Daily exposure to ozone pollution associated to increased risk of death

11.02.2020 – An international study confirms the link between daily exposure to ground level ozone and mortality risk worldwide. This new study published in The BMJ represents the largest investigation of its kind, assessing almost 50 million deaths from over 400 cities in 20 countries across the world, in which Switzerland is included.

Authors found that, on average, a 10 microgr/m3 increase in ozone is associated with an increase in mortality of 0.18%. This equates to 6,262 extra deaths each year (or 0.2% of total mortality) in the 406 cities that would have been avoided if countries had implemented stricter air quality standards in line with the WHO guideline. What’s more, smaller but still substantial mortality impacts were found even for ozone concentrations below WHO guideline levels, supporting the WHO initiative of encouraging countries to revisit current air quality guidelines and enforcing stronger emission restrictions to meet these recommendations. «Ozone-related mortality is largely preventable, and here we confirm that clean air policies with the implementation of strict air quality standards are key public health tools to reduce the health burden associated to air pollution» said Ana M Vicedo-Cabrera, head of the Research Group of Climate Change and Health at ISPM, and first author of the publication. The study included data on 8 Swiss cities (Basel, Bern, Zurich, Lugano, Luzern, St Gallen, Geneva, Lausanne) between 1995 and 2013, and found 0.23% excess mortality attributed to ozone levels above WHO guideline.

The study was performed within the Multi-Country Multi-City (MCC) Collaborative Research Network (http://mccstudy.lshtm.ac.uk), an international collaboration studying the association between environmental stressors, climate change and health. Among more than 60 institutions, the University of Bern is currently part of the MCC with Ana M. Vicedo-Cabrera (ISPM) one of the members of its scientific committee and co-representative of the Swiss data.

Ground level ozone is a highly reactive gas commonly found in urban and suburban environments, formed when pollutants, mostly related to traffic and industrial sources, react in sunlight. «More than 6 thousand deaths each year is only the tip of the iceberg» says Dr Vicedo-Cabrera. Previous studies showed that ozone can be associated to increased cardiovascular and respiratory morbidity, such embolism, ischemic heart disease and asthma exacerbations. As in the case of the other air pollutants, patients whose health status is already compromised are particularly vulnerable.

Authors conclude that these findings have important implications for the design of future public health actions, in particular to reduce the impacts of global warming, as ozone is expected to increase according to current climate change projections.