Ambient particulate air pollution, heart rate variability, and blood markers of inflammation in a panel of elderly subjects

Direct and acute cardiotoxicity of ultrafine particles in young adult and old rat hearts

BACKGROUND

Air pollution is associated with significant increases in cardiac morbidity and mortality in the general population. The elderly cohort within the general population is considered at high risk for cardiac diseases. However the degree to which air pollutants affect cardiac responses in old hearts vs. their young adult counterparts has not been systematically addressed.

OBJECTIVES

We sought to investigate the response of young adult vs. old rat hearts to the direct exposure of ultrafine particles (UFP); i.e. when the UFP are directly instilled into the cardiac vasculature, and their effects are not dependent upon UFP inhalation.

METHODS

The study was performed in isolated Langendorff-perfused rat hearts obtained from young adult (4 months old) and aged (26 months old) Fisher 344/Brown Norway rats. Two treatment groups (control and UFP-treated) were studied, and two ages (young adult and old) were studied within each group. Control hearts were perfused with buffer only, UFP-treated hearts were perfused with buffer containing ultrafine particles isolated from industrial diesel reference particulate matter. Systolic and end-diastolic pressures, positive and negative dP/dt, and coronary flow were measured.

RESULTS

Young adult and old hearts demonstrated equal functional deterioration in response to direct infusion of UFP. Developed pressure in young adult UFP-treated hearts fell from 101+/-4 to 68+/-8 mmHg (a decrease by 33%, p<0.05). In the old UFP-treated hearts developed pressure fell by 35% (from 101+/-7 to 67+/-9 mm Hg, p<0.05). Positive dP/dt was equally affected in the young adult and old UFP-treated hearts and was decreased by 28% in both groups.

CONCLUSION

Ultrafine particles when instilled directly into the cardiac vasculature were equally cardiotoxic in young adult and old rat hearts.

Exposure information in environmental health research: current opportunities and future directions for particulate matter, ozone, and toxic air pollutants

Understanding and quantifying outdoor and indoor sources of human exposure are essential but often not adequately addressed in health effect studies for air pollution. Air pollution epidemiology, risk assessment, health tracking, and accountability assessments are examples of health effect studies that require but often lack adequate exposure information. Recent advances in exposure modeling along with better information on time-activity and exposure factor data provide us with unique opportunities to improve the assignment of exposures for both future and ongoing studies linking air pollution to health impacts. In September 2006, scientists from the US Environmental Protection Agency and the Centers for Disease Control and Prevention along with scientists from the academic community and state health departments convened a symposium on air pollution exposure and health to identify, evaluate, and improve current approaches for linking air pollution exposures to disease. This manuscript presents the key issues, challenges, and recommendations identified by the exposure working group, who used case studies of particulate matter, ozone, and toxic air-pollutant exposure to evaluate health effects for air pollution. One of the overarching lessons of this workshop is that obtaining better exposure information for these different health effect studies requires both goal setting for what is needed and mapping out the transition pathway from current capabilities for meeting these goals. Meeting our long-term goals requires definition of incremental steps that provide useful information for the interim and move us toward our long-term goals. Another overarching theme among the three different pollutants and the different health study approaches is the need for integration among alternate exposure-assessment approaches. For example, different groups may advocate exposure indicators, biomonitoring, mapping methods (GIS), modeling, environmental media monitoring, and/or personal exposure modeling. However, emerging research reveals that the greatest progress comes from integration among two or more of these efforts.

Redox Dynamics of Mixed Metal (Mn, Cr, and Fe) Ultrafine Particles

The impact of particle composition on metal oxidation state, and on changes in oxidation state with simulated atmospheric aging, are investigated experimentally in flame-generated nanoparticles containing Mn, Cr, and Fe. The results demonstrate that the initial fraction of Cr(VI) within the particles decreases with increasing total metal concentration in the flame. In contrast, the initial Mn oxidation state was only partly controlled by metal loading, suggesting the importance of other factors. Two reaction pathways, one reductive and one oxidative, were found to be operating simultaneously during simulated atmospheric aging. The oxidative pathway depended upon the presence of simulated sunlight and O(3), whereas the reductive pathway occurred in the presence of simulated sunlight alone. The reductive pathway appears to be rapid but transient, allowing the oxidative pathway to dominate with longer aging times, i.e. greater than ∼8 hours. The presence of Mn within the particles enhanced the importance of the oxidative pathway, leading to more net Cr oxidation during aging implying that Mn can mediate oxidation by removal of electrons from other particulate metals.

Exposures to airborne particulate matter and adverse perinatal outcomes: a biologically plausible mechanistic framework for exploring potential

This article has three objectives: to describe the biologically plausible mechanistic pathways by which exposure to particulate matter (PM) may lead to adverse perinatal outcomes of low birth weight (LBW), intrauterine growth retardation (IUGR), and preterm delivery (PTD); review evidence showing that nutrition affects biologic pathways; and explain mechanisms by which nutrition may modify the impact of PM exposure on perinatal outcomes. We propose an interdisciplinary framework that brings together maternal and infant nutrition, air pollution exposure assessment, and cardiopulmonary and perinatal epidemiology. Five possible biologic mechanisms have been put forth in the emerging environmental sciences literature and provide corollaries for the proposed framework. The literature indicates that the effects of PM on LBW, PTD, and IUGR may manifest through the cardiovascular mechanisms of oxidative stress, inflammation, coagulation, endothelial function, and hemodynamic responses. PM exposure studies relating mechanistic pathways to perinatal outcomes should consider the likelihood that biologic responses and adverse birth outcomes may be derived from both PM and non-PM sources. We present strategies for empirically testing the proposed model and developing future research efforts.

Exposure to ultrafine carbon particles at levels below detectable pulmonary inflammation affects cardiovascular performance in spontaneously hypertensive rats

BACKGROUND

Exposure to particulate matter is a risk factor for cardiopulmonary disease but the underlying molecular mechanisms remain poorly understood. In the present study we sought to investigate the cardiopulmonary responses on spontaneously hypertensive rats (SHRs) following inhalation of UfCPs (24 h, 172 mug.m-3), to assess whether compromised animals (SHR) exhibit a different response pattern compared to the previously studied healthy rats (WKY).

METHODS

Cardiophysiological response in SHRs was analyzed using radiotelemetry. Blood pressure (BP) and its biomarkers plasma renin-angiotensin system were also assessed. Lung and cardiac mRNA expressions for markers of oxidative stress (hemeoxygenase-1), blood coagulation (tissue factor, plasminogen activator inhibitor-1), and endothelial function (endothelin-1, and endothelin receptors A and B) were analyzed following UfCPs exposure in SHRs. UfCPs-mediated inflammatory responses were assessed from broncho-alveolar-lavage fluid (BALF).

RESULTS

Increased BP and heart rate (HR) by about 5% with a lag of 1-3 days were detected in UfCPs exposed SHRs. Inflammatory markers of BALF, lung (pulmonary) and blood (systemic) were not affected. However, mRNA expression of hemeoxygenase-1, endothelin-1, endothelin receptors A and B, tissue factor, and plasminogen activator inhibitor showed a significant induction (~2.5-fold; p < 0.05) with endothelin 1 being the maximally induced factor (6-fold; p < 0.05) on the third recovery day in the lungs of UfCPs exposed SHRs; while all of these factors - except hemeoxygenase-1 - were not affected in cardiac tissues. Strikingly, the UfCPs-mediated altered BP is paralleled by the induction of renin-angiotensin system in plasma.

CONCLUSION

Our finding shows that UfCPs exposure at levels which does not induce detectable pulmonary neutrophilic inflammation, triggers distinct effects in the lung and also at the systemic level in compromised SHRs. These effects are characterized by increased activity of plasma renin-angiotensin system and circulating white blood cells together with moderate increases in the BP, HR and decreases in heart rate variability. This systemic effect is associated with pulmonary, but not cardiac, mRNA induction of biomarkers reflective of oxidative stress; activation of vasoconstriction, stimulation of blood coagulation factors, and inhibition of fibrinolysis. Thus, UfCPs may cause cardiovascular and pulmonary impairment, in the absence of detectable pulmonary inflammation, in individuals suffering from preexisting cardiovascular diseases.

Health effects of ambient air pollution--recent research development and contemporary methodological challenges

Exposure to high levels of air pollution can cause a variety of adverse health outcomes. Air quality in developed countries has been generally improved over the last three decades. However, many recent epidemiological studies have consistently shown positive associations between low-level exposure to air pollution and health outcomes. Thus, adverse health effects of air pollution, even at relatively low levels, remain a public concern. This paper aims to provide an overview of recent research development and contemporary methodological challenges in this field and to identify future research directions for air pollution epidemiological studies.

