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Air and noise pollution a dangerous cardiovascular cocktail

Exercise whilst commuting, such as for pedestrians and cyclists, has an influence on inhaled particulate matter (PM) and PM lung-deposited dose, which are significantly associated with reduced heart rate variability (HRV), according to a study published recently in Science of The Total Environment.1

The authors assessed the acute relative variation of HRV with predicted PM dose in the lungs of commuters. Personal PM exposure, heart rate (HR) and HRV were monitored in 32 young, healthy cyclists, pedestrians, bus and train passengers. Inhaled and lung deposited PM doses were determined using a numerical model of the human respiratory tract which accounted for varying ventilation rates between subjects and during commutes.

Linear mixed models were used to examine air pollution dose and HRV response relationships in 122 commutes sampled. Elevated PM2.5 and PM10 inhaled and lung deposited doses were significantly (p<0.05) associated with decreased HRV indices. Percent declines in SDNN (standard deviation of normal RR intervals) relative to resting, due to an inter-quartile range increase in PM10 lung deposited dose were stronger in cyclists and pedestrians, in comparison to bus and train passengers.

A similar trend was observed in the case of PM2.5 lung deposited dose and results for rMSSD (the square root of the squared differences of successive normal RR intervals) followed similar trends to SDNN. Inhaled and lung deposited doses accounting for varying ventilation rates between modes, individuals and during commutes have been neglected in other studies relating PM to HRV, say the authors.

Screen shot 2014-04-30 at 13.16.46

Marguerite Nyhan (Trinity College Dublin, Ireland)

Whilst the exposures to PM and exposure differences between commuting groups were small, say the authors, estimating inhaled PM and PM lung deposition using the International Commission for Radiological Protection’s (ICRP) Human Respiratory Tract (HRT) model led to significant differences in results between modes. Increased modelled inhaled PM and PM lung deposition were significantly associated with declines in HRV, and this association was most pronounced in cyclists and pedestrians, they conclude.

“Results from the study show that exercising while commuting has an influence on inhaled air pollution levels,” explains Marguerite Nyhan (Trinity College Dublin, Ireland), PhD researcher and project leader. “Cyclists on the road are frequently in the direct vicinity of traffic exhaust emissions unlike non-active commuters who take the bus or train to work. Further to this, cyclists experience much higher breathing rates than other commuters and therefore inhale disproportionate amounts of toxic air pollution”.

City authorities should take steps to protect the health of cyclists and pedestrians who do not contribute to traffic congestion or air pollution emissions, through prioritising funding for cycling infrastructure and promoting environmental policies aimed at reducing air pollution exposure of active commuters, say the authors.

Noise pollution increases events too

Long-term exposure to fine PM and night-time traffic noise are both independently associated with subclinical atherosclerosis and may both contribute to the association of traffic proximity with atherosclerosis, according to another study published recently in the European Heart Journal.2

The authors used baseline data (2000–2003) from the German Heinz Nixdorf Recall Study, a population-based cohort of 4,814 randomly selected participants. They assessed residential long-term exposure to PM with a chemistry transport model, and to road traffic noise using façade levels from noise models as weighted 24 h mean noise (Lden) and night-time noise (Lnight). Thoracic aortic calcification was quantified from non-contrast enhanced electron beam computed tomography. The authors used multiple linear regression to estimate associations of environmental exposures with ln(TAC+1), adjusting for each other, individual, and neighbourhood characteristics.

In 4,238 participants (mean age 60 years, 49.9% male), PM2.5 (aerodynamic diameter ≤2.5 µmm) and Lnight are both associated with an increasing TAC-burden of 18.1% (95% CI: 6.6; 30.9%) per 2.4 µmg/m3 PM2.5 and 3.9% (95% CI 0.0; 8.0%) per 5dB(A) Lnight, respectively, in the full model and after mutual adjustment. The authors did not observe effect measure modification of the PM2.5 association by Lnight or vice versa.

References

1. Nyhan M, McNabola A, Misstear B. Comparison of particulate matter dose and acute heart rate variability response in cyclists, pedestrians, bus and train passengers. Sci Total Environ 2014;468–469:821–31. http://dx.doi.org/10.1016/j.scitotenv.2013.08.096

2. Kälsch H, Hennig F, Moebus S, et al. Are air pollution and traffic noise independently associated with atherosclerosis: the Heinz Nixdorf Recall Study. Eur Heart J 2014;35:853–60. http://dx.doi.org/10.1093/eurheartj/eht426

Published on: April 30, 2014

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