Characterizing Determinants of Near-Road Ambient Air Quality for an Urban Intersection and a Freeway Site.

INTRODUCTION: Near-road ambient air pollution concentrations that are affected by vehicle emissions are typically characterized by substantial spatial variability with respect to distance from the roadway and temporal variability based on the time of day, day of week, and season. The goal of this work is to identify variables that explain either temporal or spatial variability based on case studies for a freeway site and an urban intersection site. The key hypothesis is that dispersion modeling of near-road pollutant concentrations could be improved by adding estimates or indices for site-specific explanatory variables, particularly related to traffic. Based on case studies for a freeway site and an urban intersection site, the specific aims of this project are to (1) develop and test regression models that explain variability in traffic-related air pollutant (TRAP) ambient concentration at two near-roadway locations; (2) develop and test refined proxies for land use, traffic, emissions and dispersion; and (3) prioritize inputs according to their ability to explain variability in ambient concentrations to help focus efforts for future data collection and model development.The key pollutants that are the key focus of this work include nitrogen oxides (NOx), carbon monoxide (CO), black carbon (BC), fine particulate matter (PM2.5; PM ≤ 2.5 µm in aerodynamic diameter), ultrafine particles (UFPs; PM ≤ 0.1 µm in aerodynamic diameter), and ozone (O3). NOx, CO, and BC are tracers of vehicle emissions and dispersion. PM2.5 is influenced by vehicle table emissions and regional sources. UFPs are sensitive to primary vehicle emissions. Secondary particles can form near roadways and on regional scales, influencing both PM2.5 and UFP concentrations. O3 concentrations are influenced by interaction with NOx near the roadway. Nitrogen dioxide (NO2), CO, PM2.5, and O3 are regulated under the National Ambient Air Quality Standards (NAAQS) because of demonstrated health effects. BC and UFPs are of concern for their potential health effects. Therefore, these pollutants are the focus of this work. METHODS: The methodological approach includes case studies for which variables are identified and assesses their ability to explain either temporal or spatial variability in pollutant ambient concentrations. The case studies include one freeway location and one urban intersection. The case studies address (1) temporal variability at a fixed monitor 10 meters from a freeway; (2) downwind concentrations perpendicular to the same location; (3) variability in 24-hour average pollutant concentrations at five sites near an urban intersection; and (4) spatiotemporal variability along a walking path near that same intersection.The study boundary encompasses key factors in the continuum from vehicle emissions to near-road exposure concentrations. These factors include land use, transportation infrastructure and traffic control, vehicle mix, vehicle (traffic) flow, on-road emissions, meteorology, transport and evolution (transformation) of primary emissions, and production of secondary pollutants, and their resulting impact on measured concentrations in the near-road environment. We conducted field measurements of land use, traffic, vehicle emissions, and near-road ambient concentrations in the vicinity of two newly installed fixed-site monitors. One is a monitoring station jointly operated by the U.S. Environmental Protection Agency (U.S. EPA) and the North Carolina Department of Environmental Quality (NC DEQ) on I-40 between Airport Boulevard and I-540 in Wake County, North Carolina. The other is a fixed-site monitor for measuring PM2.5 at the North Carolina Central University (NCCU) campus on E. Lawson Street in Durham, North Carolina. We refer to these two locations as the freeway site and the urban site, respectively. We developed statistical models for the freeway and urban sites. RESULTS: We quantified land use metrics at each site, such as distances to the nearest bus stop. For the freeway site, we quantified lane-by-lane total vehicle count, heavy vehicle (HV) count, and several vehicle-activity indices that account for distance from each lane to the roadside monitor. For the urban site, we quantified vehicle counts for all 12 turning movements through the intersection. At each site, we measured microscale vehicle tailpipe emissions using a portable emission measurement system.At the freeway site, we measured the spatial gradient of NOx, BC, UFPs, and PM, quantified particle size distributions at selected distances from the roadway and assessed partitioning of particles as a function of evolving volatility. We also quantified fleet-average emission factors for several pollutants.At the urban site, we measured daily average concentrations of nitric oxide (NO), NOx, O3, and PM2.5 at five sites surrounding the intersection of interest; we also measured high resolution (1-second to 10-second averages) concentrations of O3, PM2.5, and UFPs along a pedestrian transect. At both sites, the Research LINE-source (R-LINE) dispersion model was applied to predict concentration gradients based on the physical dispersion of pollution.Statistical models were developed for each site for selected pollutants. With variables for local wind direction, heavy-vehicle index, temperature, and day type, the multiple coefficient of determination (R2) was 0.61 for hourly NOx concentrations at the freeway site. An interaction effect of the dispersion model and a real-time traffic index contributed only 24% of the response variance for NOx at the freeway site. Local wind direction, measured near the road, was typically more important than wind direction measured some distance away, and vehicle-activity metrics directly related to actual real-time traffic were important. At the urban site, variability in pollutant concentrations measured for a pedestrian walk-along route was explained primarily by real-time traffic metrics, meteorology, time of day, season, and real-world vehicle tailpipe emissions, depending on the pollutant. The regression models explained most of the variance in measured concentrations for BC, PM, UFPs, NO, and NOx at the freeway site and for UFPs and O3 at the urban site pedestrian transect. CONCLUSIONS: Among the set of candidate explanatory variables, typically only a few were needed to explain most of the variability in observed ambient concentrations. At the freeway site, the concentration gradients perpendicular to the road were influenced by dilution, season, time of day, and whether the pollutant underwent chemical or physical transformations. The explanatory variables that were useful in explaining temporal variability in measured ambient concentrations, as well as spatial variability at the urban site, were typically localized real-time traffic-volume indices and local wind direction. However, the specific set of useful explanatory variables was site, context (e.g., next to road, quadrants around an intersection, pedestrian transects), and pollutant specific. Among the most novel of the indicators, variability in real-time measured tailpipe exhaust emissions was found to help explain variability in pedestrian transect UFP concentrations. UFP particle counts were very sensitive to real-time traffic indicators at both the freeway and urban sites. Localized site-specific data on traffic and meteorology contributed to explaining variability in ambient concentrations. HV traffic influenced near-road air quality at the freeway site more so than at the urban site. The statistical models typically explained most of the observed variability but were relatively simple. The results here are site-specific and not generalizable, but they are illustrative that near-road air quality can be highly sensitive to localized real-time indicators of traffic and meteorology.