Relation of heart failure hospitalization to exposure to fine particulate air pollution

Cardiopulmonary disease has been associated with particulate matter (PM) air pollution. There is evidence that exposure to elevated PM concentrations increases risk of acute ischemic heart disease events, alters cardiac autonomic function, and increases risk of arrhythmias. It is plausible, therefore, that PM exposure may exacerbate heart failure (HF). A case-crossover study design was used to explore associations between fine PM (PM(2.5): particles with an aerodynamic diameter < or =2.5 microm) and 2,628 HF hospitalizations. Patients lived on Utah's Wasatch Front and were drawn from those hospitalized at Intermountain Healthcare facilities with a primary diagnosis of HF. A 14-day lagged cumulative moving average of 10 microg/m(3) PM(2.5) was associated with a 13.1% (95% confidence interval 1.3 to 26.2) increase in HF admissions. The strongest PM(2.5)-HF associations were for elderly patients who had previously been admitted for HF and who required only a short period of hospitalization. HF hospitalizations are associated with lagged cumulative exposure to PM(2.5) of approximately 2 weeks. In conclusion, particulate air pollution may play a role in precipitating acute cardiac decompensation in otherwise well-managed patients with HF, perhaps through effects of PM on myocardial ischemia, cardiac autonomic function, and/or arrhythmic effects.

Effects of combustion-derived ultrafine particles and manufactured nanoparticles on heart cells in vitro

Evidence from epidemiological studies indicates that acute exposure to airborne pollutants is associated with an increased risk of morbidity and mortality attributed to cardiovascular diseases. The present study investigated the effects of combustion-derived ultrafine particles (diesel exhaust particles) as well as engineered nanoparticles (titanium dioxide and single-walled carbon nanotubes) on impulse conduction characteristics, myofibrillar structure and the formation of reactive oxygen species in patterned growth strands of neonatal rat ventricular cardiomyocytes in vitro. Diesel exhaust particles as well as titanium dioxide nanoparticles showed the most pronounced effects. We observed a dose-dependent change in heart cell function, an increase in reactive oxygen species and, for titanium dioxide, we also found a less organized myofibrillar structure. The mildest effects were observed for single-walled carbon nanotubes, for which no clear dose-dependent alterations of theta and dV/dt(max) could be determined. In addition, there was no increase in oxidative stress and no change in the myofibrillar structure. These results suggest that diesel exhaust as well as titanium dioxide particles and to a lesser extent also single-walled carbon nanotubes can directly induce cardiac cell damage and can affect the function of the cells.

Cardiovascular effects of air pollution

Air pollution is a heterogeneous mixture of gases, liquids and PM (particulate matter). In the modern urban world, PM is principally derived from fossil fuel combustion with individual constituents varying in size from a few nanometres to 10 μm in diameter. In addition to the ambient concentration, the pollution source and chemical composition may play roles in determining the biological toxicity and subsequent health effects. Nevertheless, studies from across the world have consistently shown that both short- and long-term exposures to PM are associated with a host of cardiovascular diseases, including myocardial ischaemia and infarctions, heart failure, arrhythmias, strokes and increased cardiovascular mortality. Evidence from cellular/toxicological experiments, controlled animal and human exposures and human panel studies have demonstrated several mechanisms by which particle exposure may both trigger acute events as well as prompt the chronic development of cardiovascular diseases. PM inhaled into the pulmonary tree may instigate remote cardiovascular health effects via three general pathways: instigation of systemic inflammation and/or oxidative stress, alterations in autonomic balance, and potentially by direct actions upon the vasculature of particle constituents capable of reaching the systemic circulation. In turn, these responses have been shown to trigger acute arterial vasoconstriction, endothelial dysfunction, arrhythmias and pro-coagulant/thrombotic actions. Finally, long-term exposure has been shown to enhance the chronic genesis of atherosclerosis. Although the risk to one individual at any single time point is small, given the prodigious number of people continuously exposed, PM air pollution imparts a tremendous burden to the global public health, ranking it as the 13th leading cause of morality (approx. 800000 annual deaths).

Lifestyle and environmental factors associated with inflammation, oxidative stress and insulin resistance in children

BACKGROUND

Reaching a better understanding of the modifiable factors associated with inflammatory and oxidative biomarkers in children would be relevant to the design of further investigation and prevention strategies.

OBJECTIVE

To determine the association of air pollution as well as dietary and physical activity habits with markers of inflammation, oxidative stress and insulin resistance for the first time in a population-based sample of children.

METHODS

We conducted a population-based study of 374 children, aged 10-18 years, and assessed the exposure of participants to air pollutants as well as their dietary and physical activity habits. In addition to anthropometric and blood pressure measurements, we determined the fasting serum levels of lipid profile, insulin and markers of inflammation and oxidation.

RESULTS

We found independent associations between improper air quality and plasma markers of inflammation, oxidative stress and insulin resistance. The Pollutant Standard Index (PSI) and the level of fine particulate matter were significantly associated to all biomarkers studied. The associations between different markers of air pollutants and markers of inflammation, oxidative stress and insulin resistance remained significant after adjustment for age, gender, body mass index, waist circumference, healthy eating index and physical activity level. The association of healthy eating score with CRP and insulin resistance was mediated through anthropometric indices, and physical activity had independent association with insulin resistance.

CONCLUSION

The independent influence of inflammatory/oxidative mechanisms of air pollution effects on surrogate markers of atherosclerosis from early life should be highlighted.

Effects of diesel exhaust inhalation on heart rate variability in human volunteers

OBJECTIVES

Particulate matter (PM) air pollution is associated with alterations in cardiac conductance and sudden cardiac death in epidemiological studies. Traffic-related air pollutants, including diesel exhaust (DE) may be at least partly responsible for these effects. In this experimental study we assessed whether short-term exposure to DE would result in alterations in heart rate variability (HRV), a non-invasive measure of autonomic control of the heart.

METHODS

In a double-blind, crossover, controlled-exposure study, 16 adult volunteers were exposed (at rest) in randomized order to filtered air (FA) and two levels of diluted DE (100 or 200 microg/m(3) of fine particulate matter) in 2-h sessions. Before, and at four time points after each exposure we assessed HRV. HRV parameters assessed included both time domain statistics (standard deviation of N-N intervals (SDNN), and the square root of the mean of the sum of squared differences between successive N-N intervals (RMSSD)) and frequency domain statistics (high-frequency (HF) power, low-frequency (LF) power, and the LF/HF ratio).

RESULTS

We observed an effect at 3-h after initiation of DE inhalation on the frequency domain statistics of HRV. DE at 200 microg/m(3) elicited an increase in HF power compared to FA (Delta=0.33; 95% CI: 0.01-0.7) and a decrease in LF/HF ratio (Delta=-0.74; 95% CI: -1.2 to -0.2). The effect of DE on HF power was not consistent among study participants. There was no DE effect on time domain statistics and no significant DE effect on HRV in later time points.

CONCLUSIONS

We did not observe a consistent DE effect on the autonomic control of the heart in a controlled-exposure experiment in young participants. Efforts are warranted to understand discrepancies between epidemiological and experimental studies of air pollution's impact on HRV.

Acidity enhances the formation of a persistent ozonide at aqueous ascorbate/ozone gas interfaces

The pulmonary epithelium, like most aerial biosurfaces, is naturally protected against atmospheric ozone (O(3)) by fluid films that contain ascorbic acid (AH(2)) and related scavengers. This mechanism of protection will fail, however, if specific copollutants redirect AH(2) and O(3)(g) to produce species that can transduce oxidative damage to underlying tissues. Here, the possibility that the synergistic adverse health effects of atmospheric O(3)(g) and acidic particulate matter revealed by epidemiological studies could be mediated by hitherto unidentified species is investigated by electrospray mass spectrometry of aqueous AH(2) droplets exposed to O(3)(g). The products of AH(2) ozonolysis at the relevant air-water interface shift from the innocuous dehydroascorbic acid at biological pH to a C(4)-hydroxy acid plus a previously unreported ascorbate ozonide (m/z = 223) below pH approximately 5. The structure of this ozonide is confirmed by tandem mass spectrometry and its mechanism of formation delineated by kinetic studies. Present results imply enhanced production of a persistent ozonide in airway-lining fluids acidified by preexisting pathologies or inhaled particulate matter. Ozonides are known to generate cytotoxic free radicals in vivo and can, therefore, transduce oxidative damage.

