ABSTRACT
Background Bacteria are the most diverse and widely sourced microorganisms in the indoor air of subway stations, where pathogenic bacteria can spread through the air, leading to increased health risks. Objective To understand the status and distribution characteristics of indoor air bacterial pollution in subway stations and compartments in a city of Central South China, and to provide a scientific basis for formulating intervention measures to address indoor air bacteria pollution in subways. Methods Three subway stations and the compartments of trains parking there in a city in Central South China were selected according to passenger flow for synchronous air sampling and monitoring. Temperature, humidity, wind speed, carbon dioxide (CO2), fine particulate matter (PM2.5), and inhalable particulate matter (PM10) were measured by direct reading method. In accordance with the requirements of Examination methods for public places-Part 3: Airborne microorganisms (GB/T 18204.3-2013), air samples were collected at a flow rate of 28.3 L·min−1, and total bacterial count was estimated. Bacterial microbial species were identified with a mass spectrometer and pathogenic bacteria were distinguished from non-pathogenic bacteria according to the Catalogue of pathogenic microorganisms transmitted to human beings issued by National Health Commission. Kruskal-Wallis H test was used to compare the subway hygiene indicators in different regions and time periods, and Bonferroni test was used for pairwise comparison. Spearman correlation test was used to evaluate the correlation between CO2 concentration and total bacterial count. Results The pass rates were 100.0% for airborne total bacteria count, PM2.5, and PM10 in the subway stations and train compartments, 94.4% for temperature and wind speed, 98.6% for CO2, but 0% for humidity. The overall median (P25, P75) total bacteria count was 177 (138,262) CFU·m−3. Specifically, the total bacteria count was higher in station halls than in platforms, and higher during morning peak hours than during evening peak hours (P<0.05). A total of 874 strains and 82 species were identified by automatic microbial mass spectrometry. The results of identification were all over 9 points, and the predominant bacteria in the air were Micrococcus luteus (52.2%) and Staphylococcus hominis (9.8%). Three pathogens, Acinetobacter baumannii (0.3%), Corynebacterium striatum (0.1%), and Staphylococcus epidermidis bacilli (2.2%) were detected in 23 samples (2.6%), and the associated locations were mainly distributed in train compartments during evening rush hours. Conclusion The total bacteria count in indoor air varies by monitoring sites of subway stations and time periods, and there is a risk of opportunistic bacterial infection. Attention should be paid to cleaning and disinfection during peak passenger flow hours in all areas.
ABSTRACT
Objective:To analyze the differences in whole blood selenium (Se), zinc (Zn), copper (Cu), magnesium (Mg), calcium (Ca), and iron (Fe) levels of rural older adults among areas with different soil selenium levels, and explore the main factors associated with the six nutrient elements status, so as to provide a basis for further evaluating the health risks of people in areas with different soil selenium levels.Methods:Four administrative villages were randomly selected from the Se-deficient (soil Se content < 0.175 mg/kg), Se-sufficient (soil Se content 0.175 - < 0.400 mg/kg), Se-rich (soil Se content 0.400 - < 3.000 mg/kg) and Se-excessive (soil Se content ≥3.000 mg/kg) areas, respectively, in Enshi Tujia and Miao Autonomous Prefecture (Enshi Prefecture) of Hubei Province in 2017 - 2018. And 100 elderly people aged 60 years or older (half male and half female) were randomly selected as the survey subjects in each servey site. The basic information such as general demography and lifestyle was collected through face-to-face questionnaires. Physical examination was performed and fasting venous blood was collected in the morning. The contents of blood Se, Zn, Cu, Mg, Ca, and Fe were determined by inductively coupled plasma mass spectrometry. The main factors associated with the six nutrient elements status were analyzed.Results:A total of 416 subjects were included, including 208 males and 208 females, whose average age was (72.43 ± 5.25) years, and body mass index (BMI) was (22.67 ± 3.49) kg/m 2. There were significant differences of blood Se, Zn, Cu, Mg, Ca and Fe levels between the areas with different Se levels ( Z/F = 288.30, 3.24, 14.81, 29.14, 131.28, 3.37, P < 0.05). Compared with Se-deficient and Se-sufficient areas, blood Se level was higher in Se-rich and Se-excessive areas and blood Zn level was lower in Se-excessive area ( P < 0.05); compared with Se-sufficient area, blood Cu level was lower in Se-deficient, Se-rich and Se-excessive areas, but blood Mg and Ca levels were higher ( P < 0.05), and the blood Fe level was lower in Se-excessive area ( P < 0.05). There were significant differences in the deficiency rates of Se, Zn, Cu, Mg, Ca and Fe among the elderly in different Se level areas (χ 2 = 140.83, 15.39, 31.90, 17.49, 157.60, 30.33, P < 0.01). There were significant differences in blood Zn, Cu, Ca and Fe levels between two gender groups ( P < 0.05); the blood Zn and Fe levels of the smokers were higher than those of the non-smokers, and the blood Cu level was lower than that of the non-smokers ( P < 0.05); the blood Zn and Fe levels of the drinkers were higher than those of the non-drinkers ( P < 0.05). Conclusions:The levels of six nutrient elements in the whole blood of the elderly in areas with different soil Se levels are different. To assess the health risks of the population in areas with different soil Se levels, it is necessary to consider the levels of multiple nutrient elements at the same time.