A structured review of panel studies used to investigate associations between ambient air pollution and heart rate variability

Acute Effects of Air Pollution and Noise from Road Traffic in a Panel of Young Healthy Adults

Panel studies are an efficient means to assess short-term effects of air pollution and other time-varying environmental exposures. Repeated examinations of volunteers allow for an in-depth analysis of physiological responses supporting the biological interpretation of environmental impacts. Twenty-four healthy students walked for 1 h at a minimum of four separate occasions under each of the following four settings: along a busy road, along a busy road wearing ear plugs, in a park, and in a park but exposed to traffic noise (65 dB) through headphones. Particle mass (PM_2.5, PM₁), particle number, and noise levels were measured throughout each walk. Lung function and exhaled nitrogen oxide (NO) were measured before, immediately after, 1 h after, and approximately 24 h after each walk. Blood pressure and heart rate variability were measured every 15 min during each walk. Recorded air pollution levels were found to correlate with reduced lung function. The effects were clearly significant for end-expiratory flows and remained visible up to 24 h after exposure. While immediate increases in airway resistance could be interpreted as protective (muscular) responses to particulate air pollution, the persisting effects indicate an induced inflammatory reaction. Noise levels reduced systolic blood pressure and heart rate variability. Maybe due to the small sample size, no effects were visible per specific setting (road vs. park).

Effects of the exposure to ultrafine particles on heart rate in a healthy population

The correlation amongst exposure to ultrafine particle concentrations and heart rate in a large healthy population was investigated. The study was conducted by continuously monitoring for seven days fifty volunteers in terms of exposure to particle concentrations, heart rate and physical activity performed through portable monitors. Data were analyzed adopting a linear mixed model able to manage the obtained repeated measures and to recognize a general trend resulting from the subject-specific patterns. Results show that the short-term exposure to ultrafine particle concentrations is positively associated with the heart rate for the different physical activities of the subject investigated (laying down, sitting, standing positions). In particular, a logarithmic correlation was recognized with a sharper increase of about 4-6 bpm for a variation of the particle number concentration of 2 × 10⁴ part/cm³ and a slighter effect for further increases of about 0.1-0.2 × 10^-4 bpm/(part/cm). CAPSULE: A positive correlation can be associated between the exposure to ultrafine particles and the heart rate.

Effectiveness of commercial face masks to reduce personal PM exposure

Cycling and walking are promoted as means of transportation which can contribute to the reduction of traffic pollution in urban areas. However, cyclists and pedestrians may be exposed to high concentrations of air pollutants due to their proximity to vehicle emissions. Commercial face mask respirators are widely used, in both developing and developed countries, as an individual protective measure against particle pollution. However scientific data on the efficacy of face mask respirators in reducing airborne particle exposure is limited. In this study, a custom experimental set-up was developed in order to measure the effectiveness of nine different respirators under real environmental conditions in terms of particle mass concentration below 2.5 μm (PM_2.5), particle number concentration (PNC), Lung Deposited Surface Area (LDSA) and Black Carbon concentration (BC). Face mask performances were assessed in a typical traffic affected urban background environment in the city of Barcelona under three different simulated breathing rates to investigate the influence of flow rate. Results showed a median face mask effectiveness for PM_2.5 equal to 48% in a range of 14-96%, 19% in a range of 6%-61% for BC concentration, 19% in a range of 4%-63% for PNC and 22% in a range of 5%-65% for LDSA. For each pollutant under investigation, the best performance was found always with the same mask (N7) although it is not the most expensive (in a range of price of 1 to 44, its cost was 20 euros), which has a filter on the entire surface except for the 2 exhalation valves where air cannot enter but just exit and shows a good fit on the dummy head.

Short-term effects of particulate matter in metro cabin on heart rate variability in young healthy adults: Impacts of particle size and source

BACKGROUND

Metro system has become popular in urban areas. However, short-term effects of size-fractionated particulate matter (PM) on cardiac autonomic function in metro system remain unexplored.

OBJECTIVES

To explore the contribution of ambient PM to in-cabin PM and investigate the short-term effects of exposure to size-fractionated PM and black carbon (BC) in metro system on cardiac autonomic function in young healthy adults.