Metabolic syndrome and inflammatory responses to long-term particulate air pollutants

BACKGROUND

Human data linking inflammation with long-term particulate matter (PM) exposure are still lacking. Emerging evidence suggests that people with metabolic syndrome (MS) may be a more susceptible population.

OBJECTIVES

Our goal was to examine potential inflammatory responses associated with long-term PM exposure and MS-dependent susceptibility.

METHODS

We conducted secondary analyses of white blood cell (WBC) count and MS data from The Third National Health and Nutrition Examination Survey and PM10 (PM with aerodynamic diameter < 10 microm) data from the U.S. Environmental Protection Agency Aerometric Information Retrieval System. Estimated 1-year PM10 exposures were aggregated at the centroid of each residential census-block group, using distance-weighted averages from all monitors in the residing and adjoining counties. We restricted our analyses to adults (20-89 years of age) with normal WBC (4,000-11,000 x 10(6)/L), no existing cardiovascular disease, complete PM10 and MS data, and living in current residences > 1 year (n = 2,978; age 48.5 +/- 17.8 years). Mixed-effects models were constructed to account for autocorrelation and potential confounders.

RESULTS

After adjustment for demographics, socioeconomic factors, lifestyles, residential characteristics, and MS, we observed a statistically significant association between WBC count and estimated local PM10 levels (p = 0.035). Participants from the least polluted areas (1-year PM10 < 1st quartile cutoff: 27.8 mug/m3) had lower WBC counts than the others (difference = 145 x 10(6)/L; 95% confidence interval, 10-281). We also noted a graded association between PM10 and WBC across subpopulations with increasing MS components, with 91 x 10(6)/L difference in WBC for those with no MS versus 214, 338, and 461 x 10(6)/L for those with 3, 4, and 5 metabolic abnormalities (trend-test p = 0.15).

CONCLUSIONS

Our study revealed a positive association between long-term PM exposure and hematological markers of inflammation and supported the hypothesized MS-dependent susceptibility.

Cardiac autonomic dysfunction: effects from particulate air pollution and protection by dietary methyl nutrients and metabolic polymorphisms

BACKGROUND

Particulate air pollution is associated with cardiovascular mortality and morbidity. To help identify mechanisms of action and protective/susceptibility factors, we evaluated whether the effect of particulate matter <2.5 mum in aerodynamic diameter (PM(2.5)) on heart rate variability was modified by dietary intakes of methyl nutrients (folate, vitamins B(6) and B(12), methionine) and related gene polymorphisms (C677T methylenetetrahydrofolate reductase [MTHFR] and C1420T cytoplasmic serine hydroxymethyltransferase [cSHMT]).

METHODS AND RESULTS

Heart rate variability and dietary data were obtained between 2000 and 2005 from 549 elderly men from the Normative Aging Study. In carriers of [CT/TT] MTHFR genotypes, the SD of normal-to-normal intervals was 17.1% (95% CI, 6.5 to 26.4; P=0.002) lower than in CC MTHFR subjects. In the same [CT/TT] MTHFR subjects, each 10-mug/m(3) increase in PM(2.5) in the 48 hours before the examination was associated with a further 8.8% (95% CI, 0.2 to 16.7; P=0.047) decrease in the SDNN. In [CC] cSHMT carriers, PM(2.5) was associated with an 11.8% (95% CI, 1.8 to 20.8; P=0.02) decrease in SDNN. No PM(2.5)-SSDN association was found in subjects with either [CC] MTHFR or [CT/TT] cSHMT genotypes. The negative effects of PM(2.5) were abrogated in subjects with higher intakes (above median levels) of B(6), B(12), or methionine. PM(2.5) was negatively associated with heart rate variability in subjects with lower intakes, but no PM(2.5) effect was found in the higher intake groups.

CONCLUSIONS

Genetic and nutritional variations in the methionine cycle affect heart rate variability either independently or by modifying the effects of PM(2.5).

Traffic-related air pollution in relation to incidence and prognosis of coronary heart disease

BACKGROUND

Long-term air pollution exposure is associated with increased mortality, but the association with incidence of fatal and nonfatal coronary heart disease is less certain. Moreover, it is unknown how chronic exposure to air pollution affects prognosis among survivors of a first coronary event. This study evaluated the association between long-term traffic-related air pollution exposure and incidence of nonfatal and fatal coronary events, as well as subsequent hospital readmission and mortality among myocardial infarction survivors.

METHODS

The study population comprised all residents of Rome aged 35-84 years during the period 1998-2000. Residential nitrogen dioxide (NO2) exposure as a marker of traffic pollution was assessed by a land-use regression model in 1995-1996 (R = 0.69). A total of 11,167 incident coronary events were observed (4654 fatal, including 3598 out-of-hospital coronary deaths, and 6513 nonfatal). The cohort of 6513 survivors was followed 4.0-7.5 years for readmission or mortality, starting 28 days from the date of first event. Relative risks per 10 mug/m of NO2 exposure, adjusted for age, sex, and socioeconomic status, were calculated by Poisson regression (population-based incidence) and Cox regression (cohort analysis).

RESULTS

The relative risk for incidence in coronary events per 10 mug/m of NO2 was 1.03 (95% confidence interval = 1.00-1.07). Stronger associations were found for fatal cases (1.07; 1.02-1.12) and out-of-hospital deaths (1.08; 1.02-1.13). Using NO2 exposure at the time of the first event, there was no association of air pollution exposure with either subsequent hospital readmission or mortality among survivors of the first coronary event.

CONCLUSIONS

Long-term air pollution exposure increases the risk of coronary heart disease, particularly fatal events. Hospital readmission or subsequent mortality among survivors was not associated with traffic air pollution.

Air pollution and heart rate variability: effect modification by chronic lead exposure

BACKGROUND

Outdoor air pollution and lead exposure can disturb cardiac autonomic function, but the effects of both these exposures together have not been studied.

METHODS

We examined whether higher cumulative lead exposures, as measured by bone lead, modified cross-sectional associations between air pollution and heart rate variability among 384 elderly men from the Normative Aging Study. We used linear regression, controlling for clinical, demographic, and environmental covariates.

RESULTS

We found graded, significant reductions in both high-frequency and low-frequency powers of heart rate variability in relation to ozone and sulfate across the quartiles of tibia lead. Interquartile range increases in ozone and sulfate were associated respectively, with 38% decrease (95% confidence interval = -54.6% to -14.9%) and 22% decrease (-40.4% to 1.6%) in high frequency, and 38% decrease (-51.9% to -20.4%) and 12% decrease (-28.6% to 9.3%) in low frequency, in the highest quartile of tibia lead after controlling for potential confounders. We observed similar but weaker effect modification by tibia lead adjusted for education and cumulative traffic (residuals of the regression of tibia lead on education and cumulative traffic). Patella lead modified only the ozone effect on heart rate variability.

CONCLUSIONS

People with long-term exposure to higher levels of lead may be more sensitive to cardiac autonomic dysfunction on high air pollution days. Efforts to understand how environmental exposures affect the health of an aging population should consider both current levels of pollution and history of lead exposure as susceptibility factors.

Effects of diesel exhaust particles on left ventricular function in isoproterenol-induced myocardial injury and healthy rats

The associations between ambient particulate matter with an aerodiameter less than 2.5 mu m (PM(2.5)) and congestive heart failure (CHF) have been reported. However, the underlying mechanisms remain unclear. We investigated the effect of diesel exhaust particles (DEPs) on left ventricular function in isoproterenol (ISO)-induced myocardial injury and healthy rats. Male Sprague-Dawley (SD) rats were injected with ISO or normal saline. Seven days later, both groups were further assigned to receive either DEPs or normal saline by intratracheal instillation (IT). Echocardiography was used to measure fractional shortening (FS) and left ventricular end-diastolic diameter (LVDd) 24 h before and after IT in each rat. Fractional shortening (FS) was significantly decreased in SD rats treated with ISO as compared to those treated with normal saline (p < .05, t-test). When FS and LVDd before and after treatment were compared in each rat, there was no difference for normal saline treatment in healthy or ISO groups. However, there was significantly lower FS before and after DEPs exposure in both groups (p < .05, paired t-test). When using SD rats treated with normal saline as a reference group, both SD rats treated with DEPs and ISO rats treated with normal saline had lower FS (p < .05 and .0001, respectively, t-test), while ISO rats treated with DEPs had the lowest FS (p < .0001, t-test). Echocardiographic assessment revealed that left ventricular function was impaired by acute DEPs exposure, and this LV function was further compromised in rats with preexisting ISO-induced myocardial injury.

