High humidity and NO2 co-exposure exacerbates allergic asthma by increasing oxidative stress, inflammatory and TRP protein expressions in lung tissue.

Allergic asthma is a chronic inflammatory airway disease with a high mortality rate and a rapidly increasing prevalence in recent decades that is closely linked to environmental change. Previous research found that high humidity (HH) and the traffic-related air pollutant NO2 both aggregated allergic asthma. Their combined effect and mechanisms on asthma exacerbation, however, are unknown. Our study aims to toxicologically clarify the role of HH (90%) and NO2 (5 ppm) on allergic asthma. Ninety male Balb/c mice were randomly assigned to one of six groups (n = 15 in each): saline control, ovalbumin (OVA)-sensitized, OVA + HH, OVA + NO2, OVA + HH + NO2, and OVA + HH + NO2+Capsazepine (CZP). After 38 days of treatment, the airway function, pathological changes in lung tissue, blood inflammatory cells, and oxidative stress and inflammatory biomarkers were comprehensively assessed. Co-exposure to HH and NO2 exacerbated histopathological changes and airway hyperresponsiveness, increased IgE, oxidative stress markers malonaldehyde (MDA) and allergic asthma-related inflammation markers (IL-1ß, TNF-α and IL-17), and upregulated the expressions of the transient receptor potential (TRP) ion channels (TRPA1, TRPV1 and TRPV4). Our findings show that co-exposure to HH and NO2 disrupted the Th1/Th2 immune balance, promoting allergic airway inflammation and asthma susceptibility, and increasing TRPV1 expression, whereas CZP reduced TRPV1 expression and alleviated allergic asthma symptoms. Thus, therapeutic treatments that target the TRPV1 ion channel have the potential to effectively manage allergic asthma.

Temporal characteristics and health effects related to NO2, O3, and SO2 in an urban area of Iran.

This study reports on temporal variations of NO2, O3, and SO2 pollutants and their related health effects in urban air of Khorramabad, Iran using AirQ 2.2.3 software. Based on data between 2015 and 2021, hourly NO2, O3, and SO2 concentrations increase starting at 6:00 a.m. local time until 9:00 p.m., 3:00 p.m., and 7:00 p.m. local time, respectively, before gradually decreasing. The highest monthly NO2, O3, and SO2 concentrations are observed in October, August, and September, respectively. Annual median NO2, O3, and SO2 concentrations range between 17 ppb and 38.8 ppb, 17.5 ppb-36.6 ppb, and ∼14 ppb-30.8 ppb, respectively. Two to 93 days and 17-156 days between 2015 and 2021 exhibit daily concentrations of NO2 and SO2 ≤ WHO AQGs, respectively, while 187-294 days have 8-h maximum O3 concentrations ≤ WHO AQGs. The mean excess mortality ascribed to respiratory mortality, cardiovascular mortality, hospital admissions for COPD, and acute myocardial infraction are 121, 603, 39, and 145 during 2015-2021, respectively. O3 is found to exert more significant health effects compared to SO2 and NO2, resulting in higher cardiovascular mortality. The gradual increase in NO2 and possibly O3 over the study period is suspected to be due to economic sanctions, while SO2 decreased due to regulatory activity. Sustainable control strategies such as improving fuel quality, promoting public transportation and vehicle retirement, applying subsidies for purchase of electric vehicles, and application of European emission standards on automobiles can help decrease target pollutant levels in ambient air of cities in developing countries.

Modeling, optimization and efficient use of MMT K10 nanoclay for Pb (II) removal using RSM, ANN and GA.

Regarding the long-term toxic effects of Pb (II) ions on human health and its bioaccumulation property, taking measures for its reduction in the environment is necessary. The MMT-K10 (montmorillonite-k10) nanoclay was characterized by XRD, XRF, BET, FESEM, and FTIR. The effects of pH, initial concentrations, reaction time, and adsorbent dosage were studied. The experimental design study was carried out with RSM-BBD method. Results prediction and optimization were investigated with RSM and artificial neural network (ANN)-genetic algorithm (GA) respectively. The RSM results showed that the experimental data followed the quadratic model with the highest regression coefficient value (R2 = 0.9903) and insignificant lack of fit (0.2426) showing the validity of the Quadratic model. The optimal adsorption conditions were obtained at pH 5.44, adsorbent = 0.98 g/l, concentration of Pb (II) ions = 25 mg/L, and reaction time = 68 min. Similar optimization results were observed by RSM and artificial neural network-genetic algorithm methods. The experimental data revealed that the process followed the Langmuir isotherm and the maximum adsorption capacity was 40.86 mg/g. Besides, the kinetic data indicated that the results fitted with the pseudo-second-order model. Hence, the MMT-K10 nanoclay can be a suitable adsorbent due to having a natural source, simple and inexpensive preparation, and high adsorption capacity.

