Frank J. Marsik

Insights Into the Mechanisms and Mediators of the Effects of Air Pollution Exposure on Blood Pressure and Vascular Function in Healthy Humans

Fine particulate matter air pollution plus ozone impairs vascular function and raises diastolic blood pressure. We aimed to determine the mechanism and air pollutant responsible. The effects of pollution on heart rate variability, blood pressure, biomarkers, and brachial flow-mediated dilatation were determined in 2 randomized, double-blind, crossover studies. In Ann Arbor, 50 subjects were exposed to fine particles (150 &mgr;g/m3) plus ozone (120 parts per billion) for 2 hours on 3 occasions with pretreatments of an endothelin antagonist (Bosentan, 250 mg), antioxidant (Vitamin C, 2 g), or placebo. In Toronto, 31 subjects were exposed to 4 different conditions (particles plus ozone, particles, ozone, and filtered air). In Toronto, diastolic blood pressure significantly increased (2.9 and 3.6 mm Hg) only during particle-containing exposures in association with particulate matter concentration and reductions in heart rate variability. Flow-mediated dilatation significantly decreased (2.0% and 2.9%) only 24 hours after particle-containing exposures in association with particulate matter concentration and increases in blood tumor necrosis factor &agr;. In Ann Arbor, diastolic blood pressure significantly similarly increased during all of the exposures (2.5 to 4.0 mm Hg), a response not mitigated by pretreatments. Flow-mediated dilatation remained unaltered. Particulate matter, not ozone, was responsible for increasing diastolic blood pressure during air pollution inhalation, most plausibly by instigating acute autonomic imbalance. Only particles from urban Toronto additionally impaired endothelial function, likely via slower proinflammatory pathways. Our findings demonstrate credible mechanisms whereby fine particulate matter could trigger acute cardiovascular events and that aspects of exposure location may be an important determinant of the health consequences.

Nevada STORMS project: Measurement of mercury emissions from naturally enriched surfaces

Diffuse anthropogenic and naturally mercury-enriched areas represent long- lived sources of elemental mercury to the atmosphere. The Nevada Study and Tests of the Release of Mercury From Soils (STORMS) project focused on the measurement of mercury emissions from anaturally enriched area. During the project, concurrent measurements of mercury fluxes from naturally mercury-enriched substrate were made September 1-4, 1997, using four micrometeorological methods and seven field flux chambers. Ambient air mercury concentrations ranged from 2 to nearly 200 ng m- 3 indicating that the field site is a source of atmospheric mercury. The mean day time mercury fluxes, durin p conditions of no precipitation, measured with field chambers were 50 to 360 ng m -2 h - , and with the micrometeorological methods we re 230 to 600 ng m- 2 h -1. This wide range in mercury emission rates reflects differences in method experimental designs and local source strengths. Mercury fluxes measured by many field chambers were significantly different (p < 0.05) but linearly correlated. This indicates that field chambers responded similarly to environmental conditions, but differences in experimental design and site heterogeneity had a significant influence on the magnitude of mercury fluxes. Data developed during the field study demonstrated that field flux chambers are ideal for assessment of the physicochemical processes driving mercury flux and development of an understanding of the magnitude of the influence of individual factors on flux. In general, mean mercury fluxes measured with micrometeorological methods during day time periods were nearly 3 times higher than me an fluxes measured with field flux chambers. Micrometeorological methods allow for derivation of a representative mercury flux occurring from an unconstrained system and provide an assessment of the actual magnitude and variability of fluxes occurring from an area.

Mercury Air/Surface Exchange Kinetics of Background Soils of the Tahquamenon River Watershed in the Michigan Upper Peninsula

Air/surface exchange of mercury was investigated over background soils at five sites in the Tahquamenon River watershed in the Michigan Upper Peninsula in the summer of 1998. Measurements of Hg fluxes were performed during middayperiods using the ORNL Teflon dynamic flux chamber. Mean Hg emission fluxes were 1.4±0.3–2.4±1.0 ng m-2 hr-1 for three shaded forest sites and 7.6±1.7 ng m-2 hr-1 for an open field site. Hg dry deposition was observed at a heavily shaded forest site overwet soils (mean = –0.3±0.2 ng m-2 hr-1). Theoverall mean Hg flux was 1.4±1.4 ng m-2 hr-1for the four shaded forest sites. The Hg fluxes observed at these sites are similar to those found at other northern background sites. Significant, rapid response of Hg emission to solar radiation was observed over these background soils. Artificial irrigation over these soils induced immediate andmeasurable increases in Hg emission. Soil temperature was found to be less influential to Hg air/surface exchange over these heavily shaded forest background soils than we have seen elsewhere.

