229 research outputs found
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Estimation of Exposure to Agent Orange and Other Defoliants among American Troops in Vietnam: a Methodological Approach
Two pivotal problems in determining whether exposure to herbicides has caused disease in Vietnam veterans or their offspring are definition of which troops were exposed and extent of exposure. The DoD HERBS tape is the most complete publicly available record of herbicide spraying in Vietnam. It contains about 17,000 records consisting of coordinates of spray missions, dates, chemical agent, quantity and area sprayed, and mission purpose. We have developed a set of discrete and continuous indexes of probability of exposure to herbicides for individual veterans. These probability indexes are based on HERBS tape spray data and on locations and dates of service derived from a place-and-date matrix completed by the veteran. They can take into account a conservative estimate of environmental persistence of herbicide by using first-order exponential decay kinetics with an estimated half-life of dioxin. Mean values for the continuous exposure probability indexes were significantly greater among veterans judged to be exposed according to self-reported job titles and specific military experiences than among men judged unlikely to have been exposed. Probabilistic exposure indexes based on HERBS tape for classification of likely exposure to herbicides in South Vietnam during 1965-1971 appear to be well suited for comparative classification of veterans and hence for use in epidemiologic studies
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Wynder, Ernst
This short biographical entry outlines the career of cancer research and epidemiology pioneer Ernst L. Wynder (1922-1999)
Characterization of Exposure to Agent Orange in Vietnam Veterans as a Basis for Epidemiological Studies
Between 1961 and 1970, the U.S. military engaged in massive chemical defoliation and crop destruction operations in Southeast Asia. In 1985, nearly two decades after the spraying had ceased, a landmark tort settlement was reached between a class of Vietnam veterans and the chemical manufacturers that had supplied the Agent Orange and other military herbicides to the U.S. Department of Defense. It is notable that, at the time of the settlement, there was little convincing epidemiological evidence available, either positive or negative, on the health consequences to veterans of the herbicide operations. Today, more than three decades after this massive environmental exposure, there is still a dearth of epidemiological data on the extent to which adverse health consequences resulted from the use, storage, and disposal of the herbicides in Vietnam.
This paucity of epidemiological data stands in stark contrast to the extensive amount of experimental data available on dioxin, an important contaminant in about 60% of the herbicide sprayed. Much laboratory data convincingly demonstrate dioxin's extreme toxicity. The scientific literature also is growing with respect to the carcinogenicity of the organic arsenical that was a primary component of the Agent Blue used to destroy enemy food crops. Many epidemiological studies have been carried out on other, much smaller populations exposed to the same chemicals. Indeed, when the Institute of Medicine (IOM) conducts its biennial review of the scientific literature and provides the Department of Veterans Affairs (VA) with a summary, including its appraisal of the relationship between herbicide exposure and a list of health outcomes, it relies to a large extent on the studies carried out of non-veteran populations to support its conclusions. The degree to which these other studies correctly estimate the health effects in Vietnam veterans is not known. Thus there continue to be practical ramifications to the paucity of definitive epidemiological studies on a sufficiently large exposed population of either veterans or Vietnamese citizens
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Social factors: women and cancer
Numerous factors in the social environment may affect the incidence and mortality from cancer in women. Women's work roles, possible exposure to workplace hazards, social class, social roles, social stress, access to health care, and health behaviors are among the factors that act together to help determine a woman's health and well-being
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Computer Graphics in the Solution of the Chain Deformation Problem
Go and Scheraga have given a general solution for determining the possible conformations of a section of a flexible polymeric chain between two fixed bonds (if the bonds coincide, the problem is equivalent to ring closure). Often, the fixed bonds are related by symmetry, such as that imposed by helicity or folding of antiparallel chains. A technique is shown for obtaining solutions using interactive computer graphics, whereby a plausible chain conformation or fold is approximated manually and completed by mathematical minimization. The procedure allows rapid, repetitive exploration of multiple solutions, and has many options for changing constraints. As an example, the backbone conformation of GpC, a dinucleoside phosphate, is used as a starting model, and gives upon minimization a set of backbone angles in the range of 11-fold helical RNA
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Commentary on Liu et al, ‘Prevalence and patterns of tobacco smoking among Chinese adult men and women: findings of 2010 national smoking survey’
Loomings
I first became cognizant of the massive public health problem of tobacco use in China at a 1985 IARC conference in Moscow organised by David Zaridze and Richard Peto (later Sir Richard), where Yu-Tang Gao of the Shanghai Cancer Institute reported that “about half of the male adults in Shanghai are smokers.”1 Smoking prevalence in the USA had not been that high since the early 1970s; by 1985 it was 36.8% in US white males2 and only 23.6% in more than half a million male participants in Cancer Prevention Study 2.
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Are Babies Normal
Clemons and Pagano suggested that certain anomalies in the distribution of birth weights are an artifact of digit bias arising when some hospitals report weight in grams and others in pounds and ounces. In this letter I report yet another administrative source of bias in New York City reports of low birthweight, namely, under-reporting of short-lived infants by hospital staff with incomplete knowledge of Health Code requirements. These infant deaths are often identified by NYC Department of Health inspection of medical records in selected hospitals known to have many high-risk births
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Confounding
The magnitude of confounding is examined in nine case studies of two "weak" relationships: between artificial sweeteners and bladder cancer, and between oral contraceptives and cervical dysplasia. Confounding had little or no influence on the results of any published study. The responsible epidemiologist must always consider the possibility of confounding, no less when associations are weak than when they are strong. Identification of potentially confounding variables is an integral part of good epidemiologic practice. Rarely, however, does confounding itself, especially from unidentified sources, live up to its reputation for introducing seriously spurious associations. An investigator is more likely to be led astray by undetected biases than by pure confounding
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Application of three-dimensional interactive graphics in X-ray crystallographic analysis
A program called XpY was written for the PDP-10/LDS-1 at the Princeton University Computer Graphics Laboratory, for generating and displaying models of dinucleoside phosphates. The molecule GpC, a member of this class and a fragment of the nucleic acid RNA, was subjected to X-ray diffraction analysis. The paper describes the importance of model building in X-ray analysis, and shows step by step how XpY was used to deduce the atomic coordinates of GpC from the experimental data. The program documentation is also included as an Appendix. A subjective critique of graphics is made in the Conclusions section
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Confounding
The magnitude of confounding is examined in nine case studies of two "weak" relationships: between artificial sweeteners and bladder cancer, and between oral contraceptives and cervical dysplasia. Confounding had little or no influence on the results of any published study. The responsible epidemiologist must always consider the possibility of confounding, no less when associations are weak than when they are strong. Identification of potentially confounding variables is an integral part of good epidemiologic practice. Rarely, however, does confounding itself, especially from unidentified sources, live up to its reputation for introducing seriously spurious associations. An investigator is more likely to be led astray by undetected biases than by pure confounding
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