Characteristics and assessing biological risks of airborne bacteria in waste sorting plant.

Examining the concentration and types of airborne bacteria in waste paper and cardboard sorting plants (WPCSP) is an urgent matter to inform policy makers about the health impacts on exposed workers. Herein, we collected 20 samples at 9 points of a WPCSP every 6 winter days, and found that the most abundant airborne bacteria were positively and negatively correlated to relative humidity and temperature, respectively. The most abundant airborne bacteria (in units of CFU m-3) were: Staphylococcus sp. (72.4) > Micrococcus sp. (52.2) > Bacillus sp. (30.3) > Enterococcus sp. (24.0) > Serratia marcescens (20.1) > E. coli (19.1) > Pseudomonas sp. (16.0) > Nocardia sp. (1.9). The lifetime average daily dose (LADD) for the inhalation and dermal routes for the intake of airborne bacteria ranged from 3.7 × 10-3 ≤ LADDInhalation ≤ 2.07 × 101 CFU (kg d)-1 and 4.75 × 10-6 ≤ LADDDermal ≤ 1.64 × 10-5 CFU (kg d)-1, respectively. Based on a sensitivity analysis (SA), the concentration of airborne bacteria (C) and the exposure duration (ED) had the most effect on the LADDInhalation and LADDDermal for all sampling locations. Although the Hazard Quotient of airborne bacteria was HQ < 1, an acceptable level, the indoor/outdoor ratio (1.5 ≤ I/O ≤ 6.6) of airborne bacteria typically exceeded the threshold value (I/O > 2), indicating worker's exposure to an infected environment. Therefore, in the absence of sufficient natural ventilation the indoor ambient conditions of the WPCSP studied should be controlled by supplying mechanical ventilation.

Assessment of fungal bioaerosols and particulate matter characteristics in indoor and outdoor air of veterinary clinics.

Veterinary staff are frequently exposed to various occupational hazards. The present study was aimed to investigate the air characteristics of veterinary clinics in terms of fungal bioaerosols and particulate matters. Air samples were taken every six days from the operating room, examination room and outdoor air of three veterinary clinics in Shiraz, southwest Iran. The concentrations of fungal bio-aerosols ranged from 8.05 CFU/m 3 in the outdoor air of clinic B to 47.21 CFU/m 3 in the operating room of clinic A. The predominant fungal genera identified in the studied clinics were Penicillium and Aspergillus niger, respectively. The concentrations of PM2.5 ranged from 41.88 µg/m 3 in the operating room of clinic C to 60.31 µg/m 3 in the outdoor air of the same clinic. The corresponding values for PM10 ranged from 114.40 µg/m 3 in the operating room of clinic C to 256.70 µg/m 3 in the outdoor air of the same clinic. The results of this study showed a positive correlation between the concentration of fungal bioaerosols and relative humidity (p < 0.05; r = 0.622). Besides, a negative correlation was found between the concentration of fungal bioaerosols and temperature (p < 0.05; r = 0.369). To better assess the individual exposure of veterinarians and staff in veterinary clinics, tests including nasopharyngeal sampling are recommended.

The presence of SARS-CoV-2 in raw and treated wastewater in 3 cities of Iran: Tehran, Qom and Anzali during coronavirus disease 2019 (COVID-19) outbreak.

This study aimed to identifying the presence of SARS-CoV-2 RNA in raw and treated wastewater during the COVID-19 outbreak in Tehran, Qom and Anzali cities (Iran). From three wastewater treatment plants (WWTPs), 28 treated and untreated wastewater composite samples were collected from April 4 to May 2, 2020. In this study, polyethylene glycol 6000 (PEG 6000) was used through one-step real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) for identification of RNA viruses. SARS-CoV-2 RNA was elicited from wastewater composite samples in all inlet samples taken from the three above mentioned cities. The results of outlet samples were as follows: 1) Results from Qom and East Anzali outlets showed no trace of SARS-CoV-2 RNA despite the difference in treatment disinfection method used (chlorine vs. ultraviolet (UV) disinfection). 2. In Tehran, SARS-CoV-2 RNA was not detected in any of the outlet samples taken from the modules disinfected by UV. Out of the four samples taken from the modules disinfected by chlorine, two were positive for the SARS-CoV-2 RNA which could have been caused by deficiencies in operation and maintenance. It can be concluded that meeting the standards of operation and maintenance (O&M) in WWTPs can considerably ensure that wastewater does not act as one of the roots of transmission for the disease.

