Particulate matter (PM) pollution has a significant effect on death rates in French cities, a new study shows. The research confirms the short-term impacts of PM10, but also sheds new light on the effects of smaller particulates: PM2.5 and PM10-2.5. Its results could help inform public health advice, the authors propose.
Many studies have linked PM with negative health impacts. However, most studies looking at pollution across multiple cities in Europe have, to date, focused on PM10—particles up to ten micrometres in size. Fewer studies of this kind have considered PM2.5 (particles of less than 2.5 micrometres) or PM10-2.5.
This study argues that more research is needed to better understand PM2.5 and PM10-2.5’s health impacts across Europe. Such research could also help inform a daily limit value for PM2.5 in Europe, as recommended by the WHO. At present, a daily value only exists for PM10 in Europe: in this case, 50 micrograms per cubic metre of air (μg/m3) cannot be exceeded more than 35 times a year, under the EU’s Air Quality Directive1.
To help fill this research gap, this study analysed the short-term associations between PM (PM10, PM2.5 and PM10-2.5) pollution and mortality across nine French cities. These cities represented a range of climates, geographies, urbanisation levels and pollution sources.
The researchers looked at changes in daily death rates following a rise of 10 μg/m3 for each of the three sizes of PM. Data for pollution and mortality in these cities were assessed for the period 2000-2006. A total of 548 474 people died in the nine cities during this period.
The results suggested a significant link between increases in PM and deaths from all non-accidental causes: an increase of 0.8% in mortality in response to a 10 μg/m3 rise in PM10. For PM2.5, death rates rose by 0.7% following a 10 μg/m3 rise.
PM10-2.5 had a particularly strong effect on cardiovascular and cardiac mortality, and particularly for the elderly. It was associated with a 3.9% rise in deaths from cardiovascular disease and 4.4% rise in deaths from cardiac problems for people older than 74 years old.
The researchers also found seasonal patterns in the data. For all PMs, the greatest mortality risks were in the summer. For instance, each 10 μg/m3 rise in PM2.5 in the summer was linked with an increase of 5.1% in cardiovascular-related deaths. This is more than seven times higher than the impact of a 10 μg/m3 rise averaged across the whole year.
During summer, the cardiovascular mortality also increased by 7.2% for each 10 μg/m3 rise in PM10-2.5. The researchers also observed a 5.7% increase in ischaemic (obstructed blood flow) deaths in the summer in association with PM10.
Similarly, death rates increased in response to PM on warm days (defined as days when the temperature equalled or exceeded the 97.5th percentile of the average temperature range), compared with cooler days. However, the effects varied by the type of PM. For instance, PM2.5 was more strongly linked with cerebrovascular causes of death (e.g. stroke) than PM10 in response to warm days.
The study concludes that the results confirm PM10’s impacts on mortality, as shown in earlier studies, and provide new information on the impacts of PM2.5 and PM10-2.5. This new evidence could support public health messages in relation to high pollution days. Presently in France, the public are alerted when PM10 exceeds 50 μg/m3. These results may support the case for alerts when PM2.5 and PM10-2.5 are also high. In line with WHO recommendations, the study argues that regulation values for these pollutants should be set.