Intake Fraction Research Articles

Experimental and simulated evaluations of airborne contaminant exposure in a room with a modified localized laminar airflow system.

The traditional mixing ventilation is not an energy effective approach to remove indoor air pollutants, maintain breath zone air quality, and control the airborne transmission. This study investigated the potential of a localized laminar airflow ventilation system to alleviate human exposure to pollutants. Breathing thermal manikins with sitting posture and supine posture were used to simulate the human. N2O was used as the tracer gas to simulate the indoor pollutant emission. The contaminant exposure index (εexp) and intake fraction index (IF) were used to assess the risk of human pollutant exposure for various supply air velocities given different emission source positions. Enhanced pollutant removal efficiency (Eff) (from the result) showed the qualification and desirability of the localized laminar airflow ventilation system in improving the breath zone air quality. The results showed that the CFD results could fit well with the experimental data and found out the interaction between thermal plume and supply air. The results also indicated a low εexp and IF, with over 90%, all of which were highly correlated with the supply velocity. Human's different breathing methods have little influence on the pollutant exposure so as to the location of the pollution source. This study found that localized laminar airflow ventilation system could efficiently provide fresh air to the breathing zone without sacrificing the thermal environment around human. It can be used for small region air quality control such as that in the bedroom and living room where desired air quality is favored.

Particle Resuspension Dynamics in the Infant Near-Floor Microenvironment.

Carpet dust contains microbial and chemical material that can impact early childhood health. Infants may be exposed to greater quantities of resuspended dust, given their close proximity to floor surfaces. Chamber experiments with a robotic infant were integrated with a material balance model to provide new fundamental insights into the size-dependency of infant crawling-induced particle resuspension and exposure. The robotic infant was exposed to resuspended particle concentrations from 105 to 106 m-3 in the near-floor (NF) microzone during crawling, with concentrations generally decreasing following vacuum cleaning of the carpets. A pronounced vertical variation in particle concentrations was observed between the NF microzone and bulk air. Resuspension fractions for crawling are similar to those for adult walking, with values ranging from 10-6 to 10-1 and increasing with particle size. Meaningful amounts of dust are resuspended during crawling, with emission rates of 0.1 to 2 × 104 μg h-1. Size-resolved inhalation intake fractions ranged from 5 to 8 × 103 inhaled particles per million resuspended particles, demonstrating that a significant fraction of resuspended particles can be inhaled. A new exposure metric, the dust-to-breathing zone transport efficiency, was introduced to characterize the overall probability of a settled particle being resuspended and delivered to the respiratory airways. Values ranged from less than 0.1 to over 200 inhaled particles per million settled particles, increased with particle size, and varied by over 2 orders of magnitude among 12 carpet types.

The influence of solar natural heating and NOx-O3 photochemistry on flow and reactive pollutant exposure in 2D street canyons

This study incorporates solar radiation model and NOx-O3 photochemistry into computational fluid dynamics (CFD) simulations with the standard k-ε model to quantify the integrated impacts of turbulent mixing, solar heating and chemical processes on vehicular passive (CO) and reactive (NOx, O3) pollutant dispersion within two-dimensional (2D) street canyons. Various street aspect ratios (H/W = 1, 3, 5) and solar-radiative scenarios (LST 0900, 1200, 1500) are considered. The initial source ratio of NO2 to NO is 1:10 and the background O3 concentration is 100 ppb (mole fraction). The reference Reynolds numbers are ~106–107 and Froude number ranges from 0.23 to 1.14. Personal intake fraction (P_IF) and its spatially-averaged values at the leeward-side (⟨P_IF⟩lee), windward-side (⟨P_IF⟩wind) and both street sides (⟨P_IF⟩) are adopted to evaluate pollutant exposure in near-road buildings.As H/W = 1 and 3, the clockwise single vortex is formed under neutral condition. Leeward/ground solar heating at LST 0900/1200 slightly enhance such vortex and reduce ⟨P_IF⟩. However, as H/W = 3, the single dominant vortex is separated into two counter-rotating vortices by windward solar heating at LST 1500, thus this ⟨P_IF⟩wind is significantly larger than the neutral case. As H/W = 5, the lower-level secondary anticlockwise vortex appears under neutral condition inducing much weaker wind and extremely higher pedestrian-level concentration. This two-main-vortex structure is destroyed by leeward/ground heating into single-main-vortex pattern, but dissociates into three counter-rotating vortices by windward heating. These three radiative scenarios raise pedestrian-level velocity in neutral case by about two orders, and reduce overall ⟨P_IF⟩ by two times to one order. For all cases, NO2 exposure is generally about 40%–380% larger than passive CO exposure, which indicates the conversion of NO into NO2 by depleting O3 is dominant in present NOx-O3 titration interactions. Finally, solar heating only raises air temperature by up to 2–3 K and influences chemical rate slightly, thus this impact on reactive pollutant dispersion is less significant than its effect by the enhanced turbulent mixing.