Short-term exposure to air pollution and inflammation-sensitive biomarkers

OBJECTIVES

To evaluate the effect of short-term exposure to air pollutants on inflammation-sensitive biomarkers in apparently healthy individuals.

METHODS

We enrolled all participants from The Tel-Aviv Sourasky Medical Center inflammation survey held between 2003 and 2006, excluding participants with an acute or chronic inflammatory disease, pregnancy, steroidal or nonsteroidal treatment, or a recent invasive procedure. Additional subjects were excluded for living more than 11km from the nearest air pollution monitoring station. Analysis was performed separately for men and women. Linear regression models were fitted for each inflammatory variable against air pollutant variables (particulate matter under 10microm, sulfur dioxide, nitrogen dioxide, carbon monoxide, and ozone) for increasing lag times of up to 7 days, and adjusted for all possible and known confounding parameters.

RESULTS

The study population comprised 3659 individuals (2203 males and 1456 females). We found a statistically significant negative correlation in the male population between air pollutants, mainly NO2, SO2, and CO, and fibrinogen in several lag days. A positive correlation was found for PM10 at day 7. No such correlation was found for CRP and WBC, or for the female population.

CONCLUSION

Our findings do not support the potential link between short-term exposure to air pollution and enhanced inflammation as a possible explanation for increased cardiovascular morbidity. Additional large-scale population-based studies with good methodological design are needed in order to clarify this issue.

Short-term effects of air pollution on cardiovascular diseases: outcomes and mechanisms

The effects of air pollution on health have been intensively studied in recent years. Acute exposure to environmental pollutants such as particulate and gaseous matters (carbon monoxide, nitrogen oxides, sulphur dioxide and ozone) was associated with an increased rate of events and mortality because of cardiovascular diseases. These effects were investigated in short-term studies, which related day-to-day variations in air pollution to disease, and in long-term studies, which have followed cohorts of exposed individuals over time. The evidence from the literature on the short-term cardiovascular effects of air pollutants is discussed from clinical and mechanistic points of view.

Fine oil combustion particle bioavailable constituents induce molecular profiles of oxidative stress, altered function, and cellular injury in cardiomyocytes

Epidemiological studies have shown a positive association between exposure to air particulate matter (PM) pollution and adverse cardiovascular health effects in susceptible subpopulations such as those with pre-existing cardiovascular disease. The mechanism(s) through which pulmonary deposited PM, particularly fine PM2.5, PM with mass median aerodynamic diameter <2.5 microm, affects the cardiovascular system is currently not known and remains a major focus of investigation. In the present study, the transcriptosome and transcription factor proteome were examined in rat neonatal cardiomyocyte (RCM) cultures, following an acute exposure to bioavailable constituents of PM2.5 oil combustion particles designated residual oil fly ash leachate (ROFA-L). Out of 3924 genes examined, 38 genes were suppressed and 44 genes were induced following a 1-h exposure to 3.5 microg/ml of a particle-free leachate of ROFA (ROFA-L). Genomic alterations in pathways related to IGF-1, VEGF, IL-2, PI3/AKT, cardiovascular disease, and free radical scavenging, among others, were detected 1 h postexposure to ROFA-L. Global gene expression was altered in a manner consistent with cardiac myocyte electrophysiological remodeling, cellular oxidative stress, and apoptosis. ROFA-L altered the transcription factor proteome by suppressing activity of 24 and activating 40 transcription factors out of a total of 149. Genomic alterations were found to correlate with changes in transcription factor proteome. These acute changes indicate pathological molecular alterations, which may lead to possible chronic alterations to the cardiac myocyte. These data also potentially relate underlying cardiovascular effects from occupational exposure to ROFA and identify how particles from specific emission sources may mediate ambient PM cardiac effects.

Association of heart rate variability of the elderly with personal exposure to PM 1, PM 1-2.5, and PM 2.5-10

Environmental epidemiologic studies have shown that elderly people are susceptible to particulate air pollution. The decreases in heart rate variability are important indices of health effect caused by particulate matter. The objective of this study was to investigate the effects of submicron particle (PM(1)), PM(1-2.5), and coarse particle (PM(2.5-10)) on heart rate variability parameters in the elderly. Results of our study indicated that short-term and medium-term PM exposures were associated with the reduction of heart rate variability in the elderly, with stronger effects found for coarse particles in comparison with particles of other size ranges.

Particulate air pollution, oxidative stress genes, and heart rate variability in an elderly cohort

BACKGROUND AND OBJECTIVES

We have previously shown that reduced defenses against oxidative stress due to glutathione S-transferase M1 (GSTM1) deletion modify the effects of PM(2.5) (fine-particulate air pollution of < 2.5 microm in aerodynamic diameter) on heart rate variability (HRV) in a cross-sectional analysis of the Normative Aging Study, an elderly cohort. We have extended this to include a longitudinal analysis with more subjects and examination of the GT short tandem repeat polymorphism in the heme oxygenase-1 (HMOX-1) promoter.

METHODS

HRV measurements were taken on 539 subjects. Linear mixed effects models were fit for the logarithm of HRV metrics-including standard deviation of normal-to-normal intervals (SDNN), high frequency (HF), and low frequency (LF)-and PM(2.5) concentrations in the 48 hr preceding HRV measurement, controlling for confounders and a random subject effect.

RESULTS

PM(2.5) was significantly associated with SDNN (p = 0.04) and HF (p = 0.03) in all subjects. There was no association in subjects with GSTM1, whereas there was a significant association with SDNN, HF, and LF in subjects with the deletion. Similarly, there was no association with any HRV measure in subjects with the short repeat variant of HMOX-1, and significant associations in subjects with any long repeat. We found a significant three-way interaction of PM(2.5) with GSTM1 and HMOX-1 determining SDNN (p = 0.008), HF (p = 0.01) and LF (p = 0.04). In subjects with the GSTM1 deletion and the HMOX-1 long repeat, SDNN decreased by 13% [95% confidence interval (CI), -21% to -4%], HF decreased by 28% (95% CI, -43% to -9%), and LF decreased by 20% (95% CI, -35% to -3%) per 10 microg/m(3) increase in PM.

CONCLUSIONS

Oxidative stress is an important pathway for the autonomic effects of particles.

Short-term effects of particulate matter: an inflammatory mechanism?

"Would you tell me please, which way I ought to go from here," asked Alice. "That depends a good deal on where you want to go to," said the cat. (Lewis Carroll, Alice's Adventures in Wonderland) A large number of epidemiological studies show positive correlations between increasing levels of particulate matter (PM) in urban air and short-term morbidity and mortality for diverse acute cardiopulmonary diseases. Brought about by PM increments, inflammation is thought to exacerbate preexisting inflammatory diseases. Experimental evidence suggests a hierarchical oxidative stress model, in which a weakened antioxidant defense, as observed in disease or induced by inhaled particles, increases the PM ability to cause lung inflammation, accounting for exacerbations that occur in asthmatics and in patients with chronic obstructive lung disease. The role of PM-induced inflammation leading to acute cardiovascular events such as arrhythmia, heart failure, and myocardial infarction is more speculative. There is neither clear-cut evidence in humans that inhaled PM could get as far as blood circulation nor that proinflammatory mediators are significantly released from inflamed lung tissues, nor that blood coagulability is critically altered. As a whole, data in humans indicate that short-term inflammatory responses to PM are not always detected; they are usually mild and loosely correlated with functional changes. Among these studies, the diversity of PM characteristics, dose metrics, and endpoints hampers a clear discerning of inflammatory mechanism(s). Thus, the question arises as to whether inflammation represents the mechanism of acute cardiopulmonary PM toxicities in susceptible individuals, or rather an event that may coexist with other relevant mechanism(s). This review article discusses the evidence in humans linking short-term PM increments to inflammation and to exacerbations of cardiopulmonary diseases. Although there is a large amount of data available, there still remains a gulf between the number of epidemiological and panel studies and that of controlled exposures. Research on controlled exposure needs expanding, so that the results of time-series and panel studies will be better understood and short-term standards for human exposure may be more confidently allocated.

