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Scientific research confirms the harmful effects of airborne cyanobacteria and microalgae. However, determining human exposure to these microorganisms remains a challenge. The six-stage Tisch impactor was used to collect bioaerosols from April to September 2020 in the coastal zone of the southern Baltic. The MPPD model was used for estimation of regional, lobar, and generation deposition of microorganisms in human respiratory tract. The mass deposition fraction of cyanobacteria and microalgae in the head region gradually increased with the aerosol size. The maximum deposition fractions in the trachea, bronchial, and the pulmonary region were found for particles between 2.1 and 3.3 μm. The contribution of cyanobacteria and microalgae was the highest in the head region. The majority of microorganisms found in pulmonary region dominated in particles smaller than 2.1 μm. Exposure to the ambient bioaerosols may have an adverse impact on the human health in the region of southern Baltic Sea. [Display omitted] • Bioaerosol deposition pattern in human airways was studied in Baltic coastal zone. • Multiple Path Particle Dosimetry Model was used. • In pulmonary regions majority of microorganisms was in aerosols <2.1 μm in diameter. • In acinar and peripheral airways highest mass deposition of smallest particles • Highest deposition of bioaerosols in the right lower lobe of the lungs was found. [ABSTRACT FROM AUTHOR]

Abstract Particulate matter (PM) is crucial among six criteria air pollutants, and it is frequently associated with human morbidity and mortality. According to the aerodynamic diameter, PM is classified as coarse (PM 10) and fine (PM 2.5). PM with these smaller sizes can easily enter and get deposited in the human airways. This deposited PM fraction commences the development of respiratory diseases such as asthma, chronic obstructive pulmonary disease, and even cancer. Thus, the quantification of PM deposition and its clearance in the human airway are essential for evaluating health risks. This study aims to investigate the size-segregated PM (PM 10 , PM 2.5, and PM 1) deposition in human lungs. Size-segregated PM is collected using the Grimm portable environmental dust monitor during winter season near an arterial road located in Chennai city of Tamil Nadu state, India. Multiple-Path Particle Dosimetry (MPPD) Model version 3.04 is utilized for quantifying PM deposition. In MPPD, airway structures of infants (3 and 28 months), children (3, 8, 9 and 14 years) and adults (18 and 21 years) are considered for the study. The values of PM concentration, body orientation, breathing scenario, tidal volume, pause fraction, inspiration fraction, and breathing frequency are specified in the MPPD for quantifying PM depositions. Results showed that 8-year children and 28 months infant groups are recorded with maximum and minimum size-segregated PM deposition respectively. The coarse particles (PM 10) are primarily deposited in the head (55–95%) and tracheobronchial (3–44%) regions whereas fine particles (PM 2.5 and PM 1) depositions are observed maximum in the head (36–63%) and pulmonary (28.2–52.7%) regions. Except for the adult age group, PM 2.5 has the maximum deposition percentage in tracheobronchial and pulmonary regions. In the case of lobar depositions, lower lobes receive maximum deposition (66.4%) than the upper (27.2%) and middle lobes (6.4%). PM 2.5 dominated the deposition in all five lobes of infant, children, and adults. The clearance rate of deposited PM is high in the tracheobronchial region whereas it is low in the pulmonary region. This study also concludes that PM 2.5 is the important size fraction in lung deposition. Further, the study results can be used for human health risk assessments such as oxidative potential and toxicity of deposited PM. Highlights • Total, regional and lobar depositions of PM in eight human airways are quantified. • Maximum PM deposition is observed in children airways (8 and 9 years old). • PM 10 highly deposited in Head and TB regions. • PM 2.5 and PM 1 have the maximum deposition in the alveolar region. • PM 2.5 mass deposition in first 16 generations increases with age. [ABSTRACT FROM AUTHOR]

Morphology and chemical composition altogether determine the fate of atmospheric particulate matter(PM) deposition and inhalation. Site-wise(#20 sites) and cumulative variations in morphology and chemical composition of PM 5 in Delhi showed dominance of non-spherical (sharp-edged, angular and flattened) particles followed by spherical ones, rich in elements like C, O, S, N, Al, Si, Cu, Ca, Na, Cl, Fe, Ni, Cr, Zn, Hg, Pb, Mo, etc. having potential health effects. #2650 individual particles analyzed for the morphological parameters like aspect ratio(AR), circularity factor(CIR), surface equivalent radius(SER) and area. Dominant AR and SER values found between ≥1–1.60 and > 0–0.50 μm, respectively showing dominance of non-spherical and fine-size particles in Delhi. The Multiple Path Particle Dosimetry (MPPD) Model used to study variations in deposition potential (regional deposition, lobar deposition, mass deposition and mass flux) of different PM sizes (PM 0.4 , PM 1 , PM 2.5 and PM 5) at different AR values which suggested that AR is an important input parameter of health models to get realistic and unbiased output health data. In addition, study revealed higher coarse particles deposition in the head region affecting upper respiratory tract with their non-spherical shapes whereas higher fine particles deposition in TB and pulmonary regions affecting inner parts of the lungs. [Display omitted] • Morphology and chemical composition of individual and bulk PM 5 particles analyzed on #20 sites in Delhi. • AR, CIR, SER and area of #2650 individual particles showed dominance of non-spherical and fine size particles in Delhi. • Deposition potential of ultrafine, fine and coarse particles studied using MPPD Model. • Effect of aspect ratio input on MPPD model output studied. [ABSTRACT FROM AUTHOR]

Ultrafine particles (UFPs) usually explosive growth during new particle formation (NPF) events. However, the risk of exposure to UFPs on NPF days has been ignored due to the prevalence of mass-based air quality standards. In this study, the daily deposited doses, i.e., the daily deposited particle number dose (D PNd), mass dose (D PMd), and surface area dose (D PSd), of ambient particles in the human respiratory tract in Beijing were evaluated based on the particle number size distribution (3 nm-10 µm) from June 2018 to May 2019 utilizing a Multiple-Path Particle Dosimetry Model (MPPD) after the hygroscopic growth of particles in the respiratory tract had been accounted for. Our observations showed a high frequency (72.6%) of NPF on excellent air quality days, with daily mean PM 2.5 concentrations less than 35 μg m−3. The daily D PNd on excellent air quality days was comparable with that on polluted days, although the D PMd on excellent air quality days was as low as 15.6% of that on polluted days. The D PNd on NPF days was ~1.3 times that on non-NPF days. The D PNd in respiratory tract regions decreased in the order: tracheobronchial (TB) > pulmonary (PUL) > extrathoracic (ET) on NPF days, while it was PUL > TB > ET on non-NPF days. The number of deposited nucleation mode particles, which were deposited mainly in the TB region (45%), was 2 times higher on NPF days than that on non-NPF days. Our results demonstrated that the deposition potential due to UFPs in terms of particle number concentrations is high in Beijing regardless of the aerosol mass concentration. More toxicological studies related to UFPs on NPF days, especially those targeting tracheobronchial and pulmonary impairment, are required in the future. [Display omitted] • Deposited number dose on excellent days are comparable with that on polluted days. • New particle formation (NPF) leads to high deposited number dose on excellent days. • Deposited nucleation mode particles are doubled from non-NPF days to NPF days. • Tracheobronchial region is the most readily affected part by new particle formation. [ABSTRACT FROM AUTHOR]