High Throughput Risk and Impact Screening of Chemicals in Consumer Products.

The ubiquitous presence of more than 80,000 chemicals in thousands of consumer products used on a daily basis stresses the need for screening a broader set of chemicals than the traditional well‐studied suspect chemicals. This high‐throughput screening combines stochastic chemical‐product usage with mass balance‐based exposure models and toxicity data to prioritize risks associated with household products. We first characterize product usage using the stochastic SHEDS‐HT model and chemical content in common household products from the CPDat database, the chemical amounts applied daily varying over more than six orders of magnitude, from mg to kg. We then estimate multi‐pathways near‐ and far‐field exposures for 5,500 chemical‐product combinations, applying an extended USEtox model to calculate product intake fractions ranging from 0.001 to ∼1, and exposure doses varying over more than nine orders of magnitude. Combining exposure doses with chemical‐specific dose–responses and reference doses shows that risks can be substantial for multiple home maintenance products, such as paints or paint strippers, for some home‐applied pesticides, leave‐on personal care products, and cleaning products. Sixty percent of the chemical‐product combinations have hazard quotients exceeding 1, and 9% of the combinations have lifetime cancer risks exceeding 10−4. Population‐level impacts of household products ingredients can be substantial, representing 5 to 100 minutes of healthy life lost per day, with users’ exposures up to 103 minutes per day. To address this issue, present mass balance‐based models are already able to provide exposure estimates for both users and populations. This screening study shows large variations of up to 10 orders of magnitude in impact across both chemicals and product combinations, demonstrating that prioritization based on hazard only is not acceptable, since it would neglect orders of magnitude variations in both product usage and exposure that need to be quantified. To address this, the USEtox suite of mass balance‐based models is already able to provide exposure estimates for thousands of product‐chemical combinations for both users and populations. The present study calls for more scrutiny of most impacting chemical‐product combinations, fully ensuring from a regulatory perspective consumer product safety for high‐end users and using protective measures for users.

Non-uniform risk assessment methods for personalizedventilation on prevention and control of COVID-19