METHODS

Thirty nine young healthy adults were asked to travel in metro system during 9:00-13:00 on a weekends between March and May 2017. We performed continuous ambulatory electrocardiogram monitoring for each of them, and measured real-time size-fractionated PM, BC, nitrogen dioxide, nitric oxide, carbon dioxide, ozone, noise, temperature and relative humidity in metro cabin. We also collected the data of ambient PM_2.5 (aerodynamic diameter < 2.5 µm) concentrations in Beijing. Linear regression model was used to estimate the infiltration factor of ambient PM_2.5 to assess the relationship between metro cabin PM and ambient PM. Mixed-effects model was used to estimate the associations between changes in HRV parameters and PM_0.5 (aerodynamic diameter < 0.5 µm), PM_0.5-2.5 (aerodynamic diameter between 0.5 µm and 2.5 µm), PM_2.5-10 (aerodynamic diameter between 2.5 µm and 10 µm), and BC, respectively.

RESULTS

We found that size-fractionated PM in metro systems were significantly associated with HRV parameters. Per IQR (interquartile range) increase in PM_0.5 (1.6*10⁷/m³) in 1-h moving average concentration was associated with a 13.96% (95% CI: - 18.99%, - 8.61%) decrease in SDNN (standard deviation of normal-to-normal intervals). Similar inverse associations were found between size-fractionated PM exposure and LF (low frequency power), HF (high frequency power), respectively, and smaller particles had greater effects on HRV parameters at shorter lag time. Sex of participants modified the adverse associations between size-fractionated PM and HRV. An IQR of 1-h PM_0.5 increasing was associated with a decrease of 6.05% (95% CI: - 22.87%, - 14.44%) in males and a 34.87% (95% CI: - 49.59%, - 15.85%) in females in LF (P for interaction = 0.026). The infiltration factor of ambient PM_2.5 was 0.39 (95% CI: 0.33, 0.45). It is estimated that PM_2.5 originated from ambient air may account for 20.2% of the PM measured in metro cabin. Per IQR increase in BC (5.5 μg/m³) in 5-min, 1-h, and 2-h moving averages, a primary tracer for ambient PM from combustion source, was associated with decreases of 0.84% (95% CI: - 1.20%, - 0.47%), 2.22% (95% CI: - 3.20%, - 1.22%), and 4.44% (95% CI: - 6.28%, - 2.56%) in SDNN, respectively.

CONCLUSIONS

Short-term exposure to PM may disturb metro commuter's cardiac autonomic function, and the potential effects depend on the size of PM and the sex of commuters. Ambient PM from combustion source may have adverse effects on the cardiac autonomic function of passengers in cabin.

Association of size-fractionated indoor particulate matter and black carbon with heart rate variability in healthy elderly women in Beijing

Associations between size-fractionated indoor particulate matter (PM) and black carbon (BC) and heart rate variability (HRV) and heart rate (HR) in elderly women remain unclear. Twenty-nine healthy elderly women were measured for 24-hour HRV/HR indices. Real-time size-fractionated indoor PM and BC were monitored on the same day and on the preceding day. Mixed-effects models were applied to investigate the associations between pollutants and HRV/HR indices. Increases in size-fractionated indoor PM were significantly associated with declines in power in the high-frequency band (HF), power in the low-frequency band (LF), and standard deviation of all NN intervals (SDNN). The largest decline in HF was 19% at 5-minute moving average for an interquartile range (IQR) increase (24 μg/m³ ) in PM_0.5 . The results showed that smaller particles could lead to greater reductions in HRV indices. The reported associations were modified by body mass index (BMI): Declines in HF at 5-minute average for an IQR increase in PM_0.5 were 34.5% and 1.0% for overweight (BMI ≥25 kg/m² ) and normal-weight (BMI <25 kg/m² ) participants, respectively. Moreover, negative associations between BC and HRV indices were found to be significant in overweight participants. Increases in size-fractionated indoor PM and BC were associated with compromised cardiac autonomic function in healthy elderly women, especially overweight ones.

Cardio-Respiratory Effects of Air Pollution in a Panel Study of Outdoor Physical Activity and Health in Rural Older Adults

Objective:

To examine cardio-respiratory effects of air pollution in rural older adults exercising outdoors.

Methods:

Adults 55 and over completed measurements of blood pressure, peak expiratory flow and oximetry daily, and of heart rate variability, endothelial function, spirometry, fraction of exhaled nitric oxide and urinary oxidative stress markers weekly, before and after outdoor exercise, for 10 weeks. Data were analyzed using linear mixed effect models.

