Dwayne E. Porter

Public Parks and Physical Activity Among Adolescent Girls

OBJECTIVES. Physical activity may be constrained or facilitated by local environments. The availability of neighborhood facilities for physical activity may be particularly relevant for youth, who are unable to drive and whose activity is often limited to the immediate distance they are able to walk or bicycle. Several studies have shown that proximity to recreational facilities and parks is one of the most important predictors of physical activity. Because the United States already has an extensive infrastructure of parks, with 70% of adults indicating that they live within walking distance of a park or playground, parks may be a potential venue for increasing physical activity. This might be particularly important for adolescent girls, whose physical activity levels decline substantially as they go through puberty. The goal of this study was to examine the association between park proximity, park type, and park features and physical activity in adolescent girls. PATIENTS AND METHODS. This was a cross-sectional study using baseline data from the Trial of Activity for Adolescent Girls. It included 1556 grade 6 girls who were randomly selected from 6 middle schools in each of the following 6 field site areas: Washington, DC, and Baltimore, Maryland; Columbia, South Carolina; Minneapolis, Minnesota; New Orleans, Louisiana; Tucson, Arizona; and San Diego, California. Girls wore accelerometers for 6 days to measure metabolic equivalent–weighted moderate-to-vigorous physical activity, a measure accounting for the volume and intensity of activity. Metabolic equivalent–weighted moderate-to-vigorous physical activity was calculated for the hours outside of school time using 2 different cutpoints, activity levels ≥3.0 metabolic equivalents and ≥4.6 metabolic equivalents, the latter indicating activity at the intensity of a brisk walk or higher. We mapped all of the parks within 1 mile of each girls home. Trained staff used a checklist to document the presence of facilities and amenities at each park, including passive amenities, such as drinking fountains, restrooms, and areas with shade, as well as active amenities like basketball courts, multipurpose fields, playgrounds, and tennis courts. RESULTS. Mean nonschool metabolic equivalent–weighted moderate/vigorous physical activity, using the 4.6 metabolic equivalent cutoff, was 611.1 minutes (range: 49.7–4718.6 metabolic equivalent minutes per 6 days) and 1704.8 metabolic equivalent minutes per 6 days (range: 276.2–5792.6 metabolic equivalent minutes per 6 days) when using the 3.0 metabolic equivalent cutpoint. Many girls had multiple parks within a 1-mile radius of their homes: 57% had ≥1 type of park, the majority being neighborhood or community parks; 42% had between 1 and 3 parks, 37% had ≥4 parks, and 14% had ≥8 parks. The type, number, and specific parks features were associated with girls nonschool metabolic equivalent–weighted moderate/vigorous physical activity. At the 4.6 metabolic equivalent cutpoint, higher levels of nonschool metabolic equivalent–weighted moderate/vigorous physical activity were associated with both neighborhood and community parks (22 metabolic equivalent minutes) and miniparks (40 metabolic equivalent minutes). Each park, regardless of type, in the half-mile around each girls home was associated with an increase in nonschool metabolic equivalent–weighted moderate/vigorous physical activity by 2.8% or 17.2 nonschool minutes of metabolic equivalent–weighted moderate/vigorous physical activity per 6 days. Beyond a half-mile, each park increased nonschool metabolic equivalent–weighted moderate/vigorous physical activity by 1.1% or 6.7 metabolic equivalent minutes per 6 days. For the average girl with 3.5 parks within a 1-mile radius of home, the presence of parks accounted for 36.5 extra nonschool metabolic equivalent minutes per 6 days, ∼6% of total nonschool metabolic equivalent–weighted moderate/vigorous physical activity. Using the 3.0 metabolic equivalent cutpoint, this sums to an additional 68 metabolic equivalent minutes of nonschool metabolic equivalent–weighted moderate/vigorous physical activity over 6 days, or 4% of the total. The most common amenities in the parks were playgrounds, multipurpose fields, and picnic areas. Slightly more than one third of girls lived within a half-mile of a park with a basketball court, and >20% had access to walking paths and tennis courts in their local park. Higher levels of nonschool metabolic equivalent–weighted moderate/vigorous physical activity per 6 days were associated with walking paths (13 metabolic equivalent minutes), running tracks (82 metabolic equivalent minutes), playgrounds (28 metabolic equivalent minutes), and basketball courts (30 metabolic equivalent minutes). Parks with streetlights and floodlights were also associated with an increase of 18 and 22 minutes of nonschool metabolic equivalent–weighted moderate/vigorous physical activity, respectively. With the 3.0 metabolic equivalent cutoff for metabolic equivalent–weighted moderate/vigorous physical activity, additional nonschool metabolic equivalent minutes more than doubled when girls had miniparks (92 metabolic equivalent minutes), natural resource areas (36 metabolic equivalent minutes), walking paths (59 metabolic equivalent minutes), and running tracks (208 metabolic equivalent minutes) within a half-mile of their homes. Skateboard areas and special-use parks were negatively associated with nonschool metabolic equivalent–weighted moderate/vigorous physical activity in adolescent girls. CONCLUSIONS. Adolescent girls who live near more parks, particularly near those with amenities that are conducive to walking and with active features, engage in more nonschool metabolic equivalent–weighted moderate/vigorous physical activity than those with fewer parks. Whether this is because of actual use of the parks or neighborhood choice could not be determined. Although the magnitude of the association between parks and additional minutes of metabolic equivalent–weighted moderate/vigorous physical activity was small for an individual, amounting to an average of 4%–6% of a girls total nonschool metabolic equivalent–weighted moderate/vigorous physical activity, it is likely to have a large population-level association. Because of the potential population level impact, the use of parks to promote physical activity should be further studied.