<p indent="0mm">Ventilation is an important measure to prevent the transmission of COVID-19 in indoor environment. The protection effect of personalized ventilation in disease control has been preliminarily verified in previous studies. It is considered as one of the promising measures to control airborne transmission indoors due to its high ventilation efficiency with direct delivery of fresh and clean air to the occupant’s breathing zone. Especially for vehicles like aircrafts and coaches, in which the personalized ventilation has been used for years, its applications in COVID-19 epidemic control should be further explored. However, most of the present airborne infection risk prediction models are based on the assumption that the exhaled pathogens are evenly distributed in the room. The non-uniform distribution of pathogens in indoor environment cannot be accurately predicted with these models when applying localized ventilation or considering the short-ranged transmission of airborne pathogens. In this study, five different non-uniform risk assessment models were verified by the tracer particle experiments with thermal manikins. The assessment methods included exposure risk index (<italic>ε</italic>_bz), personal exposure effectiveness (PEE), intake fraction (IF), dose-response model (<italic>P</italic>(<italic>t</italic>)) and infection risk reduction ratio (<italic>η</italic>). Two breathing thermal manikins were used to simulate two seated passengers in public transportation placed side by side. The nebulized aerosols with similar size distribution to human breathing were released from the source manikin’s mouth. The concentration of the received particles at the receptor’s breathing zone was sampled with an aerodynamic particle sizer (APS). The receptor’s exposure level of droplets released by the exhalation of the infector was predicted accordingly considering the usage patterns of the personalized ventilation. The applicability of each model for predicting the risk of airborne transmission of SARS-CoV-2 was discussed. The results show that the five assessment methods are all based on the measurement results of the droplet concentration in the breathing zone of the exposed occupant. These models can predict the intervention effect of personalized ventilation on the airborne exposure or infection risk, and the trends of the predicted results are basically consistent. The relative exposure level can be predicted by exposure risk index <italic>ε</italic>_bz, PEE and IF, which can be used to simply assess the exposure risk of SARS-CoV-2. The dose-response model can directly assess the infection risk of specific airborne disease such as COVID-19, but only when the viability and infectivity of the virus are accurately determined. And infection risk index <italic>η</italic> can evaluate the infection risk reduction ratio due to the use of personalized ventilation. These assessment methods can all reflect the problems of risk increase caused by lateral spread and accelerated diffusion of the droplet-laden air due to the application of personalized ventilation to the infector. The protective effect for the exposed occupant can also be evaluated by these models when PV is used for the receptor. The exposure risk of the receptor can be lowered by using the personalized ventilation and the protection effect is increased by using higher volume of clean air. This study can provide support and reference for the evaluation and development of novel ventilation methods for airborne disease control in indoor environment and provide basis for assessment of the transmission risk of COVID-19 under non-uniform conditions.

ESTIMACIÓN DE LA FRACCIÓN INHALADA DE CONTAMINANTES PRIMARIOS DEL AIRE EN LA CIUDAD DE MEDELLÍN

Intake fraction was estimated for measured pollutants in Medellín city: suspended particulates (PM10 and PM2.5), carbon monoxide (CO) and nitrogen oxides (NOx). The applicable method for primary pollutants was used, according to the existing air quality data in terms of emissions and concentrations, as a factor that can be used in the evaluation of the impact on human health due to the sources of air pollution. The data of emissions, attributable exposure concentration, amount population and breathing rates were processed for calculation. Given the importance of the spatial and temporal relationship of the variables, all data were from 2015, the last period in which the inventory of atmospheric emissions was updated. Areas of spatial representativeness were considered, obtaining cells with a CSF greater than 0.9 in Politécnico Jaime Isaza Cadavid (MED-PJIC) (PM10 and CO) and Universidad Nacional Núcleo el Volador (MED-UNNV) (PM2.5 and NOx) stations. Yearly averages of the intake fraction were: 475 and 29 ppm for PM10 and CO, respectively, at MED-PJIC station, and 151 and 64 ppm for PM2.5 and NOx, respectively, at MED-UNNV station. The intake fraction values were analyzed too by weighted respiration rates by age groups, and by hourly, daily, monthly and daily weekday averages of concentration and pollutant emission values.

The effect of exhaust emissions from a group of moving vehicles on pollutant dispersion in the street canyons

Moving vehicles are the primary emission source of road pollution and the vehicle-induced turbulence (VIT) affecting the flow field in the street canyon. This paper used the dynamic mesh updating method to simulate the air pollution under the real situation of vehicle movement and exhaust emission in the street canyon. The dispersion characteristics of vehicular exhaust under various vehicle arrangements were analyzed. The personal intake fraction (P_IF) was introduced as an index to analyze the impact of factors such as vehicle speed and ambient wind velocity on the pollution exposure level of pedestrians. Based on the general assumptions in the study of street canyon pollution that vehicle-induced turbulence (VIT) is a continuous turbulence source and vehicle exhaust pollutants is a uniform pollution source, the conditions of the hypothesis are preliminarily explored. The research indicates that VIT can be regarded as a continuous turbulence source when vehicles maintain a “safe distance” on the road and form a stable traffic flow. Moreover, according to the range of dispersion of exhaust pollution, a “healthy distance” was proposed to guide driver to avoid direct impact of exhaust emitted from the vehicles in front.

