Joy Lawrence

Measurement of particulate aliphatic and polynuclear aromatic hydrocarbons in Santiago de Chile : source reconciliation and evaluation of sampling artifacts

Abstract Using a novel sampler, particulate organic compounds were collected in Santiago de Chile from June 9 to August 10, 1997. This sampler consists of a diffusion denuder to remove gas-phase organics prior to particle collection, a Teflon filter, and a PUF cartridge downstream of the filter. PAHs and n -alkanes were measured using gas chromatography/mass spectrometry analysis. Volatilization of particles collected on the Teflon filter varied from 15 to 85% for both n -alkanes and PAHs, with strong dependence on molecular weight. The relative distribution of n -alkanes and the values of molecular diagnostic ratios, such as Carbon preference index, indicated a mixed origin with strong anthropogenic input. Indeed, CPI values ranged from 0.66 to 1.96 (for the whole range of n -alkanes). The percent contribution of leaf “wax” n -alkanes (4.55–20.83%) indicated the low contribution of biogenic sources. In addition, the distribution pattern of PAHs was characteristic of anthropogenic emissions. The dominant contribution of combustion-related PAHs (CPAHs), 74–84%, indicated that vehicular emissions was the major source of PAHs.

Field validation of a semi-continuous method for aerosol black carbon (aethalometer) and temporal patterns of summertime hourly black carbon measurements in southwestern PA

Two methods for measuring aerosol elemental carbon (EC) are compared. Three-hour integrated carbon samples were collected on quartz filters during the summer of 1990 in Uniontown, PA, primarily during episodes of elevated particulate pollution levels. These samples were analyzed for EC and organic carbon (OC) using a thermo/optical reflectance (TOR) method. Aerosol black carbon (BC) was measured using an Aethalometer, a semi-continuous optical absorption method. The optical attenuation factor for ambient BC was supplied by the instrument manufacturer. Three-hour average concentrations were calculated from the semi-continuous BC measurements to temporally match the EC/OC integrated quartz filter samples. BC and EC concentrations are highly correlated over the study period (R2=0.925). The regression equation is BC (μg m-3)=0.95 (±0.04) EC−0.2 (±0.4). The means of 3 h average measurements for EC and BC are 2.3 and 2.0 μg m-3, respectively, average concentrations of EC and BC ranged from 0.6 to 9.4 and 0.5 to 9.0 μg m-3 respectively. TOR OC and EC concentrations were not highly correlated (R2=0.22). The mean OC/EC ratio was 1.85. The 10-week Aethalometer hourly dataset was analyzed for daily and weekly temporal patterns. A strong diurnal BC pattern was observed, with peaks occurring between 7 a.m. and 9 a.m. local time. This is consistent with the increase in emissions from ground level combustion sources in the morning, coupled with poor dispersion before daytime vertical mixing is established. There was also some indication of a day-of-week effect on BC concentrations, attributed to activity of local ground level anthropogenic sources. Comparison of BC concentrations with co-located measurements of coefficient of haze in a separate field study in Philadelphia, PA, during the summer of 1992 showed good correlation between the two measurements (R2=0.82).

Mechanisms of Inhaled Fine Particulate Air Pollution–induced Arterial Blood Pressure Changes

Background Epidemiologic studies suggest a positive association between fine particulate matter and arterial blood pressure, but the results have been inconsistent. Objectives We investigated the effect of ambient particles on systemic hemodynamics during a 5-hr exposure to concentrated ambient air particles (CAPs) or filtered air (FA) in conscious canines. Methods Thirteen dogs were repeatedly exposed via permanent tracheostomy to CAPs (358.1 ± 306.7 μg/m3, mean ± SD) or FA in a crossover protocol (55 CAPs days, 63 FA days). Femoral artery blood pressure was monitored continuously via implanted telemetry devices. We measured baroreceptor reflex sensitivity before and after exposure in a subset of these experiments (n = 10 dogs, 19 CAPs days, 20 FA days). In additional experiments, we administered α-adrenergic blockade before exposure (n = 8 dogs, 16 CAPs days, 15 FA days). Blood pressure, heart rate, rate–pressure product, and baroreceptor reflex sensitivity responses were compared using linear mixed-effects models. Results CAPs exposure increased systolic blood pressure (2.7 ± 1.0 mmHg, p = 0.006), diastolic blood pressure (4.1 ± 0.8 mmHg; p < 0.001), mean arterial pressure (3.7 ± 0.8 mmHg; p < 0.001), heart rate (1.6 ± 0.5 bpm; p < 0.001), and rate–pressure product (539 ± 110 bpm × mmHg; p < 0.001), and decreased pulse pressure (−1.7 ± 0.7 mmHg, p = 0.02). These changes were accompanied by a 20 ± 6 msec/mmHg (p = 0.005) increase in baroreceptor reflex sensitivity after CAPs versus FA. After α-adrenergic blockade, responses to CAPs and FA no longer differed significantly. Conclusions Controlled exposure to ambient particles elevates arterial blood pressure. Increased peripheral vascular resistance may mediate these changes, whereas increased baroreceptor reflex sensitivity may compensate for particle-induced alterations in blood pressure.

