Outdoor Particle Concentrations Research Articles

Socioeconomic inequity of measured indoor and outdoor exposure to PM2.5: 5 Years of data from 14,000 low-cost particle monitors

Multiple studies have considered socioeconomic or ethnic group inequities in outdoor fine particle (PM2.5) concentrations. Due to the lack of indoor measurements, these studies are forced to assume that indoor exposures are directly related to outdoor concentrations. In general, this assumption may be reasonable, but it is violated when indoor-generated fine particles form a substantial contribution to total potential indoor exposure. We now have for the first time access to long-term (months or years) indoor potential exposures, made possible by the development of low-cost optical particle counters. A large database of 120 million hourly PM2.5 indoor and outdoor concentrations measured by 10,000 outdoor and >4000 indoor PurpleAir monitors over a 5-year period (2017–2021) in three West Coast states (Washington, Oregon, California) has been used to compare with US Census 2021 estimates of median household income, educational attainment, housing characteristics, and ethnic groups. Clear evidence of inequities is found using indoor as well as outdoor PM2.5 concentrations.

Particle characterization in commercial buildings: A cross-sectional study in 40 offices in Singapore

There is a knowledge gap in understanding how existing office buildings are protecting occupants from exposure to particles from both indoor and outdoor sources. We report a cross-sectional study involving weekly measurements of size-resolved indoor and outdoor particle concentrations in forty commercial building offices in Singapore. The outdoor and indoor particles size distributions were single mode with daytime peak number concentrations at 36.5 nm and 48.7 nm. Outdoor concentrations were significantly greater than indoors for all particle diameters. Indoor particle concentrations were generally low due to: 1) relatively high indoor particle removal (IPR) rates; 2) low indoor source strengths; and 3) low indoor particle of outdoor proportion (IPOP). We found that the ventilation system type had a substantial effect on indoor particle levels, IPR and IPOP. Through linear mixed model analyses, we identified dependencies of IPR rates with the use of MERV13 filters in supply air and filter maintenance frequency, IPOP with the use of MERV13 filters in the fresh air and supply air ducts and low particle source strength with regular daily cleaning presumably due to dust reservoir removal. Lastly, the contribution of outdoor sources was mainly seen for ultrafine and fine particles but less pronounced for coarse particles. This study provided detailed understanding of particle exposure in building offices and their influencing factors, facilitating future research on health impact of particle exposures.

A field measurement study of the effects of outdoor pollutants and room volumes on indoor fine particle and ozone concentrations

Air pollution, represented by ozone (O3) and fine particulate matter (PM2.5), threatens the health of urban residents. This study examined 24 residential buildings in Nanjing to investigate the factors that affect indoor ozone and PM2.5 concentrations. Windows closed/open state, room geometry, ventilation rate, and pollutant removal and emission rates are taken as influencing factors. The correlation between influence factors and indoor air quality was analyzed to help residents in Nanjing understand which factors significantly affect indoor air quality. Fitted methods were employed to assess the removal and emission rates of pollutants. It was found that for the bedroom of 10–20 m2 (i.e., 30–60 m3), the air change rate (ACR, h−1) of infiltration is relatively more correlated with the room volume than other room volumes. The increase in indoor ozone concentration due to windows opening is below the indoor air quality standard in China (160 μg/m3) and the USA (70 μg/m3) under the test period in these measured cases. Therefore, when natural ventilation is adopted for residential buildings in Nanjing, outdoor fine particle concentrations should be a priority concern.

Feasibility of applying an electrostatic precipitator integrated with a naturally ventilated double-skin façade in residential buildings