Intermittent occupancy combined with ventilation: An efficient strategy for the reduction of airborne transmission indoors

It is important that efficient measures to reduce the airborne transmission of respiratory infectious diseases (including COVID-19) should be formulated as soon as possible to ensure a safe easing of lockdown. Ventilation has been widely recognized as an efficient engineering control measure for airborne transmission. Room ventilation with an increased supply of clean outdoor air could dilute the expiratory airborne aerosols to a lower concentration level. However, sufficient increase is beyond the capacity of most of the existing mechanical ventilation systems that were designed to be energy efficient under non-pandemic conditions. We propose an improved control strategy based on source control, which would be achieved by implementing intermittent breaks in room occupancy, specifically that all occupants should leave the room periodically and the room occupancy time should be reduced as much as possible. Under the assumption of good mixing of clean outdoor supply air with room air, the evolution of the concentration in the room of aerosols exhaled by infected person(s) is predicted. The risk of airborne cross-infection is then evaluated by calculating the time-averaged intake fraction. The effectiveness of the strategy is demonstrated for a case study of a typical classroom. This strategy, together with other control measures such as continuous supply of maximum clean air, distancing, face-to-back layout of workstations and reducing activities that increase aerosol generation (e.g., loudly talking and singing), is applicable in classrooms, offices, meeting rooms, conference rooms, etc.

In Memoriam: Kirk R. Smith.

In Memoriam: Kirk R. Smith.

Numerical studies of passive and reactive pollutant dispersion in high-density urban models with various building densities and height variations

Vehicular pollutant exposure in the near-road buildings of high-density urban areas has been rarely studied. This paper investigates the impacts of high-density building morphology on passive (CO) and reactive (NOx-O3) pollutant dispersion in three-dimensional (3D) urban-like models, e.g. medium (street width W = 30 m,λp = 0.25, λf = 0.6) and compact (W = 18 m,λp = 0.39,λf = 0.94) layouts with uniform (H = 72 m) or various heights (H1 = 48 m,H2 = 96 m). Personal intake fraction P_iF and its spatially-averaged value for the entire building wall (<P_iF>W) are utilized for exposure assessment.Some meaningful findings are proposed: 1) When wind blows through neighborhood-scale (~1 km) urban models, it decelerates rapidly and then reaches a flow balance where pedestrian-level velocity and pollutant exposure vary depending on building densities and height variations. 2) Uniform-height cases attain overall <P_iF>W of ~0.3–1.3 ppm in target streets. The compact layout (λf = 0.94) experiences weaker vertical exchange where downward helical flows transport more pollutants to windward wall than medium-type (λf = 0.6), inducing two-order larger windward-side <P_iF>W (~1 ppm) than leeward-side (~0.01 ppm). 3) Building height variations obtain greater velocity and smaller <P_iF>W (~0.2–1.0 ppm) in front of taller buildings than those behind them (<P_iF>W~2.6–4.2 ppm). 4) No matter with or without height variations, densifying building arrays (λf = 0.6 to 0.94) raises windward-side <P_iF>W and mitigates leeward-side <P_iF>W, but overall <P_iF>W for both sides of target streets only change slightly. 5) With present NOx-O3 photochemistry (source emissions NO:NO2 = 10:1, background [O3] = 20 ppbv), NO2 exposure is 40%–230% larger than passive CO exposure, but NO is near to CO. This study implies the near-road pollutant exposure in high-density urban models is sensitive to building morphology which should be carefully designed.

