Joseph J. Martin

Residential hazards, high asthma prevalence and multimorbidity among children in Saginaw, Michigan

OBJECTIVES Comorbidities complicate our understanding of childhood asthma and its risk factors. This study examined the relationships between asthma, self-reported burden of disease symptoms and residential hazards in a representative sample of households in Saginaw, Michigan. STUDY DESIGN A population-based cross-sectional survey. METHOD The study involved 643 households randomly selected from the City of Saginaw (Michigan) with children 12 years of age or younger or pregnant woman. The survey was completed using random digit dialing, Computer-Assisted Telephone Interviewing (CATI) method. The audit instrument for residential hazards developed for the study was used to gather information on 71 household hazards organized in eight scales (dimensions): structural scale, moisture/mold scale, electrical scale, ventilation and combustion appliances scale, pest scale, pets scale, fire scale, and lifestyle-associated factors scale. The data were used to calculate an aggregate score of the household hazard index (HHI) for each housing unit. We also collected information on 43 symptoms of diseases likely to be associated with exposure to residential hazards as well as the demographic characteristics for each household. RESULTS Asthma prevalence rate among the 1206 children was 18.9% with 27.7% of households reporting at least one asthmatic child. The prevalence of health hazards in households of Saginaw was pervasively high with the rate for each of 29 hazards being over 30%. The HHI was found to be a good predictor of health outcomes in homes; the following linear regression equation describes the relationship between childhood asthma and the scores for individual scales of HHI: Number of Asthmatic Children=0.009(Structural)+0.004(Mold) +0 .019(Pests)-0.023(Pets)-0.029(Fire); (r(2)=0.054; p-value<0.001). Children who were living in housing units classified as high risk (top 25% of the HHI score) were found to be disproportionately afflicted with asthma, allergic reaction and burden of symptoms compared to children who lived in low-risk homes. Average number of symptoms in the households was 14±10 and the top 25% of the households had over 26 symptoms. Asthma was associated (comorbid) with each of the 40 symptoms (out of the 43) in the inventory scale, and the HHI was found to be a good predictor of the symptom burden (total count of symptoms) in participating households. CONCLUSIONS Recognition of the large extent of comorbidity in asthmatic children has implications for the way in which this disease should be treated or managed. In addition, the study of comorbidity between asthma and related risk factors may be important in understanding complex exposure-disease relationships which could lead to more effective interventions.

The Constant Volume Heat Capacity of Gases

Little experimental data are available on the constant volume heat capacity of gases. Although the problems of constant volume calorimetry for gases have received less attention than those of constant pressure calorimetry, there are good thermodynamic reasons for making constant volume measurements. Consequently, a large volume gas calorimeter has been developed which yields heat capacity values that are reliable to within roughly one per cent, and modifications are indicated which will improve this precision. Data that have been obtained on several gases at appreciable densities have been correlated on a reduced property basis. Analysis of the constant volume heat capacity at several densities and temperatures has indicated some necessary characteristics that must be possessed by an equation of state for the pressure-volume-temperature behavior of a gas. By extrapolation to zero density the ideal-gas heat capacity can be compared with the predictions of statistical mechanics.