Nitrogen dioxide: a traffic-related pollutant with significant health impacts

Nitrogen dioxide (NO₂) is an invisible pollutant produced mainly by fuel combustion. In Bucharest, road traffic is one of the main sources of NO₂ emissions, and concentrations can vary from one area to another. Although it cannot be seen with the naked eye, the level of this pollutant in the air we breathe has a significant impact on human health, particularly in cases of prolonged exposure.

According to the World Health Organization, NO₂ can irritate the respiratory tract and aggravate existing respiratory conditions. Children are particularly vulnerable to the effects of this pollutant, which can contribute to worsening asthma symptoms and impaired lung function in those living with the condition. Research also points to harmful effects on the cardiovascular systems of children and adolescents: both short and long-term exposure to NO₂ is associated with higher blood pressure and an increased risk of hypertension. Furthermore, exposure during pregnancy, particularly in the first trimester, is associated with a higher risk of asthma and allergic rhinitis in children.

Air pollution is one of the greatest threats to public health in Europe. Across the continent, 9 out of 10 people breathe air containing pollutant concentrations above the levels recommended by the World Health Organization. According to the European Environment Agency, approximately 34,000 deaths in the European Union in 2023 were attributable to exposure to nitrogen dioxide concentrations exceeding the recommended level. In Romania, the number of deaths attributable to exposure to this pollutant was estimated at 2,218 in the same year.

“Nitrogen dioxide pollution, generated mainly by road traffic and industry, poses a direct and proven threat to our health. Global studies involving tens of millions of people confirm that exposure to NO₂ increases the risk of hospitalisation due to asthma exacerbations by more than 26%. People living in densely populated urban areas are particularly vulnerable, especially during the cold season. In addition, patients with COPD lose years of life when exposed to air with elevated nitrogen dioxide concentrations, while the risk of death among older people is significantly higher. Exposure to this pollutant is also associated with an increased incidence of lung cancer, a link demonstrated even among non-smokers. Exposure to heavy traffic pollution, particularly among children, older people and patients with chronic respiratory conditions, increases the risk of illness, leading to more years lived with disease and a lower quality of life. Every step we take to reduce air pollution means lives saved and healthier lungs for all of us,” says Associate Professor Beatrice Mahler, MD.

New European air quality standards

In Romania, nitrogen dioxide pollution has been a concern for the European Commission since 2020, when infringement proceedings were initiated against the country due to NO₂ limit values being exceeded in five cities: Bucharest, Brașov, Cluj-Napoca, Iași and Timișoara.

Against this backdrop, European Union Directive 2024/2881 on ambient air quality introduces stricter standards that must be met by 2030. For nitrogen dioxide (NO₂), the annual limit value will be reduced from 40 µg/m³ to 20 µg/m³ as of 1 January 2030. Member States have until 11 December 2026 to transpose the directive into national legislation.

“Bucharest faces a serious problem both in terms of nitrogen dioxide pollution and the insufficient monitoring of this pollutant. Without complete, accurate and representative data, authorities cannot properly assess population exposure or adopt effective measures to protect public health. Supplementary monitoring using passive sampling tubes is an accessible and effective way to identify areas with high NO₂ concentrations, particularly along heavily trafficked roads. The results of these measurements should serve as the basis for effective public policies to reduce pollution, rather than remain just statistics. Bucharest needs an improved monitoring network, as well as bold measures to reduce pollution, particularly the introduction of a Low Emission Zone across the city, which would limit emissions generated by road traffic and help provide cleaner air for residents,” says Oana Neneciu, Executive Director of the Ecopolis Centre for Sustainable Policies.

The passive sampling tubes will collect nitrogen dioxide from the air over a period of 28 days, across all six districts of Bucharest. Of the 50 locations, 22 are situated along main boulevards, 22 on secondary streets, five near schools and one in a park. The locations were carefully selected based on common criteria established for all partner countries involved in the project. The samples will subsequently be analysed at a laboratory in Switzerland. The results will be shared once the analysis is complete, showing how pollutant levels vary across different areas of the city.

NO₂ monitoring is part of the See What You Breathe campaign, a European initiative coordinated by the Polish Smog Alert association and funded by the Clean Air Fund. The campaign is taking place in nine EU countries (Bulgaria, Germany, Spain, France, Greece, Italy, Ireland, Poland and Romania) and aims to bring air pollution into the public spotlight through measurements and awareness-raising activities about pollutants and their health impacts. In Romania, the Ecopolis Centre for Sustainable Policies is implementing the initiative locally by conducting measurements and communicating the results, with the aim of raising awareness about air pollution and creating opportunities for collaboration with public authorities.

About Ecopolis Centre for Sustainable Policies

The Ecopolis Centre for Sustainable Policies is a non-governmental environmental organisation established in 2009. Its mission is to turn the principles of sustainable development into practical solutions and public policies that have a positive impact on society. The organisation focuses on environmental research, education and civic engagement, as well as monitoring and promoting public policies that contribute to environmental protection and improved quality of life. By working with experts, citizens and public authorities, Ecopolis supports the identification and implementation of practical solutions to Romania's environmental challenges. Ecopolis launched Aerlive.ro, Bucharest's leading independent air quality monitoring platform, and runs projects dedicated to reducing pollution and improving quality of life in urban areas.

About Polish Smog Alert

Polish Smog Alert is a civic movement established in Poland in 2015, bringing together dozens of organisations and citizen groups committed to improving air quality and protecting public health. The organisation works to reduce air pollution through awareness-raising and educational campaigns, advocating for effective regulations and monitoring the measures adopted by public authorities. Over the years, it has run initiatives highlighting the health impacts of air pollution, produced reports and analyses, and collaborated with scientists, doctors, local authorities and civil society organisations. The movement is an independent citizens' initiative, founded on the belief that clean air is a fundamental right for everyone.

About Clean Air Fund

Clean Air Fund is the world's largest philanthropic organisation dedicated to tackling air pollution. It supports initiatives to improve air quality, ranging from community-level projects to collaboration with governments and policymakers. The organisation funds and supports groups that promote the use of data, raise public awareness and advocate for concrete measures to reduce pollution. To date, it has funded more than 600 projects and spent over USD 154 million towards this goal. Its work focuses on regions where the need and potential for impact are greatest, including the European Union, Ghana, India, Indonesia, South Africa and the United Kingdom, and aims to bring air pollution higher up the international agenda.