Degradation of Nitrogen Fraction in Kacang Goats Feed Supplementation &lt;i&gt;Calliandra&lt;/i&gt;&lt;i&gt; сalothyrsus &lt;/i&gt;Substituted Soybean Meal

The aim of the study was to evaluate the use of Calliandra leaves (Calliandra calothyrsus) as a protein source in the Kacang goat’s diet and as an alternative to substitute the use of soybean meal (SBM) in goat’s diets. The proportion of C. calothyrsus feed substitution and SBM is T1 = odot grass (ad libitum) + 100% SBM; T2 = odot grass (ad libitum) + 25% C. calothyrsus + 75% SBM; T3 = odot grass (ad libitum) + 50% C. calothyrsus + 50% SBM; T4 = odot grass (ad libitum) + 75% C. calothyrsus + 25% SBM; and T5 = odot grass (ad libitum) + 100% C. calothyrsus. The last 10 days, collections was conducted include total collections of feeding, the residue of the feed, and feces. The parameters observed were intake and nutrient digestibility of dry matter (DM), crude protein (CP), neutral detergent insoluble nitrogen (NDIN) (% CP), and acid detergent insoluble nitrogen (ADIN) (% CP). Data obtained from the study were analyzed using a one-way analysis of variance, then if the results show significant differences, it will be analyzed further with Duncan's new multiple range test. The results showed that C. calothyrsus substitution treatment of 25 to 100% (T2, T3, T4, T5) gives noticeable influence (P&lt;0.05) for nutrient intakes, excretion (feces), and digested nutrients. The highest intake and digestible fraction of N-NDF, N-ADF, NDIN, and ADIN is the T5 treatment, which is the replacement of SBM with 100% C. calothyrsus (P&lt;0.05).

Analysis of consumer behavior for the estimation of the exposure to chemicals in personal care products

In this study, the main objective was to implement an integrative modelling framework in order to support the prioritization and screening of chemicals present in personal care products (PCPs) regarding their potential to expose users across multiple possible pathways. Here, we implemented an exposure-based framework based on product intake fractions (PiFs) calculated using a two-compartment model reproducing the skin uptake and the competing volatilization of chemicals applied on skin during PCP use. The implemented framework enabled to simultaneously and comprehensively accommodate coupled chemical specific parameters (i.e. physical and chemical properties of the candidate chemicals), exposure information specific for product-chemical combinations, and survey data informing on consumer behavior. A case-study, based on the usage pattern data of 22 PCPs investigated among Swiss individuals (Garcia-Hidalgo et al., 2017a) and 113 candidate chemicals chosen for their suspected presence in the PCP categories of interest was defined to evaluate the applicability of the framework. Nonnegative matrix factorization (NMF) and hierarchical clustering were subsequently applied to identify chemicals with the highest exposure potential and to highlight most relevant mixtures of chemicals on the basis of the specific usage patterns of the considered survey individuals.

Effects of envelope features on wind flow and pollutant exposure in street canyons

Traffic pollution has posed a serious threat to the health of near-road city residents and pedestrians, especially in high-density cities. However, the influences of envelope features, including balconies, overhangs and wing walls, on pollutant exposure to near road residents and pedestrians have not been fully understood. This paper investigates the effects of three commonly-used envelope features on wind flow and pollutant exposure to residents in street canyon with three different aspect ratios. The evaluation metrics of personal intake fraction and daily pollutant exposure are used to quantitatively assess the influences caused by different envelope features on healthy risk of near-road residents and pedestrians, alongside with wind flow pattern and pollutant distribution. The results show that these envelope features have increased the risk of pollutant exposure for the leeward side residents, while the risk of pollutant exposure for the windward side residents is reduced for most cases, in particular for the first floor. This observation is especially prominent when the canyon has the highest aspect ratio among the tested ratios, with the increased ratio of personal intake fraction reaching up to 540%. Moreover, the pollutant concentration is overall higher on leeward side of upstream building than that of windward side of downstream building. These findings can help urban planners and architects to build healthy and sustainable urban environment.