One of the main advantages of applying a double-skin façade (DSF) is allowing natural ventilation. As concerns about high outdoor particle concentrations increase, maintaining comfortable indoor air quality through natural ventilation in buildings with DSFs becomes difficult. An electrostatic precipitator (ESP) integrated with a DSF (EPID) has been proposed for maximizing the natural ventilation in buildings with polluted outdoor air. In this study, the particle removal performance and ozone generation of the EPID were experimentally evaluated to determine the feasibility of applying it in residential buildings. An EPID prototype was constructed, and laboratory experiments were performed to measure the single-pass particle removal efficiency and concentration of ozone, a byproduct of the ESP. The results showed that the average particle removal efficiency (77.4 ± 5.5%) at the upper ESP position is similar to that at the lower ESP position (78.5 ± 11.6%) for 0.25–1.82 μm particles at 9 kV applied voltage and 0.5 ms−1 inlet air velocity. When the inlet air velocity increases to 2.0 ms−1, the particle removal efficiency decreases to 39.7% depending on the ESP position. Moreover, the ESP position significantly influences the particle removal efficiency because it changes the inlet air velocity, especially at low applied voltages. Our results highlight the importance of determining the appropriate ESP position in the EPID for residential applications because low-voltage operation is recommended for the safety of occupants and reduction in ozone generation. In addition, at 0.5 ms−1 inlet air velocity, at which the EPID has excellent removal performance, the net ozone concentrations are 33.0 ppb and 35.7 ppb at 6 kV and 9 kV, respectively, which are all lower than the threshold (50 ppb), regardless of the ESP position. The results of this study verify the feasibility of applying the EPID and have important implications for future EPID designs and developing control strategies to improve the indoor air quality of naturally ventilated residential buildings with DSFs.

Long-Term Indoor-Outdoor PM2.5 Measurements Using PurpleAir Sensors: An Improved Method of Calculating Indoor-Generated and Outdoor-Infiltrated Contributions to Potential Indoor Exposure.

Low-cost monitors make it possible now for the first time to collect long-term (months to years) measurements of potential indoor exposure to fine particles. Indoor exposure is due to two sources: particles infiltrating from outdoors and those generated by indoor activities. Calculating the relative contribution of each source requires identifying an infiltration factor. We develop a method of identifying periods when the infiltration factor is not constant and searching for periods when it is relatively constant. From an initial regression of indoor on outdoor particle concentrations, a Forbidden Zone can be defined with an upper boundary below which no observations should appear. If many observations appear in the Forbidden Zone, they falsify the assumption of a single constant infiltration factor. This is a useful quality assurance feature, since investigators may then search for subsets of the data in which few observations appear in the Forbidden Zone. The usefulness of this approach is illustrated using examples drawn from the PurpleAir network of optical particle monitors. An improved algorithm is applied with reduced bias, improved precision, and a lower limit of detection than either of the two proprietary algorithms offered by the manufacturer of the sensors used in PurpleAir monitors.

Impact of ventilation methods on indoor particle concentrations in a daycare center.

The objective of this study was to quantify the influence of ventilation methods on children's exposure to indoor particles in a daycare center located in an urban area. The ventilation methods applied to the center were monitored for 1 year. It appears that indoor PM10 and PM2.5 concentrations of the center were basically determined by outdoor conditions. The fluctuations in outdoor particle concentration also affected the ventilation behavior during class. The windows and doors of the classroom were frequently closed during both class hours and nights when the outdoor particle concentrations were at high levels. Statistically significant differences in the I/O ratios were found among the ventilation methods. The PM10 I/O ratio with the closed windows was significantly higher (p < 0.01) than that with the open windows, and when the mechanical fans were operated, the I/O ratio dramatically decreased (p < 0.01). The I/O ratio of PM2.5 showed a similar trend to that of PM10 except for the mechanical fan operation. The filters rated lower than MERV 11 appear to be insufficient to remove submicron particles from the mechanically supplied outdoor air when the PM2.5 concentrations are high, such as during the heating period.

Influence of number of visitors and weather conditions on airborne particulate matter mass concentrations at the Plitvice Lakes National Park, Croatia during summer and autumn.

We investigated the influence of local meteorological conditions and number of visitors on ambient particulate matter (PM) mass concentrations and particle fraction ratios at the Plitvice Lakes National Park between July and October 2018. Outdoor mass concentrations of particles with aerodynamic diameters of less than 1, 2.5, and 10 μm (PM1, PM2.5, and PM10, respectively) and indoor PM1 were measured with two light-scattering laser photometers set up near the largest and most visited Kozjak Lake. Our findings suggest that the particles mainly originated from background sources, although some came from local anthropogenic activities. More specifically, increases in both indoor and outdoor mass concentrations coincided with the increase in the number of visitors. Indoor PM1 concentrations also increased with increase in outdoor air temperature, while outdoor PMs exhibited U-shaped dependence (i.e., concentrations increased only at higher outdoor air temperatures). This behaviour and the decrease in the PM1/PM2.5 ratio with higher temperatures suggests that the production and growth of particles is influenced by photochemical reactions. The obtained spectra also pointed to a daily but not to weekly periodicity of PM levels.

