Data drive decisions. In this age of globalization, society's thirst for information is nearly unquenchable. All sectors of modern society, from education and research to manufacturing and commerce, require real-time data for effective decision making. Even the efficiency of everyday tasks such as automobile travel is enhanced by data from continuous satellite positioning systems to keep us on the right track.
The public health sector is no different. Responding to emerging and reemerging health threats with limited resources requires quality data on which to base decisions. While results from epidemiologic studies are invaluable in understanding the relationships among risk factors and disease, underpinning all sound public health decisions is the analysis and interpretation of tracking or surveillance data. Accurate and timely tracking data allow public health authorities to determine disease impacts and trends, recognize clusters and outbreaks, identify populations and geographic areas most affected, and assess the effectiveness of interventions. Without the broad information base supplied by comprehensive tracking systems, public health officials are frequently forced to make critical decisions based solely on epidemiologic studies of limited scope and power or even on anecdotal reports of disease burden.
The importance of the environment in the causation of disease has been recognized for millennia. The ancient Greek scientist, Hippocrates, wrote about the effects of climate and food in causing disease in his book, On Air, Water, and Places.1 From the middle ages up to the postulation of the germ theory in the mid-1800s, miasma ("bad air") was thought to be responsible for a host of illnesses, including malaria and cholera. While the miasma mystery appears to be resolved, there are still many unknowns in the complex relationships between the world in which we live and our health. Chronic diseases comprise the majority of illnesses and deaths in the United States2 and environmental exposures may play a role in the development or exacerbation of many of these illnesses. Various cancers, asthma, and heart disease have all been linked in epidemiologic investigations with exposures to environmental contaminants. However, the data generated by a comprehensive environmental public health tracking (EPHT) system are necessary to more thoroughly determine what risk environmental exposures may pose in the development of disease.
In September 2000, after 18 months of careful study and review, the Pew Environmental Health Commission released a report on the state of environmental public health in the United States. The Commission reported that the environmental public health system in the United States was fragmented, neglected, and ineffective.3 The first recommendation by the Commission was for the federal government to establish a national EPHT network to link information on environmentally related diseases, human exposures, and environmental hazards. The information from this network would be used to respond to, and eventually reduce, the burden of these diseases on the nation's population.
In response to the Pew Commission's report, the Centers for Disease Control and Prevention (CDC) initiated the national EPHT program. EPHT is the ongoing collection, integration, analysis, and dissemination of environmental hazard, exposure, and health data. A key aspect of EPHT is the integration of health, exposure, and environmental data, applying the model first proposed by Thacker et al.4 The development and utility of this system depends on the availability, timeliness, and compatibility of existing environmental hazard, exposure, and health effects data.
Hazards include chemical compounds, physical agents, and biologic toxins. Hazard information is frequently collected for regulatory purposes and, therefore, the types and frequency of the data collected and the collection methods may be less than ideal for public health surveillance purposes. However, a comprehensive and functioning EPHT must have data on environmental contaminants and hazards that are standardized, collected regularly, and interpretable for public health purposes. These data are integral to determining the role of environmental hazards in the development of disease.
Exposure tracking is the monitoring of individuals, communities, or populations for the presence of an environmental agent or its metabolite. Biomonitoring is the measurement of levels of contaminants or their metabolites in human specimens, such as blood or urine. Nationally, the CDC reports on blood and urine levels of 116 chemicals or their metabolites taken from a representative sample of the US population as a whole.5 However, there is currently little ongoing biomonitoring data collection that is applicable to an environmental health tracking system at the state or community level. Inclusion of laboratory data on actual measurements of exposures in individuals would greatly enhance the utility of the EPHT program. Other types of exposure data in an EPHT system may include estimates of populations exposures derived from sophisticated modeling of hazard data, such as the modeling of ozone exposure by EPA and NOAA that utilizes air monitoring data and meteorologic information.6
The third critical component of the EPHT is health effects data. Sources for health effects information include traditional public health surveillance resources such as vital statistics, disease registries, annual surveys such as the National Health Interview Survey, and administrative systems such as hospital discharge data. Although valuable to public health authorities, these sources represent a piece meal approach to health surveillance and do not comprise the integrated, standardized database needed to understand the potential role of the environment in the development of many of the chronic conditions on which the EPHT is focused. These conditions include birth defects, developmental disabilities, asthma, cancer, and neurologic diseases, among others.
A unique aspect of EPHT is the integration of the data among the hazard, exposure, and health effects components. The EPHT goal is to build a national surveillance system that links standardized data from multiple environmental monitoring, human and community exposure, and health outcome databases. This linkage process may be the most difficult task in building the EPHT. The data systems are of varying quality, are generally not standardized, and are collected for reasons other than public health surveillance.
This issue is composed of a series of articles that describe in detail the processes and obstacles of building the EPHT. The three general areas that are highlighted describe the importance of incorporating the latest advancements in communication and data technology; the critical role of public health science, surveillance methods, and epidemiology in the development and utilization of EPHT; and the value of collaboration and partnerships to bring this project to fruition. The authors represent the broad range of scientific disciplines and experience that have been brought to bear in developing this complicated tracking program.
The public has great interest in the role of the environment in the development of disease. A recent poll of voters showed an overwhelming majority (92%) believed that environmental factors are an important cause of disease.7 A national EPHT program that incorporates standardized environmental, exposure, and health outcome sources into an integrated surveillance system is critical to begin to explore the associations among environmental contaminants and disease. The CDC, in collaboration with our partners in state and local health departments, universities, and nongovernmental organizations, is committed to building this surveillance program and incorporating it into the nation's public health system.
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