Characterizing honey bee exposure and effects from pesticides for chemical prioritization and life cycle assessment

Agricultural pesticides are key contributors to pollinator decline worldwide. However, methods for quantifying impacts associated with pollinator exposure to pesticides are currently missing in comparative risk screening, chemical substitution and prioritization, and life cycle impact assessment methods. To address this gap, we developed a method for quantifying pesticide field exposure and ecotoxicity effects of honey bees as most economically important pollinator species worldwide. We defined bee intake and dermal contact fractions representing respectively oral and dermal exposure per unit mass applied, and tested our model on two pesticides applied to oilseed rape. Our results show that exposure varies between types of forager bees, with highest dermal contact fraction of 59 ppm in nectar foragers for lambda-cyhalothrin (insecticide), and highest oral intake fractions of 32 and 190 ppm in nectar foragers for boscalid (fungicide) and lambda-cyhalothrin, respectively. Hive oral exposure is up to 115 times higher than forager oral exposure. Combining exposure with effect estimates yields impacts, which are three orders of magnitude higher for the insecticide. Overall, nectar foragers are the most affected forager type for both pesticides, dominated by oral exposure. Our framework constitutes an important step toward integrating pollinator impacts in chemical substitution and life cycle impact assessment, and should be expanded to cover all relevant pesticide-crop combinations.

Effect of traffic tidal flow on pollutant dispersion in various street canyons and corresponding mitigation strategies

Abstract Increasing traffic emission presents a high risk of exposure to residents in near-road buildings. Traffic tidal flow (TTF) has gradually become one of the most important components of urban traffic congestion. By computational fluid dynamics simulation, the present study examines the airflow, spatial distribution of pollutant concentration, and personal intake fraction (IF_p) of CO in five street canyon structures (shallow, regular, deep, step-up, and step-down street canyons), with non-uniform TTF-induced traffic emission considered. Optimal urban design devices (wind catchers) are subsequently introduced to reduce IF_p. The results suggest that leeward IF_p is far higher in concentration than the windward wall in the shallow, regular, step-up, and step-down street canyons but lower than the windward side in the deep street canyon under different TTF conditions. Moreover, the TTF condition SL (leeward source)/SW (windward source)=3/1 leads to a higher leeward IF_p in the shallow, regular, deep, and step-up street canyons, compared with SL/SW=1/3; however, no significant difference in windward IF_p is found under the different TTF conditions. The highest IF_p and lowest IF_p for both TTF configurations occur in the step-down and shallow street canyons, respectively. Finally, the effect of wind catchers (WCs) varies between the street canyon structures under different TTF conditions. WCs can lead to at least 30.6% reduction in leeward overall average IF_p ( ) in the shallow, regular, step-up, and step-down street canyons, as well as 12.8%–78.4% decrease in windward 〈IF_p〉 owing to the WCs in the regular, deep, step-up, and step-down street canyons.

Numerical investigations of reactive pollutant dispersion and personal exposure in 3D urban-like models

With satisfactory validation by experimental data, we perform computational fluid dynamic(CFD) simulations with the standard k-ε model to investigate how NO–NO2–O3 photochemistry and turbulent mixing influence reactive pollutant dispersion and vehicular NOx exposure in 21-row(neighborhood-scale~1 km) three-dimensional(3D) medium-dense urban models with an approaching wind parallel(perpendicular) to the main(secondary) streets. Personal intake fraction P_iF and its spatially-averaged values for the entire building (i.e. building intake fraction <P_iF>B) are adopted for reactive/passive exposure analysis with/without NOx-O3-photochemistry.Some meaningful findings are proposed: 1) There are flow adjustment processes coupling turbulent mixing and chemical reactions through urban areas (i.e. secondary Street 1 to 20). NO–NO2–O3 photochemistry induces O3 depletion and NO conversion into NO2 producing significant increase in NO2 exposure and slight decrease in NO exposure compared with passive dispersion. 2) With span-wise NOx sources, Street 10 in the fully-developed region experiences weaker wind and subsequently greater <P_iF>B(0.207 ppm) than Street 3(0.135 ppm) in the upstream flow-adjustment region. <P_iF>B descends exponentially from the target building toward downstream, and Street 10 experiences quicker decay rates. 3) With stream-wise NOx sources along the main street, <P_iF>B first ascends, then reaches equilibrium values (e.g.0.046–0.049 ppm). 4) If background O3 concentration [O3] rises from 20 ppbv to 40 and 100 ppbv, more NO is oxidized by O3 to generate NO2. As [O3] = 20 ppbv, if NO–NO2 emission ratio decreases from 10 to 5, NO2 exposure is partly offset but NO exposure change little. Present methodologies are confirmed effective to investigate impacts of more complicated meteorological conditions and chemical mechanisms on exposure in urban districts.

