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R Neutra

Publications and source records attributed to R Neutra.

At least 19 recordsLinked to original sources
PubMed1993

Approaches to disease cluster investigations in a state health department.

Classical tests for clustering rarely have a major role in the investigation of disease clusters at the neighbourhood level performed by a health department. When examining a single cluster, the boundaries are often ill-defined, and the dimension (geographic, occupational, iatrogenic) is rarely obvious. Furthermore, using cluster tests to routinely scan disease registries looking for clusters is undesirable for several reasons. A better approach is to be vigilant for unusual environmental exposures, and to evaluate the impact they may have. In this context, cluster techniques may serve as part of a larger investigation that includes other epidemiologic approaches.

Air Pollutants↗
PubMed1992

Clusters galore: insights about environmental clusters from probability theory.

The posterior probability of a causal explanation given that an environmental cancer cluster is statistically significant depends on the prior probability of an environmentally caused cluster, the sensitivity of the statistical test and its specificity. The prior probability is low, because it is rare to have enough carcinogen in the general environment to cause a relative risk of cancer high enough to achieve statistical significance in a small geographic area. The sensitivity and specificity are not great. The likelihood that a census tract escapes statistically significant elevations in all 80 types of cancer can be calculated. Many of the thousands of census tracts will, by chance alone, have at least one type of cancer whose elevation is statistically significant. Actual observation from a large cancer registry confirms this probabilistic prediction. Applying the principles of Bayes' Theorem would suggest that most statistically significant environmental cancer clusters are not due to environmental carcinogens. One would have to investigate hundreds of environmental cancer clusters to find one with a true environmental cause.

Bayes Theorem↗
PubMed1992

Optimization of protein-production by the baculovirus expression vector system in shake flasks.

Shake flasks were successfully employed for the cultivation of Spodoptera frugiperda (Sf-9) insect cells and for the production of beta-galactosidase, a recombinant model protein, utilizing the baculovirus expression vector system. The culture doubling time and maximal cell density were 20 h and 5 x 10(6) cells/ml respectively. The optimal liquid volumes for flasks rotating at 100 rpm were 25-40% of the flask total volume. Enzyme production (about 600 mg/l) was best at a multiplicity of infection of between 1 and 20 and at a cell density at time of infection of 0.7 x 10(6) cells/ml. At a rotation speed of 100 rpm, Pluronic F-68 had no effect on growth and enzyme production.

Animals↗
PubMed1991

Symptom prevalence and odor-worry interaction near hazardous waste sites.

Retrospective symptom prevalence data, collected from over 2000 adult respondents living near three different hazardous waste sites, were analyzed with respect to both self-reported "environmental worry" and frequency of perceiving environmental (particularly petrochemical) odors. Significant positive relationships were observed between the prevalence of several symptoms (headache, nausea, eye and throat irritation) and both frequency of odor perception and degree of worry. Headaches, for example, showed a prevalence odds ratio of 5.0 comparing respondents who reported noticing environmental odors frequently versus those noticing no such odors and 10.8 comparing those who described themselves as "very worried" versus "not worried" about environmental conditions in their neighborhood. Elimination of respondents who ascribed their environmental worry to illness in themselves or in family members did not materially affect the strength of the observed associations. In addition to their independent effects, odor perception and environmental worry exhibited positive interaction as determinants of symptom prevalence, as evidenced by a prevalence odds ratio of 38.1 comparing headaches among the high worry/frequent-odor group and the no-worry/no-odor group. In comparison neighborhoods with no nearby waste sites, environmental worry has been found to be associated with symptom occurrence as well. Potential explanations for these observations are presented, including the possibility that odors serve as a sensory cue for the manifestation of stress-related illness (or heightened awareness of underlying symptoms) among individuals concerned about the quality of their neighborhood environment.

Adult↗
PubMed1991

Hypotheses to explain the higher symptom rates observed around hazardous waste sites.

