Antibiotics in ambient fine particulate matter from two metropolitan cities in China: Characterization, source apportionment, and health risk assessment.

Excessive production and widespread application of antibiotic has led to residues in environmental matrices worldwide. There is limited knowledge of the concentrations of antibiotics bound to ambient fine particulate matter (PM2.5) and their health risks. We investigated the occurrence, sources, environmental driving factors, and health risks of antibiotics in PM2.5 samples collected from Beijing and Shijiazhuang, China, during periods of high air pollution. Using ultra-high performance liquid chromatography-tandem mass spectrometry, 25 antibiotics were detected in PM2.5 at concentrations ranging from undetectable to 774.7 pg/m3. These compounds were predominantly tetracyclines and macrolides. The positive matrix factorization model was used to pinpoint the main sources of these antibiotics as pharmaceutical and medical waste, sewage treatment plants, and livestock emissions, with contributions of 39.1 %, 31.7 %, and 29.2 % respectively, to the total concentrations. Crucial environmental driving factors were determined using a linear mixed-effects model and random forest model. Most antibiotics showed a positive correlation with gaseous pollutants and a negative correlation with meteorological factors. PM2.5, PM10, and CO had the highest influence. The estimated daily intake and hazard quotient (HQ) were calculated to assess the human inhalation exposure risks for these antibiotics, and children aged 0-6 years had the highest intake of 102.8 pg/kg/day. Although the calculated health risk of antibiotic inhalation was low (HQ < 1), considering that exposure to antibiotics via inhalation occurs over long periods and these compounds accumulate, further attention should be given to health risks associated with this exposure. Our results provide valuable insight for environmental planning and policymaking concerning antibiotic pollution and its associated health risks.