Background Polycyclic aromatic hydrocarbons (PAHs) readily adsorb onto the surface of fine particulate matter (PM_2.5) and are representative components of organic pollutants in the atmosphere. PAHs are known for their significant carcinogenic, teratogenic, and mutagenic toxicity, and long-term exposure to PAHs has adverse effects on human health. Objective To investigate the concentration, composition, and pollution sources of 16 priority PAHs in PM_{2. 5} of Yanta District, Xi'an, and to evaluate the associated health risks. Methods PM_2.5 samples were collected from March 2023 to February 2024. The concentrations of 16 PAHs (ΣPAHs) were determined by high performance liquid chromatography (HPLC). Diagnostic ratios (DR) and positive matrix factorization (PMF) were used to identify the sources of PAHs. Pearson correlation analysis was applied to examine the relationship between PAHs concentrations and meteorological factors. Furthermore, the toxicity of individual PAHs was converted into benzo[a]-pyrene (BaP) toxicity equivalents to calculate the toxicity of total PAHs. An incremental lifetime carcinogenic risk (ILCR) model was established to evaluate the health risks of PAHs inhalation across different demographic groups. Results The average concentration of ΣPAHs in PM_2.5 of Yanta District, Xi'an followed a seasonal descending order: winter (15.71 ng·m⁻³) > spring (5.55 ng·m⁻³) > autumn (4.34 ng·m⁻³) > summer (1.47 ng·m⁻³). The relative abundances of PAHs in PM_2.5 varied significantly by ring number, 4-ring PAHs accounted for the largest proportion, followed by 5-ring, 3-ring and 6-ring PAHs, while 2-ring PAHs were the least abundant. This ring distribution pattern remained consistent across seasons. The contribution rates of different emission sources to ΣPAHs concentration exhibited seasonal variations. Source apportionment revealed that industrial and traffic emissions were major contributors in spring; traffic emissions dominated in summer and autumn; and coal, natural gas, and biomass combustion were the predominant sources in winter. Correlation analysis showed that ΣPAHs concentration was highly positively correlated with atmospheric pressure and negatively correlated with temperature, but not significantly correlated with precipitation, wind speed, solar radiation, and relative humidity. The ILCR model indicated significant seasonal differences (winter > spring > autumn > summer) in inhalation health risks between adults and children, primarily due to variations in inhalation rates and body weight. Adults faced higher health risks than children across all seasons. Conclusion PAHs pollution in PM_2.5 of Yanta District, Xi 'an is primarily driven by traffic emissions and the combustion of coal, natural gas, and biomass. PAHs concentrations are significantly influenced by meteorological factors, particularly air pressure, and temperature. Inhalation exposure poses distinct health risks to adults in winter. To effectively reduce ΣPAHs concentrations and mitigate air pollution, emission controls on winter coal combustion should be prioritized.

Objective To evaluate the implementation effect of Malaria Elimination Project supported by the Global Fund in Shaanxi Province so as to provide the evidence for the scientific implementation of Malaria Elimination Action Plan and the exami-nation and evaluation work. Methods The data of malaria prevention and control work were collected and analyzed statistically in 27 counties from 2010 to 2012 in order to evaluate the measures and effects of malaria control. Results There were 64 reported cases in the project areas from 2010 to 2012,and the average annual incidence rate was 0.15/10 million with a declining trend. The infected area sources of patients were mainly imported overseas accounting for 79.69%of the total cases. The blood completion rate of febrile patients was 94.14%,and the scope of the blood smears testing work had expanded to 88 counties(including 61 third-class counties). The training coverage rate of malaria prevention knowledge and skills had achieved to 100%. The awareness rates of malaria prevention and control were 91.68%and 89.44%in the students and local residentsrespectively. The case reporting with-in 24 h after diagnosed,epidemiological case study and outbreak disposal,laboratory testing and confirming and the other case management capabilities had also improved significantly. Conclusions The implementation of the Global Fund Malaria Project in Shaanxi Province has accelerated the process of Malaria Elimination work and improved significantly the malaria control ability in the project areas.