Gamma radiation in the mineral hot springs of Ardabil, Iran: Assessment of Environmental Dose Rate and health risk for swimmers.

The main aim of this study was to evaluate gamma radiation level in the mineral hot springs of Ardabil province in Iran. In addition, the cancer risk of gamma radiation was assessed for swimmers. Natural gamma radiation was measured using Ion Chamber Survey Meter 451B in 22 springs throughout the province. Gamma was measured at 20 cm and 100 cm above the ground level in 15 locations of each spring. Excess lifetime cancer risk was calculated to investigate the risk of exposure to gamma radiation. The highest and lowest annual absorbed dose rate of gamma were found to be 1.17(10-3) and 1.99(10-3) Sv/y at the height of 20 cm above the ground level and 5.26(10-4) and 1.52(10-3) Sv/y at the height of 100 cm above the ground level, respectively. Excess lifetime cancer risk ranged from 4.57(10-4) to 7.76(10-4) at the height of 20 cm and from 2.06(10-4) to 5.94(10-4) at the height of 100 cm which are lower than global average of 1.45(10-3) declared by the United Nations. Although the risk level in this study is lower than the global average, protective and preventive measures should be considered by individuals and authorities in these areas to reduce the effects of gamma radiation on the health of the swimmers.

Dataset on specifications, carcinogenic and non-carcinogenic risk of volatile organic compounds during recycling paper and cardboard.

Emissions of volatile organic compounds (VOCs) were studied during paper and cardboard recycling from a paper and cardboard solid waste recycling factory (PCSWRF). Data are summarized in this article for the following quantities for a PCSWRF during the winter in Tehran, Iran: VOC concentrations (µg m-3), the percentage of detected VOCs, exposure indices (Ei) of individual and total VOCs (TVOCs), inhalation lifetime cancer risk (LTCR) of VOCs, the hazard quotient (HQ) of VOCs, sensitivity analysis (SA) for VOC exposure in different age groups (birth to <81), and Spearman's rank correlation coefficients (r) between VOC concentrations and meteorological parameters. For more insight please see "Characteristics and Health Effects of Volatile Organic Compound Emissions during Paper and Cardboard Recycling"[1], https://doi.org/10.1016/j.scs.2019.102005.

Characteristics and health risk assessment of polycyclic aromatic hydrocarbons associated with dust in household evaporative coolers.

This study reports a characterization of indoor polycyclic aromatic hydrocarbons (PAHs) associated with dust (dust-PAHs) in household evaporative coolers and their associated health effects. Extensive analysis showed that the indoor dust-PAHs stemmed mostly from pyrogenic sources (vehicular emissions) with mean total concentrations limited between 131 and 429 ng g-1. The distribution pattern of PAHs based on number of rings exhibited the following order of decreasing relative abundance: 4 > 3 > 5 > 6 > 2 rings. Results indicate that the mutagenicity of dust-PAHs exceeded their carcinogenicity, but that the potential carcinogenic effects are still significant. The mean lifetime cancer risk for different age groups for three pathways based on Model 2 (dermal (1.39 × 10-1 to 1.91 × 10-2), ingestion (2.13 × 10-3 to 8.08 × 10-3) and inhalation (1.62 × 10-7 to 4.06 × 10-7)) was 7.4-146 times higher than values predicted by Model 1 (dermal (5.13 × 10-5 to 3.03 × 10-3), ingestion (9.34 × 10-5 to 1.31 × 10-3) and inhalation (7.13 × 10-20 to 1.68 × 10-20)). Hence, exposure to dust-PAHs in household evaporative coolers lead to high risk, especially for children (less than 11 years) (HQ = 2.71 × 10-20 to 54.8 and LTCRs = 7.13 × 10-20 to 1.39 × 10-1). Strategies should be considered to eliminate such pollutants to protect people, especially children, from the non-carcinogenic and carcinogenic effects by changing household evaporative coolers with other cooling systems.