Reactive mercury in the troposphere: Model formation and results for Florida, the northeastern United States, and the Atlantic Ocean

Received 7 November 2006; revised 22 June 2007; accepted 13 August 2007; published 11 December 2007. [1] We describe the development of a model for transport and photochemistry of atmospheric mercury at the regional scale, along with an application to the eastern United States and adjacent Atlantic Ocean and Gulf of Mexico, and comparison with aircraftbased measurements in Florida. The model is the Community Multiscale Air Quality model (CMAQ) with modifications to include an integrated solution for gas phase and aqueous photochemistry. The expanded chemistry includes O3 ,N Ox, organics, sulfur, halogens and mercury. Divalent reactive gaseous mercury (RGM) is formed slowly through gas phase reactions and removed rapidly by aqueous reactions in cloud water. Model results show that elevated RGM (up to 260 pg m � 3 ) forms intermittently over the Atlantic Ocean in air masses that have a cloud-free history. Aircraft measurements in Florida show RGM varying between 10 and 250 pg m � 3 and increasing with altitude, a pattern that is consistent with model results. Ambient RGM would increase by 50% if aqueous reduction reactions were omitted. The model predicts that ambient elemental mercury and RGM anticorrelate in regions where RGM is produced photochemically and correlate in regions dominated by direct emissions. Model results also suggest positive correlations between RGM and SO2, reactive nitrogen and H2O2, which may be used to identify photochemically produced versus directly emitted RGM. RGM in the model is strongly correlated with O3 during pollution events, and ozone formation from anthropogenic precursors is predicted to cause a significant increase in RGM.

An investigation of source–receptor relationships for mercury in south Florida using event precipitation data

A recent pilot study suggested that local anthropogenic sources may play an important role in the atmospheric deposition of mercury (Hg) in South Florida. To examine the potential impacts of these local anthropogenic sources of Hg, the South Florida Atmospheric Mercury Monitoring Study (SoFAMMS) was conducted from 6 August to 6 September 1995. The major goals of the SoFAMMS were to investigate potential source–receptor relationships between anthropogenic point-source emissions in south-east Florida (Dade and Broward Counties) and the atmospheric deposition of Hg and other trace elements across this region, which includes the Florida Everglades. As part of SoFAMMS, daily event precipitation samples were collected concurrently at 17 sites across the study domain during the 1-month period. All samples were analyzed for Hg and other trace elements. The volume-weighted mean concentrations of Hg measured at the 17 sites during the study ranged from 13 to 31 ng l−1. While these monthly means indicated a significant site-to-site variation in Hg concentration, even greater differences between sites were observed on an event basis. Concentrations of Hg in individual daily event precipitation samples ranged from 5 to 113 ng l−1. Similar spatial and temporal variations in precipitation concentrations were observed for other trace elements as well. These variations could not be accounted for by rainfall amounts alone. The spatial and temporal patterns observed suggest that local sources strongly influence atmospheric wet deposition across this region. Extensive elemental composition and meteorological precipitation data (including WSR-88D radar data from Miami, FL) were combined in an effort to look at the history of precipitation storm cells impacting the sampling sites and their spatial relationships to potential anthropogenic sources. Two sample periods are presented which demonstrate not only the impacts of local anthropogenic sources, but that these impacts fluctuate as a function of the mesoscale meteorological transport conditions. These preliminary findings indicate that local sources of Hg to South Florida and the Everglades may be more substantial than previous estimates.

PHOTOCHEMISTRY OF OZONE FORMATION IN ATLANTA, GA-MODELS AND MEASUREMENTS*

Chemical measurements made during an air pollution event in Atlanta, GA have been compared with results from several photochemical simulations. Measurements included Os, primary reactive organic gases (ROG), aldehydes, PAN, total reactive nitrogen (NO,,) and HzOz, with vertical profiles for primary ROG. Photochemical models using two different chemical representations and a range of assumptions about winds, vertical mixing and emissions were used to simulate the event. Results show that assumptions about vertical mixing can cause a variation in simulated surface concentrations of primary hydrocarbons of a factor of two or more. A tendency to underestimate isoprene was found in comparison with measured vertical profiles. The models tend to overestimate concentrations of HCHO, H,02 and PAN in comparison with measurements. Peak 0s and concurrent NO, from helicopter measurements was used as a basis for evaluating individual model scenarios. Scenarios were developed with different Op-NO,-ROG sensitivity, but only the NO,-sensitive scenarios are consistent with measured 09, NO, and isoprene. Key word index: Ozone, nitrogen oxides, hydrocarbons, photochemical smog, hydrogen, peroxide.

Measurement of surface mercury fluxes at active industrial gold mines in Nevada (USA).

Mercury (Hg) may be naturally associated with the rock units hosting precious and base metal deposits. Active gold mines are known to have point source releases of Hg associated with ore processing facilities. The nonpoint source release of Hg to the air from the large area (hundreds to thousands of hectares) of disturbed and processed material at industrial open pit gold mines has not been quantified. This paper describes the field data collected as part of a project focused on estimating nonpoint source emissions of Hg from two active mines in Nevada, USA. In situ Hg flux data were collected on diel and seasonal time steps using a dynamic flux chamber from representative mine surfaces. Hg fluxes ranged from <1500 ng m(-2) day(-1) for waste rock piles (0.6-3.5 μg g(-1)) to 684,000 ng m(-2) day(-1) for tailings (2.8-58 μg g(-1)). Releases were positively correlated with material Hg concentrations, surface grain size, and moisture content. Highest Hg releases occurred from materials under active cyanide leaching and from tailings impoundments containing processed high-grade ore. Data collected indicate that as mine sites are reclaimed and material disturbance ceases, emissions will decline. Additionally local cycling of atmospheric Hg (deposition and re-emission) was found to occur.

