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Biomedical subjects

J H Stebbings

Publications and source records attributed to J H Stebbings.

7 recordsLinked to original sources
PubMed1992

Gamma distribution and house 222Rn measurements.

The statistical distribution of 222Rn measurements from basements and first floors of homes in northeastern Pennsylvania was investigated. The gamma distribution was statistically significantly superior to the normal distribution (p less than 0.005) in describing the frequency distribution of the logarithm of observed 222Rn levels. The fit to the data was closer both in the central portion and in the upper tail. The gamma distribution has certain characteristics that make it generally useful in the study of environmental toxic agents where several different exposures over a lifetime occur and must be combined, as for risk assessment or for statistical power calculations for epidemiologic studies.

Air Pollution, Indoor↗
PubMed1991

Prediction of 222Rn from topography in Pennsylvania.

The relationships of Rn levels in basements and first floors of homes to topographic location in a northeastern ridge and valley section of Pennsylvania were investigated. Topographic variables relating to elevation and slope were quantified and related to house Rn levels using both conventional and classification and regression tree (CART) analyses. The original interest was in using topographic correlates to estimate missing values in epidemiologic studies. In this area, Rn levels are usefully predicted by relative and absolute elevations and nearness to hills and ridges. Three- to fourfold differences in geometric mean Rn levels can be obtained for categories representing significant portions of the population of houses. The relationship of first-floor to basement Rn levels was found to be curvilinear and modestly affected by topography.

Air Pollutants, Radioactive↗
PubMed1979

Identifying a susceptible subgroup: effects of the Pittsburgh air pollution episode upon schoolchildren.

Pulmonary function test results on 224 parochial schoolchildren collected during and after the Pittsburgh air pollution episode of November 1975 were reanalyzed to determine whether a small subgroup of susceptible children could be defined. Individual regressions of three-quarter second forced expiratory volumes (FEV.75) and forced vital capacities (FVC) on time over the six-day study period were calculated, and the distributions of individual slopes for the four exposed and two control schools were compared. Excesses of strong upward trends in the exposed areas would suggest effects of suspended particulate air pollution by indicating significant improvement following the episode. A highly statistically significant excess of strong upward trends in the FVC among exposed students was observed, and was consistent by sex and by school within sex. Approximately 10--15% of the students appear susceptible to an average impairment of about 20% of the FVC. The findings are limited by the small number of subjects with strong post-episode upward trends in the FVC, and by lack of validation by replication of the study design, but do suggest that episode levels of suspended particulates induce lung damage, and that this may occur only in a small susceptible subgroup. Children with low baseline pulmonary function values, histories of asthma, or with acute respiratory symptoms immediately following the episode were not found to be especially susceptible to these effects of suspended particulates.

Air Pollution↗
PubMed1978

Panel studies of acute health effects of air pollution. II. A methodologic study of linear regression analysis of asthma panel data.

Panel studies relating illness, such as asthma attacks, cardiopulmonary symptoms, and acute respiratory symptoms, to daily air pollution and weather are important in environmental epidemiology. A study of the practical robustness of multiple linear regression procedures, which have been the preferred statistical models in analyses, is presented. The study is based on data from three asthma panels in Chattanooga, Tennessee, collected in 1972-1973. Linear regression models, commonly used, which incorporate only minimum temperature and an air pollutant were found to be potentially misleading; such models are highly sensitive to reporting trends in the data and do not correct adequately for weather variables. Temporal and spatial control strategies were employed and proved to be useful in detecting problems in the data due to undiscovered intervening variables. True day-to-day relationships estimated by a pair-day analysis were frequently inconsistent with "daily" effects estimated by the usual regression models and suggested that, in fact, the asthma panel data contained no useful information concerning day-to-day relationships.

Adolescent↗