Bioaerosols in the waterpipe cafés: genera, levels, and factors influencing their concentrations.

This study was conducted in order to assess the exposure to bacterial and fungal bioaerosols in the air of waterpipe cafés (AWPCs), in the hose of waterpipe (HWP), and in the water bowl of the waterpipe (WBWP) and to investigate the factors influence increasing the contamination levels in waterpipe cafés in Ardabil. From all the 50 cafés studied, the samples were taken from air and from water contained in water bowl and hose for bacterial and fungal analyses. The results demonstrated that the mean numbers of bacteria and fungi in the indoor air of café, hose, and water bowl were 33.90 ± 14.86 and 25.24 ± 1.99 CFU/m3, 72.16 ± 29.55 and 72.78 ± 42.45 CFU/plate, 53.7 ± 25.46 and 25.26 ± 13.94 CFU/ml, respectively. The predominant bacterial genera in waterpipe cafés were Pseudomonas and Bacillus in air, Staphylococcus and Pseudomonas in the hose, and Staphylococcus and Pseudomonas in the water bowl, respectively. The predominant fungal species in waterpipe cafés were Penicillium and Cladosporium in air, yeast and Fusarium in the hose, and Paecilomyces and yeast in the water bowl, respectively. The results of statistical analysis showed that there was a significant relationship between the mean concentrations of bacterial aerosol and qualitative variables such as type of heating system, materials of wall and ceiling, traditional restaurants, interior supermarkets, moisturized walls, the number of people, area of cafés, and temperature. But there was no significant relationship between these variables and the mean concentration of fungal aerosols. The results also showed that the levels of bioaerosols were high in the air, hose, and water bowl of the waterpipe. Therefore, cafés can be a potential source for the transmission of pathogenic agents and increase the risk of respiratory diseases among waterpipe smoking individuals.

A case study of BTEX characteristics and health effects by major point sources of pollution during winter in Iran.

This study characterized spatio-temporal variations in the concentration of benzene, toluene, ethylbenzene, and xylene (BTEX) compounds in the vicinity of gas and compressed natural gas (CNG) stations in Tehran, Iran. Health risk assessment (HRA) was computed using Monte Carlo simulations (MCS) for evaluating inhalation lifetime cancer risk (LTCR), the hazard quotient (HQ), and sensitivity analysis (SA) for BTEX exposure in different age groups (birth to <81) and as a function of distance (0-250 m) from the center of the stations. For all monitoring stations, the average values of benzene, toluene, ethylbenzene, and xylene in winter were 466.09 ±â€¯132.25, 873.13 ±â€¯233.51, 493.05 ±â€¯141.22, and 910.57 ±â€¯145.40 µg m-3, respectively. The mean wintertime ratios of T/B for the 12 stations ranged from 1.69 to 2.04. Furthermore, there was no significant relationship between the concentration of BTEX with either the specific month or distance from the center of stations (p > 0.05). Factors promoting BTEX formation in the study region were fuel evaporation and gas/CNG station emissions. The LTCRs for the target compounds in the winter for different age groups and distances from the center of stations was limited to 2.11 × 10-4 to 1.82 × 10-3 and 2.30 × 10-4 to 2.01 × 10-3, respectively, which exceeded proposed values by U.S. EPA. Moreover, the HQs for BTEX for three age groups and distances were limited to between 2.89 × 10-5 and 9.33 × 10-2, which were lower than the acceptable limit (HQs < 1). The results of this work are applicable to similar areas that are heavily populated with vehicular traffic. This study motivates a closer look at mitigation strategies to limit the health effects of carcinogenic emissions such as benzene and ethylbenzene from gas/CNG stations.

Characteristics and health effects of formaldehyde and acetaldehyde in an urban area in Iran.

