Summer 2014 ozone assessment

The European Union (EU) has defined various standards to protect human health against pollution by ozone, including: information threshold, alert threshold, and long-term objective (LTO). During summer 2014, concentrations of ground-level ozone significantly exceeded these standards. However, the number of exceedances was lower than in many previous years, continuing the long-term downward trend observed over the last 25 years. The first standard, information threshold (whereby a 1 hour concentration of 180 μg/m3 triggers an obligation to inform the population on possible risks), was exceeded at approximately 9% of all stations providing data. The alert threshold (which is triggered when a 1 hour concentration exceeds 240 μg/m3 and requires countries to take immediate action) was exceeded only 4 times. The long-term objective (LTO, i.e. the maximum daily 8-hour mean concentration of ozone should not exceed 120 μg/m3) was exceeded in almost all Member States and in 81% of all reporting stations.