Occupant behavior and indoor particulate concentrations in daycare centers

‘Occupant behavior’ is the primary mechanism determining indoor particulate concentrations. Various indoor human activities generate particulate matter. Human-building interactions, such as window opening behavior, change the number of outdoor particulate matter introduces to the building. ‘Daycare center’ where young children spend considerable time has an occupant schedule distinguished from other types of buildings. In the study, we analyzed the effects of occupant behavior on indoor particle concentrations in daycare centers by on-site monitoring. The measurements were performed in four daycare centers located in Gyeonggi-do, South Korea. Optical particle counters(OPS, model 3330, TSI Inc., Shoreview, MN, USA) were used for particulate concentration monitoring. The source strengths of particles resuspended by each human activity were calculated, and their contributions to indoor particle concentrations were evaluated. Further, characteristics of human-building interactions and their corresponding impacts on indoor air quality were also analyzed. Results showed that particle resuspension was greater when occupants were awake (mean, 41.0 particles·min−1) than when they were asleep (mean, 9.2 particles·min−1), and the contribution of occupant status was also higher when awake (37–70% vs. 8–18%) for particles sized (0.3–10.0 μm). Analyzing five detailed human activities, vacuuming (9.8·107 particles·min−1) emitted the highest amount of particulate matter per person, followed by physical activity (4.8·107 particles·min−1), sedentary activity (1.9·107 particles· min−1), meals (1.9·107 particles·min−1), and nap time (8.1·106 particles·min−1). The study suggests that vacuuming should be avoided while children are occupied. This research also shows that children could be exposed to high daily average indoor particulate concentration (up to 1217 particles·cm−3) when windows were opened for an extended period of time while poor outdoor air quality. These results indicate that indoor air quality can be severely degraded by opening windows without considering the level of outdoor particle concentration.

Study on the change of indoor and outdoor air quality with height in high-rise buildings during the initial heating period

The indoor and outdoor pollutant concentrations of a high-rise building in Xi’an was tested and analyzed during the initial heating period in this paper. Also the relationship between indoor and outdoor pollutant concentration, building height and outdoor meteorological parameters in different periods was an-alyzed at the same time. Compare and analyze the ratio of indoor and outdoor particle concentration (I/O value) in different time periods. The results showed that during the test period, the concentration of partic-ulate matter reached the highest value at noon and the lowest value after dusk. The I/O value tends to de-crease with the increase of the building height, but at some moments there is a situation where the I/O value is greater than 1. The research results of this paper can provide a theoretical basis for indoor particulate control and architectural design of high-rise buildings.

Indoor-outdoor relationship of PM2.5 mass concentrations in severe cold regions based on a coupled canopy model

• The indoor-outdoor particle diffusion model for cities in severely cold regions were established. • The concentration distribution between indoor and outdoor environments in a residential area were investigated. • There is a lag of about 2 h for indoor PM 2.5 mass concentrations relative to outdoors in conditions of the infiltration in the residential home. • The I/O ratios were greater for higher floors of buildings in the vertical direction. In the recent years, air pollution has become increasingly serious. Residential areas are the places where urban residents spend most their time. Air quality in residential areas and indoor environments significantly affects human health. The particle pollution characteristics of the cities in severely cold regions are spectacular due to unique climate characteristics of these cities, their urban energy consumption structures, underlying surfaces and architectural shape. All these characteristics significantly differ from those of other cities, and this difference is the main driver of unique particle pollution characteristics. This study established an indoor-outdoor particle diffusion model for cities in severely cold regions and it can be used to evaluate the relationship between indoor and outdoor particle concentrations. First, we found that there is a time lag of about 2 h for indoor PM 2.5 mass concentrations relative to outdoors in conditions of the infiltration in the residential home.As for the relationship between indoor and outdoor PM 2.5 , the simulation results showed that the I/O ratios were greater for higher floors of buildings because of the differences in outdoor meteorological conditions in the vertical direction. In addition, indoor source emissions and large openings could significantly influence indoor particle concentration levels.

