Charles E. Rodes

Characterization of indoor-outdoor aerosol concentration relationships during the Fresno PM exposure studies

Particle size distributions were measured indoors and outdoors of a single, detached residence during the Fresno particulate matter exposure studies in winter (February 1-28, 1999) and spring (April 18-May 16, 1999). Data was collected for particle sizes ranging from about 0.01 to 2.5

Differences in blood pressure and vascular responses associated with ambient fine particulate matter exposures measured at the personal versus community level.

Background Higher ambient fine particulate matter (PM2.5) levels can be associated with increased blood pressure and vascular dysfunction. Objectives To determine the differential effects on blood pressure and vascular function of daily changes in community ambient- versus personal-level PM2.5 measurements. Methods Cardiovascular outcomes included vascular tone and function and blood pressure measured in 65 non-smoking subjects. PM2.5 exposure metrics included 24 h integrated personal- (by vest monitors) and community-based ambient levels measured for up to 5 consecutive days (357 observations). Associations between community- and personal-level PM2.5 exposures with alterations in cardiovascular outcomes were assessed by linear mixed models. Results Mean daily personal and community measures of PM2.5 were 21.9±24.8 and 15.4±7.5 μg/m3, respectively. Community PM2.5 levels were not associated with cardiovascular outcomes. However, a 10 μg/m3 increase in total personal-level PM2.5 exposure (TPE) was associated with systolic blood pressure elevation (+1.41 mm Hg; lag day 1, p<0.001) and trends towards vasoconstriction in subsets of individuals (0.08 mm; lag day 2 among subjects with low secondhand smoke exposure, p=0.07). TPE and secondhand smoke were associated with elevated systolic blood pressure on lag day 1. Flow-mediated dilatation was not associated with any exposure. Conclusions Exposure to higher personal-level PM2.5 during routine daily activity measured with low-bias and minimally-confounded personal monitors was associated with modest increases in systolic blood pressure and trends towards arterial vasoconstriction. Comparable elevations in community PM2.5 levels were not related to these outcomes, suggesting that specific components within personal and background ambient PM2.5 may elicit differing cardiovascular responses.

Variations of NO, NO2 and O3 concentrations downwind of a Los Angeles freeway:

Abstract A sampling study was conducted to quantify the relationships of NO, NO2 and O3 concentrations with distance downwind of the San Diego freeway in Los Angeles. By continuously, monitoring at a site upwind (background) of the freeway and at selected downwind sites, patterns of NO, NO2 and O3 concentrations were detailed. Minimal separation distances of the samplers from the roadway to eliminate measurable influence were estimated to be approx 400–500 m for NO, NO2 and O3. A spatial model was fitted to the empirical NO and NO2 data, which incorporated the effects of dilution, reaction and background level on measured downwind concentration. This model fit the experimental data closely and indicated that: 1. (1) the decrease of NOx downwind of the freeway can be expressed by a simple exponential dilution, 2. (2) the reaction of NO and O3 downwind of the freeway is not well mixed and deviates from the ideal photostationary state, and 3. (3) the simple rate equations for the reaction of NO with O3 and the photodissociation of NO2 could be combined with a simple exponential dilution term to define the measured concentrations of NO2.

Resuspension of Particulate Matter from Carpet Due to Human Activity

This work investigated the resuspension and subsequent translocation of particulate matter (PM) from carpeted flooring surfaces due to walking. In addition, the effect of HVAC systems and ceiling fans on mixing and/or translocation of resuspended PM was studied. Testing took place both in a residence with a well-worn, soiled carpet and in an environmental test chamber. Prescribed walking occurred with PM measurements taken at multiple sampling heights. Scanning electron microscopy (SEM) of carpet fibers was used to determine the fraction of dust available for resuspension. These data, in conjunction with resuspended mass concentrations from this study, were used to generate emission factors by particle size for walking on both new and worn carpet. Carpet loading does not affect the emission factor, indicating that the amount of resuspended PM is directly proportional to the available PM in the carpet. While relative humidity (RH) plays an important role in resuspension from new carpets, with high RH enhancing resuspension, it has the opposite affect with old carpets, with increased RH decreasing resuspension. With the HVAC system on, translocated particles 1.2 m horizontally from the source had number concentrations of approximately 20–40% of those at the source. With a ceiling fan on, extensive mixing was noted with little difference seen in particle resuspension by height. With the ceiling fan off, there was very little mixing present and particle size varied substantially by height.

Carbon Monoxide Exposures of Washington Commuters

The potential for directly monitoring public exposure to air pollutants has been realized with the development of personal exposure monitors. The microenvironmental approach to exposure assessment involves monitoring the concentrations within microenvironments thought to contribute significantly to a population’s total exposure. This paper focuses on the commuting microenvironment, because of the suspected large contribution that commuting makes to the total population exposure to carbon monoxide (CO). In particular, this paper presents typical CO concentrations, to which automobile, bus, and rail commuters of the Washington, D.C. metropolitan area were exposed, on 15 hypothetical routes during winter 1983. In addition, the paper assesses the relative importance of several factors that explain variability in CO levels inside automobiles during rush-hour periods. The study found that automobile commuters were exposed to average CO concentrations that typically ranged from 9 to 14 ppm over trips that typica...

