1.4 The Workshop and Overview Presentations
The 2-day workshop generally followed the agenda shown in Appendix C. Dr. Catherine McKinney (Centers for Disease Control and Prevention) facilitated the workshop, which opened with introductions, both by panelists and observers, and was followed by four overview presentations (summarized below). For the remainder of the workshop, some panelists gave presentations and all panelists provided recommendations, observations, and comments when answering the questions. The workshop was a free-flowing discussion among the panelists, and did not focus on trying to reach a consensus on any issue. A record of the panelists' discussions is presented in Sections 2 through 6, with key findings highlighted in the Executive Summary.
Following is a summary of the four overview presentations, which were delivered before the panelists addressed the charge questions:
Dr. Henry Falk, M.D., Assistant Administrator, ATSDR. Dr. Falk gave an overview of ATSDR, explaining how the agency works with the Environmental Protection Agency (EPA), other federal agencies, state and local health departments, and communities to address public health issues related to environmental contamination. He also gave an overview of how soil-pica behavior factors into ATSDR's public health assessments and EPA's decision making process for Superfund.
Noting that the complex issue of exposures to contaminated soil arises at many hazardous waste sites, Dr. Falk stressed that the panelists' inputs might weigh heavily in ATSDR's future evaluations of the public health implications of soil-pica behavior. Dr. Falk concluded his presentation by acknowledging that soil-pica is particularly important for evaluating health risks to children--a topic that his colleague, Dr. Rob Amler, would discuss in greater detail, as described below.
Dr. Rob Amler, M.D., Chief Medical Officer, ATSDR. Dr. Amler's presentation reviewed various ongoing activities that support ATSDR's Child Health Initiative, which addresses special vulnerabilities of children who live near hazardous waste sites. He first listed many reasons why children tend to have higher exposures to environmental contaminants: children often find openings in fences around restricted sites, they play vigorously in soil and water, and they breathe, drink, and eat more--on a body weight basis--than do adults.
Dr. Amler noted that these reasons, coupled with the fact that children's exposures can occur during critical developmental stages and that persistent health effects might result from these exposures, have caused ATSDR and other agencies to focus research and outreach on children's health issues. Acknowledging that quantifying children's exposures can often be difficult, particularly for soil ingestion pathways, Dr. Amler stressed that the panelists' inputs on soil-pica behavior will be an important consideration for future site evaluations.
Dr. David Mellard, Ph.D., Toxicologist, ATSDR. Dr. Mellard's presentation focused on the primary goal of the workshop--how ATSDR should evaluate exposures to children who exhibit soil-pica behavior. Dr. Mellard explained that ATSDR views "pica" as the intentional ingestion of large quantities of soil, which primarily occurs among preschool children. He then reviewed an approach typically used to evaluate residential exposure pathways for pica children, with key factors being the assumed soil ingestion rate and the duration over which this ingestion occurs.
Dr. Mellard noted that soil ingestion rates of 5,000 mg/day have been documented in a few studies in the scientific literature, but the duration over which ingestion at this level occurs has not been studied. Dr. Mellard found it reasonable to assume that some children might have these very high daily ingestion rates at least once in their preschool lives, and he thought it was possible that soil-pica children might exhibit these very high daily ingestion rates several times a week, for several weeks in a row. However, given that such assumptions can lead to important remediation decisions, Dr. Mellard said that ATSDR seeks expert input on both the prevalence of soil-pica behavior and the ingestion rates among those who exhibit pica behavior. To highlight the importance of these issues, Dr. Mellard concluded his presentation by describing a site with extensive arsenic contamination in residential soils, where exposures among soil-pica children could be at levels known to be associated with adverse health effects.
Mr. Michael Maes and Mr. Anthony Thomas, Community Members. Mr. Maes is a resident in a neighborhood that was recently designated a Superfund site because of extensive arsenic contamination in soils--a designation that has caused heightened awareness in his community about soil ingestion and pica behavior. Mr. Maes listed several examples of behaviors among his community members that might be of concern, such as children ingesting soils and sediments while playing near large puddles, a teenager who said that she craves to eat dirt several times a year, and women of Mexican descent who consume dirt when they become pregnant.
Given these anecdotal accounts of soil ingestion, Mr. Maes believed that soil-pica behavior was an important issue for his community, and he looked forward to the panelists' insights on the prevalence and significance of this behavior. Mr. Anthony Thomas echoed many of these concerns, and wondered about the adverse health effects in individuals who exhibit soil-pica behavior.