US and Canadian pharmacy residencies and fellowships: 1995.

OBJECTIVE: To report statistical information about pharmacy postgraduate experiential training programs in the US and Canada. DATA SOURCE: RESFILE-95 database. MEASUREMENTS: A questionnaire is mailed annually to the contact listed for each residency or fellowship in the RESFILE database. The data for this report were entered into the database between June and December 1994. The information obtained on the survey includes (1) program type and accreditation status, (2) primary focus of the program, (3) number of positions, (4) stipend, (5) availability to BS graduates. RESULTS: Six hundred sixty-eight programs are listed in the RESFILE database, including 540 residences (70% accredited and 30% nonaccredited) and 128 fellowships. Fifty programs are located in Canada. There are a total of 1070 positions available, with a mean of 1.6 positions per program. Pharmacy practice residencies constitute 55% of accredited residencies in the US. General hospital residencies account for 88% of Canadian programs. Primary/ambulatory care residencies are the most common specialty focus. Infectious disease is the most common fellowship focus. The mean stipend for all programs is $24,837. Overall, at least 90% of the responding programs offer specified benefits. Forty-eight percent of the residency programs are available to BS graduates; most fellowships are not. Having completed a previous generalist residency is frequently preferred but often is not required to perform a specialty residency or fellowship. CONCLUSIONS: The statistical data in this report will be useful to those assessing the role of postgraduate experiential training, institutions in the process of developing a residency or fellowship, and those considering application to enter such programs.

When my child was born: maternal reactions to the birth of a child.

A 32-item multiple choice test, "When My Child Was Born," was designed to measure maternal perceptions of their reactions at the time of their child's birth. A total of 200 mothers were administered the test. The population included 97 mothers of children with cleft lip/palate and 103 mothers of physically normal children. Factor analyses identified three factors: Maternal Positive Affect, Paternal Affect, and Parental Anxiety. On all factors, normal subject had the highest scores, and mothers of children with defects had the lowest scores. The findings suggest that the test measures both current and projected feelings of the mothers about the birth of their child.

Cognitive, self-concept, and body image measures of normal, cleft palate, and obese adolescents.

Using discriminant function analyses, this study attempted to establish linear combinations of variables that would identify group membership correctly. Groups of normal (N = 100), cleft palate (N = 51), and obese (N = 22) adolescents responded to measures of cognitive sytle and structure, body image, and self-concept. Linear combinations of congitive measures were not effective in differentiating group membership. Body image measures, in combination, clearly distinguished obese adolescents from the other two groups. A linear combination of self-concept measures differentiated adolescents with clefts from normals, with the former group having a pattern of higher self-esteem and lower perceived acceptability by their parents.

Maternal and child locus of control and field-dependence in cleft palate children.

The cleft palate experience includes events which are beyond the control of cleft palate children and their mothers. To investigate whether the experiences relate to other maternal and child variables, 44 cleft palate children, 9--18 years of age, and their mothers were compared to 61 control children and their mothers. Maternal variables included locus of control and perceived reactions to the child's birth. Child variables included locus of control, field dependence, parental perceptions, and teacher ratings. Mothers of children with cleft palates indicated a significantly greater negative impact at their children's births but did not indicate greater externality. Children with clefts were significantly more external in control, were more field-dependent, perceived parental reactions as more negative, and had more negative academic ratings. Mothers who were more external in locus of control had children who were more field-dependent and had more external control.

When I was born: perceived parental reactions of adolescents.

A 32-item multiple choice test, When I Was Born, was designed to measure adolescents' perceptions of parental reactions at the time of their births. A total of 372 subjects, ages 11 through 20 years, were administered the test. The population included 140 physically normal subjects, 97 adolescents with acquired physical problems, and 135 subjects with congenital physical anomalies. Factor analyses of test data using 100 normal subjects as the criterion population identified four factors: Parental Emotion, Parental Apprehension, Parental Pride, and Parental Nurturance. On all four factors, normal subjects had the highest scores, and subjects with congenital anomalies had the lowest scores. The findings suggest that the test measures both adolescents' projected feelings about parental reactions at their birth and the current impact of a physical problem on the child.