted levels varied significantly between tissues. Lower chlorinated, metabolically unstable, non-planar PCB-54 was enriched in enamel, while higher chlorinated, metabolically resistant, planar PCB-169 was preferentially retained in pulp. The ratio of planar to non-planar PCB homologues and pesticides (PCB-169/-155, PCB-80/-54, HCB/4,4'-DDE) decreased in the order pulp>dentine>enamel, suggesting that besides compound's lipophilicity and the tissue's lipid content, other physicochemical properties of organochlorines and tissue specific characteristics affect their distribution.