Effect of Occupant Activity on Indoor Particle Concentrations in Korean Residential Buildings

Due to the recent industrial development and COVID-19 pandemic, people are spending more time indoors. Therefore, indoor air quality is becoming more important for the health of occupants. Indoor fine particles are increased by outdoor air pollution and indoor occupant activities. In particular, smoking, cooking, cleaning, and ventilation are occupant activities that have the largest impact on indoor particle concentrations. In this study, indoor and outdoor particle concentrations were measured in ten apartment houses in South Korea for 24 h. Indoor particle concentrations were measured in the kitchen and living room to evaluate the impact of cooking, one of the most important sources of indoor particles. An occupant survey was also conducted to analyze the influence of occupant activities. It was found that the impact of outdoor particles on indoor particle concentrations in winter was not significant. The largest particle source was cooking. In particular, a large amount of particles was generated by broiling and frying. In addition, cooking-generated particles are rapidly dispersed to the living room, and this was more obvious for small particles. It is expected that this result will be statistically generalized if the particle concentration of more houses is analyzed in the future.

A ventilator that responds to outdoor conditions for ventilation and air filtration

Because of haze and fog in some countries, the outdoor air is polluted and cannot be directly drawn into rooms for ventilation. A ventilator with air filtration may be required. However, as outdoor particulate concentrations vary greatly with time, it is not ideal to operate high-efficiency particulate air (HEPA) filtration continually. This investigation proposed a ventilator with multiple modes of ventilation and air filtration. The ventilator could be switched between modes according to the outdoor and indoor air conditions. The ventilation rate and indoor particle concentrations in a test room equipped with the proposed ventilator were modelled by the EnergyPlus software program and validated with experimental data. The validated model was then used to evaluate indoor air quality and energy consumption in a hypothetical apartment located in each of five different climatic zones in China. The performance of the proposed ventilator was compared to that of a market-available outdoor air blower. It was found that to obtain the same acceptable indoor air quality, the necessary operating time for the proposed ventilator in the HEPA filtration mode was approximately 70% shorter than for the outdoor air blower, and the ventilator required approximately 30% less operating energy. In some southern cities in China, mechanically driven medium-efficiency filtration was sufficient to reduce the PM2.5 concentration to the acceptable level.

Laboratory and field investigation of portable air cleaners’ long-term performance for particle removal to be published in: Building and environment

As an effective measure of improving indoor air quality, portable air cleaners (PACs) have been widely used in residential buildings to reduce indoor particle concentration. However, the air cleaner's filter performance may degrade over time during the dust loading process. In this study, the laboratory cumulate clean mass (CCM) tests, which are aimed to reflect the lifetime of the filter, were conducted with cigarette smoke challenging. Although the airflow rate decreased with the increased pressure drop, it was found that the reduced PAC's effectiveness was primarily caused by the significant decrease in single-pass efficiency after cigarette smoke loading in laboratory. The main reason was the elimination of electrostatic force by the organic matters contained in cigarette smoke, which was confirmed by the surface potential change after dust loading. Therefore, such test may not be truly representative of the ambient aerosol challenging in actual application. Long-term field monitoring of five PACs was then carried out in actual homes. Outdoor particle concentration greatly influences the field cumulate clean mass (CCMfield) through room infiltration. The decay rates of typical PAC's field clean air delivery rate (CADRfield) versus CCMfield were obtained, ranging from 0.042 to 0.149%/(mg/m2). A new service life prediction method was proposed considering the decline of PAC's CADRfield and the required CADR to keep indoor PM2.5 concentration below 25 μg/m3. In an archetypal case, if a PAC runs for 12 h per day, its service life is only about 1–3 months when outdoor average PM2.5 concentration ranges from 75 to 250 μg/m3.

Influence of methodology on the estimation of the particle surface area dose received by a population in all-day activities

