Joseph E. Bunnell

Medical geology: a globally emerging discipline

Medical Geology, the study of the impacts of geologic materials and processes on animal and human health, is a dynamic emerging discipline bringing together the geoscience, biomedical, and public health communities to solve a wide range of environmental health problems. Among the Medical Geology described in this review are examples of both deficiency and toxicity of trace element exposure. Goiter is a widespread and potentially serious health problem caused by deficiency of iodine. In many locations the deficiency is attributable to low concentrations of iodine in the bedrock. Similarly, deficiency of selenium in the soil has been cited as the principal cause of juvenile cardiomyopathy and muscular abnormalities. Overexposure to arsenic is one of the most widespread Medical Geology problems affecting more than one hundred million people in Bangladesh, India, China, Europe, Africa and North and South America. The arsenic exposure is primarily due to naturally high levels in groundwater but combustion of mineralized coal has also caused arsenic poisoning. Dental and skeletal fluorosis also impacts the health of millions of people around the world and, like arsenic, is due to naturally high concentrations in drinking water and, to a lesser extent, coal combustion. Other Medical Geology issues described include geophagia, the deliberate ingestion of soil, exposure to radon, and ingestion of high concentrations of organic compounds in drinking water. Geoscience and biomedical/public health researchers are teaming to help mitigate these health problems as well as various non-traditional issues for geoscientists such as vector-borne diseases.

Health Effects of Toxic Organic Substances from Coal: Toward “Panendemic” Nephropathy

Coal contains myriad organic compounds, some known to be toxic and others that are potentially toxic. Toxic organic compounds found in coal of particular interest include: i) condensed aromatic structures (e.g., polycyclic aromatic hydrocarbons), which can act as mutagens, cancer promoters, and endocrine disrupters; ii) aromatic amines, which have probable nephrotoxic activity; and iii) heterocyclic compounds, which may be carcinogenic and nephrotoxic. Toxic organic compounds can be leached from coal into water supplies, and longterm human exposure to these compounds may lead to disease occurrence, including cancer and renal disease. Despite these potential hazards, little is known about the impact and toxicity of organic substances derived from coal in water supplies. One example of a disease hypothesized to be linked to coal-derived toxic organic compounds in water supplies is Balkan endemic nephropathy (BEN). In this paper, we summarize results from our studies linking BEN to the leaching of toxic organic compounds from low rank (lignite) Pliocene coal deposits into water supplies (well and spring water) of the rural villages where the disease occurs. We also introduce the idea of panendemic nephropathy (PEN) for BEN-like diseases that are linked to coal-derived toxic organic compounds in water supplies, but that occur outside the Balkans. Preliminary results supporting the PEN hypothesis are presented, with results from proposed PEN areas in Wyoming (WY) and Louisiana (LA). Results of toxicological studies of the effects of organic compounds isolated from water supplies in BEN and PEN areas on human cell cultures are also discussed. China, India, Turkey, and Portugal represent other areas where BEN-like diseases may occur, as a result of the presence of extensive low rank coal deposits and rural populations using untreated water in contact with coal in these nations.

Possible health impacts of naturally occurring uptake of aristolochic acids by maize and cucumber roots: links to the etiology of endemic (Balkan) nephropathy

The original publication of the article includes errors in the affiliation of Vuk Maksimović, Calin A. Tatu and Jelena D. Maksimović and in the Acknowledgments. The correct affiliation and Acknowledgments appear in this erratum. Acknowledgments This work was supported by the Serbian Ministry of Science (grant number 173040). All the experiments were performed on equipment provided by the Institute for Multidisciplinary Research and Serbian Ministry of Science. Part of this work was supported by grants from the US Geological Survey (Reston, VA, USA), University of Medicine and Pharmacy, Timisoara, Romania, and NATO (CLG grant # 980104).

GIS in Human Health Studies

Databases used in the field of medical geology are generally comprised of geospatial and/or temporal elements. Although these are not requirements for all medical geology research projects, much of the discussion in this chapter will be focused on databases incorporated into geographic information systems (GIS). GIS are computer-based (or manual) methods that allow a user to input, store, retrieve, manipulate, analyze, and output spatial data (Aronoff 1989). There are four major systems of GIS: engineering mapping systems (computer-aided design/computer-assisted mapping; CAD/CAM), geographic base file systems, image processing systems, and generalized thematic mapping systems. Various software packages are available that perform one or more of these systems, and the relative ability to move data back and forth between them can be critical to the needs and success of a particular GIS. Relational databases are the most commonly used types of databases in GIS (Cromley and McLafferty 2002). Relational database management models are convenient for linking formerly disparate databases together in a GIS. The databases to be joined must share one common attribute, usually an identifier such as coded patient number, sample site, or latitude/longitude. Other database management structures, such as hierarchical and network systems, are not as well suited to health GIS applications, although they may be useful for extremely large databases.