Pulmonary Retention of Particulate Matter is Associated with Airway Inflammation in Allergic Rats Exposed to Air Pollution in Urban Detroit

A collaborative research study was conducted in order to improve our understanding of the source-to-receptor pathway for ambient fine particulate matter (aerodynamic diameter ≤ 2.5 μ m; PM2.5) and subsequently to investigate the identity and sources of toxic components in PM2.5 responsible for adverse health effects in allergic humans. This research used a Harvard fine particle concentrator to expose Brown Norway rats, with and without ovalbumin-induced allergic airway disease, to concentrated air particles (CAPs) generated from ambient air in an urban Detroit community where the pediatric asthma rate was three times higher than the national average. Rats were exposed to CAPs during the exposure periods in July (mean = 676 μg/m3) and September (313 μg/m3) of 2000. Twenty-four hours after exposures lung lobes were either lavaged with saline to determine cellularity and protein in bronchoalveolar lavage fluid (BALF), or removed for analysis by inductively coupled plasma–mass spectrometry (ICP-MS) to detect ambient PM2.5-derived trace element retention. PM2.5 trace elements of anthropogenic origin, lanthanum (La), vanadium (V), manganese (Mn), and sulfur (S), were recovered from the lung tissues of CAPs-exposed rats. Recovery of those pulmonary anthropogenic particles was further increased in rats with allergic airways. In addition, eosinophils and protein in BALF were increased only in allergic animals exposed to CAPs. These results demonstrate preferential retention in allergic airways of air particulates derived from identified local combustion sources after a short-term exposure. Our findings suggest that the enhancement of allergic airway responses by exposure to PM2.5 is mediated in part by increased pulmonary deposition and localization of potentially toxic elements in urban air.

The Influence of Meteorological Conditions on the Wet Deposition of Mercury in Southern Florida

Abstract Source–receptor relationships for mercury (Hg) and other trace elements wet deposited in southeastern Florida were investigated using daily event precipitation samples collected over a 1-yr period in 1995–96. Data collected in Davie, Florida, showed significantly higher (2.2 times) volume-weighted mean (VWM) Hg concentrations during the spring and summer seasons relative to winter. A meteorological tracer analysis, utilizing the ratio of trace elements lanthanum (La) to cerium (Ce), determined that “feed” air to precipitation cells arriving at the site incorporated local urban emissions more frequently during the spring and summer seasons. Using Weather Surveillance Radar-1988 Doppler (WSR-88D) data, analysis of precipitation-cell path histories for events collected at 17 sites in southeastern Florida over 1 month in the summer of 1995 showed significantly higher (2.0 times) VWM Hg concentrations in events with easterly cell paths than in those with westerly paths for storms arriving at Everglade...

Atmospheric transport of speciated mercury across southern Lake Michigan: Influence from emission sources in the Chicago/Gary urban area.

Quantifying the local and regional impacts of speciated mercury (Hg) emissions from major urban and industrial areas is critical for understanding Hg transport and cycling in the environment. The Chicago/Gary urban area is one location where Hg emissions from industrial sources are significant and the regional transport of emissions may contribute to elevated ambient Hg concentrations at downwind locations. From July to November 2007, we collected semi-continuous measurements of gaseous elemental Hg (Hg(0)), fine particulate bound Hg (Hgp), and divalent reactive gaseous Hg (RGM) in Chicago, IL and Holland, MI to characterize the impact of Chicago/Gary source emissions on Hg concentrations in southwest Michigan and to improve our overall understanding of speciated Hg transport and deposition. The mean (and median) concentrations of Hg(0), Hgp, and RGM in Chicago were 2.5ng/m(3) (1.9ng/m(3)), 9pg/m(3) (5pg/m(3)), and 17pg/m(3) (6pg/m(3)), respectively. In Holland the mean (and median) concentrations were 1.3ng/m(3) (1.3ng/m(3)), 6pg/m(3) (6pg/m(3)), and 8pg/m(3) (2pg/m(3)), respectively. Cluster analysis of 24-hour HYSPLIT back-trajectories associated with the semi-continuous Hg measurements indicated that southwest transport from Chicago/Gary to Holland occurred during approximately 27% of the study. In Holland, under this transport regime, we observed a five-fold increase in RGM relative to the median concentration of the other transport clusters. We applied the HYSPLIT dispersion model to two case study periods to further quantify the impact of Chicago/Gary sources on southeast Michigan and investigate the role of direct transport and dispersion of speciated Hg emissions. Results suggested that more than 50% of the maximum RGM concentrations observed in Holland during the selected periods could be attributed to direct transport of primary RGM emissions from Chicago/Gary. The remaining RGM fractions are believed to be associated with Hg(0) oxidation during transport over Lake Michigan.