Selected Trichothecenes in Barley Malt and Beer from Poland and an Assessment of Dietary Risks Associated with their Consumption.

Eighty-seven samples of malt from several Polish malting plants and 157 beer samples from the beer available on the Polish market (in 2018) were tested for Fusarium mycotoxins (deoxynivalenol (DON), nivalenol (NIV)), and their modified forms ((deoxynivalenol-3-glucoside (DON-3G), nivalenol-3-glucoside (NIV-3G), 3-acetyldeoxynivalenol (3-AcDON)). DON and its metabolite, DON-3G, were found the most, among the samples analyzed; DON and DON-3G were present in 90% and 91% of malt samples, and in 97% and 99% of beer samples, respectively. NIV was found in 24% of malt samples and in 64% of beer samples, and NIV-3G was found in 48% of malt samples and 39% of beer samples. In the malt samples, the mean concentration of DON was 52.9 µg/kg (range: 5.3–347.6 µg/kg) and that of DON-3G was 74.1 µg/kg (range: 4.4–410.3 µg/kg). In the beer samples, the mean concentration of DON was 12.3 µg/L (range: 1.2–156.5 µg/L) and that of DON-3G was 7.1 µg/L (range: 0.6–58.4 µg/L). The concentrations of other tested mycotoxins in the samples of malt and beer were several times lower. The risk of exposure to the tested mycotoxins, following the consumption of beer in Poland, was assessed. The corresponding probable daily intakes (PDIs) remained a small fraction of the tolerable daily intake (TDI). However, in the improbable worst-case scenario, in which every beer bottle consumed would be contaminated with mycotoxins present at the highest level observed among the analyzed beer samples, the PDI would exceed the TDI for DON and its metabolite after the consumption of a single bottle (0.5 L) of beer.

Qualitative assessment on premature human mortality due to the emission of fine particulate matter from the Matarbari coal power plant

AbstractThis study reports the probability of increased mortality of people within the political border of Bangladesh due to the emission of fine particulate matter with diameters of 2.5 microns or less (PM2.5) from the Matarbari coal power plant (MCPP). A Gaussian plume dispersion model has been used for this estimation. The PM2.5 emission rate data are unavailable as the construction of MCPP is still in its initial stage; therefore, the anticipated PM2.5 emission rate has been estimated based on data from a number of coal‐fired power plants in India and China. To make this study more meaningful, two different emission rates have been considered representing the best‐case and worst‐case scenarios. In both cases, the intake fraction has been found to be 0.12×10−2, and the value of relative risk varies between 1.134 and 1.374, respectively. Finally, it is estimated that approximately 11.5 million people inside Bangladesh will be exposed to the PM2.5 emission from MCPP, and between 7,667 and 17,675 people will experience premature death every year.

Integrated impacts of turbulent mixing and NOX-O3 photochemistry on reactive pollutant dispersion and intake fraction in shallow and deep street canyons