Heart rate variability in rodents: uses and caveats in toxicological studies

Heart rate variability (HRV) is a measure of cardiac pacing dynamics that has recently garnered a great deal of interest in environmental health studies. While the use of these measures has become popular, much uncertainty remains in the interpretation of results, both in terms of human and animal research. In humans, HRV endpoints, specifically chronic alterations in baseline HRV patterns, have been reasonably well characterized as prognostic indicators of adverse outcomes for a variety of diseases. However, such information is lacking for reversible HRV changes that may be induced by short-term exposures to environmental toxicants. Furthermore, there are minimal substantive data, either acute or chronic, regarding the pathological interpretation or prognostic value of toxicant-induced changes in HRV in rodents. The present report summarizes the physiological and clinical aspects of HRV, the methodological processes for obtaining these endpoints, and previous human and animal studies in the field of environmental health. Furthermore, we include a discussion of important caveats and recommendations for the interpretation of HRV data in animal research.

Air pollution and serum C-reactive protein concentration in children

BACKGROUND

Few biological markers that allow evaluation of the effects of air pollution on human health have been identified. This study evaluated the association of serum C-reactive protein (CRP) concentration in children with their respiratory symptoms and air pollution.

METHODS

Respiratory symptoms and serum concentrations of CRP were examined in 2,094 school children living in 3 communities with different concentrations of air pollutants in Chiba Prefecture, Japan in 2001. The relationships between serum CRP concentration and sex, age, respiratory symptoms, and various environmental factors were analyzed.

RESULTS

Serum CRP concentration decreased with age, and was significantly higher both in children who were bottle-fed in infancy and whose mothers smoked. Children with wheeze had significantly higher serum CRP concentration than those without wheeze. After adjustment for potential confounding factors, increased serum CRP concentrations of the 90th percentile (1.4 mg/L) or above were significantly associated with atmospheric concentration of suspended particulate matter (SPM) (odds ratio [OR] =1.49 for the range of observed concentrations, 95% confidence interval [CI]: 1.07-2.06) and sulfur dioxide (SO(2)) (OR =1.45, 95% CI: 1.04-2.03). In a two-pollutant model including SPM and nitrogen dioxide (NO(2)) concentrations, increased serum CRP concentrations were also associated with SPM (OR =1.94, 95% CI: 1.08-3.50), but no such association was found with NO(2) (OR =0.62, 95% CI: 0.26-1.48).

CONCLUSION

Serum CRP concentration is related to wheezing and the degree of air pollution. Because the concentrations of air pollutants are highly correlated, it is difficult to elaborate on which pollutant has a stronger effect on serum CRP concentrations.

Health effects of airborne particulate matter: do we know enough to consider regulating specific particle types or sources?

Researchers and regulators have often considered preferentially regulating the types of ambient airborne particulate matter (PM) most relevant to human health effects. While few would argue the inherent merits of such a policy, many believe there may not yet be enough information to differentially regulate PM species. New evidence, using increasingly sophisticated methodologies, has become available in the last several years, allowing more accurate assessment of exposure and resultant associations with specific types of PM, or PM derived from different sources. Such new studies may also allow differentiation of effects from different chemical components in the same study against the same health endpoints. This article considers whether this new evidence might be adequate to allow us to "speciate" PM types or sources by severity of health effects. We address this issue with respect to two widespread sources of PM, emissions from motor vehicles and coal-fired power plants. Emissions from less widespread sources, residual oil and steel/coking facilities, are also discussed in order to illustrate how health effects associated with such emissions might instead be associated with more widespread sources when accurate exposure information is unavailable. Based upon evaluation of studies and methodologies which appear to contain the most accurate information on exposure and response to important emissions, including variable local emissions, it is concluded that public health will likely be better protected by reduction of various vehicular emissions than by continued regulation of the total mass of fine PM (PM <2.5 microm, or PM2.5) as if all PM in this mode is equitoxic. However, the knowledge base is incomplete. Important remaining research questions are identified.

Associations between particulate sulfate and organic carbon exposures and heart rate variability in patients with or at risk for cardiovascular diseases

OBJECTIVE

It is still unknown whether specific components in fine particles are associated with heart rate variability (HRV) reduction.

METHODS

We recruited 46 patients with or at risk for cardiovascular diseases to measure 24-hour HRV by ambulatory electrocardiographic monitoring. Fixed-site air-monitoring stations were used to represent participants' exposures to particles with aerodynamic diameters less than 10 microm (PM 10) and 2.5 microm (PM2.5), and particulate components of sulfate, nitrate, organic carbon (OC) and elemental carbon, and gaseous pollutants.

RESULTS

We found that HRV reduction was associated with sulfate, OC, and PM2.5 but not with the other five pollutants in single-pollutant models. Sulfate was found to remain in significant association with HRV reduction adjusting for OC and PM2.5 in three-pollutant models.

CONCLUSIONS

Exposures to sulfate and OC in PM2.5 were associated with HRV reduction in patients with or at risk for cardiovascular diseases.

Night heart rate variability and particulate exposures among boilermaker construction workers

BACKGROUND

Although studies have documented the association between heart rate variability (HRV) and ambient particulate exposures, the association between HRV, especially at night, and metal-rich, occupational particulate exposures remains unclear.

OBJECTIVE

Our goal in this study was to investigate the association between long-duration HRV, including nighttime HRV, and occupational PM(2.5) exposures.

METHODS

We used 24-hr ambulatory electrocardiograms (ECGs) to monitor 36 male boilermaker welders (mean age of 41 years) over a workday and nonworkday. ECGs were analyzed for HRV in the time domain; rMSSD (square root of the mean squared differences of successive intervals), SDNN (SD of normal-to-normal intervals over entire recording), and SDNN(i) (SDNN for all 5-min segments) were summarized over 24-hr, day (0730-2130 hours), and night (0000-0700 hours) periods. PM(2.5) (particulate matter with an aerodynamic diameter </= 2.5 microm) exposures were monitored over the workday, and 8-hr time-weighted average concentrations were calculated. We used linear regression to assess the associations between HRV and workday particulate exposures. Matched measurements from a nonworkday were used to control for individual cardiac risk factors.

RESULTS

Mean (+/- SD) PM(2.5) exposure was 0.73 +/- 0.50 mg/m(3) and ranged from 0.04 to 2.70 mg/m(3). We observed a consistent inverse exposure-response relationship, with a decrease in all HRV measures with increased PM(2.5) exposure. However, the decrease was most pronounced at night, where a 1-mg/m(3) increase in PM(2.5) was associated with a change of -8.32 [95% confidence interval (CI), -16.29 to -0.35] msec nighttime rMSSD, -14.77 (95% CI, -31.52 to 1.97) msec nighttime SDNN, and -8.37 (95% CI, -17.93 to 1.20) msec nighttime SDNN(i), after adjusting for nonworking nighttime HRV, age, and smoking.

CONCLUSION

Metal-rich particulate exposures were associated with decreased long-duration HRV, especially at night. Further research is needed to elucidate which particulate metal constituent is responsible for decreased HRV.

Air pollution and inflammation (interleukin-6, C-reactive protein, fibrinogen) in myocardial infarction survivors

BACKGROUND

Numerous studies have found that ambient air pollution has been associated with cardiovascular disease exacerbation.

OBJECTIVES

Given previous findings, we hypothesized that particulate air pollution might induce systemic inflammation in myocardial infarction (MI) survivors, contributing to an increased vulnerability to elevated concentrations of ambient particles.

METHODS

A prospective longitudinal study of 1,003 MI survivors was performed in six European cities between May 2003 and July 2004. We compared repeated measurements of interleukin 6 (IL-6), fibrinogen, and C-reactive protein (CRP) with concurrent levels of air pollution. We collected hourly data on particle number concentrations (PNC), mass concentrations of particulate matter (PM) < 10 microm (PM(10)) and < 2.5 microm (PM(2.5)), gaseous pollutants, and meteorologic data at central monitoring sites in each city. City-specific confounder models were built for each blood marker separately, adjusting for meteorology and time-varying and time-invariant covariates. Data were analyzed with mixed-effects models.

RESULTS

Pooled results show an increase in IL-6 when concentrations of PNC were elevated 12-17 hr before blood withdrawal [percent change of geometric mean, 2.7; 95% confidence interval (CI), 1.0-4.6]. Five day cumulative exposure to PM(10) was associated with increased fibrinogen concentrations (percent change of arithmetic mean, 0.6; 95% CI, 0.1-1.1). Results remained stable for smokers, diabetics, and patients with heart failure. No consistent associations were found for CRP.

CONCLUSIONS

Results indicate an immediate response to PNC on the IL-6 level, possibly leading to the production of acute-phase proteins, as seen in increased fibrinogen levels. This might provide a link between air pollution and adverse cardiac events.

