Environmental Epidemiology, Volume 2 Use of the Gray Literature and Other Data in Environmental Epidemiology (1997) / Chapter Skim
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5 Data Systems and Opportunities for Advances
5 Data Systems and Opportunities for Advances
Pages 94-129
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From page 94... ...
(1992~; for other discussions of state and local data systems see, for instance, Health Officers Association of California (1986) , National Governors' Association (1989)
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From page 95... ...
Considerations of cost, urgency, and limited special expertise often require that officials rely on analyses of existing data that were gathered for other purposes. Epidemiologic studies of the classical kind involve the measurement of both the health status and the environmental exposure (or internal dose)
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From page 96... ...
Modification of public-health policies depends on knowledge of such relations, identified largely through analyses of secondary data. DATA-COLLECTION SYSTEMS: WHAT THEY MEASURE Evaluation of the relation between an environmental pollutant and human health requires data to characterize exposures to the pollutant, including concentrations in the environment, the probability and characteristics of human exposure, and the distributions of internal doses, as well as trends or differences in the health status of exposed people.
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From page 97... ...
Monitoring sites can be selected to characterize those types of environments, as in the stratified sampling of air in urban areas and rural areas. Alternatively, one might select monitoring sites on the basis of a stratified probability-sampling scheme to yield data that are representative of the distribution of environments.
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From page 98... ...
Many pollution-related data systems have emphasized the characterization of pollutant sources, rather than the distribution and fate of pollutants in the environment or the potential exposures of humans. Representative data (as opposed to comprehensive data)
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From page 99... ...
However, study sites are often selected because the potential exposure is considered high or because of complaints about symptoms, so sites are not characteristic of ordinary population exposures. These studies do, however, attempt to characterize explicitly the scope or potential for human exposure in these presumably extreme settings, and they may contribute information on the relation between the environmental distribution of pollutants and human exposure or internal dose.
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From page 100... ...
Detailed information on human exposures generally requires the use of personal monitors or structured activity questionnaires, but these tools are expensive and time-consuming. Thus, most systems contain information on small populations chosen to be characteristic, but not necessarily representative, of the target population.
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From page 101... ...
INTERNAL DOSE Like information on human exposure, information on internal dose is rarely collected systematically (table 5-5~. Occasional studies of biologic markers of specific agents in small, defined populations are plentiful, but
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From page 102... ...
Direct measures of internal dose are not usually included in health-assessment studies (conducted by ATSDR) or health-hazard evaluations (conducted by NIOSH)
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From page 103... ...
The National Health and Nutrition Examination Survey (NHANES) , conducted by the National Center for
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From page 104... ...
Given the followup capabilities of NHANES, detailed exposure data could be collected in subgroups of the entire sample that are identified as having received internal doses of particular interest. However, when the probability of exposure is small, the actual number of participants who could be studied to characterize the specific exposure would be small, possibly zero, and NHANES might not be sensitive enough.
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From page 105... ...
program of the National Cancer Institute, which collects cancer incidence and survival data from approximately 10% of the US population, and the Birth Defects Monitoring Program (BDMP) of the National Center for Environmental Health is gathered by abstracters trained in coding and abstracting from hospital records.
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From page 106... ...
, could be used to collect exposure and health-status information at the state level, but are limited to information that could be reliably solicited by the telephone interview method used. Untapped resources that could provide systematic information on the health status of populations include routine medical examinations and school test-performance scores.
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From page 107... ...
Conversely, emissions data from the Toxic Release Inventory, data on ambient concentrations of various pollutants (EPA, 1991) , and lists of toxic-waste sites (Commission for Racial Justice, United Church of Christ, 1987)
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From page 108... ...
108 TABLE 5-6 Data-Collection Systems: Health Status ENVIRONMENTAL EPIDEMIOLOGY Data-System Name Description Vital Records National Vital Statistics Program National Surveys National Health and Nutrition Examination Survey National Health Interview Survey Surveillance Systems Birth Defects Monitoring Program Surveillance, Epidemiologic, and End Results Program Response Epidemiologic Studies Epidemiologic investigations Data from birth, death, and marriage records Survey of a probability sample of the US population that includes interview, examination, and physiologic testing Interview survey of a probability sample of the US population that includes rotating special topics, including knowledge of risk factors, such as radon, and occupational chemical exposures Information sent by participating hospitals on birth defects diagnosed and recorded in the newborn period Demographic and diagnostic information on patients identified as having some form of cancer Centers for Disease Control and ATSDR; these studies in response to public concerns of potential exposures and health effects often include observational data on health status that is not experiencing a change in the probability of an illness. The 1-in1,000 event will occur, by definition, one time in 1,000, and if many thousands of clusters could be defined (by time interval, geographic location, specific health end point, etc.)
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From page 109... ...
DATA SYSTEMS AND OPPORTUNITIES FOR ADVANCES 109 Coverage/Sample + Primary Objective Design Linking Data Monitoring National: Residential comprehensive geographic codes, job title Monitoring National: represents Residential noninstitutionalized geographic codes, population personal history, job title Monitoring National: represents Residential noninstitutionalized geographic codes, population job title Monitoring National: covers None only participating hospitals Monitoring Participating Broad geographic geographic areas codes; fine detail available in special studies Health-hazard National: None detection compendium, based on reports lain to find that some disease is more common in some segment than in others, with a low p value. LINKING DATA SYSTEMS Linking several data systems can improve information on both exposure and health.
