2005 Progress Report: Exposure Assessment of Children and Metals in Mining Waste: Composition, Environmental Transport, and Exposure Patterns

EPA Grant Number: R831725C002
Subproject: this is subproject number 002 , established and managed by the Center Director under grant R831725
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Harvard Center for Children’s Environmental Health and Disease Prevention Research
Center Director: Hu, Howard
Title: Exposure Assessment of Children and Metals in Mining Waste: Composition, Environmental Transport, and Exposure Patterns
Investigators: Shine, James P. , Spengler, John D.
Institution: Harvard T.H. Chan School of Public Health
EPA Project Officer: Callan, Richard
Project Period: June 1, 2004 through May 31, 2009 (Extended to May 31, 2011)
Project Period Covered by this Report: June 1, 2005 through May 31, 2006
RFA: Centers for Children's Environmental Health and Disease Prevention Research (2003) RFA Text |  Recipients Lists
Research Category: Children's Health , Health Effects , Health

Objective:

The objectives of this research project are to:  (1) assess the utility of size fractionation and sequential extraction studies for characterizing chat; (2) conduct a nested case-control study of the determinants of high versus low burdens of metals amongst children participating in Project 1 (R831725C001); and (3) produce standardized homogenized chat for Projects 3 and 4 (R831725C003 and R831725C004, respectively).

Progress Summary:

During the past year, we focused on characterizing the speciation and fate of metals in chat (mine waste) piles and within Tar and Lytle Creeks.  We conducted an additional sampling trip to the Tar Creek area in May 2005. During this trip, we collected approximately 35 chat samples from 3 major chat piles and 125 water samples, including locations along the entire length of Tar and Lytle Creeks and two major sources of metal loading into creeks:  chat pile runoff and acid mine drainage.

We also made significant progress in the household and human exposure assessment component of this project, a collaboration between Projects 1 and 2.

Chat Piles

In total, we have collected and analyzed samples from three to four locations at six of the largest chat piles located close to residential areas and the banks of Tar and Lytle Creeks.  We have assessed spatial variability within and among piles, as well as differences in metal concentrations in eight different size fractions, ranging from greater than 4 mm down to less than 37 μm.  Total concentrations of Zn, Pb, and Cd were found to increase with decreasing particle size––up to 10 percent Zn and 0.7 percent Pb by mass and 200 ppm Cd in the less than 37 µm size fraction, the size most susceptible to windborne transport.  Working with Analytical Core B, we collected and analyzed respirable particles that contained concentrations up to 22 percent Zn and 1.6 percent Pb in the smallest size fraction (0.16-1 μm), which is significant for exposure via inhalation.

On a subset of samples, we also have assessed the mineralogy and speciation of metals in chat samples, because total metal concentrations alone do not determine metal mobility and bioavailability.  The results of sequential extraction experiments have demonstrated that in the less than 37 μm fraction, up to 50 to 70 percent of Zn, Pb, and Cd are mobile in relatively weak extraction solutions (pH 7 MgCl2 or pH 5 acetic acid), suggesting that a significant pool of metals could be mobilized under environmental conditions.  We have conducted preliminary X-ray diffraction (XRD) analyses as a way to assess directly the mineralogy of metal in the samples.

In-Stream Metal Fate and Transport

Another major thrust of our research is to assess the sources of metal loading and instream mobility of metals in Tar Creek, which ultimately drains in the Grand Lake o’ the Cherokees, a major recreational area.  Although acid mine drainage originating from abandoned mine shafts has been a well-documented source of metal loading, our preliminary results suggest that for Cd, Pb, and to a lesser extent Zn, chat pile runoff may contribute the majority of these metals into Tar Creek.

Household and Human Exposure Assessment

Project 2 also includes a household and human exposure assessment study as a collaborative effort between Project 1 and Project 2.  During two sampling trips in early and late 2005, household exposure media samples were collected at 35 residences that were home to infants participating in the birth cohort who were in the range of 3 to 9 months old at the time of sampling.  Sampling targets at each house included drinking water, upholstery and floor dust, indoor air (PM2.5), and outdoor yard soil (four locations).  In addition, we established ongoing sampling of respirable particulate matter in ambient air in three locations.  Inhome surveys of behavior and eating patterns also were conducted.

