Search

Ozone reaction with human surfaces is an important source of ultrafine particles indoors. However, 1-20 nm particles generated from ozone-human chemistry, which mark the first step of particle formation and growth, remain understudied. Ventilation and indoor air movement could have important implications for these processes. Therefore, in a controlled-climate chamber, we measured ultrafine particles initiated from ozone-human chemistry and their dependence on the air change rate (ACR, 0.5, 1.5, and 3 h-1) and operation of mixing fans (on and off). Concurrently, we measured volatile organic compounds (VOCs) and explored the correlation between particles and gas-phase products. At 25-30 ppb ozone levels, humans generated 0.2-7.7 × 1012 of 1-3 nm, 0-7.2 × 1012 of 3-10 nm, and 0-1.3 × 1012 of 10-20 nm particles per person per hour depending on the ACR and mixing fan operation. Size-dependent particle growth and formation rates increased with higher ACR. The operation of mixing fans suppressed the particle formation and growth, owing to enhanced surface deposition of the newly formed particles and their precursors. Correlation analyses revealed complex interactions between the particles and VOCs initiated by ozone-human chemistry. The results imply that ventilation and indoor air movement may have a more significant influence on particle dynamics and fate relative to indoor chemistry.

Airborne transmission has been confirmed as one of three principal ways of SARS-CoV-2 transmission. To reduce the transmission of SARS-CoV-2 indoors, understanding the distribution of respiratory droplets (or aerosols) present in human breath seems therefore important. To study whether the CO2 concentration can be used as a proxy for the number of exhaled particles present in an occupied space, the distribution of particles with different diameters (0.3, 0.5, 1.0, 2.5, 5.0 and 10 ?m) and CO2 concentrations were monitored in a classroom setting with six healthy subjects. Additionally, numbers of particles with the same sizes were measured in the breath of the same six healthy subjects separately. Results showed that (1) on the contrary to CO2, the main source of indoor particles came from outdoor air, and not from occupants; (2) the impacts of ventilation regimes on indoor particle numbers were different to the impacts on CO2 concentrations; and (3) almost no significant relationship between the number of indoor particles and CO2 concentration was observed. Based on these results, this study could therefore not conclude that the CO2 concentration in a classroom can be used as a proxy for the number of exhaled particles by the occupants., Indoor Environment

Airborne transmission has been confirmed as one of three principal ways of SARS-CoV-2 transmission. To reduce the transmission of SARS-CoV-2 indoors, understanding the distribution of respiratory droplets (or aerosols) present in human breath seems therefore important. To study whether the CO2 concentration can be used as a proxy for the number of exhaled particles present in an occupied space, the distribution of particles with different diameters (0.3, 0.5, 1.0, 2.5, 5.0 and 10 ?m) and CO2 concentrations were monitored in a classroom setting with six healthy subjects. Additionally, numbers of particles with the same sizes were measured in the breath of the same six healthy subjects separately. Results showed that (1) on the contrary to CO2, the main source of indoor particles came from outdoor air, and not from occupants; (2) the impacts of ventilation regimes on indoor particle numbers were different to the impacts on CO2 concentrations; and (3) almost no significant relationship between the number of indoor particles and CO2 concentration was observed. Based on these results, this study could therefore not conclude that the CO2 concentration in a classroom can be used as a proxy for the number of exhaled particles by the occupants., Indoor Environment

The aim of this study was to assess the impact of ventilation and filtration conditions on particle concentrations in an orthopedic operating room. Total particle, viable particle, and CO2 concentration were measured under three different situations, namely before air filter replacement, after air filter replacement, and in an operating room with a new air conditioning system. Before air filter replacement, the mean values of airflow, total particle concentration, and viable particle concentration were 706 m3/h, 15.0 × 106 ± 4.0 × 106 particles/m3, and 57 CFU/m3, respectively. After replacement, the airflow increased to 1954 m3/h, and total and viable particle concentrations decreased to 0.4 × 106 ± 0.2 × 106 particles/m3 and 24 CFU/m3, respectively. In the room with a new air conditioning system, the airflow was 2051 m3/h, and total and viable particle concentrations were 0.3 × 106. ± 0.1 × 106 particles/m3 and 15 CFU/m3, respectively. The CO2 levels were 663 ppm (before), 659 ppm (after), and 574 ppm (new room). The results showed that inappropriate or no maintenance of filters in an air conditioning system had significant negative effects on indoor air quality in operating rooms. Air conditioning systems operating with saturated filters can be affected by pressure drop, which can lead to a reduction in airflow, thereby resulting in an increase in the average total particle and viable particle concentrations and the risk of infection in operating rooms. However, the results showed that the CO2 concentration was not affected by the filter replacement.

