Chelsey A Juarez, R. Ramey, David T. Flaherty, Belinda S. Akpa
{"title":"Oxygen and Hydrogen Isotopes in Human Hair and Tap Water: Modeling Relationships in a Modern Mexican Population","authors":"Chelsey A Juarez, R. Ramey, David T. Flaherty, Belinda S. Akpa","doi":"10.1353/hub.2017.0054","DOIUrl":null,"url":null,"abstract":"This study investigated the relationship between <sup>18</sup>O and <sup>2</sup>H isotopes in samples of Mexican hair and drinking water. The purpose of this study was twofold: to quantify the relationship between isotopes in Mexican hair and tap water, in order to understand the impact of water stress and differing socioeconomic status on accurate predictions of drinking water; and to determine whether currently existing semimechanistic models can accurately represent the relationship between hair and tap water. This study used a subset of paired samples of human hair (<em>n</em> = 62) and tap water (<em>n</em> = 76). Isotope values in tap water ranged from –11.4‰ to –4.3‰ and –79.1‰ to –22.5‰, and in hair from +9.5‰ to +16.1‰ and –90.8‰ to –53.7‰, for δ<sup>18</sup>O and δ<sup>2</sup>H, respectively. The most depleted δ<sup>18</sup>O and δ<sup>2</sup>H hair values came from individuals in the state of Morelos. For modern Mexican populations, positive correlations between isotopes in hair and water were not significant, with correlation coefficients <em>r</em> = 0.61 (<em>p</em> = 0.05) and <em>r</em> = 0.60 (<em>p</em> = 0.06) for <sup>18</sup>O and <sup>2</sup>H, respectively. Error-in-variables regression yielded linear fits that were somewhat better for <sup>2</sup>H relative to <sup>18</sup>O: δ<sup>18</sup>O<sub>h</sub> = 0.183 [±0.132] δ<sup>18</sup>O<sub>tw</sub> + 15.7 [±0.9]‰ (r<sup>2</sup> = 0.23); δ<sup>2</sup>H<sub>h</sub> = 0.181 [±0.076] δ<sup>2</sup>H<sub>tw</sub> – 64.0 [±3.0]‰ (r<sup>2</sup> = 0.34). In short, data from this Mexican population did not exhibit the strong relationships between isotope values of <sup>18</sup>O and <sup>2</sup>H in tap water and hair that have been characteristic of other populations studied to date. Given the economic stratification of this region and the poor correlation between hair and water samples, the authors considered the possibility that <em>l</em>, the fraction of the diet derived from local sources, and <em>f</em><sub>s</sub>, the fraction of nonexchangeable H in keratin that was fixed in vivo, are local rather than global parameters for this population. The authors estimated different values of <em>l</em> and <em>f</em><sub>s</sub> for each location. Given the anticipated importance of the nonlocal dietary contribution, they treated the isotopic content of nonlocal food and the offset parameters for predicting isotopes in locally derived food as tuning parameters and compared the results with parameters based on the American supermarket diet. They found that, although O and H isotopes in water and hair maintained similar geographic distributions, O and H isotopes in tap water explained only a small part of the variation observed in hair samples. Compared to the standard American supermarket diet, the Mexican estimates for nonlocal diet and local diet offsets predicted regional distributions of <em>l</em> and <em>f</em><sub>s</sub> that cleanly segregated urban areas from rural towns.","PeriodicalId":13053,"journal":{"name":"Human Biology","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2019-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Human Biology","FirstCategoryId":"99","ListUrlMain":"https://doi.org/10.1353/hub.2017.0054","RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"Medicine","Score":null,"Total":0}
引用次数: 0
Abstract
This study investigated the relationship between 18O and 2H isotopes in samples of Mexican hair and drinking water. The purpose of this study was twofold: to quantify the relationship between isotopes in Mexican hair and tap water, in order to understand the impact of water stress and differing socioeconomic status on accurate predictions of drinking water; and to determine whether currently existing semimechanistic models can accurately represent the relationship between hair and tap water. This study used a subset of paired samples of human hair (n = 62) and tap water (n = 76). Isotope values in tap water ranged from –11.4‰ to –4.3‰ and –79.1‰ to –22.5‰, and in hair from +9.5‰ to +16.1‰ and –90.8‰ to –53.7‰, for δ18O and δ2H, respectively. The most depleted δ18O and δ2H hair values came from individuals in the state of Morelos. For modern Mexican populations, positive correlations between isotopes in hair and water were not significant, with correlation coefficients r = 0.61 (p = 0.05) and r = 0.60 (p = 0.06) for 18O and 2H, respectively. Error-in-variables regression yielded linear fits that were somewhat better for 2H relative to 18O: δ18Oh = 0.183 [±0.132] δ18Otw + 15.7 [±0.9]‰ (r2 = 0.23); δ2Hh = 0.181 [±0.076] δ2Htw – 64.0 [±3.0]‰ (r2 = 0.34). In short, data from this Mexican population did not exhibit the strong relationships between isotope values of 18O and 2H in tap water and hair that have been characteristic of other populations studied to date. Given the economic stratification of this region and the poor correlation between hair and water samples, the authors considered the possibility that l, the fraction of the diet derived from local sources, and fs, the fraction of nonexchangeable H in keratin that was fixed in vivo, are local rather than global parameters for this population. The authors estimated different values of l and fs for each location. Given the anticipated importance of the nonlocal dietary contribution, they treated the isotopic content of nonlocal food and the offset parameters for predicting isotopes in locally derived food as tuning parameters and compared the results with parameters based on the American supermarket diet. They found that, although O and H isotopes in water and hair maintained similar geographic distributions, O and H isotopes in tap water explained only a small part of the variation observed in hair samples. Compared to the standard American supermarket diet, the Mexican estimates for nonlocal diet and local diet offsets predicted regional distributions of l and fs that cleanly segregated urban areas from rural towns.
期刊介绍:
Human Biology publishes original scientific articles, brief communications, letters to the editor, and review articles on the general topic of biological anthropology. Our main focus is understanding human biological variation and human evolution through a broad range of approaches.
We encourage investigators to submit any study on human biological diversity presented from an evolutionary or adaptive perspective. Priority will be given to interdisciplinary studies that seek to better explain the interaction between cultural processes and biological processes in our evolution. Methodological papers are also encouraged. Any computational approach intended to summarize cultural variation is encouraged. Studies that are essentially descriptive or concern only a limited geographic area are acceptable only when they have a wider relevance to understanding human biological variation.
Manuscripts may cover any of the following disciplines, once the anthropological focus is apparent: human population genetics, evolutionary and genetic demography, quantitative genetics, evolutionary biology, ancient DNA studies, biological diversity interpreted in terms of adaptation (biometry, physical anthropology), and interdisciplinary research linking biological and cultural diversity (inferred from linguistic variability, ethnological diversity, archaeological evidence, etc.).