Samples are analyzed by either inductively coupled plasma mass spectroscopy (ICP/MS) or by X-ray fluorescence (XRF) for elements of primary interest (Pb, Zn, Mn, As, Cd, Cu, and Fe) and secondary particles for source receptor analysis.  XRF is being provided by a new collaboration with Professor Dan Brabander of the Geosciences Department, Wellesley College.  Arrangements are being made to send samples to the National Exposure Research Laboratory, U.S. Environmental Protection Agency (EPA) for high-resolution XRF.  EPA will assist the study by analyzing the PM2.5 and PM10 samples (week long) collected at three ambient sites (Picher, N. Miami, and Quapaw), as well as the integrated PM2.5 samples collected in homes.

Preliminary results suggest that Pb dust concentrations were highly correlated with Zn concentrations (Spearman correlation coefficient rs = 0.82, p ≤ 0.0001, n = 40) and also showed modest correlations with As (rs = 0.54, p = 0.0003), Cu (rs = 0.56, p ≥ 0.0002), and Fe (rs = 0.67, p = 0.0001), suggesting common sources.  Dust from homes located close to the major chat piles contained higher Zn concentrations than those located further away from the Superfund site.

Significance

The results of our work are relevant both to the residents of the Tar Creek area as well as to the other projects within the Children’s Center.  Understanding the chat piles as sources of metal loading via wind-borne and aqueous transport is important for minimizing exposure and contamination to the surrounding ecosystems.  Characterizing the metal concentrations and bioavailability in chat material is a necessary step for exposure assessment of residents in the Tar Creek area (Project 1) and for laboratory-based experiments of metal absorption and subsequent behavioral impacts in rats (Projects 3 and 4).

Future Activities:

As part of our ongoing work to assess the chemical characteristics of metals in the chat piles, we will continue to use XRD to assess the mineralogy of chat piles, in conjunction with Daniel Brabander of Wellesley College.  We also are planning a series of column-leaching experiments to study the kinetics of metal release, as well as the effect of flow rate and pH, to predict the fate of mobilized metals within chat piles and the potential role of chat piles as a source of metal loading into surface and ground water throughout the site.  Additional water sampling trips will focus on using conservative tracers to estimate relative flow rates to better quantify metal loading under hi-flow and low-flow conditions.

The household and human exposure assessment study has expanded in scope from its original design to address potential sources of metals exposure with better precision.  We are accomplishing this within the constraints of a reduced budget but developing collaborations, shifting support, and relying heavily on our trainees.

In addition to continuing with our sampling and analyses, the coming year will be spent communicating our initial results in manuscripts for publication.

Journal Articles:

No journal articles submitted with this report: View all 6 publications for this subproject

Supplemental Keywords:

children, Native American, tribal, mixtures, lead, PBPK, community, Superfund, intervention, environmental management,, RFA, Health, Scientific Discipline, INTERNATIONAL COOPERATION, ENVIRONMENTAL MANAGEMENT, Waste, Health Risk Assessment, Hazardous Waste, Children's Health, Hazardous, Risk Assessment, community-based intervention, epidemiology, fate and transport , developmental toxicity, Human Health Risk Assessment, neurodevelopmental toxicity, children's environmental health, biological markers, metal wastes, mining waste, human health risk, metals, mining wastes

Relevant Websites:

http://www.hsph.harvard.edu/niehs/children Exit

Progress and Final Reports:

Original Abstract
  • 2004 Progress Report
  • 2006
  • 2007
  • 2008 Progress Report
  • 2009
  • Final

  • Main Center Abstract and Reports:

    R831725    Harvard Center for Children’s Environmental Health and Disease Prevention Research

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R831725C001 Metals, Nutrition, and Stress in Child Development
    R831725C002 Exposure Assessment of Children and Metals in Mining Waste: Composition, Environmental Transport, and Exposure Patterns
    R831725C003 Manganese, Iron, Cadmium, and Lead Transport from the Environment to Critical Organs During Gestation and Early Development in a Rat Model
    R831725C004 Metals Neurotoxicity Research Project