Air pollution and emergency admissions in Boston, MA

STUDY OBJECTIVE

Many studies have shown that ambient particulate air pollution (PM) is associated with increased risk of hospital admissions and deaths for cardiovascular or respiratory causes around the world. In general these have been analysed in association with PM(10) and ozone, whereas PM(2.5) is now the particle measure of greatest health and regulatory concern. And little has been published on associations of hospital admissions and PM components.

DESIGN

This study analysed hospital admissions for myocardial infarction (15 578 patients), and pneumonia (24 857 patients) in associations with fine particulate air pollution, black carbon (BC), ozone, nitrogen dioxide (NO(2)), PM not from traffic, and carbon monoxide (CO) in the greater Boston area for the years 1995-1999 using a case-crossover analysis, with control days matched on temperature.

MAIN RESULTS

A significant association was found between NO(2) (12.7% change (95% CI: 5.8, 18)), PM(2.5) (8.6% increase (95% CI: 1.2, 15.4)), and BC (8.3% increase (95% CI: 0.2, 15.8)) and the risk of emergency myocardial infarction hospitalisation; and between BC (11.7% increase (95% CI: 4.8, 17.4)), PM(2.5) (6.5% increase (95% CI: 1.1, 11.4)), and CO (5.5% increase (95% CI: 1.1, 9.5)) and the risk of pneumonia hospitalisation.

CONCLUSIONS

The pattern of associations seen for myocardial infarction and pneumonia (strongest associations with NO(2), CO, and BC) suggests that traffic exposure is primarily responsible for the association with heart attacks.

Penalized solutions to functional regression problems

Recent technological advances in continuous biological monitoring and personal exposure assessment have led to the collection of subject-specific functional data. A primary goal in such studies is to assess the relationship between the functional predictors and the functional responses. The historical functional linear model (HFLM) can be used to model such dependencies of the response on the history of the predictor values. An estimation procedure for the regression coefficients that uses a variety of regularization techniques is proposed. An approximation of the regression surface relating the predictor to the outcome by a finite-dimensional basis expansion is used, followed by penalization of the coefficients of the neighboring basis functions by restricting the size of the coefficient differences to be small. Penalties based on the absolute values of the basis function coefficient differences (corresponding to the LASSO) and the squares of these differences (corresponding to the penalized spline methodology) are studied. The fits are compared using an extension of the Akaike Information Criterion that combines the error variance estimate, degrees of freedom of the fit and the norm of the bases function coefficients. The performance of the proposed methods is evaluated via simulations. The LASSO penalty applied to the linearly transformed coefficients yields sparser representations of the estimated regression surface, while the quadratic penalty provides solutions with the smallest L(2)-norm of the basis functions coefficients. Finally, the new estimation procedure is applied to the analysis of the effects of occupational particulate matter (PM) exposure on the heart rate variability (HRV) in a cohort of boilermaker workers. Results suggest that the strongest association between PM exposure and HRV in these workers occurs as a result of point exposures to the increased levels of particulate matter corresponding to smoking breaks.

Effect of ambient particulate matter exposure on hemostasis

Epidemiological studies have linked levels of particulate matter (PM) in ambient air to cardiovascular mortality and hospitalizations for myocardial infarction (MI) and stroke. Thrombus formation plays a primary role in potentiating acute cardiovascular events, and this study was undertaken to determine whether pulmonary exposure to PM alters hemostasis. PM was collected from the Chapel Hill, NC airshed and was administered to mice by intratracheal instillation at a dose previously shown to exacerbate myocardial ischemia-reperfusion injury. Twenty-four hours after exposure, an increase occurred in the number of circulating platelets and plasma concentrations of fibrinogen and soluble P-selectin. The concentration of tissue factor pathway inhibitor (TFPI) in plasma was decreased, whereas the plasma concentration of plasminogen activator inhibitor (PAI-1) was increased. Consistent with these observations, bleeding time from a tail-tip transection was shortened. These results provide evidence that PM exposure alters hemostasis in otherwise healthy animals and may thereby promote clot formation and impede clot resolution in susceptible individuals. The results also establish definite hemostatic endpoints that can be used to further investigate the effects of dose and particle characteristics on the toxicity of ambient particles.

Coarse particulate matter (PM2.5-10) affects heart rate variability, blood lipids, and circulating eosinophils in adults with asthma

INTRODUCTION

We investigated whether markers of airway and systemic inflammation, as well as heart rate variability (HRV) in asthmatics, change in response to fluctuations in ambient particulate matter (PM) in the coarse [PM with aerodynamic diameter 2.5-10 microm (PM(2.5-10))] and fine (PM(2.5)) size range.

METHODS

Twelve adult asthmatics, living within a 30-mile radius of an atmospheric monitoring site in Chapel Hill, North Carolina, were followed over a 12-week period. Daily PM(2.5-10) and PM(2.5) concentrations were measured separately for each 24-hr period. Each subject had nine clinic visits, at which spirometric measures and peripheral blood samples for analysis of lipids, inflammatory cells, and coagulation-associated proteins were obtained. We also assessed HRV [SDNN24HR (standard deviation of all normal-to-normal intervals in a 24-hr recording), ASDNN5 (mean of the standard deviation in all 5-min segments of a 24-hr recording)] with four consecutive 24-hr ambulatory electrocardiogram measurements. Linear mixed models with a spatial covariance matrix structure and a 1-day lag were used to assess potential associations between PM levels and cardiopulmonary end points.

RESULTS

For a 1-microg/m(3) increase in coarse PM, SDNN24HR, and ASDNN5 decreased 3.36% (p = 0.02), and 0.77%, (p = 0.05) respectively. With a 1-microg/m(3) increase in coarse PM, circulating eosinophils increased 0.16% (p = 0.01), triglycerides increased 4.8% (p = 0.02), and very low-density lipoprotein increased 1.15% (p = 0.01). No significant associations were found with fine PM, and none with lung function.

CONCLUSION

These data suggest that small temporal increases in ambient coarse PM are sufficient to affect important cardiopulmonary and lipid parameters in adults with asthma. Coarse PM may have underappreciated health effects in susceptible populations.

Particulate air pollution, progression, and survival after myocardial infarction

OBJECTIVE

Several studies have examined the effect of particulate pollution (PM) on survival in general populations, but less is known about susceptible groups. Moreover, previous cohort studies have been cross-sectional and subject to confounding by uncontrolled differences between cities.

DESIGN

We investigated whether PM was associated with progression of disease or reduced survival in a study of 196,000 persons from 21 U.S. cities discharged alive following an acute myocardial infarction (MI), using within-city between-year exposure to PM. We constructed city-specific cohorts of survivors of acute MI using Medicare data between 1985 and 1999, and defined three outcomes on follow-up: death, subsequent MI, and a first admission for congestive heart failure (CHF). Yearly averages of PM(10) (particulate matter with aerodynamic diameter < 10 microm) were merged to the individual annual follow-up in each city. We applied Cox's proportional hazard regression model in each city, with adjustment for individual risk factors. In the second stage of the analysis, the city-specific results were combined using a meta-regression.

RESULTS

We found significant associations with a hazard ratio for the sum of the distributed lags of 1.3 [95% confidence interval (CI), 1.2-1.5] for mortality, a hazard ratio of 1.4 (95% CI, 1.2-1.7) for a hospitalization for CHF, and a hazard ratio of 1.4 (95% CI, 1.1-1.8) for a new hospitalization for MI per 10 microg/m(3) PM(10).

CONCLUSIONS

This is the first long-term study showing a significant association between particle exposure and adverse post-MI outcomes in persons who survived an MI.

Is air pollution a cause of cardiovascular disease? Updated review and controversies

Particulate matter (PM) air pollution is associated with an increased risk of cardiovascular morbidity and mortality. The focus of this review will be on the role that both acute and chronic exposure to PM plays in causing cardiovascular disease and on the latest major new findings and controversies in this field of research. Even short-term exposure to PM2.5 over a few hours can trigger myocardial infarctions, cardiac ischemia, arrhythmias, heart failure, stroke, exacerbation of peripheral arterial disease, and sudden death. Chronic exposure to moderately elevated levels also enhances the risk for developing a variety of cardiovascular diseases, possibly including hypertension and systemic atherosclerosis. Recent epidemiologic studies have furthered our understanding of the linkage between air pollutants and human health, with a multitude of plausible mechanistic explanations having been demonstrated experimentally during the past few years. Although a number of finer details relating to both the epidemiology and the mechanisms involved require more investigation, the overall weight of evidence is now sufficient to implicate PM exposure as a cause of cardiovascular disease. Without doubt, exposure to particulate matter can play a causal role in triggering a host of acute cardiovascular events via many mechanisms. Although long-term air pollution exposure has been shown to promote the development of atherosclerosis, the clinical significance of this relation requires more investigation.

