Measurements of airborne 212Pb and 220Rn at varied indoor locations within the United States

Measurements have been made at varied locations within the United States comparing the concentration of 212Pb in air with that of the progeny of 222Rn to see if 212Pb is typically a significant contributor to indoor radioactivity. Auxiliary measurements were made comparing 220Rn with 222Rn. In terms of potential alpha-particle energy, 212Pb is significant (the ratio of its contribution to the combined contribution of 218Po, 214Pb, and 214Bi averaged about 0.6) and may warrant greater consideration as a component of indoor radioactivity. Correlations were found between the concentration of 220Rn progeny and 222Rn progeny, and the concentration of 220Rn and 222Rn. Environmental factors such as transport pathways and ventilation rates which exert a common influence on the concentrations of airborne isotopes provide a possible explanation for these correlations.     

Seasonal variation of births in rural southwestern Nigeria

A total of 12 708 live births registered between 1965 and 1975 in Igbo Ora, a rural area in southwestern Nigeria, were examined for seasonal variation using trigonometric regression analysis. The monthly number of registered births showed a significant seasonal pattern with a peak in May and corresponding minima in November. The extent of the seasonal variation above and below the annual mean was about 7%. There has been no significant shift in both the month of peak occurrence and the magnitude of the variation within the 11-year period of study. It is thought that the observed seasonal pattern may be related to climatic factors as well as sociocultural patterns of life associated with cyclical farming activities characteristic of a predominantly agricultural community.     

Seasonal variation in perceived indoor environment and nonspecific symptoms in a temperate climate

Few epidemiological studies have examined the effects of season on symptoms typical of sick building syndrome (SBS). The present study aims to clarify seasonal variation in a perceived indoor environment and SBS symptoms in a temperate climate. A total of 116 workers were recruited from office buildings in southern Japan that presented no apparent serious indoor problems. A validated questionnaire was distributed four times, once at the end of each season. Seasonal effects on the perceived indoor environment and SBS symptoms were investigated with a parametric test for repeated measurement of categorical data. Logits were used as the response function, and were compared to overall logits to determine the relevant odds ratios (OR). The effect of season/building interaction was also evaluated. Significant seasonal variation in the perceived indoor environment was found for temperature, dryness, air stuffiness, and static electricity (p for season, <0.05), although the seasonal patterns for temperature and dryness differed according to the building (p for interaction, <0.05). Symptoms in the mucous membrane (eyes, nose, and throat) and skin increased considerably in the winter and spring (p for season, <0.05), whereas general symptoms varied little, but such seasonality of symptoms was not modified by the building factor. The associations between perception of indoor environments and mucous and skin symptoms became stronger during winter and spring. The present results suggest that perceived indoor environments, nonspecific symptoms and their associations are closely associated with the season among office workers in a temperate climate.     

Long-term studies of hantavirus reservoir populations in the southwestern United States: a synthesis

A series of intensive, longitudinal, mark-recapture studies of hantavirus infection dynamics in reservoir populations in the southwestern United States indicates consistent patterns as well as important differences among sites and host-virus associations. All studies found a higher prevalence of infection in older (particularly male) mice; one study associated wounds with seropositivity. These findings are consistent with horizontal transmission and transmission through fighting between adult male rodents. Despite very low rodent densities at some sites, low-level hantavirus infection continued, perhaps because of persistent infection in a few long-lived rodents or periodic reintroduction of virus from neighboring populations. Prevalence of hantavirus antibody showed seasonal and multiyear patterns that suggested a delayed density-dependent relationship between prevalence and population density. Clear differences in population dynamics and patterns of infection among sites, sampling periods, and host species underscore the importance of replication and continuity of long-term reservoir studies. Nevertheless, the measurable associations between environmental variables, reservoir population density, rates of virus transmission, and prevalence of infection in host populations may improve our capacity to model processes influencing infection and predict increased risk for hantavirus transmission to humans.     

Regulatory control of indoor Rn

Regulation of indoor Rn is explored in the context of cost-effectiveness of regulatory action. Evaluation of cost (i.e., mitigation expenses) and benefits (i.e., savings associated with medical expenses and lost productivity related to lung cancer) at various action levels indicate that regulatory programs would be economically inefficient and unreasonable if standards were established at or below the current EPA action guide (150 Bq m-3 or less). For the approximately 95% of U.S. homes with Rn levels near or below 150 Bq m-3, government programs should continue to focus on public information and consumer protection. For the small number of homes with high Rn levels, government programs should focus on identifying high risk homes and encouraging homeowners to reduce Rn levels. Because of the potential for substantial risk reduction, such efforts would be cost-effective in these homes.     

Multi-state surveys of indoor 222Rn

The U.S. Environmental Protection Agency provides assistance to states in conducting surveys of indoor 222Rn. Alabama, Kentucky, Tennessee, Wisconsin, and Wyoming completed statistically designed surveys during the 1986-1987 heating season. In all states, probability-based samples of 5800 houses were tested using charcoal canisters exposed for 48 h. Thus, sample results can be validly extrapolated to the target population of all owner-occupied, ground-level houses having listed telephone numbers. Estimates of population parameters (e.g., median) and their associated confidence intervals are given for each state, for geographic regions within states, and for basement and nonbasement houses. Results confirm that 222Rn concentration varies widely from one state to another and from one geographic region to another within a state; however, the same pattern of differences was not evident in basement or nonbasement houses. Short-term 222Rn readings appear to follow a log-normal distribution.     

