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

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

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

Exposure Opportunity Models for Agent Orange, Dioxin, and Other Military Herbicides Used in Vietnam, 1961–1971

Nearly 19.5 million gallons of herbicides were sprayed on the Republic of Vietnam between 1961 and 1971 for military purposes. Amounts of spray and patterns of applications are available in an electronic file called HERBS that contains records of 9141 defoliation missions, including detailed coordinates of US Air Force Ranch Hand aircraft flight paths, along with chemical agent and gallonage sprayed. Two classes of models for use in epidemiological and environmental studies that utilize the HERBS data for estimating relative exposure opportunity indices are presented: a discrete "hits" model that counts instances of proximity in time and space to known herbicide applications, and a continuous exposure opportunity index, E4, that takes into account type and amount of herbicide sprayed, distance from spray application, and time interval when exposure may have occurred. Both direct spraying and indirect exposure to herbicide (or dioxin) that may have remained in the local environment are considered, using a conservative first-order model for environmental disappearance. A correction factor for dermal versus respiratory routes of entry has been incorporated. E4 has a log-normal distribution that spans six orders of magnitude, thus providing a substantial amount of discrimination between sprayed and unsprayed areas. The models improve on earlier ones by making full use of the geometry of the HERBS spray flight paths of Ranch Hand aircraft. To the extent possible so many decades after the War, the models have been qualitatively validated by comparison with recent dioxin soil and biota samples from heavily contaminated areas of Vietnam, and quantitatively validated against adipose dioxin obtained in epidemiological studies of Vietnamese. These models are incorporated within a geographic information system (GIS) that may be used, as one would expect, to identify locations such as hamlets, villages, and military installations sprayed by herbicide. In a novel application, the GIS also facilitates quantitative risk assessment in epidemiological and ecological studies by applying the models within a framework of historical reconstruction of exposure history of individuals based upon their location histories

Thermodynamic Properties of Poly(trans 1,4-butadiene) Crystals. Relationship to Molecular Structure

Heat capacity measurements of melt crystallized poly( trans-1,4-butadiene) (PTBD) were carried out in the 50-130" region and the entropy change from 73" to the melting point, 139", was calculated. A value of the entropy change obtained using the rotational isomeric state approximation is found to underestimate the experimental entropy change. Theoretical energy calculations were carried out using empirical potential energy functions for a single PTBD chain, a unit cell and a lattice of cells. Minimization of the lattice energy with respect to two of the monoclinic cell constants for the low-temperature crystal form gave results in good agreement with X-ray diffraction data. The energy of transition from the low-temperature form was calculated and a theoretical heat capacity curve was obtained

The role of the Union Health and Safety Committee in evaluating the health hazards of hospital workers: A case study

The Union Health and Safety Committee is an important tool for evaluating and reducing job-related health risks among hospital workers. The experience of one such committee which effectively performed this duty at New York University Medical Center has led to a city-wide survey by District 1199 of working conditions and health status among hospital laboratory workers. Results showed a possible association of hepatitis with some job practices and led to constructive suggestions for improving working conditions and reducing disease risk among hospital workers

Pyrethroid Insecticides-Time for a Closer Look

This is an invited commentary on a report of increased mortality, especially from heart disease, in persons with high compared to low urinary levels of 3-PBA, a metabolic product of pyrethroids indicative of human exposure. The data were drawn from NHANES, an annual survey of the US population that includes interview and clinical measurements. The findings are of concern because of the importance of pyrethroids in controlling infectious disease vectors, especially mosquitos that can carry malaria parasites or West Nile virus. The observations warrant further studies, but alternative explanations need to be considered, since specific exposure sources or products were not identified, comparable non-occupational pesticide-related risks from pesticide exposures are unusual, and pyrethroid cardiotoxicity has been reported mainly in animal models

Women's Occupations, Smoking, and Cancer and Other Diseases

This article addresses three major questions: (1) What jobs do women hold, and in what industries do they work? (2) How much do women smoke, and how is their smoking related to their jobs and to other social factors? (3) How does the combination of occupation and smoking influence women's risk for developing cancer and other diseases

Finding a Chair That Fits

Article on workplace chair ergonomics distributed as a fact sheet by the Women’s Occupational Health Resource Center (WOHRC). The WOHRC (1979-1987) was a research and training program devoted to identifying and better understanding hazards faced by women workers. WOHRC was housed in Columbia’s School of Public Health and directed by Professor Jeanne Mager Stellman. WOHRC was a designated OSHA New Directions Training program, and also received support from other federal and private agencies. As a New Directions project, WOHRC trained thousands of workers and professionals in hazard recognition and accident and illness prevention for women workers. In order to carry out its public health programs, WOHRC developed and disseminated original educational materials. The materials were designed to be authoritative while at the same time accessible to non-professional users (e.g. the workers). WOHRC published a monthly newsletter that contained a “fact sheet” focusing on a particular job or a particular hazard. The fact sheets were also made available individually or collected into “fact packs” of related materials