Environmental Epidemiology, Volume 2 Use of the Gray Literature and Other Data in Environmental Epidemiology (1997) / Chapter Skim
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7 Review of the Gray Literature from State Reports
7 Review of the Gray Literature from State Reports
Pages 154-172
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From page 154... ...
This chapter continues that assessment by rev~ew~ng selected studies on this subject from the gray literature, that is, studies that are available to the public but not published in the indexed scientific and technical literature. This chapter explains the process that the committee used to identify selected studies from the gray literature for assessment; presents a general review and assessment of those studies using criteria developed by the committee evaluates in depth some reports that specifically examined reproductive hazards of exposures to hazardous wastes and other materials and notes briefly some recent unpublished reports on human health and the environment that come from central Europe, where environmental contamination appears to be considerable.
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From page 155... ...
To understand better the question of why the gray literature is not published, the committee undertook to obtain a collection of such studies that had been produced by state health departments and others. Defined criteria were used to assess the quality, strengths, and weaknesses of each study and to estimate whether each report would be publishable in the peer-reviewed literature.
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From page 156... ...
The study investigates the association of biologically plausible (to state officials) health outcomes with potential exposure to hazardous wastes.
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From page 157... ...
We necessarily focused on state reports, to the exclusion of other kinds of gray literature that may be quite different in important ways. Further, since only certain states participated and since the states themselves selected which reports to send, the reports reviewed by the committee would in no way represent a crosssection of all studies conducted by those states, nor would they represent studies conducted by all states.
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From page 158... ...
The following factors were examined. Study Design There is a relation between study power, sample size, prevalence of exposure, and expected rates of a given outcome in the study and control population.
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From page 159... ...
For example, the validity of self-reported medical diagnoses is improved if they are verified with medical records. Study Results Results of a study are stronger if the magnitude of the association between exposure and health outcome is greater; however, this must be balanced with the public-health significance of the outcome; i.e., a highly elevated relative risk of a minor and rare health problem may be less important than a less-elevated risk of a common and more-serious condition.
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From page 160... ...
The committee found the general lack of exposure assessment to be a significant weakness in these reports from the gray literature, and the characteristic most in need of improvement.
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From page 161... ...
and lack of information on confounding factors. Few of these gray literature studies used clinical testing or medical examinations to assess health end points.
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From page 162... ...
This is not to say that the studies were of no value; many studies in the gray literature clearly have objectives other than the advancement of scientific knowledge, such as to allay public worries or to show official concern. STATE STUDIES OF REPRODUCTIVE END POINTS To focus attention on the problems and prospects for environmental epidemiology, the committee considered evidence from the gray literature on the possible association of environmental pollution with adverse reproductive outcomes.
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From page 163... ...
Because the outcomes of interest are rare and small populations were covered by most of the investigations, the committee assumes that these 113 investigations may have generally had low power. MICHIGAN DEPARTMENT OF PUBLIC HEALTH: EVALUATION OF CONGENITAL MALFORMATION RATES FOR MIDLAND AND OTHER SELECTED MICHIGAN COUNTIES COMPARED NATIONALLY AND STATEWIDE, MAY 4, 1983 The Michigan Department of Public Health examined birth defect rates in the Midland, Mich., area, the site of a substantial chemical industry, for the years 1970-1980 in response to concerns from the community about environmental and occupational exposures to certain chemicals.
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From page 164... ...
Out-migration is a smaller problem; 92% of live births and fetal deaths with a selected anomaly born to Midland County residents are delivered in Midland County. The second part of the study evaluates the data from the birth and fetal-death records from the Michigan Department of Public Health.
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From page 165... ...
Investigators found 4 anomalies (cleft lip with or without cleft palate, cleft palate without cleft lip, hypospadias, and hip dislocation without CNS defects) to have significantly higher rates in Midland County than in the state of Michigan for the years 1970-1975.
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From page 166... ...
After age adjustment, they found a miscarriage rate among whites of 17.4% + 2.9% and among blacks of 13.2% + 2.1%. The researchers commented that white women in the study might be more likely to have their miscarriages recorded because they were more likely to seek medical attention and to release their medical records.
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From page 167... ...
UNIVERSITY OF TEXAS HEALTH SCIENCE CENTER AT HOUSTON, SCHOOL OF PUBLIC HEALTH: W JOHANSON, AN ANALYSIS OF A HEALTH EFFECTS SURVEY CONDUCTED BY RESIDENTS LIVING NEAR A TOXIC-WASTE SITE, DECEMBER 1991 THESIS FOR MASTER OF PUBLIC HEALTH DEGREE, THE UNIVERSITY OF TEXAS HEALTH SCIENCE CENTER AT HOUSTON, SCHOOL OF PUBLIC HEALTH For years, concern had been expressed that exposures from wastedisposal facilities near Brio, Tex., endangered the health of nearby residents.
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From page 168... ...
They also evaluated the rates of reported birth defects and used data obtained from the CDC Congenital Malformations Surveillance Report (CDC, 1988) to estimate expected rates.
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From page 169... ...
They commented that this would be expected because there was a higher proportion of whites in Midland County than in the state and because higher rates of oral cleft are reported in whites than in blacks. Similarly, the Louisiana study found different miscarriage rates among whites and blacks, indicating that race is a confounder.
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From page 170... ...
Urban living tends to be correlated with greater smoking and alcohol drinking, as well as access to health services factors that clearly influence health outcomes and their recording. A marked urban gradient is evident for many diseases, including lung cancer.
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From page 171... ...
1988. Congenital Malformations Surveillance Report, January 1982-December 1985.
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From page 172... ...
1983. Evaluation of Congenital Malformation Rates for Midland and Other Selected Michigan Counties Compared Nationally and Statewide, 1970-1981.
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