In everyday life, people are exposed to different concentrations of airborne particles depending on the microenvironment where they perform their different activities. Such exposure can lead to high sub-micron particle doses. The received dose depends on particle concentration to which people are exposed (typically expressed in terms of number or surface area), time spent in each activity or microenvironment (time activity pattern) and amount of air inhaled (inhalation rate). To estimate an actual value of the received dose, all these parameters should be measured under real-life conditions; in fact, the concentrations should be measured on a personal scale (i.e. through a direct exposure assessment), whereas time activity patterns and inhalation rates specific to the activity performed should be considered. The difficulties in obtaining direct measurements of these parameters usually lead to adopt time activity patterns and inhalation rates already available in scientific literature for typical populations, and local outdoor particle concentrations measured with fixed monitoring stations and extrapolated for all the other microenvironments.To overcome these limitations, we propose a full-field method for estimating the received dose of a population sample, in which all the parameters (concentration levels, time activity patterns and inhalation rates) are measured under real-life conditions (also including the inhalation rates, that were evaluated on the basis of the measured heart rates). Specifically, 34 volunteers were continuously monitored for seven days and the data of sub-micron particle concentrations, activities performed, and inhalation rates were recorded. The received dose was calculated with the proposed method and compared with those obtained from different simplified methodologies that consider typical data of particle concentrations, time activity patterns and inhalation rates obtained from literature. The results show that, depending on the methodology used, the differences in the received daily dose can be significant, with a general underestimation of the most simplified method.

Cooking and electronic cigarettes leading to large differences between indoor and outdoor particle composition and concentration measured by aerosol mass spectrometry.

We spend about two thirds of our time in private homes where airborne particles of indoor and outdoor origins are present. The negative health effects of exposure to outdoor particles are known. The characteristics of indoor airborne particles, though, are not well understood. This study assesses the differences in chemical composition of PM1 (<1 μm) inside and outside of an occupied Swedish residence in real time with a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and an Aethalometer. The chemical composition and concentration of particles indoors showed large differences compared to outdoors. The average indoor concentration was 15 μg m-3 and was higher than the outdoor 7 μg m-3. Organics dominated indoor particle composition (86% of the total mass) and originated from indoor sources (cooking, e-cigarette vaping). The average indoor to outdoor ratios were 5.5 for organic matter, 1.0 for black carbon, 0.6 for sulphate, 0.1 for nitrate, 0.2 for ammonium and 0.2 for chloride. The occupancy time accounted for 97% of the total measured period. Four factors were identified in the source apportionment of organic particle fraction by applying positive matrix factorization (PMF): two cooking factors, one e-cigarette factor and one outdoor contribution (OOA) organic factor penetrated from outside.

Infiltration of fine particles in urban buildings

Singapore is a tropical country that can be affected by outdoor fine particle air pollution. Little information is available on the penetration of outdoor fine particles into daycare environments. Our study attempted to address the following objectives: to measure indoor infiltration factor (Finf of PM2.5 from outdoor fine particles and to determine the building parameters that modifies the indoor PM2.5. We collected indoor/outdoor 1-min PM2.5. from 50 daycare environments. We noted high indoor and outdoor concentrations of fine particles due to the presence of regional haze pollution. Indoor and outdoor fine particle concentrations are significantly highest for daycares located near highways while indoor to outdoor ratios were significantly lower for air-conditioning use in daycares. Mean Finf±SD of 0.65±0.19 in daycare rooms which are naturally ventilated and lower Finf±SD values of 0.46±0.22 for those that are air-conditioned. The penetration coefficients and air exchange rates were higher in naturally ventilated daycares (0.78 vs 0.61 and 1.47 vs 0.86 h−1 respectively). Our findings show that children remaining indoor in daycares where air conditioning is used can reduce PM2.5 exposures during outdoor pollution episodes.

Site- and house-specific and meteorological factors influencing exchange of particles between outdoor and indoor domestic environments

The aim of this study was to investigate the influence of site- and house-specific as well as meteorological factors on indoor and outdoor particle concentrations. Particle number (PN) and particle mass (PM) concentrations were monitored in 62 houses in Brescia, Northern Italy, during two winter monitoring periods. Measurements were conducted in houses of non-smokers and without the activation of any internal aerosol sources from domestic activities such as cooking and cleaning. Indoor and outdoor particle concentrations were measured for 30 min in each house. A wide-range aerosol spectrometer (MINIWRAS 1371, GRIMM) was used to detect 41 classes of particles from 10 nm to 35 μm. The effects of natural ventilation on indoor particle concentrations were also considered by measuring PM and PN indoor/outdoor ratios before and after a window was opened for a period of 15 min. An ANOVA analysis was performed on a sub-dataset of 35 houses to evaluate the dependence of PN and PM concentrations on site- and house-specific as well as meteorological factors. The house energy class was significantly related to indoor particle concentrations, and window dimensions seemed to influence the concentrations both before and after the ventilation period. We found that some factors, e.g., the floor level, need further investigation.