Influence of Personal Exposure to Particulate Air Pollution on Cardiovascular Physiology and Biomarkers of Inflammation and Oxidative Stress in Subjects With Diabetes

OBJECTIVE

We investigated whether personal exposure to particulate matter </= 10 microm in diameter (PM10) contributes to impaired cardiovascular function and increased systemic inflammation and oxidative stress in diabetic patients.

METHODS

We monitored 25 patients' personal exposure to PM10 for 24 hours and then measured their heart rate, blood pressure, brachial arterial diameter, flow-mediated vasodilation (FMD), plasma cytokines, and thiobarbituric acid reactive substances (TBARS), which is an oxidative stress marker. We repeated this procedure for 7 weeks on each subject. We tested the associations using mixed-effects models.

RESULTS

PM10 was significantly positively associated with FMD and TBARS but inversely associated with end-systolic basal brachial arterial diameter (P < 0.05). Moreover, in subjects not taking vasoactive medications, PM10 was significantly positively associated with blood pressure but inversely associated with artery flow.

CONCLUSION

Elevated PM10 may contribute to oxidative stress and impaired cardiovascular function in patients with diabetes mellitus.

Ambient source-specific particles are associated with prolonged repolarization and increased levels of inflammation in male coronary artery disease patients

Ambient particulate air pollution has been associated with altered cardiac function and systemic inflammation. We reported repolarization changes and variations in markers of inflammation in association with ambient particulate exposure in a panel of male coronary artery disease (CAD) patients. The objective of this analysis was to identify the specific sources associated with these effects. A panel of male CAD patients participated in 12 clinical visits in Erfurt, Germany. We used 56 patients' 5min ECG recordings for the analysis of repolarization parameters QT interval and T wave amplitude, and 57 patients' plasma samples to determine the biomarkers von Willebrand factor (vWF) and C-reactive protein (CRP). Linear and logistic regression models were used to analyze the associations between five particle source factors (airborne soil, local traffic-related ultrafine particles, combustion-generated aerosols, diesel traffic-related particles, and secondary aerosols) and these health parameters adjusting for trend, weekday and meteorological variables. An increase in QT interval and a decrease in T wave amplitude were observed in association with traffic-related particles exposure during 0-23h before the ECG recordings. The inflammatory marker vWF increased in association with both traffic-related particles and combustion-generated aerosols at different exposure lags. All source particles had positive associations with CRP levels above the 90th percentile (8.5mg/l). These results suggest that traffic-related and combustion-generated particles show stronger adverse health impact with regard to cardiac effects, and that particles from different sources induce an acute phase response in these patients.

Interaction between resting pulmonary ventilation function and cardiac autonomic function assessed by heart rate variability in young adults

An association between ambient air pollution and reduced cardiac autonomic function assessed by heart rate variability (HRV) mainly in elderly persons has been suggested by a number of epidemiological studies, but the link between the HRV and pulmonary function in humans remains unknown although such air pollution should primarily affect pulmonary function. To clarify this link, pulmonary ventilation parameters such as oxygen uptake (V(O(2))) and carbon dioxide output (V(CO(2))), as well as the HRV with spectral analysis (high- and low-frequency components of HRV, i.e., CCV(HF) and CCV(LF), reflecting cardiac parasympathetic and sympathetic activities, respectively), were measured in 66 healthy women aged 19-20 years after an overnight fast of 12 h. Significant correlations were found between the CCV(HF) of HRV and both the end-tidal carbon dioxide concentration (FET(CO(2))) and gas exchange ratio (V(CO(2))/V(O(2))) in the subjects (partial correlation coefficients r = 0.354 and 0.320, respectively), whereas there was no significant connection between the FET(CO(2)) and the V(CO(2))/V(O(2)). Similarly, the CCV(LF) correlated significantly with the resting tidal volume of lung (r = 0.364). These findings suggest that resting pulmonary ventilation function interacts with cardiac autonomic function assessed by the HRV, at least in healthy young adults, which may be useful for explaining the pathophysiology concerning the short-term effect of air pollution such as fine particulate matter on cardiovascular function.

Focused Exposures to Airborne Traffic Particles and Heart Rate Variability in the Elderly

BACKGROUND

: Exposure to airborne particles may increase cardiac risk by altering autonomic balance. Because these risks may be particularly great for traffic-related particles, we examined associations between particles and heart rate variability as 44 subjects participated in 4 repeated trips aboard a diesel bus.

METHODS

: Twenty-four hour electrocardiograms were correlated with continuous particle concentrations using generalized additive models controlling for subject, weekday, time, apparent temperature, trip type, activity, medications, and autoregressive terms. Associations were assessed for short- and medium-term moving averages of measured concentrations.

RESULTS

: Heart rate variability was negatively associated with fine particulate matter. Positive associations were demonstrated with heart rate and the low-to-high frequency power ratio. Associations were strongest with 24-hour mean concentrations, although strong short-term associations also were found during bus periods, independent of daily exposures. Overall, associations were greatest for high-frequency power with the following effects per interquartile change in the 24-hour mean concentrations: -15% (95% confidence interval = -17% to -14%) for PM2.5 (4.6 mug/m); -19% (-21% to -17%) for black carbon (459 ng/m); and -14% (-15% to -12%) for fine particle counts (39 pt/cm). For each interquartile change in the 5-minute PM2.5 concentration (10 mug/m) aboard the bus, an 11% (95% confidence interval = -14% to -8%) decrease in high-frequency power was observed.

CONCLUSIONS

: This investigation indicates that fine particles are negatively associated with heart rate variability, with an overall trend towards reduced parasympathetic tone. Although daily associations were evident for all particles, short-term associations were predominantly limited to traffic-related particles.

[Air pollution and cardiovascular and cerebrovascular disease. Pathophysiologic basis and groups at risk]

The pathophysiologic basis of the harmful action of air pollutants rests principally on their proinflammatory and prothrombotic effects. The principal pollutants currently identified as responsible for these effects are fine suspended particles (PM2.5) and ozone. Inflammatory effects, initially localized in the lungs, then become systemic. Analysis of groups at the highest risk of atherothrombotic events suggests the elderly may be most sensitive to the effects of air pollution.

Long-term exposure to urban air pollution and myocardial infarction

BACKGROUND

Cohort studies have reported increased risks of cardiopulmonary mortality from long-term air pollution exposure, but the evidence is limited and inconclusive. We studied the association between long-term exposure to source-specific air pollution and myocardial infarction (MI) in a case-control study of first-time MI cases and population controls age 45 to 70 years in Stockholm county in 1992 to 1994.

METHODS

Home addresses during several decades were combined with historical emission databases and dispersion models to obtain annual mean levels of pollutants from traffic and heating during 30 years for 1397 cases and 1870 controls. Nitrogen dioxide (NO2), carbon monoxide (CO), and particulate matter with an aerodynamic diameter less than 10 microm (PM10) were used as indicators of traffic emissions and sulfur dioxide (SO2) as an indicator of emissions from residential heating.

RESULTS

There was no association between long-term average air pollution exposure and overall MI, but an increased risk of fatal MI was suggested, especially for out-of-hospital death. After adjustment for cardiovascular risk factors, the odds ratio for fatal MI associated with a 5th to 95th percentile difference in 30-year average exposure was 1.51 (95% confidence interval = 0.96-2.16) for NO2, 1.22 (0.98-1.52) for CO, 1.39 (0.94-2.07) for PM10, and 1.24 (0.77-2.02) for SO2. For out-of-hospital death, the odds ratio related to NO2 exposure was 2.17 (1.05-4.51).

CONCLUSIONS

This study provides some support for an association between long-term air pollution exposure and fatal cardiovascular disease.