Kriging in estuaries: as the crow flies, or as the fish swims?

Abstract Geostatistical methods are becoming an essential tool for understanding the spatial distribution of biological and chemical species in estuaries. At the heart of these methods are the spatial prediction/mapping methods known as “kriging”; these can construct statistically optimal predictions for data at unobserved locations using a relatively small, spatially explicit sample. The prediction at any given location is a weighted average of the sample values, where the weights depend on the distances between the sample sites and the target location. For most geostatistical settings, distances are computed “as the crow flies”, i.e. Euclidean distance. For measurements made in estuarine streams, however, intuition suggests that distances between sites should be measured “as the fish swims”, i.e. the length of the shortest in-water path between two sites. Our study evaluated the relative accuracy of eight kriging methods for predicting contaminant and water quality variables measured in an urbanized estuary in South Carolina. The eight methods were defined by all combinations of three factors, each at two levels: (a) Distance metric (Euclidean vs. in-water); (b) semivariogram type (spherical vs. linear) and (c) model trend component (distance to the inlet mouth; without vs. with). For four of the eight variables studied, the in-water distances provided prediction accuracy improvement on the order of 10–30% of prediction error variance. In two of these cases, the improvement only occurred when in-water distances were used together with a model trend component. Choice of semivariogram did not have much effect on prediction accuracy. Although the overall improvement in prediction accuracy was unpredictable and modest, considering the additional difficulties associated with in-water distances, the results suggest that the integration of Geographic Information System (GIS)-based network analysis with kriging using in-water distances merits further research.

Groundwater uranium and cancer incidence in South Carolina

ObjectiveThis ecologic study tested the hypothesis that census tracts with elevated groundwater uranium and more frequent groundwater use have increased cancer incidence.MethodsData sources included: incident total, leukemia, prostate, breast, colorectal, lung, kidney, and bladder cancers (1996–2005, SC Central Cancer Registry); demographic and groundwater use (1990 US Census); and groundwater uranium concentrations (nxa0=xa04,600, from existing federal and state databases). Kriging was used to predict average uranium concentrations within tracts. The relationship between uranium and standardized cancer incidence ratios was modeled among tracts with substantial groundwater use via linear or semiparametric regression, with and without stratification by the proportion of African Americans in each area.ResultsA total of 134,685 cancer cases were evaluated. Tracts with ≥50% groundwater use and uranium concentrations in the upper quartile had increased risks for colorectal, breast, kidney, prostate, and total cancer compared to referent tracts. Some of these relationships were more likely to be observed among tracts populated primarily by African Americans.ConclusionSC regions with elevated groundwater uranium and more groundwater use may have an increased incidence of certain cancers, although additional research is needed since the design precluded adjustment for race or other predictive factors at the individual level.

Spatial accessibility and availability measures and statistical properties in the food environment.

Spatial accessibility is of increasing interest in the health sciences. This paper addresses the statistical use of spatial accessibility and availability indices. These measures are evaluated via an extensive simulation based on cluster models for local food outlet density. We derived Monte Carlo critical values for several statistical tests based on the indices. In particular we are interested in the ability to make inferential comparisons between different study areas where indices of accessibility and availability are to be calculated. We derive tests of mean difference as well as tests for differences in Morans I for spatial correlation for each of the accessibility and availability indices. We also apply these new statistical tests to a data example based on two counties in South Carolina for various accessibility and availability measures calculated for food outlets, stores, and restaurants.

Hypertension and hematologic parameters in a community near a uranium processing facility

BACKGROUNDnEnvironmental uranium exposure originating as a byproduct of uranium processing can impact human health. The Fernald Feed Materials Production Center functioned as a uranium processing facility from 1951 to 1989, and potential health effects among residents living near this plant were investigated via the Fernald Medical Monitoring Program (FMMP).nnnMETHODSnData from 8216 adult FMMP participants were used to test the hypothesis that elevated uranium exposure was associated with indicators of hypertension or changes in hematologic parameters at entry into the program. A cumulative uranium exposure estimate, developed by FMMP investigators, was used to classify exposure. Systolic and diastolic blood pressure and physician diagnoses were used to assess hypertension; and red blood cells, platelets, and white blood cell differential counts were used to characterize hematology. The relationship between uranium exposure and hypertension or hematologic parameters was evaluated using generalized linear models and quantile regression for continuous outcomes, and logistic regression or ordinal logistic regression for categorical outcomes, after adjustment for potential confounding factors.nnnRESULTSnOf 8216 adult FMMP participants 4187 (51%) had low cumulative uranium exposure, 1273 (15%) had moderate exposure, and 2756 (34%) were in the high (>0.50 Sievert) cumulative lifetime uranium exposure category. Participants with elevated uranium exposure had decreased white blood cell and lymphocyte counts and increased eosinophil counts. Female participants with higher uranium exposures had elevated systolic blood pressure compared to women with lower exposures. However, no exposure-related changes were observed in diastolic blood pressure or hypertension diagnoses among female or male participants.nnnCONCLUSIONSnResults from this investigation suggest that residents in the vicinity of the Fernald plant with elevated exposure to uranium primarily via inhalation exhibited decreases in white blood cell counts, and small, though statistically significant, gender-specific alterations in systolic blood pressure at entry into the FMMP.

