Open Journal of Soil Science, 2013, 3, 23-29 doi:10.4236/ojss.2013.31004 Published Online March 2013 (http://www.scirp.org/journal/ojss) 23 Background Soil Mercury: An Unrecognized Source of Blood Mercury in Infants? Pamela F. Heckel 1 , Tim C. Keener 2 , Grace K. LeMasters 1 1 College of Medicine, University of Cincinnati, Cincinnati, USA; 2 College of Engineering and Applied Science, University of Cin- cinnati, Cincinnati, USA. Email: Pheckel@cdc.gov Received December 18 th , 2012; revised January 9 th , 2013; accepted January 31 st , 2013 ABSTRACT Introduction: During the past four decades, mercury (Hg) research focused on fish consumption has explained less than 22% of Hg in human blood. One overlooked exposure pathway for infants and young children is the concentration of Hg in soils. Although 75% of the U.S. population lives in urban areas near industrial facilities, minimal data exist regarding the concentration and speciation of Hg in residential soils. Chronic exposure through ingestion of low concentrations of Hg in soils may explain a portion of the blood Hg levels noted in infants. Methods: Three relatively unexposed residential sites in a suburban community were selected. The primary route of contamination was atmospheric deposition. Soils were digested in a nitric acid-hydrofluoric acid solution and analyzed by cold vapor atomic absorption spectrophotometry. Measured concentrations of total Hg in local suburban soil samples were compared to levels measured in a national study of 27 remote and rural sites. The Al-Shahristani pharmacokinetic model, developed after the 1971 Iraqi Methyl Hg poisoning incident, was used to calculate the blood Hg concentration in a hypothetical year-old infant. Results: Soil samples contained Hg concentrations ranging from 0.01 to 0.24 ppm w . The distribution of Hg in the soil samples was non-linear and non-normal. The mean soil Hg concentrations at the three locations were 0.08, 0.05 and 0.08 ppm. Calculated blood Hg concentrations for a 10 kg, year-old infant due to ingestion of soil (200 mg/day) containing 0.2, 0.4 and 0.8 ppm Hg were 0.08, 0.17 and 0.26 μg/L, respectively. Con- clusions: The pilot study data appear to support the hypothesis that chronic, low-level soil ingestion may be a signifi- cant source of Hg for infants. Further study is warranted. Keywords: Mercury; Blood Mercury; Pharmacokinetics; Air Toxics 1. Introduction Mercury (Hg) is a known potent toxicant and is found in the blood, brain and kidney tissues [1]. Organic methyl mercury (CH 3 Hg) is associated with fish consumption, whereas inorganic Hg corresponds to exposure from dental amalgams and other sources of Hg vapor [2]. Elemental mercury (Hg 0 ) crosses the placenta and con- centrates in the fetus [3]. There have also been several publications that summarized past research into the speciation of Hg and related biomarkers [4-7]. Decades of research indicate that the developing infant brain is highly susceptible to damage from neurotoxin- cants such as Hg [8]. Research over the past 30 years has confirmed the presence of Hg in fish. Although a statis- tical analysis indicates a link between fish consumption and Hg concentrations in infant cord blood, the correla- tion is weak. Nevertheless, the United States Environ- mental Protection Agency (USEPA) issued fish con- sumption advisories for pregnant women [1]. Weekly records of dietary intake of fish by women during their pregnancy in Poland explained only 22% of the variabil- ity of Hg in umbilical cord blood [9]. A weak dose-re- sponse relationship (r 2 = 0.21) between fish consumption and infant cord blood Hg was confirmed in another study of pregnancies among women living along the St. Law- rence River who ate an average of 3.5 fish meals/month [10]. Thus, in both studies, fish consumption explained 22% or less of the Hg in cord blood. Hundreds of studies have examined the possible Hg contribution from foods, but none of the exposures correlated above 22% with blood concentrations. Therefore, other routes of exposure need to be considered. According to the 2000 census, more than 75% of the United States population lives in urban areas [11]. Our pilot study determined the concentration of Hg in topsoil in the suburbs of an industrialized metropolis. We sug- gest that there may be a link between Hg in soil and Hg in infant blood due to increased hand-to-mouth behaviors during the first two years of life, based in part to a similar Copyright © 2013 SciRes. OJSS