This study reports a spatiotemporal characterization of formaldehyde and acetaldehyde in the summer and winter of 2017 in the urban area of Shiraz, Iran. Sampling was fulfilled according to EPA Method TO-11 A. The inverse distance weighting (IDW) procedure was used for spatial mapping. Monte Carlo simulations were conducted to evaluate carcinogenic and non-cancer risk owing to formaldehyde and acetaldehyde exposure in 11 age groups. The average concentrations of formaldehyde/acetaldehyde in the summer and winter were 15.07/8.40 µg m-3 and 8.57/3.52 µg m-3, respectively. The formaldehyde to acetaldehyde ratios in the summer and winter were 1.80 and 2.43, respectively. The main sources of formaldehyde and acetaldehyde were photochemical generation, vehicular traffic, and biogenic emissions (e.g., coniferous and deciduous trees). The mean inhalation lifetime cancer risk (LTCR) values according to the Integrated Risk Information System (IRIS) for formaldehyde and acetaldehyde in summer and winter ranged between 7.55 × 10-6 and 9.25 × 10-5, which exceed the recommended value by US EPA. The average LTCR according to the Office of Environmental Health Hazard Assessment (OEHHA) for formaldehyde and acetaldehyde in summer and winter were between 4.82 × 10-6 and 2.58 × 10-4, which exceeds recommended values for five different age groups (Birth to <1, 1 to <2, 2 to <3, 3 to <6, and 6 to <11 years). Hazard quotients (HQs) of formaldehyde ranged between 0.04 and 4.18 for both seasons, while the HQs for acetaldehyde were limited between 0.42 and 0.97.

Concentration and type of bioaerosols before and after conventional disinfection and sterilization procedures inside hospital operating rooms.

Operating rooms (ORs) in hospitals are sensitive wards because patients can get infections. This work aimed to characterize the type and concentration of bioaerosols in nine ORs of an educational hospital before and after sterilization and disinfection. During 2017, fungal samples were incubated at 25-28 °C for 3-7 days and bacterial samples at 37 °C for 24-48 h. The study results showed that the concentrations of fungi before cleaning procedures (for both of disinfection and sterilization) were limited from 4.83 to 18.40 CFU/m3 and after cleaning procedures ranged from 1.90 to 8.90 CFU/m3. In addition, the concentrations of bacteria before cleaning procedures were limited 14.65-167.40 CFU/m3 and after cleaning procedures ranged from 9.50 to 38.40 CFU/m3. The difference between the mean concentrations of airborne bioaerosols before and after sterilization was significantly different than the suggested value of 30 CFU/m3 (p ≤ 0.05). The bacterial concentration was higher than the recommended value (30 CFU/m3) in 41% of the ORs. The main fungal species identified in the indoor air of ORs (before vs. after sterilization) were A. fumigatus (25.6 vs. 18.3%), A. Niger (11.6 vs. 5.8%), Penicillium spp. (5.5 vs. 3.3%), Alternaria spp. (2.8 vs. 0.7%), Fusarium spp. (9.7 vs. 3.7%), Mucor spp. (15 vs. 12.7%), Cephalotrichum spp. (1.7 vs. 0.8%), A. Flavus (24.6 vs. 18.5%), Cladosporium spp. (2.6 vs. 0.8%), and Trichoderma spp. (0 vs. 0.9%). The growth of biological species even after sterilization and disinfection likely resulted from factors including poor ventilation, sweeping of OR floors, inadequate HVAC filtration, high humidity, and also lack of optimum management of infectious waste after surgery. Designing well-constructed ventilation and air-conditioning systems, replacing HEPA filters, implementing more stringent, frequent, and comprehensive disinfection procedures, and controlling temperature and humidity can help decrease bioaerosols in ORs.

BTEX in indoor air of beauty salons: Risk assessment, levels and factors influencing their concentrations.

Concentrations of benzene, toluene, ethylbenzene, and xylene (BTEX) were investigated in indoor air quality of 50 beauty salons in Ardabil, Iran (2017). Ten liters of air samples were collected from each salons regarding the recommended method and analyzed by GC-FID for BTEX concentration. Also, structural and operational conditions of the salons were studied with a self-designed questioner. The results of this study show that the mean concentration of benzene (32.40 ±â€¯26.38) higher than the recommended levels by Health Canada, ANSES and HKSAR. Among the BTEX, ethylbenzene (62.38 ±â€¯32.37) has the most concentrations in the salons. Subsequently, the cancer risk values in different age groups of birth to <6, 6 to <21, and 21 to <81 for benzene (1.83 × 10-3, 2.76 × 10-4 and 1.50 × 10-4, respectively) and ethylbenzene (4.9 × 10-4, 7.30 × 10-5 and 3.52 × 10-5, respectively) for long time exposure were drastically higher than the recommended levels. The results showed that the benzene concentration is significantly influenced by the structural and operational conditions of type of ventilation system, area of the salons, the number of people in the salon, number of services in the salons, and while doing of bridal makeup.

Characteristics and health effects of BTEX in a hot spot for urban pollution.