Five studies were carried out around hazardous waste sites in California in which the main route of exposure was to low-level parts per billion concentrations of either gaseous emissions or airborne dust particles. Although there was no evidence suggesting excesses in cancer or birth defects, the total number and the prevalence of many of subjective symptoms were higher in areas near the site than in control neighborhoods. We discuss a number of causal processes that could explain these results. We conclude that a classical toxicological response and mass psychogenic illness are not valid explanations. Recall bias may explain part of the pattern. We present data from situations where stress alone from environmental anxiety has produced a similar magnitude of excess symptoms in populations. The fact that excess symptoms in waste site neighbors is found primarily in those who complain of odors or who are worried about environmental chemicals suggests the possibility that autonomic, stress-mediated mechanisms or behavioral sensitization are active in the genesis of these symptoms. A variety of confounders were controlled for. The hypothesis that chemically "acquired immune deficiency" can cause subtle symptomatology as a prodrome to subsequent serious disease has been raised in testimony at several toxic tort trials about waste sites. Although this hypothesis seems unlikely, particularly at sites such as the ones we studied with low airborne exposures, if true it would have profound regulatory implications.

Anxiety↗
PubMed1990

Pregnancy outcomes in women potentially exposed to solvent-contaminated drinking water in San Jose, California.

During 1980-1981, solvents leaked from an underground storage tank of a semiconductor firm in southern Santa Clara County, California, contaminating local drinking water. The contaminated well was closed in December 1981. An epidemiologic study conducted in 1983 confirmed statistically significant excesses of adverse pregnancy outcomes in an exposed community compared with an unexposed community, but could not establish a causal connection between the leak and the adverse outcomes. This study expanded the first study; adverse pregnancy outcomes occurring in 1980-1985 were studied in two communities exposed to the contaminated drinking water and in two demographically comparable but unexposed communities. The period 1980-1981 was the time period in which the well was considered to have been contaminated and 1982-1985 was considered the postcontamination time period. Both exposed and unexposed communities were considered unexposed during the latter period (1982-1985). Out of 10,055 households surveyed, interviews were conducted with 1,105 women who reported one or more eligible pregnancies. Miscarriages and birth defects were validated by medical record review or physician reports. Although the authors again observed statistically significant excesses of spontaneous abortions and birth defects in the originally studied exposed area in 1980-1981, they observed deficits of these outcomes in the second exposed study area. Adjustment for potential confounders did not alter these findings. Analyses of pregnancy outcomes during 1981 in relation to exposure estimates based on hydrogeologic modeling of water and contaminant distribution within the exposed areas also indicated that the leak was not likely to have caused the observed excesses of adverse pregnancy outcomes in the originally studied area.

Abnormalities, Drug-Induced↗
PubMed1988

How do cancer risks predicted from animal bioassays compare with the epidemiologic evidence? The case of ethylene dibromide.

Cancer risks for ethylene dibromide (EDB) were estimated by fitting several linear non-threshold additive models to data from a gavage bioassay. Risks predicted by these models were compared to the observed cancer mortality among a cohort of workers occupationally exposed to the same chemical. Models that accounted for the shortened latency period in the gavaged rats predicted upper bound risks that were within a factor of 3 of the observed cancer deaths. Data from an animal inhalation study of EDB also were compatible with the epidemiologic data. These findings contradict those of Ramsey et al. (1978), who reported that extrapolation from animal data produced highly exaggerated risk estimates for EDB-exposed workers. This paper explores the reasons for these discrepant findings.

Animals↗
PubMed1987

Risk assessment.

Explore the source record for details and available documents.

Environmental Pollutants↗
PubMed1987

Secular rates and correlates for gastroschisis in California (1968-1977).

This study reports on an epidemiological investigation of gastroschisis using birth certificate data from California for the period of 1968-1977. Gastroschisis has been reported to be on the increase in a number of countries. The distribution of the 166 California gastroschisis cases reported during this time period indicated a clear upward secular trend (P less than .001) with the rate per 1,000 increasing from .006 in 1968 to .089 by 1977. This secular trend was observed in every maternal age group and for gravidity level 1. Gastroschisis also occurred more frequently among younger mothers (P less than .001) and low gravidity mothers (P less than .001). Omphalocele, another eventration defect, was also examined but did not display an upward secular trend.

Abdominal Muscles↗
PubMed1987

Exposure to aerial malathion application and the occurrence of congenital anomalies and low birthweight.

