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01.12.2015 | Research article | Ausgabe 1/2015 Open Access

BMC Public Health 1/2015

Geographic clustering of elevated blood heavy metal levels in pregnant women

BMC Public Health > Ausgabe 1/2015
Katherine E. King, Thomas H. Darrah, Eric Money, Ross Meentemeyer, Rachel L. Maguire, Monica D. Nye, Lloyd Michener, Amy P. Murtha, Randy Jirtle, Susan K. Murphy, Michelle A. Mendez, Wayne Robarge, Avner Vengosh, Cathrine Hoyo
Wichtige Hinweise

Competing interests

The authors declare that there are no competing financial interests.

Authors’ contributions

KEK—completed the regression models, preliminary geospatial analysis and drafted the manuscript. THD—measured metals in human blood, edited the output and interpreted concentrations. He also wrote the methods section corresponding to the measurement of human blood samples and edited the manuscript. EM—conducted the final GIS analysis and wrote the methods section corresponding to GIS analysis. He also edited the manuscript. R. Meentemeyer—assisted Dr. Money in geospatial analysis, and directed the analysis. R. Maguire—designed the substudy and collected the environment sample, coordinated their measurements and was responsible for writing the corresponding methods section, and edited the manuscript. MDN—contributed to manuscript writing. LM—instrumental in interpretation of data, contributed to design of follow-up study to collect environmental samples. APM—oversight of study participant identification, accrual, and sample transfer to Dr. Murphy’s lab and contributed to manuscript writing. RJ—provided insights on analytic approach, interpretation and edited manuscript. SKM—oversight in peripheral blood sample collection, and contributed to manuscript writing. MAM—contributed to manuscript writing. WR—designed the sub-study for collection and measurement of cadmium and lead in environmental samples (i.e. soil and water). AV—provided insights on analytic approach, interpretation of metal concentrations and edited the manuscript. CH—conceived the research question, designed the study, provided oversight in data collection, analysis and co-drafted the manuscript. All authors have read and approved the final manuscript.



Cadmium (Cd), lead (Pb), mercury (Hg), and arsenic (As) exposure is ubiquitous and has been associated with higher risk of growth restriction and cardiometabolic and neurodevelopmental disorders. However, cost-efficient strategies to identify at-risk populations and potential sources of exposure to inform mitigation efforts are limited. The objective of this study was to describe the spatial distribution and identify factors associated with Cd, Pb, Hg, and As concentrations in peripheral blood of pregnant women.


Heavy metals were measured in whole peripheral blood of 310 pregnant women obtained at gestational age ~12 weeks. Prenatal residential addresses were geocoded and geospatial analysis (Getis-Ord Gi* statistics) was used to determine if elevated blood concentrations were geographically clustered. Logistic regression models were used to identify factors associated with elevated blood metal levels and cluster membership.


Geospatial clusters for Cd and Pb were identified with high confidence (p-value for Gi* statistic <0.01). The Cd and Pb clusters comprised 10.5 and 9.2 % of Durham County residents, respectively. Medians and interquartile ranges of blood concentrations (μg/dL) for all participants were Cd 0.02 (0.01–0.04), Hg 0.03 (0.01–0.07), Pb 0.34 (0.16–0.83), and As 0.04 (0.04–0.05). In the Cd cluster, medians and interquartile ranges of blood concentrations (μg/dL) were Cd 0.06 (0.02–0.16), Hg 0.02 (0.00–0.05), Pb 0.54 (0.23–1.23), and As 0.05 (0.04–0.05). In the Pb cluster, medians and interquartile ranges of blood concentrations (μg/dL) were Cd 0.03 (0.02–0.15), Hg 0.01 (0.01–0.05), Pb 0.39 (0.24–0.74), and As 0.04 (0.04–0.05). Co-exposure with Pb and Cd was also clustered, the p-values for the Gi* statistic for Pb and Cd was <0.01. Cluster membership was associated with lower education levels and higher pre-pregnancy BMI.


Our data support that elevated blood concentrations of Cd and Pb are spatially clustered in this urban environment compared to the surrounding areas. Spatial analysis of metals concentrations in peripheral blood or urine obtained routinely during prenatal care can be useful in surveillance of heavy metal exposure.
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