Emissions from fossil fuels, industry, and traffic have the strongest impact on cytotoxic and inflammatory responses to particulate matter. Particle size and emission sources affect the chemical composition of particles, and differences in composition cause variation in particle harmfulness. This is shown in a recent Doctoral Thesis by M.Sc. Teemu Rönkkö, who studied the relationships between particle composition and toxicological effects of inhalable urban ambient air particulate matter collected in Nanjing, China.
In this multidisciplinary study, the chemical composition of size-segregated particulate matter was determined, and the particles were used to expose human alveolar epithelial cells alone or in combination with immune cells. Based on the chemical composition, the emission sources of the particles and changes in their relative proportions were examined. The effects of season, location, time of day, and local emission restrictions on the harmfulness and composition of the particles were also assessed based on data from several collection campaigns. Particle collection was carried out in Nanjing, both in the busy city centre and in an urban background area, where the traffic density was significantly lower.
Atmospheric particulate matter is the most significant environmental risk factor for human health worldwide. The majority of deaths associated with particulate matter are caused by cardiovascular disease, but they also have a clear impact on mortality through respiratory diseases, infections, and cancer. In addition, particulate matter exposure is associated with the onset and exacerbation of several other health outcomes, such as asthma, diabetes, and neurological diseases. These effects are related to the ability of particulate matter to cause both local inflammation in the respiratory system and a systemic inflammatory condition throughout the body. In addition, particles or their components can be transported through the bloodstream to other organs.
The results obtained in the study show that the most significant sources of particulate emissions in Nanjing during the particle collection period were coal combustion and industry, traffic and liquid fossil fuels, soil-derived dust, and a combination of various unspecified combustion emissions. The effects of these emission sources were clearly different between different seasons and collection sites. The proportion of traffic emissions was significantly higher in the particles collected from the city centre, while the composition of the particles in the background area was influenced more by the soil material and the combination of different combustion emissions.
In addition to emission sources and chemical composition, toxicological responses also varied depending on collection time and location. In addition, the time of day was found to influence the toxicological properties of the particles. This is affected by both the change in emission sources depending on the time of day as well as different atmospheric conditions and processes. All emission sources were found to influence the particle-induced toxicological responses. However, the intensity of the effects varied between responses. Particle size had a strong influence on which responses showed effects and on the intensity of responses.
Overall, the study shows that the composition of particulate matter and its adverse effects vary both over time and location, following variations in emission sources as well as atmospheric conditions. By identifying the main emission sources in each area and their harmfulness, it is possible to produce health-relevant data based on toxicological evidence and use these to develop measures to reduce the health effects of air pollution.
The doctoral dissertation of Master of Science Teemu Rönkkö, entitled Urban ambient air particulate matter – chemical variation and toxicity in vitro: Toxicological effects of PM from the highly polluted city of Nanjing, China will be examined at the Faculty of Science and Forestry on the 4th of December online. The opponent in the public examination will be Professor Johan Øvrevik of Norwegian Institute of Public Health and the University of Oslo, and the custos will be Associate Professor Pasi Jalava of the University of Eastern Finland. The public examination will be held in English.