Results:

Pooled estimates combining 2013 (n = 36 participants) and 2014 (n = 41) indicated that an interquartile increase in the air quality health index (AQHI) was associated with a significant (P < 0.05) increase in heart rate (2.1%) and significant decreases in high frequency power (−19.1%), root mean square of successive differences (−9.5%), and reactive hyperemia index (−6.5%).

Conclusions:

We observed acute subclinical adverse effects of air pollution in rural older adults exercising outdoors.

Effects of Diesel Exhaust on Cardiovascular Function and Oxidative Stress

SIGNIFICANCE

Air pollution is a major global health concern with particulate matter (PM) being especially associated with increases in cardiovascular morbidity and mortality. Diesel exhaust emissions are a particularly rich source of the smallest sizes of PM ("fine" and "ultrafine") in urban environments, and it is these particles that are believed to be the most detrimental to cardiovascular health. Recent Advances: Controlled exposure studies to diesel exhaust in animals and man demonstrate alterations in blood pressure, heart rate, vascular tone, endothelial function, myocardial perfusion, thrombosis, atherogenesis, and plaque stability. Oxidative stress has emerged as a highly plausible pathobiological mechanism by which inhalation of diesel exhaust PM leads to multiple facets of cardiovascular dysfunction.

CRITICAL ISSUES

Diesel exhaust inhalation promotes oxidative stress in several biological compartments that can be directly associated with adverse cardiovascular effects.

FUTURE DIRECTIONS

Further studies with more sensitive and specific in vivo human markers of oxidative stress are required to determine if targeting oxidative stress pathways involved in the actions of diesel exhaust PM could be of therapeutic value. Antioxid. Redox Signal. 28, 819-836.

The influence of lifestyle on airborne particle surface area doses received by different Western populations

In the present study, the daily dose in terms of particle surface area received by citizens living in five cities in Western countries, characterized by different lifestyle, culture, climate and built-up environment, was evaluated and compared. For this purpose, the exposure to sub-micron particle concentration levels of the population living in Barcelona (Spain), Cassino (Italy), Guilford (United Kingdom), Lund (Sweden), and Brisbane (Australia) was measured through a direct exposure assessment approach. In particular, measurements of the exposure at a personal scale were performed by volunteers (15 per each population) that used a personal particle counter for different days in order to obtain exposure data in microenvironments/activities they resided/performed. Non-smoking volunteers performing non-industrial jobs were considered in the study. Particle concentration data allowed obtaining the exposure of the population living in each city. Such data were combined in a Monte Carlo method with the time activity pattern data characteristics of each population and inhalation rate to obtain the most probable daily dose in term of particle surface area as a function of the population gender, age, and nationality. The highest daily dose was estimated for citizens living in Cassino and Guilford (>1000 mm²), whereas the lowest value was recognized for Lund citizens (around 100 mm²). Indoor air quality, and in particular cooking and eating activities, was recognized as the main influencing factor in terms of exposure (and thus dose) of the population: then confirming that lifestyle (e.g. time spent in cooking activities) strongly affect the daily dose of the population. On the contrary, a minor or negligible contribution of the outdoor microenvironments was documented.

Cardiovascular health effects following exposure of human volunteers during fire extinction exercises

BACKGROUND

Firefighters have increased risk of cardiovascular disease and of sudden death from coronary heart disease on duty while suppressing fires. This study investigated the effect of firefighting activities, using appropriate personal protective equipment (PPE), on biomarkers of cardiovascular effects in young conscripts training to become firefighters.

METHODS

Healthy conscripts (n = 43) who participated in a rescue educational course for firefighting were enrolled in the study. The exposure period consisted of a three-day training course where the conscripts participated in various firefighting exercises in a constructed firehouse and flashover container. The subjects were instructed to extinguish fires of either wood or wood with electrical cords and mattresses. The exposure to particulate matter (PM) was assessed at various locations and personal exposure was assessed by portable PM samplers and urinary excretion of 1-hydroxypyrene. Cardiovascular measurements included microvascular function and heart rate variability (HRV).

RESULTS

The subjects were primarily exposed to PM in bystander positions, whereas self-contained breathing apparatus effectively abolished pulmonary exposure. Firefighting training was associated with elevated urinary excretion of 1-hydroxypyrene (105%, 95% CI: 52; 157%), increased body temperature, decreased microvascular function (-18%, 95% CI: -26; -9%) and altered HRV. There was no difference in cardiovascular measurements for the two types of fires.