Relationships between air pollution and preterm birth in California

Air pollution from vehicular emissions and other combustion sources is related to cardiovascular and respiratory outcomes. However, few studies have investigated the relationship between air pollution and preterm birth, a primary cause of infant mortality and morbidity. This analysis examined the effect of fine particulate matter (PM(2.5)) and carbon monoxide (CO) on preterm birth in a matched case-control study. PM(2.5) and CO monitoring data from the California Air Resources Board were linked to California birth certificate data for singletons born in 1999-2000. Each birth was mapped to the closest PM monitor within 5 miles of the home address. County-level CO measures were utilised to increase sample size and maintain a representative population. After exclusion of implausible birthweight-gestation combinations, preterm birth was defined as birth occurring between 24 and 36 weeks' gestation. Each of the 10 673 preterm cases was matched to three controls of term (39-44 weeks) gestation with a similar date of last menstrual period. Based on the case's gestational age, CO and PM(2.5) exposures were calculated for total pregnancy, first month of pregnancy, and last 2 weeks of pregnancy. Exposures were divided into quartiles; the lowest quartile was the reference. Because of the matched design, conditional logistic regression was used to adjust for maternal race/ethnicity, age, parity, marital status and education. High total pregnancy PM(2.5) exposure was associated with a small effect on preterm birth, after adjustment for maternal factors (adjusted odds ratio [AOR] = 1.15, [95% CI 1.07, 1.24]). The odds ratio did not change after adjustment for CO. Results were similar for PM(2.5) exposure during the first month of pregnancy (AOR = 1.21, 95% CI [1.12, 1.30]) and the last 2 weeks of pregnancy (AOR = 1.17, 95% CI [1.09, 1.27]). Conversely, CO exposure at any time during pregnancy was not associated with preterm birth (AORs from 0.95 to 1.00). Maternal exposure to PM(2.5), but not CO, is associated with preterm birth. This analysis did not show differences by timing of exposure, although more detailed examination may be needed.

Exposures to airborne particulate matter and adverse perinatal outcomes: a biologically plausible mechanistic framework for exploring potential effect modification by nutrition

OBJECTIVES

The specific objectives are threefold: to describe the biologically plausible mechanistic pathways by which exposure to particulate matter (PM) may lead to the adverse perinatal outcomes of low birth weight (LBW), intrauterine growth retardation (IUGR), and preterm delivery (PTD); review the evidence showing that nutrition affects the biologic pathways; and explain the mechanisms by which nutrition may modify the impact of PM exposure on perinatal outcomes.

METHODS

We propose an interdisciplinary conceptual framework that brings together maternal and infant nutrition, air pollution exposure assessment, and cardiopulmonary and perinatal epidemiology. Five possible albeit not exclusive biologic mechanisms have been put forth in the emerging environmental sciences literature and provide corollaries for the proposed framework.

CONCLUSIONS

Protecting the environmental health of mothers and infants remains a top global priority. The existing literature indicates that the effects of PM on LBW, PTD, and IUGR may manifest through the cardiovascular mechanisms of oxidative stress, inflammation, coagulation, endothelial function, and hemodynamic responses. PM exposure studies relating mechanistic pathways to perinatal outcomes should consider the likelihood that biologic responses and adverse birth outcomes may be derived from both PM and non-PM sources (e.g., nutrition). In the concluding section, we present strategies for empirically testing the proposed model and developing future research efforts.

A novel application of capnography during controlled human exposure to air pollution

Background

The objective was to determine the repeatability and stability of capnography interfaced with human exposure facility.

Methods

Capnographic wave signals were obtained from five healthy volunteers exposed to particle-free, filtered air during two consecutive 5 min intervals, 10 min apart, within the open and then the sealed and operational human exposure facility (HEF). Using a customized setup comprised of the Oridion Microcap^® portable capnograph, DA converter and AD card, the signal was acquired and saved as an ASCII file for subsequent processing. The minute ventilation (VE), respiratory rate (RR) and expiratory tidal volume (V_TE) were recorded before and after capnographic recording and then averaged. Each capnographic tracing was analyzed for acceptable waves. From each recorded interval, 8 to 19 acceptable waves were selected and measured. The following wave parameters were obtained: total length and length of phase II and III, slope of phase II and III, area under the curve and area under phase III. In addition, we recorded signal measures including the mean, standard deviation, mode, minimum, maximum – which equals end-tidal CO₂ (EtCO₂), zero-corrected maximum and true RMS.

Results

Statistical analysis using a paired t-test for means showed no statistically significant changes of any wave parameters and wave signal measures, corrected for RR and V_TE, comparing the measures when the HEF was open vs. sealed and operational. The coefficients of variation of the zero-corrected and uncorrected EtCO₂, phase II absolute difference, signal mean, standard deviation and RMS were less than 10% despite a sub-atmospheric barometric pressure, and slightly higher temperature and relative humidity within the HEF when operational.

Conclusion

We showed that a customized setup for the acquisition and processing of the capnographic wave signal, interfaced with HEF was stable and repeatable. Thus, we expect that analysis of capnographic waves in controlled human air pollution exposure studies is a feasible tool for characterization of cardio-pulmonary effects of such exposures.

Inhalation of diluted diesel engine emission impacts heart rate variability and arrhythmia occurrence in a rat model of chronic ischemic heart failure

Both increase in cardiac arrhythmia incidence and decrease in heart rate variability (HRV) have been described following human and experimental animal exposures to air pollutants. However, the potential causal relationship between these two factors remains unclear. Incidence of ventricular arrhythmia and HRV were evaluated during and after a 3 h period of Diesel engine exhaust exposure in ten healthy and ten chronic ischemic heart failure (CHF, 3 months after coronary ligation) Wistar rats using implantable ECG telemetry. Air pollutants were delivered to specifically designed whole body individual exposure chambers at particulate matter concentrations similar to those measured inside cabins of cars inserted in congested urban traffic. Recordings were obtained from unrestrained and unsedated vigil rats. Immediate decrease in RMSSD was observed in both healthy (6.64 +/- 2.62 vs. 4.89 +/- 1.67 ms, P < 0.05) and CHF rats (8.01 +/- 0.89 vs. 6.6 +/- 1.37 ms, P < 0.05) following exposure. An immediate 200-500% increase in ventricular premature beats was observed in CHF rats only. Whereas HRV progressively returned to baseline values within 2.5 h after exposure start, the proarrhythmic effect persisted as late as 5 h after exposure termination in CHF rats. Persistence of ventricular proarrhythmic effects after HRV normalization suggests that HRV reduction is not the mechanism of cardiac arrhythmias in this model. Our methodological approach, closely reflecting the real clinical situations, appeared to be a unique tool to provide further insight into the pathophysiological mechanisms of traffic related airborne pollution health impact.

Recent exposure to particulate matter and C-reactive protein concentration in the multi-ethnic study of atherosclerosis

Ambient levels of particulate matter have been linked to cardiovascular disease. The mechanisms mediating these associations are poorly understood. One candidate mechanism is inflammation. Using data from the Multi-Ethnic Study of Atherosclerosis (2000-2002), the authors investigated the relation between exposure to particulate matter of less than or equal to 2.5 microm in diameter (PM2.5) and C-reactive protein concentration in 5,634 persons aged 45-84 years who were free of cardiovascular disease. Data from US Environmental Protection Agency monitors were used to estimate PM2.5 exposures for the prior day, prior 2 days, prior week, prior 30 days, and prior 60 days. Only the 30-day and 60-day mean exposures showed a weak positive association with C-reactive protein, and confidence intervals were wide: relative increases in C-reactive protein per 10 microg/m3 of PM2.5 adjusted for person-level covariates were 3% (95% confidence interval (CI): -2, 10) for a 30-day mean and 4% (95% CI: -3, 11.0) for a 60-day mean. The means of 7-day, 30-day, and 60-day exposures were weakly, positively, and nonsignificantly associated with the odds of C-reactive protein of greater than or equal to 3 mg/liter: adjusted odds ratios were 1.05 (95% CI: 0.96, 1.15), 1.12 (95% CI: 0.98, 1.29), and 1.12 (95% CI: 0.96, 1.32), respectively. Slightly stronger associations were observed in persons without other risk factors for elevated C-reactive protein, but this heterogeneity was not statistically significant. The authors' results are not compatible with strong effects of particulate matter exposures on population levels of C-reactive protein.

The pharmacology of particulate matter air pollution-induced cardiovascular dysfunction

Since the London fog of 1952, in which more than 4000 people were killed in 4 days, the combined efforts of scientists from several disciplines, including those from the environmental health, clinical and biomedical disciplines, have raised serious concerns about the impact of air pollutants on human health. These environmental pollutants are rapidly being recognized as important and independent risk factors for several diseases such as asthma, chronic obstructive pulmonary disease, lung cancer, atherosclerosis, ischemic heart disease and stroke. Although the relative effects of particulate matter air pollution (aerodynamic diameter <10 microm, or PM(10)) are greater for respiratory than for cardiovascular deaths, the number of deaths attributable to PM(10) is much larger for cardiovascular than for respiratory reasons due to the higher prevalence of cardiovascular disease in the general population. This review summarizes current understanding of the mechanisms underlying the associations between PM(10) exposure and cardiovascular morbidity and mortality.