Tracing fetal and childhood exposure to lead using isotope analysis of deciduous teeth

Abstract

We report progress in using the isotopic composition and concentration of Pb in the dentine and enamel of deciduous teeth to provide a high resolution time frame of exposure to Pb during fetal development and early childhood. Isotope measurements (total Pb and 208 Pb/ 206 Pb, 207 Pb/ 206 Pb ratios) were acquired by laser ablation inductively coupled mass spectrometry at contiguous 100micron intervals across thin sections of the teeth; from the outer enamel surface to the pulp cavity. Teeth samples (n=10) were selected from two cohorts of children, aged 5-8 years, living in NE England. By integrating the isotope data with histological analysis of the teeth, using the daily incremental lines in dentine, we were able to assign true estimated ages to each ablation point (first 2-3 years for molars, first 1-2 years for incisors + pre-natal growth). Significant differences were observed in the isotope composition and concentration of Pb between children, reflecting differences in the timing and sources of exposure during early childhood. Those born in 2000, after the withdrawal of leaded petrol in 1999, have the lowest dentine Pb levels (<0.2µgPb/g) with 208 Pb/ 206 Pb (mean ±2σ: 2.126-2.079) 208 Pb/ 206 Pb (mean ±2σ: 0.879-0.856) ratios that correlate very closely with modern day Western European industrial aerosols (PM 10 , PM 2.5 ) suggesting that diffuse airborne pollution was probably the primary source and exposure pathway. Legacy lead, if present, is insignificant. For those born in 1997, dentine lead levels are typically higher (>0.4µgPb/g) with 208 Pb/ 206 Pb (mean ±2σ: 2.145-2.117) 208 Pb/ 206 Pb (mean ±2σ: 0.898-0.882) ratios that can be modelled as a binary mix between industrial aerosols and leaded petrol emissions. Short duration, high intensity exposure events (1-2 months) were readily identified, together with evidence that dentine provides a good proxy for childhood changes in the isotope composition of blood Pb. Our pilot study confirms that laser ablation Pb isotope analysis of deciduous teeth, when carried out in conjunction with histological analysis, permits a reconstruction of the timing, duration and source of exposure to Pb during early childhood. With further development, this approach has the potential to study larger cohorts and appraise environments where the levels of exposure to Pb are much higher.

Determinants of blood and saliva lead concentrations in adult gardeners on urban agricultural sites

“…In this regard, the isotopic composition of blood Pb offers a potential way forward. Blood Pb values can be modelled using existing data for known anthropogenic sources (legacy leaded petrol, PM2.5-10 airborne particulates, coal ash, domestic and imported Pb ores used for the manufacture of in-house Pb pipes) (Hodgson et al, 2015;Shepherd et al, 2009Shepherd et al, , 2016. These will vary according to spatial and demographic factors but will provide an evidence-based isotopic framework for more informed public health intervention measures.…”

Translating Analytical Techniques in Geochemistry to Environmental Health

“…While in situ isotopic studies of biological samples are limited [ 12 , 13 ], the potential for future studies looks extremely promising in mapping sample heterogeneity. For example, Pb isotopic analysis of teeth can be used to trace modern fetal and childhood exposure to lead [ 14 ], while secondary teeth can preserve isotopic signatures of geographic location, diet, and health in mummified human remains [ 15 ], demonstrating that recent advancements in ICP-MS, specifically the coupling of LA systems, have expanded an entire field of research.…”

Toxicological profile for lead

“…Dentin appears to continue to accumulate Pb after eruption of the tooth; therefore, dentin Pb is thought to reflect exposure that occurs up to the time the teeth are shed or extracted (Gulson 1996;Gulson and Wilson 1994;Rabinowitz 1995;Rabinowitz et al 1993). The technique of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) allows measurement of Pb levels in regions of dentin formed at various times during deciduous tooth formation in utero and after birth (Arora et al 2014;Shepherd et al 2016). Accumulation of Pb in dentin of permanent teeth may continue for the life of the tooth (Steenhout 1982;Steenhout and Pourtois 1981).…”

“…Arora et al (2014) found that Pb levels in primary (prenatal) dentin were more strongly correlated with PbBs at birth (correlation coefficient, r=0.69, n=27), whereas Pb levels in secondary (postnatal) dentin were more strongly correlated with CBLI (r=0.38, n=75). Shepherd et al (2016) combined LA-ICP-MS with histological determinations of dentin age to reconstruct the history of incorporation of environmental Pb from various sources.…”