We employ computational fluid dynamics (CFD) simulations with NO-NO2-O3 chemistry to investigate the impacts of aspect ratios (H/W = 1,3,5), elevated-building design, wind catchers and two background ozone concentrations ([O3]b = 100/20 ppb) on reactive pollutant dispersion in two-dimensional (2D) street canyons. Personal intake fraction of NO2 (P_IFNO2) and its spatial mean value in entire street (i.e. street intake fraction <P_IFNO2>) are calculated to quantify pollutant exposure in near-road buildings. Chemical reaction contribution of NO2 exposure (CRC<P_IF>), O3 depletion rate (dozone) and photostationary state defect (δps) are used to analyze the interplay of turbulent and chemical processes.As H/W increases from 1, 3 to 5 with [O3]b = 100 ppb, the flow pattern turns from single-main-vortex structure to two-counter-rotating-vortex structure, and pedestrian-level velocity becomes 1–2 orders smaller. The high-dozone regions and low-|δps| regions get larger with more complete chemical reactions. Consequently, passive <P_IFNO2> rises 1 order (4.09–5.71 ppm to 41.76 ppm), but reactive <P_IFNO2> only increases several times (17.80–21.28 ppm to 58.50 ppm) and the contribution of chemistry (CRC<P_IF>) decreases with higher H/W. Thus, chemistry raises <P_IFNO2 > more effectively in shallow street canyons (H/W = 1–3). In deep street canyons (H/W = 5), elevated-building design and wind catchers destroy two-counter-rotating-vortex structure, improve street ventilation and reduce passive <P_IFNO2> by 2 and 1 orders (41.76 ppm to 0.38–5.16 ppm), however they only reduce reactive <P_IFNO2> by about 97.5% and 75% (58.50 ppm to 1.61–14.48 ppm). Such building techniques induce lower O3 depletion rate but greater chemical contribution. Finally, raising [O3]b from 20 to 100 ppb causes greater O3 depletion rate and chemical contribution and produces larger <P_IFNO2>. For deep street canyons, the impact of higher [O3]b on <P_IFNO2> is weaker than that in shallow street canyons, while it becomes stronger when fixing elevated-building design and wind catchers. This study provides some innovative findings on reactive pollutant exposure in 2D street canyons and offers effective CFD methodologies to evaluate pollutant exposure with more complicated chemistry and urban configurations.

Integrated impacts of tree planting and street aspect ratios on CO dispersion and personal exposure in full-scale street canyons

Validated by experimental data, this paper performs computational fluid dynamics (CFD) simulations to investigate the influence of tree plantings on urban airflow and vehicular CO exposure in two-dimensional (2D) street canyons with various aspect ratios (building height/street width, AR = H/W = 0.5, 1, 3, 5) and ground-level source. The impacts of tree canopy bottom height (Htb = 2 m, 6 m), tree stand density (y-density = 0.33, 0.67, 1) and leaf area density (LAD = 0.5, 1, 2 m2/m3) are considered. Personal intake fraction (P_IF) and its spatial mean value in leeward and windward sides (<P_IF>lee, <P_IF>wind) and for entire streets (street intake fraction, <P_IF>) are adopted to assess overall pollutant exposure.For cases without trees, only one main vortex exists in shallow streets with AR = 0.5-3 and <P_IF> as AR = 3 (5.80 ppm) slightly exceeds AR = 0.5-1 (3.98-3.84 ppm). However, two counter-rotating vortexes appear in deep streets (AR = 5), inducing 1-2 orders smaller pedestrian-level velocity (U/Uref~10−4-10−3) and one-order greater <P_IF> (46.80 ppm) than shallow streets. Trees always weaken wind in streets and raise <P_IF> more in shallower streets by 46.0% as AR = 0.5 (3.98 ppm-5.81 ppm), 26.0-45.9% as AR = 1 (3.84 ppm to 4.84-5.60 ppm), 16.2-50.3% as AR = 3 (5.80 ppm to 6.74-8.72 ppm), but only 8.5-23.4% as AR = 5 (46.80 ppm to 50.78-57.73 ppm). Particularly, as AR = 1, trees raise <P_IF>lee (5.87 ppm) by 27.1-57.2%, while <P_IF>wind (1.80 ppm) only by 0%-23.3%. Higher Htb, smaller y-density or LAD produce less increase of <P_IF>. As AR = 3, vegetation increases <P_IF>lee (8.84 ppm) by 21.2%-66.4% but little affects <P_IF>wind (2.76 ppm). Lower Htb produces smaller <P_IF> differing from AR = 1. As AR = 5, vegetation increases <P_IF>wind (63.97 ppm) by 15.1-36.6% but reduces <P_IF>lee (29.63 ppm) by 5.2-8.5%. Although further investigations are still required for design purpose, this paper provides effective methodologies to quantify how vegetation influences street-scale pollutant exposure.