Cardiac Oxidative Stress and Electrophysiological Changes in Rats Exposed to Concentrated Ambient Particles are Mediated by TRP-Dependent Pulmonary Reflexes

Previous studies suggest that, through the stimulation of pulmonary nervous endings, ambient particles modulate the autonomic tone on the heart leading to cardiac oxidant stress and dysfunction. In this paper we investigated the effect of blockade of vanilloid receptor 1 (Transient Receptor Potential Vanilloid Receptor 1 [TRPV1]) on concentrated ambient particles (CAPs)-induced cardiac oxidative stress and dysfunction in a rat model of inhalation exposure. Capsazepine (CPZ), a selective antagonist of TRPV1, was given ip or as an aerosol immediately before exposure to CAPs. Control and CPZ-treated rats were exposed to filtered air or CAPs aerosols for 5 h using the Harvard Ambient Particle Concentrator (mean PM(2.5) mass concentration: 218 +/- 23 mug/m(3)). At the end of the exposure we measured cardiac oxidative stress (in situ chemiluminescence [CL]), lipid peroxidation (thiobarbituric acid reactive substances [TBARS]), and tissue edema. Cardiac function was monitored throughout the exposure. CPZ (ip or aerosol) decreased CAPs-induced CL, lipid TBARS, and edema in the heart, indicating that blocking TRP receptors, systemically or locally, decreases heart CL. CAPs exposure led to significant decreases in heart rate (CAPs 350 +/- 32 bpm, control: 370 +/- 29), and in the length of the QT, RT, Pdur and Tpe intervals. These changes were observable immediately upon exposure and were maintained throughout the 5 h of CAPs inhalation. Changes in cardiac rhythm and electrocardiogram morphology were prevented by CPZ. These data suggest that current abnormalities in CAPs-exposed rats alter the action potentials leading to changes in conduction velocity and ventricular repolarization, and that triggering of TRPV1-mediated autonomic reflexes in the lung is essential for the observed changes in cardiac rhythms.

Measurement of atmospheric formic and acetic acids : methods evaluation and results from field studies

Formic and acetic acids are important contributors to atmospheric acidity, present in low and subparts per billion by volume (ppbv) range. This paper presents the results of laboratory and field studies to evaluate the performance of an annular denuder system to collect gas-phase formic and acetic acids. The collection efficiencies for formic and acetic acids by a KOH-coated annular denuder have been determined to be 99.1% and 98.5%, with precisions of 1.9% and 1.2% and capacities greater than 5.08 and 1.36 mg, respectively. The extracts of samples with chloroform added as a biocide have been shown to be stable for storage periods of 4 months at 4°C in the dark. Interference by aldehydes with measurement of formic acid and acetic acid was determined to be small

Chronic Social Stress and Susceptibility to Concentrated Ambient Fine Particles in Rats

Background Epidemiologic evidence suggests that chronic stress may alter susceptibility to air pollution. However, persistent spatial confounding between these exposures may limit the utility of epidemiologic methods to disentangle these effects and cannot identify physiologic mechanisms for potential differential susceptibilities. Objectives Using a rat model of social stress, we compared respiratory responses to fine concentrated ambient particles (CAPs) and examined biological markers of inflammation. Methods Twenty-four 12-week-old male Sprague-Dawley rats were randomly assigned to four groups [stress/CAPs, stress/filtered air (FA), nonstress/CAPs, nonstress/FA]. Stress-group animals were individually introduced into the home cage of a dominant male twice weekly. Blood drawn at sacrifice was analyzed for immune and inflammatory markers. CAPs were generated using the Harvard ambient particle concentrator, which draws real-time urban ambient fine particles, enriching concentrations approximately 30 times. CAPs/FA exposures were delivered in single-animal plethysmographs, 5 hr/day for 10 days, and respiratory function was continuously monitored using a Buxco system. Results Stressed animals displayed higher average C-reactive protein, tumor necrosis factor-α, and white blood cell counts than did nonstressed animals. Only among stressed animals were CAPs exposures associated with increased respiratory frequency, lower flows, and lower volumes, suggesting a rapid, shallow breathing pattern. Conversely, in animals with elevated CAPs exposures alone, we observed increased inspiratory flows and greater minute volumes (volume of air inhaled or exhaled per minute). Conclusions CAPs effects on respiratory measures differed significantly, and substantively, by stress group. Higher CAPs exposures were associated with a rapid, shallow breathing pattern only under chronic stress. Blood measures provided evidence of inflammatory responses. Results support epidemiologic findings that chronic stress may alter respiratory response to air pollution and may help elucidate pathways for differential susceptibility.