This study reports a spatiotemporal characterization of toluene, benzene, ethylbenzene, and xylenes concentrations (BTEX) in an urban hot spot in Iran, specifically at an bus terminal region in Shiraz. Sampling was carried out according to NIOSH Compendium Method 1501. The inverse distance weighting (IDW) method was applied for spatial mapping. The Monte Carlo simulation technique was applied to evaluate carcinogenic and non-carcinogenic risk owing to BTEX exposure. The highest average BTEX concentrations were observed for benzene in the morning (at 7:00-9:00 A.M. local time) (26.15 ±â€¯17.65 µg/m3) and evening (at 6:00-8:00 P.M. local time) (34.44 ±â€¯15.63 µg/m3). The benzene to toluene ratios in the morning and evening were 2.02 and 3.07, respectively. The main sources of BTEX were gas stations and a municipal solid waste transfer station. The inhalation lifetime cancer risk (LTCR) for benzene in the morning and evening were 1.96 × 10-4 and 2.49 × 10-4, respectively, which exceeds the recommended value by US EPA and WHO. The hazard quotient (HQ) of all these pollutants was less than 1. The results of this work have implications for public health near 'hot spots' such as IKBT where large populations are exposed to carcinogenic emissions.

Method development for determination of migrated phthalate acid esters from polyethylene terephthalate (PET) packaging into traditional Iranian drinking beverage (Doogh) samples: a novel approach of MSPE-GC/MS technique.

In the current study, a novel magnetic solid phase extraction (MSPE) technique combined with a gas chromatography/mass spectroscopy (GC/MS) was developed to determine the phthalate ester content of bottled Doogh samples. Doogh is a yogurt-based drinking beverage, which is frequently consumed in Middle East and Balkans. It is produced by stirring yogurt in Chern separation machine and consists of substances such as water, yogurt, and salt in addition to aqueous extracts of native herbs. The magnetic multi-walled carbon nanotubes (MWCNT-Fe3O4) were used as adsorbents of phthalate acid esters (PAEs) due to a superior adsorption capability of hydrophobic compounds. In this context, the quantity of the extractable migrated phthalate esters (dibutyl phthalate (DBP), dimethyl phthalate (DMP), butyl benzyl phthalate (BBP), diethyl phthalate (DEP), di-N-octyl phthalate (DNOP), and bis (2-ethylhexyl) phthalate (DEHP)) from polyethylene terephthalate (PET) bottles into Doogh samples was measured. The correlation between the concentration of migrated PAEs and some factors such as the type of Doogh (gaseous and without gas), difference in brand (five brands), volume (1500 and 300 mL), and the storage time also was investigated. The migration level into Doogh samples was increased by incorporating of gas as well as increasing the volume of PET bottles. Also, with elaborating of storage time, the migration of some phthalates such as DEHP (the mean from 2419.85 ng L-1 in the first week to 2716.15 ng L-1 in the second month), DEP, and total phthalate was increased. However, no significant difference in concentrations of migrated phthalate esters among different examined brands was noted. Finally, the concentration of migrated PAEs from bottle into all the examined Doogh samples was below the defined standards by EPA; 6 µg/L for DEHP in drinking water. Graphical abstract ᅟ.

Seasonal Variation in Culturable Bioaerosols in a Wastewater Treatment Plant.

Bioaerosols produced from Wastewater Treatment Plants (WWTPs) can pose health risks to plant workers and nearby inhabitants. There is a gap in air quality data for WWTPs in developing countries. The present study aimed to measure airborne bacterial and fungal concentrations in a WWTP in southwestern Iran between September 2015 and May 2016. Active sampling was conducted around operational units, and a total of 600 bacterial and fungal samples were collected. Spatial and seasonal comparisons were made. The highest average concentrations of culturable bacterial aerosol at seasonally dependent locations were, in decreasing order, 2581 ± 401 and 1952 ± 390 CFU m-3 for the selector and aeration tanks, respectively, in autumn; 1363 ± 299 CFU m-3 for the aeration tank in winter; and 1738 ± 350 CFU m-3 for the screw pump in spring. Furthermore, the predominant genera of airborne fungi isolated from the air of the WWTP in all three seasons were Cephalotrichum spp., Alternaria spp., Penicillium spp., Monilia spp., and Aspergillus spp. The results of this work emphasize the necessity of controlling WWTP workers' exposure to bioaerosols when bacteria and fungi become aerosolized during aeration.