INDOOR AND AMBIENT EXPOSURE TO COAL COMBUSTION BY-PRODUCTS, TEMPERATURE INVERSIONS, AND RESPIRATORY DISEASE

Building healthy communities in environmental justice areas (“Health EJA”), is a biopsychosocial model that was developed as an evaluatory and qualitative tool to assist in rebuilding environmental justice/polluted communities and to evaluate social justice issues in health. An evaluation of the area around Chester, Pennsylvania was performed using the model as a result of the findings in the EPA Environmental Risk Study and the landmark litigation. The EPA findings were: 1) there are a large number of TSDF facilities and sites located around Chester, PA; 2) blood lead levels of children were unacceptably high in 60% of samples; 3) the cancer and non-cancer risks from pollution sources exceeded EPA acceptable levels; 4) air emissions from facilities in and around Chester provided a cancer and non-cancer risk to residents; and 5) the health risks from subsidence fishing in Chester and the Delaware River is unacceptably high. Using the model “Health EJA”, the environmental justice area around Chester was evaluated and solutions were posed to the Environmental Justice Advisory Board of the State Department of Environmental Protection. Those solutions included: 1) identification of health disparities in this community; 2) identification of mental health issues and population in this community; 3) recommendations for reducing environmental burden and attracting new non-polluting businesses that assist and link in building a healthy community and healthy economy; 4) funding for medical care with court ordered victim assistance funds; 5) identification of appropriate health promotions to address identified health disparities; and 6) identification of community environmental racism issues and solutions posed.

Toxicological Pathways of Relevance to Medical Geology

This article provides an overview of toxicological pathways that is important in studying the effects of the natural environment on human health (medical geology). The article is divided into four sections. The introduction defines medical geology and the role of toxicology in this discipline. The section on exposure pathways examines various ways in which toxins are mobilized within the geologic environment, and the toxic impacts of different exposure routes using various examples from medical geology. The section on metabolism and effects of xenobiotics examines how toxins are transported within the body and the ways in which xenobiotics affect metabolism and metabolism changes xenobiotics (making them more or less toxic), with special emphasis on the aryl hydrocarbon receptor pathway. The final section discusses toxicological approaches in medical geology, including methods for isolating xenobiotics from environmental samples for toxicological testing, the use of cell cultures and animal models in toxicological studies, and molecular biological methods of importance.

Navajo coal and air quality in Shiprock, New Mexico

Among the Navajo people, high levels of respiratory disease, such as asthma, exist in a population with low rates of cigarette smoking. Air quality outdoors and indoors affects respiratory health. Many Navajo Nation residents burn locally mined coal in their homes for heat, as coal is the most economical energy source. The U.S. Geological Survey (USGS) and Diné College, in cooperation with the Navajo Division of Health, are conducting a study in the Shiprock, New Mexico, area to determine if indoor use of this coal might be contributing to some of the respiratory health problems experienced by the residents. Researchers in this study will (1) examine respiratory health data, (2) identify stove type and use, (3) analyze samples of coal that are used locally, and (4) measure and characterize air quality inside selected homes. Interim results are summarized below. Inversions.—In the Shiprock area of the San Juan basin, people are exposed to poor air quality outdoors when atmospheric thermal inversions trap combustion products from two nearby large-capacity coal-fired powerplants (fig. 1). The number of respiratory incidents in the Shiprock area increases in winter (when inversions are more common) and decreases in summer. This increase may be related to inversions and to burning coal, wood, and other materials indoors for heating during the winter. Respiratory health data.—Our study indicates that people living in Shiprock are more than five times as likely to be seen at the Northern Navajo Medical Center (NNMC) Indian Health Service facility for respiratory complaints as are residents of other nearby communities that are less affected by inversions. Another notable finding is that Shiprock residents under the age of 5 and over 56 are more than twice as likely to be treated at NNMC for respiratory issues as would be expected of the entire Shiprock population. The very young and the elderly spend more time indoors during winter when coal may be used for home heating, and people in these age groups may have immune systems that are compromised relative to the systems of people between 5 and 56. Stove type and use.—The use of a properly operated and maintained stove designed to burn coal should not significantly lower air quality indoors. The research team surveyed 137 households that used coal-burning stoves in 2004 and found that one-quarter of them were burning coal in stoves that were designed to operate at lower temperatures for burning wood and that many of the stoves had visible cracks or were poorly vented to the outside (fig. 2). According to the results of this study, people can reduce their risk of respiratory disease by doing the following: Cleaning and properly maintaining coal-burning stoves Properly venting those stoves Using a stove designed for the appropriate fuel Safely handling coal and ash Coal analyses.—Most of the coal used by our survey participants came from the Navajo mine at the Four Corners Power Plant. Samples of coal from Shiprock area homes, as well as from the mines and powerplants, have been analyzed for their chemical composition. No significant differences were found in the quality of coal from those various sources, and no dangerous levels of trace elements, such as mercury, were detected. Particulate matter.—When coal is burned, numerous potentially harmful materials are released into the air. Of particular concern are small particles known as PM 2.5 (particulate matter 2.5 micrometers or less in diameter). These particles, less than 1/30th the diameter of a human hair, are small enough that they can travel deep into the lungs and can directly enter the bloodstream. PM 2.5 can then be transported to any organ in the body, and they have been implicated as a cause of heart disease among other ailments. From a human health standpoint, the composition of the particles may be even more important than their size. USGS scientists are currently measuring the amount of PM 2.5 indoors and outdoors and analyzing that material in the laboratory to determine what chemical elements and compounds make up or are stuck to the particles. Results.—This collaborative study of USGS scientists with Navajo students, residents, and health officials is providing valuable training for Navajo students in geographic information science (GIS), public health research methods, and geochemistry. Final results of the study will be provided to Tribal leaders, who can use the data in developing community practices that improve the public health effects of coal used for home heating in the Navajo Nation.