Maximizing data quality in the gravimetric analysis of personal exposure sample filters

The weighing of particle sampler filters has always been plagued by problems in the weighing environment: humidity, temperature, drafts, vibration, and electrostatic charges on the filters. These are particularly critical for samples with small mass collections, such as those encountered in personal exposure monitoring for PM25. While modern electronic balances offer substantial reductions in the effects of temperature and vibration, these balances are still sensitive to factors such as thermal drafts and zero shifts from tilting. Drafts may be controlled through room ventilation modifications, and zero drift can be eliminated by computer-assisted data collection algorithms. A less well-understood influence is static charge, which is often controlled with a simple radioactive neutralizer. Although radioactive neutralizes are effective, their effectiveness decays rapidly with time, and their use may be objectionable for nontechnical reasons. We have analyzed a number of environmental factors influencing gravimetric microbalance operations and have developed methods to minimize or eliminate them.

The 1999 Fresno Particulate Matter Exposure Studies: Comparison of Community, Outdoor, and Residential PM Mass Measurements

ABSTRACT Two collaborative studies have been conducted by the U.S. Environmental Protection Agency (EPA) National Exposure Research Laboratory (NERL) and National Health and Environmental Effects Research Laboratory to determine personal exposures and physiological responses to par-ticulate matter (PM) of elderly persons living in a retirement facility in Fresno, CA. Measurements of PM and other criteria air pollutants were made inside selected individual residences within the retirement facility and at a central outdoor site on the premises. In addition, personal PM exposure monitoring was conducted for a subset of the participants, and ambient PM monitoring data were available for comparison from the NERL PM research monitoring platform in central Fresno. Both a winter (February 1-28, 1999) and a spring (April 19-May 16, 1999) study were completed so that seasonal effects could be

Estimating distributions of long-term particulate matter and manganese exposures for residents of Toronto, Canada

Methylcyclopentadienyl manganese tricarbonyl (MMT), a manganese-based gasoline additive, has been used in Canadian gasoline for about 20 yr. Because MMT potentially increases manganese levels in particulate matter resulting from automotive exhausts, a population-based study conducted in Toronto, Canada assessed the levels of personal manganese exposures. Integrated 3-day particulate matter (PM2.5) exposure measurements, obtained for 922 participant periods over the course of a year (September 1995–August 1996), were analyzed for several constituent elements, including Mn. The 922 measurements included 542 participants who provided a single 3-day observation plus 190 participants who provided two observations (in two different months). In addition to characterizing the distributions of 3-day average exposures, which can be estimated directly from the data, including the second observation for some participants enabled us to use a model-based approach to estimate the long-term (i.e. annual) exposure distributions for PM2.5 mass and Mn. The model assumes that individuals’ 3-day average exposure measurements within a given month are lognormally distributed and that the correlation between 3-day log-scale measurements k months apart (after seasonal adjustment) depends only on the lag time, k, and not on the time of year. The approach produces a set of simulated annual exposures from which an annual distribution can be inferred using estimated correlations and monthly means and variances (log scale) as model inputs. The model appeared to perform reasonably well for the overall population distribution of PM2.5 exposures (mean=28 μg m-3). For example, the model predicted the 95th percentile of the annual distribution to be 62.9 μg m-3 while the corresponding percentile estimated for the 3-day data was 86.6 μg m-3. The assumptions of the model did not appear to hold for the overall population of Mn exposures (mean=13.1 ng m-3). Since the population included persons who were potentially occupationally exposed to Mn (in non-vehicle-related jobs), we used responses to questionnaire items to form a subgroup consisting of non-occupationally exposed participants (671 participant periods), for which the model assumptions did appear to hold. For that subpopulation (mean=9.2 ng m-3), the model-predicted 95th percentile of the annual Mn distribution was 16.3-ng m-3, compared with 21.1 ng m-3 estimated for the 3-day data.

A Field Comparison of PM10 Inlets at Four Locations

A comprehensive field study was conducted comparing the performance of PM10 inlets under a variety of field conditions. Inlets for low flow, medium flow, and high flow samplers were evaluated at four sampling locations providing a range of concentrations and particle sizes. Sampler precisions were determined at each location along with the regression parameter estimates comparing sampler types. The daily distributions of mass by aerodynamic diameter were measured using the Wide Range Aerosol Classifier and the composited data reported. The expected mass concentrations were calculated using the sampler effectiveness data and the size distributions and then compared to the measured values. This permitted examination of the utility of the proposed Federal Reference Method (FRM) approach for specifying PM10 samplers. The comparison results indicate that the precisions of the PM10 samplers are well within the FRM requirements. The performance of the inlets as characterized by wind tunnel testing provided compu...

Preliminary assessment of 10 μm particulate sampling at eight locations in the united states

Abstract The first year of data for 10 μm particles from the Environmental Protection Agencys Inhalable Particulate Network are summarized and discussed. The discussion includes comparison among the various samplers and particulate size fractions. The data base is composed of measurements made on an every-sixth-day sampling schedule at eight different locations in 1982, This preliminary review indicates that the overall ratio of the 10 μm fraction (PM10) to Total Suspended Particulate (TSP) is 0.485 and the relationship is reasonably linear. The relationships between PM10 and the 15 μm fraction (IP) are very linear for all sites, increasing the utility of the existing Inhalable Particulate data bases.