Elsevier

The Lancet

Volume 349, Issue 9065, 31 May 1997, Pages 1582-1587
The Lancet

Articles
Increased plasma viscosity during an air pollution episode: a link to mortality?

https://doi.org/10.1016/S0140-6736(97)01211-7Get rights and content

Summary

Background

Air pollution episodes have been consistently associated with increased mortality, and most strikingly with mortality due to cardiovascular disease. One hypothesis to explain this association is that inflammation of the peripheral airways caused by pollution might increase blood coagulability. We have tested this hypothesis in a cross-sectional study by comparing measurements of plasma viscosity during a severe episode of air pollution during 1985 with those made on less polluted days.

Methods

Plasma viscosity was measured as part of the MONICA Augsburg survey during the winter of 1984–85 in 3256 randomly selected men and women aged 25–64 years. Daily mean concentrations of air pollutants and meteorological variables were measured in Augsburg as part of the automated Bavarian air-quality network. We compared measurements of plasma viscosity made in 324 people who attended for screening during the pollution episode and in 2932 people screened during the remainder of the survey period.

Findings

In January, 1985, high concentrations of sulphur dioxide (mean 200 μg/m3) and total suspended particles (mean 98 μg/m3) were recorded during a 13-day period in Augsburg. In men, the odds ratio for plasma viscosity above the 95th percentile of the distribution (1·38 mPa s) was 3·6 (95% CI 1·6–8·1) comparing measurements during the air pollution episode with non-episode measurements after adjustment for cardiovascular risk factors and meteorological variables. The corresponding odds ratio for women (95th percentile of plasma viscosity 1·37 mPa s) was 2·3 (1·0–5·3). High concentrations of carbon monoxide were also associated with increased plasma viscosity in women.

Interpretation

During the 1985 air pollution episode, an increased risk of extreme values of plasma viscosity was observed in both men and women. Altered blood rheology due to inflammatory processes in the lung that induce an acute-phase reaction might therefore be part of the pathological mechanisms linking air pollution to mortality.

Introduction

Increased mortality in the general population has been observed at times when concentrations of ambient air pollutants are raised.1, 2, 3 The excess deaths were attributable to cardiovascular as well as respiratory causes. The involvement of the cardiovascular system was strongly supported by analyses showing an association between concentrations of particulate matter and hospital admissions for ischaemic heart disease and congestive heart failure.4, 5 In addition, evidence from seven large cities in the USA showed that high concentrations of carbon monoxide were associated with hospital admission for congestive heart failure.6 Although the link between air pollutants and exacerbation of pre-existing respiratory impairment has been well established and seems biologically plausible,7 little is known about the biological mechanisms linking ambient air pollution with exacerbation of cardiovascular diseases. Seaton and colleagues8 postulated that inflammation in the peripheral airways caused by air pollutants might increase the coagulability of the blood, and thereby lead to an increased number of deaths.

Our aim was to test this hypothesis in the data collected in the first MONICA survey in Augsburg, Germany, between October, 1984, and June, 1985. We investigated whether plasma viscosity (which is determined by fibrinogen and other large asymmetrical plasma proteins such as immunoglobulin M and α2-macroglobulin) was higher on days with increased air pollution than on less polluted days in a random sample of the population. In January, 1985, there was an air pollution episode all over Europe, which led to high concentrations of sulphur dioxide and total suspended particles (TSP) throughout western and central Europe.9 Increased mortality, hospital admissions, and ambulance requests were reported during this episode compared with a control period in the Ruhr area of Germany.10 These effects were more pronounced for cardiovascular diseases (19% increase in hospital admissions) than for respiratory diseases (7% increase in hospital admissions). The analyses presented here focus on the question: was plasma viscosity higher than normal in a random sample of the population in Augsburg during the days of the 1985 air pollution episode?

Section snippets

MONICA survey Augsburg

The first MONICA survey in Augsburg (southern Germany) was carried out in 1984–85. 4022 (79%) of the 5069 randomly selected eligible individuals, aged 25–64 years, took part.11 This report is based on a subsample of 3256 men and women in whom plasma viscosity was measured,12 whose blood samples were obtained on the day of the interview, and who had no acute infections. There were no differences in conventional cardiovascular risk variables between the subgroup and the total sample.11, 12 All

Results

Between Jan 4 and Jan 7, 1985, there was a steep increase in daily mean sulphur dioxide concentrations from 43 μg/m3 to 181 μg/m3. Until Jan 19, sulphur dioxide concentrations above 150 μg/m3 were recorded (figure 2). Table 1 gives the average concentrations of the air pollutants restricted to the days of the MONICA survey. During the air pollution episode in Augsburg, average sulphur dioxide concentrations of 200 μg/m3 were recorded, whereas on all other days of the MONICA survey the

Discussion

During the 1985 air pollution episode, plasma viscosity was high in a random sample of the population of Augsburg. The raised values persisted after adjustment for known cardiovascular risk factors and for meteorological features associated with high plasma viscosity. In addition, there appeared to be an independent association between carbon monoxide and high plasma viscosity in women.

The design of the study was cross-sectional, so the variability in plasma viscosity was determined mainly by

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