Development of a data management framework in support of southeastern tidal creek research

The NOAA Center of Excellence for Oceans and Human Health Initiative (OHHI) at the Hollings Marine Laboratory (HML) is developing a data management framework that supports an integrated research program across scientific disciplines. The primary focus of the database is to support environmental research focused on tidal creek watershed systems. Specifically, the current data holdings include physical water quality parameters, nutrients, pathogens, chemical contaminants, benthic and nekton species abundances and human dimensions data from Georgia, North Carolina and South Carolina dating to 1994. These data are not from a single long-term research project but are derived from several state and federal research programs and integrated into a common database model to support current research being conducted under the OHHI program at HML. The Tidal Creek database was developed with the intent to support a well documented and open system, thus metadata elements from common metadata standards including the Dublin Core ISO 15836:2003 and Federal Geographic Data Committee (FGDC-STD-001-1998) are components of the database model. The result is a semantic database framework with descriptive ancillary data at the record level including methods, investigator names, date, locations and other descriptive elements. The primary users of the database are project personnel to meet analytical needs. The database is also available through a number of web-based applications that are designed to give users the necessary information to evaluate and access data. In addition, data can be accessed with Open Geospatial Consortium (OGC) standards, and species records and abundances are being made available to the Ocean Biogeographic Information System (OBIS). Overall, the Tidal Creek database summarizes the response of tidal creeks and watersheds to coastal development, and serves as a repository for environmental, demographic, and socioeconomic data in the Southeast.

Antibiotics as CECs: An Overview of the Hazards Posed by Antibiotics and Antibiotic Resistance

ABSTRACT Monitoring programs have traditionally monitored legacy contaminants but are shifting focus to Contaminants of Emerging Concern (CECs). CECs present many challenges for monitoring and assessment, because measurement methods dont always exist nor have toxicological studies been fully conducted to place results in proper context. Also some CECs affect metabolic pathways to produce adverse outcomes that are not assessed through traditional toxicological evaluations. Antibiotics are CECs that pose significant environmental risks including development of both toxic effects at high doses and antibiotic resistance at doses well below the Minimum Inhibitory Concentration (MIC) which kill bacteria and have been found in nearly half of all sites monitored in the US. Antimicrobial resistance has generally been attributed to the use of antibiotics in medicine for humans and livestock as well as aquaculture operations. The objective of this study was to assess the extent and magnitude of antibiotics in the environment and estimate their potential hazards in the environment. Antibiotics concentrations were measured in a number of monitoring studies which included Waste Water Treatment Plants (WWTP) effluent, surface waters, sediments and biota. A number of studies reported levels of Antibiotic Resistant Microbes (ARM) in surface waters and some studies found specific ARM genes (e.g. the blaM-1 gene) in E. coli which may pose additional environmental risk. High levels of this gene were found to survive WWTP disinfection and accumulated in sediment at levels 100-1000 times higher than in the sewerage effluent, posing potential risks for gene transfer to other bacteria.in aquatic and marine ecosystems. Antibiotic risk assessment approaches were developed based on the use of MICs and MIC Ratios [High (Antibiotic Resistant)/Low (Antibiotic Sensitive) MIC] for each antibiotic indicating the range of bacterial adaptability to each antibiotic to help define the No Observable Effect Concentration (NOEC) for each antibiotic which were compared to maximum Measured Exposure Concentrations (MEC) in the environment to predict individual environmental risks. Four antibiotics had high MEC/NOEC and high MIC ratios and were identified as higher risks for concern based upon this approach, but only Triclosan had MEC/NOEC ratios >1 and was recommended for monitoring in future studies.

A content analysis of Internet resources about the risks of seafood consumption

Abstract Seafood consumption is a main source of human exposure to certain environmental contaminants. Therefore, it is valuable to assess the online health risk messages focused on this topic, as people in the US are increasingly accessing the Internet for health-related information. Previous research indicates that online health information tends to be written at a reading level that is more advanced than ability of the general population. The purpose of this research was to examine the content and readability of Internet resources targeted toward consumers in the US regarding the health risks from consumption of contaminated seafood. Sources for analysis were gathered through a targeted search of state and national government websites, as well as through a Google search. The overall mean readability level was Grade 9.21, which is slightly above the average reading level of US adults. Future research should evaluate the accuracy of the health risk messages, as well as consumer perceptions of risk.