Study on the multivariate prediction model and exposure level of indoor and outdoor particulate concentration in severe cold region of China

Atmospheric particulate matter( PM10, PM2.5) has been the main pollutant in most cities of China in recent years, and the exposure concentration is related to the incidence of human diseases and mortality. The time spent indoors is more than 80% for modern people. Therefore, study on the correlation and exposure level of indoor and outdoor atmospheric particles is important. To research the exposure level in the heating season and non-heating season of indoor and outdoor particulate concentration in severe cold region of China, a total of 110 samples of four types of buildings (office, classroom, urban residence and rural residence) in Daqing, a typical city of severe cold region in China, were tested by particle monitor. Based on the indoor and outdoor environmental parameters, multiple linear regression (MLR) and principal component regression (PCR), established the indoor particulate concentration prediction models. The short and long term exposure of different people in different environments in severe cold region of China was analyzed based on the people's time-activity pattern with the measured data and model. The results showed that as for the short term indoor and outdoor exposure of different people, the average combined exposure of urban people in heating season is 60.0% higher than that in non-heating season, and rural people in heating season 30.2% higher than that in non-heating season. As for the long term indoor and outdoor exposure of different people, the annual average combined exposure of urban people was 9.6% higher than that of rural people. While all for urban and rural people, differences in respiratory rates between genders resulted in an average potential dose of 21. 8% higher in male than in female.

Size-dependent characteristics of diurnal particle concentration variation in an underground subway tunnel.

Understanding characteristics of diurnal particle concentration variation in an underground subway tunnel is important to reduce subway passengers' exposure to high levels of toxic particle pollution. In this study, real-time particle monitoring for eight consecutive days was done at a shelter located in the middle of a one-way underground subway tunnel in Seoul, Republic of Korea, during the summer of 2015. Particle mass concentration was measured using a dust monitor and particle number concentration using an optical particle counter. From the diurnal variations in PM10, PM2.5, and PM1, concentrations of particles larger than 0.54μm optical particle diameter were affected by train frequency whereas those of particles smaller than 0.54μm optical particle diameter were not changed by train frequency. Number concentration of particles smaller than 1.15μm optical particle diameter was dependent on outdoor ambient air particle concentration level, whereas that of particles larger than 1.15μm optical particle diameter was independent of outdoor ambient air due to low ventilation system transmission efficiency of micrometer-sized particles. In addition, an equation was suggested to predict the diurnal particle concentration in an underground tunnel by considering emission, ventilation, and deposition effects.

Testing the performance of one and two box models as tools for risk assessment of particle exposure during packing of inorganic fertilizer

Modelling of particle exposure is a useful tool for preliminary exposure assessment in workplaces with low and high exposure concentrations. However, actual exposure measurements are needed to assess models reliability. Worker exposure was monitored during packing of an inorganic granulate fertilizer at industrial scale using small and big bags. Particle concentrations were modelled with one and two box models, where the emission source was estimated with the fertilizer's dustiness index. The exposure levels were used to calculate inhaled dose rates and test accuracy of the exposure modellings. The particle number concentrations were measured from worker area by using a mobility and optical particle sizer which were used to calculate surface area and mass concentrations. The concentrations in the worker area during pre-activity ranged 63,797–81,073 cm−3, 4.6 × 106 to 7.5 × 106 μm2 cm−3, and 354 to 634 μg m−3 (respirable mass fraction) and during packing 50,300 to 85,949 cm−3, 4.3 × 106 to 7.6 × 106 μm2 cm−3, and 279 to 668 μg m−3 (respirable mass fraction). Thus, the packing process did not significantly increase the exposure levels. Chemical exposure was also under control based on REACH standards. The particle surface area deposition rate in respiratory tract was up to 7.6 × 106 μm2 min−1 during packing, with 52%–61% of deposition occurring in the alveolar region. Ratios of the modelled and measured concentrations were 0.98 ± 0.19 and 0.84 ± 0.12 for small and big bags, respectively, when using the one box model, and 0.88 ± 0.25 and 0.82 ± 0.12, when using the two box model. The modelling precision improved for both models when outdoor particle concentrations were included. This study shows that exposure concentrations in a low emission industrial scenario, e.g. during packing of a fertilizer, can be predicted with a reasonable accuracy by using the concept of dustiness and mass balance models.