Measurement and speciation of gas and particulate phase organic acidity in an urban environment: 1. Analytical

In the previous paper we discussed the sampling and analytical techniques used to measure the concentrations of gas and particulate phase organic acids. This paper presents the results of a field study conducted in Philadelphia, Pennsylvania, during the summer of 1992, to investigate the chemistry and origins of gas and particulate phase organic acids. The concentrations of formic acid and most of the particulate phase organic acids were found to be significantly higher during the day than at night. Organic acids constituted 5.5% of the particulate fine mass (PM2.5); sulfates, ammonium, and elemental carbon were larger components of particulate fine mass, constituting 40, 15, and 9%, respectively. Dicarboxylic acids and even-carbon monocarboxylic acids were found to account for a large fraction of particulate weak acidity; odd-carbon monocarboxylic acids accounted for a very small fraction. The pronounced even-carbon preference of the monocarboxylic acid distribution suggests a biogenic origin. To investigate the origin of gas and particulate phase organic acids with regard to other species measured as part of the same field study, specific rotation factor analysis (SRFA) was applied to the daytime and nighttime concentrations of several species over the study period. During the daytime, four sources (transport, local combustion, biogenic, and photochemical) accounted for 92–99% of the particulate phase and 60–75% of the gas phase organic acids. At night, 68–87% of gas and particulate organic acids were contributed by four significant sources (transport, daytime concentration related, local combustion, and biogenic).

Concentrated Ambient Particles Alter Myocardial Blood Flow During Acute Ischemia in Conscious Canines

Background Experimental and observational studies have demonstrated that short-term exposure to ambient particulate matter (PM) exacerbates myocardial ischemia. Objectives We conducted this study to investigate the effects of concentrated ambient particles (CAPs) on myocardial blood flow during myocardial ischemia in chronically instrumented conscious canines. Methods Eleven canines were instrumented with a balloon occluder around the left anterior descending coronary artery and catheters for determination of myocardial blood flow using fluorescent microspheres. Telemetric electrocardiographic and blood pressure monitoring was available for four of these animals. After recovery, we exposed animals by inhalation to 5 hr of either filtered air or CAPs (mean concentration ± SD, 349.0 ± 282.6 μg/m3) in a crossover protocol. We determined myocardial blood flow during a 5-min coronary artery occlusion immediately after each exposure. Data were analyzed using mixed models for repeated measures. The primary analysis was based on four canines that completed the protocol. Results CAPs exposure decreased total myocardial blood flow during coronary artery occlusion by 0.12 mL/min/g (p < 0.001) and was accompanied by a 13% (p < 0.001) increase in coronary vascular resistance. Rate–pressure product, an index of myocardial oxygen demand, did not differ by exposure (p = 0.90). CAPs effects on myocardial blood flow were significantly more pronounced in myocardium within or near the ischemic zone versus more remote myocardium (p interaction < 0.001). Conclusions These results suggest that PM exacerbates myocardial ischemia by increased coronary vascular resistance and decreased myocardial perfusion. Further studies are needed to elucidate the mechanism of these effects.

Continuous Measurements of Ambient Particle Deposition in Human Subjects

The total deposition fraction (TDF) of fine and ultrafine aerosols was measured in a group of six healthy adults exposed to polydisperse ambient aerosols in Boston. Fifteen repeated inhalation-exhalation cycles were conducted during a given exposure session. Deposition efficiency for particles with aerodynamic diameter ranging from 63.5 to 2045 nm was determined using the average concentration of inhaled and exhaled particles measured during these cycles. Deposition efficiencies ranged from 7.3±18.7%(240-275 nm) to 98.6±28.1%(1545-2045 nm). Subjects exhibited similar deposition patterns with minimum efficiencies between 200-400 nm. Results from ANOVA and mixed-model regression analyses showed significant differences (p < 0.05) in particle deposition efficiency by particle size as well as among the subjects. Deposition efficiencies varied most among the subjects for particles between 100 and 1000 nm in size. A comparison with the ICRP model showed good agreement, with best agreement for male subjects and particle sizes <400 nm.

Aged particles derived from emissions of coal-fired power plants: The TERESA field results

The Toxicological Evaluation of Realistic Emissions Source Aerosols (TERESA) study was carried out at three US coal-fired power plants to investigate the potential toxicological effects of primary and photochemically aged (secondary) particles using in situ stack emissions. The exposure system designed successfully simulated chemical reactions that power plant emissions undergo in a plume during transport from the stack to receptor areas (e.g., urban areas). Test atmospheres developed for toxicological experiments included scenarios to simulate a sequence of atmospheric reactions that can occur in a plume: (1) primary emissions only; (2) H2SO4 aerosol from oxidation of SO2; (3) H2SO4 aerosol neutralized by gas-phase NH3; (4) neutralized H2SO4 with secondary organic aerosol (SOA) formed by the reaction of α-pinene with O3; and (5) three control scenarios excluding primary particles. The aged particle mass concentrations varied significantly from 43.8 to 257.1 µg/m3 with respect to scenario and power plant. The highest was found when oxidized aerosols were neutralized by gas-phase NH3 with added SOA. The mass concentration depended primarily on the ratio of SO2 to NOx (particularly NO) emissions, which was determined mainly by coal composition and emissions controls. Particulate sulfate (H2SO4 + neutralized sulfate) and organic carbon (OC) were major components of the aged particles with added SOA, whereas trace elements were present at very low concentrations. Physical and chemical properties of aged particles appear to be influenced by coal type, emissions controls and the particular atmospheric scenarios employed.