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From page 110... ...
Studies with Information on Environmental Concentrations and Health Status, but Not Other Risk Factors: Many studies that have examined correlations between measurements and health assessments have failed to adjust for other risk factors, environmental or otherwise, often because relevant data do not exist. Linkage with mortality data is common and generally straightforward because of the virtually complete ascertainment of deaths and the use of
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From page 111... ...
Although characteristics of individual subjects were not available, Pope noted strong associations between indicators of respiratory health, particulate pollution, and the operation of a nearby steel mill. Studies with Information on Health Status and Nonconcentration Measures of Environmental Status: The studies discussed above used ambient-concentration data from monitoring stations mainly as a surrogate for the probability that personal exposures were sufficient to affect health, but models can use other sources of environmental data.
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From page 112... ...
It is suspected that some noncommunicable diseases (e.g., some cancers and diabetes) are increasing in frequency because of unknown factors in the environment.
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From page 113... ...
· Capable of producing information that can be combined with similar data systems, so as to increase sample sizes; this requires the collection of data in a standardized fashion. · Capable of being linked to other data sources, e.g., exposure data, which would require personal identifiers and provisions for confidentiality.
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From page 114... ...
Epidemiologic research is often expensive and time-consuming, especially where longitudinal studies of large populations are involved, so there is reason to consider "piggy-backing" needed research on other kinds of studies. For example, prospective cohort studies that are not directly related to the environment could possibly be inexpensively modified to collect additional data relevant to many of the objectives of environmental epidemiology.
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From page 115... ...
ACTIVE SURVEILLANCE OF EMERGENCY ROOMS AND HOSPITAL ADMISSIONS Changes in the frequency of emergency visits or hospital admissions for specific conditions can provide information about acute environmental insults. On a long-term basis, hospital admission rates measure the prevalence of serious disease in the community, though a major disadvantage is the inability of nearly all existing systems to distinguish between first and repeat admissions for the same condition.
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From page 116... ...
. While disease registries have not yet been established, the National Exposure Registry is further developed and is the focus of this discussion.
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From page 117... ...
The document is reviewed by ATSDR and, according to the resources available, the site is either approved or disapproved for establishment of an exposure registry. Final sites selected may also be based on the size of the population needed for the subregistry (TeAnne Burg, ATSDR, personal communication, 1993~.
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From page 118... ...
The National Exposure Registry will contain multiple subregistries. The registry is to be maintained indefinitely, but the various subregistries may have a limited life (e.g., 5, 10, or 30 years)
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From page 119... ...
Passive reporting systems as currently constituted would not be able to identify such changes reliably; indeed, much-larger fluctuations would frequently occur through variation in reporting or by chance. The ideal for surveillance of noncommunicable diseases is accurate incidence data across broad areas, long periods, and many diseases.
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From page 120... ...
To evaluate complex interactions between environmental exposures and health effects, detailed and extensive information on individual subjects is often needed, and populations may have to be followed for long
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From page 121... ...
ATSDR's National Exposure Registry, for example, is subject to the Privacy Act. Although the registry is generally prohibited from disclosing personal information without written consent (which is routinely collected from participants through an informed-consent form)
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From page 122... ...
· Can the data systems of different agencies He Neck, with return of the linked data to both agencies at the same level of detail as was provided? · Should all data systems that obtain information on individual subjects collect personal identifiers in a consistent way and maintain them in a confidential data file for use later?
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From page 123... ...
The confidentiality issues have been solved largely by returning only anonymous data to investigators for analysis. However, when informed consent for linkage to vital-statistics data in the future had been obtained for a randomized trial of breast-cancer screening, individually identified information was returned to the investigators after linkage to the National Mortality Data Base (Miller et al., 1992~.
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From page 124... ...
Pollutant sources and ambient concentrations have been a focus of regulatory efforts. Assessment of the general health status of the population is usually a health-policy effort, largely independent of environmental health, so there is a paucity of data on human exposures and human internal doses.
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From page 125... ...
Although each environmental-epidemiologic issue could be addressed by a specially designed data system, such an approach would be prohibitively resource intensive, and ecologic analysis will often be the only feasible way to make general inferences about exposure and health. Even in a confined, compromise data system, detailed exposure patterns or the morbidity of each person simply cannot be obtained.
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From page 126... ...
The National Exposure Registry and the NHANES I Epidemiologic Followup Study are examples of such mechanisms. In addition, the National Death Index is a useful resource for the public-health community.
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From page 127... ...
1988a. Policies and Procedures for Establishing a National Registry of Persons Exposed to Hazardous Substances (National Exposure Registry)
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From page 128... ...
Report of the Project Team to the National Task Force on Health Information. Ottawa: National Centre for Health Information, Statistics Canada.
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From page 129... ...
1992. Estimating human exposure to environmental pollutants: availability and utility of existing databases.
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