Elevated exposure to airborne particulate matter is linked to deleterious health and well-being outcomes. Exposure assessment can be improved through enhanced understanding of source-receptor relationships, for example as expressed in the inhalation intake fraction metric. This study provides new knowledge about how inhalation intake of airborne particles varies with spatially varying indoor emissions. In a controlled environmental chamber with low background particle levels, we monitored the time- and size-resolved particle concentrations at multiple locations including the subject's breathing zone. We investigated two types of particle emissions: (i) controlled releases from several specific indoor locations; and (ii) natural release from skin and clothing for a range of simulated occupant activities. Findings show that particles released proximate to the human envelope caused a total inhalation intake fraction of 7–10 per thousand, which was 1.5–16 × higher than the intake fraction for other indoor release locations. These outcomes reflect the influence of emissions-receptor proximity combined with the efficient transport of particles by means of the thermal plume to the breathing zone. The results show that the well-mixed representation of an indoor environment could underestimate the inhalation intake by 40–90% for various localized indoor emissions, and by up to 3 × for particles emitted from the human envelope. The post-release exposure period contributed substantially to total inhalation intake. For particles released naturally from the human envelope, inhalation intake fractions varied with activity type and were higher for a subject when seated rather than walking.

Elevated exposure to airborne particulate matter is linked to deleterious health and well-being outcomes. Exposure assessment can be improved through enhanced understanding of source-receptor relationships, for example as expressed in the inhalation intake fraction metric. This study provides new knowledge about how inhalation intake of airborne particles varies with spatially varying indoor emissions. In a controlled environmental chamber with low background particle levels, we monitored the time- and size-resolved particle concentrations at multiple locations including the subject's breathing zone. We investigated two types of particle emissions: (i) controlled releases from several specific indoor locations; and (ii) natural release from skin and clothing for a range of simulated occupant activities. Findings show that particles released proximate to the human envelope caused a total inhalation intake fraction of 7–10 per thousand, which was 1.5–16 × higher than the intake fraction for other indoor release locations. These outcomes reflect the influence of emissions-receptor proximity combined with the efficient transport of particles by means of the thermal plume to the breathing zone. The results show that the well-mixed representation of an indoor environment could underestimate the inhalation intake by 40–90% for various localized indoor emissions, and by up to 3 × for particles emitted from the human envelope. The post-release exposure period contributed substantially to total inhalation intake. For particles released naturally from the human envelope, inhalation intake fractions varied with activity type and were higher for a subject when seated rather than walking.

Background Extensive epidemiological studies have provided evidence of an association between elevated outdoor particulate air pollution and adverse health effects. However, while people typically spend majority of time indoors, there is limited knowledge on airborne indoor particles and on the correlation between the concentrations of indoor particles and health effects. Even insights into the influence of differently sized indoor particles on human health are still rare.Objective The association between differentially sized indoor air particles and the development of respiratory diseases was studied for three year aged children.Methods Short-term measurements of particle mass and number concentrations were carried out in children's rooms. Information on possible particle sources (smoking habits, type of heating, and traffic) and respiratory outcomes were obtained from questionnaires. Measured indoor particle concentrations were correlated with possible sources of indoor particles and with respiratory health impacts.Results Daily smoking, smoking more than 5 cigarettes per day at home and traffic density in front of the window of children's room were found to be related to indoor exposure by particles of different diameters. High indoor particle exposures were associated with an increased risk for the development of obstructive bronchitis and in some extent of non-obstructive bronchitis. The strongest impact was observed for the mass concentration of particles < 1 µm and the number concentration of particles > 0.5 µm. The risk increases still remain significant if tested for stability changing the number of adjustment variables or omitting randomly selected cases, respectively.Conclusion Our results show significant associations between indoor particle concentrations and the risks for respiratory diseases in young children. The applied short-term measurements can help to assess the health risks of indoor particles with different sizes within epidemiol

We compared the school environment, asthma and allergy in 10 schools in Taiyuan, China, with eight schools in Uppsala, Sweden. In total 2193 pupils (mean age 13 years) participated. Chinese pupils had more respiratory symptoms, particularly daytime breathlessness after exercise (29.8% vs. 7.1%; P < 0.001), while cat allergy (1.2% vs. 6.6%; P < 0.001) and dog allergy (1.3% vs. 4.0%; P < 0.01) was less common. Cumulative incidence of asthma (1.8% vs. 9.5%; P < 0.001) and doctor's diagnosed asthma (1.2% vs. 9.0%; P < 0.001) were less common in China, indicating an under-diagnosis of asthma. Chinese classrooms were colder (mean 14.7 vs. 21.4 degrees C), more humid (mean 42% vs. 31% RH) and had higher CO2-levels (mean 2211 vs. 761 ppm). Levels of cat (Fel d1), dog (Can f1) allergens were low in settled dust from China (< 200 ng/g dust), but high in airborne dust on Petri-dishes (GM 16.8 ng/m2/day for Fel d1 and 17.7 for Can f1). The Swedish settled dust contained cat, dog and horse allergens in high levels (median 1300 ng/g, 1650 ng/g, 1250 U/g dust, respectively). In conclusion, there were large differences in the school environment, and in respiratory symptom and allergy. Allergen measurements in settled dust only may largely underestimate the classroom exposure. Practical Implications There is a need to improve the school environment, both in China and Sweden. The Swedish schools contained high levels of cat, dog and horse allergens and more amounts of open shelves and textiles that can accumulate dust and allergens. The air measurements indicated that Chinese schools may contain significant amounts of cat and dog allergen, and analysis of settled dust only may not reflect the true allergen exposure. Since the Chinese schools had no mechanical ventilation, they could not fulfill the ventilation standard in winter, and hence there is a need for improving the ventilation. The great discrepancy between respiratory symptoms and reports on asthma, and the