The association between exposure to low dose malathion, after its aerial application to 13,000 square miles in the San Francisco Bay area, and the occurrence of birth defects and low birthweight was examined using newborn hospital discharge data and vital records. No biologically plausible pattern of association was found. Limitations in the data and analysis are discussed.

Abnormalities, Drug-Induced↗
PubMed1985

Relationship of health locus of control to lifestyle change programs.

The relationship of health locus of control (HLC) scores to changes in physical parameters of 339 participants in a lifestyle change program was examined. Physical parameters included weight, blood pressure, low density lipoproteins, triglycerides, and the ratio between cholesterol and high density lipoproteins. Data were collected on admission and on completion of the 24-day residential program, and at a 6-month followup. There were significant changes in HLC scores (p less than .001) from admission to discharge. Weight changes at 6 months were positively correlated with admission HLC composite scores (p less than .01) and chance dimension (p less than .05) scores. There were negative correlations at 6 months between admission powerful other scores and changes in triglycerides (p less than .01) and changes in the ratio of cholesterol and high density lipids (p less than .01).

Aged↗
PubMed1984

Statistical association between cancer incidence and major-cause mortality, and estimated residential exposure to air emissions from petroleum and chemical plants.

An ecologic study design was used to investigate the relationship between exposure to air emissions produced by the petroleum and chemical industries, and average annual cancer incidence and major cause mortality rates among whites in Contra Costa County, California. Estimates for the exposure to major industrial sources of sulfur dioxide, hydrocarbons and oxides of nitrogen were used to subdivide the county by level of exposure to petroleum refinery and chemical plant emissions. Cancer incidence and major cause mortality rates were then calculated for whites in each of the exposure areas. In both males and females, residential exposure to petroleum and chemical air emissions was associated with an increased incidence of cancer of the buccal cavity and pharynx. In males, age-adjusted incidence rates for cancers of the stomach, lung, prostate and kidney and urinary organs were also associated with petroleum and chemical plant air emission exposures. In both sexes, we found a strong positive association between degree of residential exposure and death rates from cardiovascular disease and cancer, and a less strong positive association between exposure and death rates from cerebrovascular disease. There was also a positive association in men for deaths from cirrhosis of the liver. Although these observed associations occurred across areas of similar socioeconomic and broad occupational class, confounding variables and the "ecologic fallacy" must be considered as possible explanations. In particular, the stronger findings in men suggest an occupational explanation of the cancer incidence trends, and the effect observed in cirrhosis mortality suggests that lifestyle variables such as alcohol consumption were not adequately controlled for. While the public health implications of our findings remain unclear, the evidence presented is sufficient to warrant follow-up studies based on individual data in which possible biases can be more readily controlled.

Air Pollutants↗
PubMed1983

Roles for epidemiology: the impact of environmental chemicals.

Aside from the well-recognized role of documenting the extent of any health impact from exposure to environmental chemicals, epidemiology has other potential roles. Arguing by analogy from the function of epidemiology in the infectious disease field, two practical public health functions are mentioned. The first is rumor abatement: simply characterizing the population exposed and documenting the frequency of salient complaints and providing this to the affected population, so as to separate fact from fiction. Another practical public health function is to review available data bases to document the number of individuals exposed to such chemicals and a review of gross trends by place and time to set public fears in proper perspective. There are important descriptive scientific functions as well, namely, to document any syndromes or symptom patterns which may be associated with chemical exposures and to document the natural history and progression of clinical and preclinical conditions associated with chemical exposures. The sensitivity, specificity and predictive value of tests for preclinical disease are discussed.

Communication↗
PubMed1980

Control of confounding in the assessment of medical technology.

Separation of the effects of extraneous variables from the effects of a factor under study (often termed control of confounding) is one of the key prerequisites for validly estimating the magnitude of the study factor's effects. Because of the phenomenon of confounding by indication, confounding of effects of different factors is a common problem in the assessment of medical technology. We give several examples illustrating that the decision of whether a recorded variable is a confounder in a data-set must be decided on the basis of subject-matter knowledge and clinical judgement. There is no alternative to use of such judgement; statistical selection procedures based on significant tests, such as stepwise regression, can be particularly misleading.

Cesarean Section↗