Benchmarking variation in coding accuracy across the United States

The objective of this study was to measure the consistency of coded medical data through information managers' reports of the overall coding error level in patients' medical records. Using a cross-sectional design, we examined the reported percent of records containing coding errors significant enough to change a diagnostic related group (DRG). Results indicate about 87 percent, 9 percent, and 5 percent of respondents reported that significant coding errors existed in less than 5 percent, 6-10 percent, and greater than 10 percent of the medical records in their institutions, respectively. Significant variation was found in the accuracy and consistency of coding practice and associated data quality across key demographic and organizational variables. Significantly large error rates in coded data exist in some organizations. Given variations across key demographic characteristics, providers may tend to distrust all coded data, when aggregated. As the United States moves toward an evidence-based medicine environment, the use of current patient data classification methods may be of limited value without increased attention to coding practices.     

Soil as a source of indoor 220Rn.

Two suggestions for sources of indoor 220Rn (thoron) have appeared in the literature: 1) building materials and outside air, and 2) soil beneath the house. Due to the difficulty of 220Rn measurement and limited data, both suggestions lack sufficient supporting evidence. We have investigated sources of indoor 220Rn in seven occupied houses in northern New Mexico, U.S. A two-filter system was used to measure indoor 220Rn levels continuously, and 220Rn progeny were measured with single filters and specialized alpha-track detectors. The amount of 220Rn entry from soil was curtailed by cutting off soil gas flow to the indoor air with subfloor depressurization mitigation systems. Four of the houses showed significant reductions in 220Rn with mitigation systems on. The average effect for these houses was to reduce indoor 220Rn levels by 70%. The other three houses had no clear reductions but in one of these houses, the mitigation system was not effective for stopping soil gas flow. Our results provide some of the most clear evidence to date supporting soil as an important source of indoor 220Rn.     

The health of Hispanics in the southwestern United States: an epidemiologic paradox

Recent reports in the literature on the health status of southwestern Hispanics, most of whom are Mexican Americans, are reviewed critically. The review is organized into the following sections: infant mortality, mortality at other ages, cardiovascular diseases, cancer, diabetes, other diseases, interview data on physical health, and mental health. Despite methodological limitations of much of the research, it can be concluded with some certainty that the health status of Hispanics in the Southwest is much more similar to the health status of other whites than that of blacks although socioeconomically, the status of Hispanics is closer to that of blacks. This observation is supported by evidence on such key health indicators as infant mortality, life-expectancy, mortality from cardiovascular diseases, mortality from major types of cancer, and measures of functional health. On other health indicators, such as diabetes and infectious and parasitic diseases, Hispanics appear to be clearly disadvantaged relative to other whites. Factors explaining the relative advantages or disadvantages of Hispanics include cultural practices, family supports, selective migration, diet, and genetic heritage. The recently completed Hispanic Health and Nutrition Examination Survey will go a long way to provide answers to many questions regarding the health of Hispanics in the Southwest or elsewhere.     

Physical activity and breast cancer risk among women in the southwestern United States

Physical activity may influence breast cancer risk through multiple mechanisms and at different periods in life. In this study we evaluate breast cancer risk associated with total and vigorous physical activity at ages 15, 30, and 50 years and the referent year prior to diagnosis/selection. Participants were non-Hispanic white (NHW) (1527 cases and 1601 control subjects) and Hispanic/American Indian (HAI) (798 cases and 924 controls) women. Both total and vigorous activity reduced risk of breast cancer in a dose-response manner. Among premenopausal women, only high total metabolic equivalent of the task (MET) hours of activity during the referent year was associated with reduced breast cancer risk in NHW women (odds ratio [OR] 0.62; 95% confidence interval [CI] 0.43, 0.91). Among postmenopausal women, physical activity had the greatest influence among women not recently exposed to hormones. Among these women, high total lifetime activity reduced risk of breast cancer for both NHW (OR 0.60; 95% CI 0.36, 1.02; p trend 0.01) and HAI women (OR 0.52; 95% CI 0.23, 1.16; p trend 0.07). Additionally, high total MET hours of activity at age 30 years (OR 0.56; 95% CI 0.37, 0.85) and at age 15 years (OR 0.57; 95% CI 0.38, 0.88) reduced breast cancer risk among postmenopausal NHW women not recently exposed to hormones. Among HAI women, more recent activity performed during the referent year and at age 50 appeared to have the greatest influence on breast cancer risk. Among postmenopausal NHW women. there was a significant interaction between physical activity and hormone replacement therapy (p value, 0.01), while among postmenopausal HAI women, physical activity interacted with body mass index (p value, 0.04). These data suggest that physical activity is important in reducing risk of breast cancer in both NHW and HAI women.     

Geographic distribution and genetic diversity of Whitewater Arroyo virus in the southwestern United States

The purpose of this study was to extend our knowledge of the geographic distribution and genetic diversity of the arenavirus(es) associated with Neotoma species (woodrats) in the southwestern United States. Infectious arenavirus was recovered from 14 (3.3%) of 425 woodrats. The virus-positive species included N. albigula in New Mexico and Oklahoma, N. cinerea in Utah, N. mexicana in New Mexico and Utah, and N. micropus in Texas. Analyses of viral nucleocapsid protein gene sequence data indicated that all the isolates were strains of the Whitewater Arroyo virus, an arenavirus previously known only from northwestern New Mexico. Analyses of the sequence data also indicated that there can be substantial genetic diversity among strains of Whitewater Arroyo virus from conspecific woodrats collected from different localities and substantial genetic diversity among strains from different woodrat species collected from the same locality.