CONCLUSION

Observations from this fire extinction training show that PM exposure mainly occurs in situations where firefighters removed the self-contained breathing apparatus. Altered cardiovascular disease endpoints after the firefighting exercise period were most likely due to complex effects from PM exposure, physical exhaustion and increased core body temperature.

Oxidative Stress and Cardiovascular Risk: Obesity, Diabetes, Smoking, and Pollution: Part 3 of a 3-Part Series

Oxidative stress occurs whenever the release of reactive oxygen species (ROS) exceeds endogenous antioxidant capacity. In this paper, we review the specific role of several cardiovascular risk factors in promoting oxidative stress: diabetes, obesity, smoking, and excessive pollution. Specifically, the risk of developing heart failure is higher in patients with diabetes or obesity, even with optimal medical treatment, and the increased release of ROS from cardiac mitochondria and other sources likely contributes to the development of cardiac dysfunction in this setting. Here, we explore the role of different ROS sources arising in obesity and diabetes, and the effect of excessive ROS production on the development of cardiac lipotoxicity. In parallel, contaminants in the air that we breathe pose a significant threat to human health. This paper provides an overview of cigarette smoke and urban air pollution, considering how their composition and biological effects have detrimental effects on cardiovascular health.

Comparison of spatiotemporal prediction models of daily exposure of individuals to ambient nitrogen dioxide and ozone in Montreal, Canada

BACKGROUND

In previous studies investigating the short-term health effects of ambient air pollution the exposure metric that is often used is the daily average across monitors, thus assuming that all individuals have the same daily exposure. Studies that incorporate space-time exposures of individuals are essential to further our understanding of the short-term health effects of ambient air pollution.

OBJECTIVES

As part of a longitudinal cohort study of the acute effects of air pollution that incorporated subject-specific information and medical histories of subjects throughout the follow-up, the purpose of this study was to develop and compare different prediction models using data from fixed-site monitors and other monitoring campaigns to estimate daily, spatially-resolved concentrations of ozone (O₃) and nitrogen dioxide (NO₂) of participants' residences in Montreal, 1991-2002.

METHODS

We used the following methods to predict spatially-resolved daily concentrations of O₃ and NO₂ for each geographic region in Montreal (defined by three-character postal code areas): (1) assigning concentrations from the nearest monitor; (2) spatial interpolation using inverse-distance weighting; (3) back-extrapolation from a land-use regression model from a dense monitoring survey, and; (4) a combination of a land-use and Bayesian maximum entropy model. We used a variety of indices of agreement to compare estimates of exposure assigned from the different methods, notably scatterplots of pairwise predictions, distribution of differences and computation of the absolute agreement intraclass correlation (ICC). For each pairwise prediction, we also produced maps of the ICCs by these regions indicating the spatial variability in the degree of agreement.

RESULTS

We found some substantial differences in agreement across pairs of methods in daily mean predicted concentrations of O₃ and NO₂. On a given day and postal code area the difference in the concentration assigned could be as high as 131ppb for O₃ and 108ppb for NO₂. For both pollutants, better agreement was found between predictions from the nearest monitor and the inverse-distance weighting interpolation methods, with ICCs of 0.89 (95% confidence interval (CI): 0.89, 0.89) for O₃ and 0.81 (95%CI: 0.80, 0.81) for NO₂, respectively. For this pair of methods the maximum difference on a given day and postal code area was 36ppb for O₃ and 74ppb for NO₂. The back-extrapolation method showed a higher degree of disagreement with the nearest monitor approach, inverse-distance weighting interpolation, and the Bayesian maximum entropy model, which were strongly constrained by the sparse monitoring network. The maps showed that the patterns of agreement differed across the postal code areas and the variability depended on the pair of methods compared and the pollutants. For O₃, but not NO₂, postal areas showing greater disagreement were mostly located near the city centre and along highways, especially in maps involving the back-extrapolation method.

CONCLUSIONS

In view of the substantial differences in daily concentrations of O₃ and NO₂ predicted by the different methods, we suggest that analyses of the health effects from air pollution should make use of multiple exposure assessment methods. Although we cannot make any recommendations as to which is the most valid method, models that make use of higher spatially resolved data, such as from dense exposure surveys or from high spatial resolution satellite data, likely provide the most valid estimates.