Characterizing of fine particulate matter (PM1) on the platforms and outdoor areas of underground and surface subway stations

A campaign was conducted to assess the PM₁ concentration and elemental composition on the platforms and adjacent outdoor areas of an underground subway station (Imam Khomeini) and a surface subway station (Sadeghiye) in Tehran from June 2014 to November 2014. The respective mean concentrations of PM₁ on the platforms and in the outdoor areas of Imam Khomeini station were 42.04 and 30.92 µg/m³ and for Sadeghiye station 31.42 and 26.02 µg/m³. Statistical analyses demonstrated that the platforms of the Imam Khomeini and Sadeghiye stations were influenced by the adjacent ambient air of these stations (p < 0.05). PM₁ was found to be highly enriched with Fe on the platforms of metro systems, which were more frequently encountered in the Imam Khomeini station than the Sadeghiye station as 41.06% and 37.73% of the total PM₁ mass respectively. Minor elements, particularly Ba, Pb, Cr, Cu, Ni, Mn, Ti, V, and Zn, were elevated for the platform of Imam Khomeini and, to a lesser degree, the platform of Sadeghiye stations, which may be due to abrasion processes between rail tracks, wheels, and brake pads.     

Characterization of metal(loid)s in indoor and outdoor PM2.5 of an office in winter period

The characterization of indoor (a naturally ventilated office) and outdoor (adjacent courtyard) metals in PM_2.5 during a winter period in Xi'an, China were carried out. The results indicated that the average mass concentrations of PM_2.5 in indoor and outdoor environments all exceeded the daily average limit of 75 µg m^–3 set by the Chinese government. The dominant metals in PM_2.5 were Ca, Al, Zn, Mg, Fe, and Pb in both indoor and outdoor air. Concentration of As was much higher than the standard of 6 ng m^–3 issued by the government. Enrichment factor analysis showed that anthropogenic emissions might be the primary sources of As, Cd, Pb, and Zn, while crust was the main origin of Co. A majority of indoor-to-outdoor concentration ratios of metal were lower than 1 indicating mostly the contribution of outdoor sources rather than indoor ones. As and Cr in both indoor and outdoor air posed the highest noncarcinogenic and carcinogenic risks, respectively. The noncarcinogenic and carcinogenic risks were 2.74 and 2.54 × 10^?4 indoor and 4.04 and 3.87 × 10^?4 outdoor, which suggested that possible adverse health effects should be of concern.     

Metal Content in Air Samples Collected in an Urban Zone in Tampico,México: A First Survey

With the aim to know possible risks to the population, Cd, Co, Cr, Cu, Mn, Ni, Pb, and Tl were determined for the first time in airborne samples of particulate matter in an urban zone in Tampico, México, during the winter of 2003. The 24-hour PM₁₀ samples were collected every 6 days on quartz-filters by using a high volume sampler and analyzed by Inductively Coupled Plasma Optical Emission Spectrometer. Standard reference material was used to verify metal recovery. The maximum PM₁₀ and lead concentrations were 12.05 and 0.040 μ g/m³, respectively, not exceeding Méxican standard values. The greatest metal concentration was that of manganese with 0.90 μ g/m³, followed by Cu and Ni with 0.17 and 0.012 μ g/m³, respectively. Agglomerates, well-defined particles, and heavy metals (e.g., Mn and Cu) were found in PM₁₀ using Scanning Electron Microscopy and Energy Dispersive Spectroscopy. Meteorological conditions associated with the sampling period showed that Pb and Ni are being continuously emitted, and that Mn, Cu, and Co could come from one industry located to the WSW of the region. All of these concentrations do not constitute a potential risk to human health, although it is necessary to continue studying the high concentrations of Mn and Cu in longer sampling periods.     

The modeling and health risk assessment of PM2.5 from Tema Oil Refinery

Fine particulate matters (PM_2.5) are known to pose serious health problems compared to other air pollutants. The current study employed air dispersion modeling system (AERMOD) to simulate the concentration of PM_2.5 from Tema Oil Refinery (TOR) and to assess the non-cancer risk and mortalities of the exposed population. In addition, the effects of local climatic factors on the distribution and concentration of PM_2.5 within the three main seasons (Major Raining Season (MRS), Low Raining Season (LRS) and Dry Season (DS)) were investigated. The AERMOD results showed that both 24-h (38.8 µg m^?3) and annual (12.6 µg m^?3) PM_2.5 concentration levels were in exceedance of the international limits. However, a decreasing trend in seasonal PM_2.5 concentrations was observed. Health risk assessment (HRA), indicated by hazard index (HI), revealed that the amount of Al₂O₃ present in the PM_2.5 caused a significant non-carcinogenic health risk to the exposed population (both adults and children) within the Metropolis (HI = 2.4 for adults and HI = 1.5 for children). Additionally, cardiopulmonary disease related mortalities due to PM_2.5 exposure (181 deaths for adults and 24 deaths for children) were found high compared to deaths caused by lung cancer (137 deaths for adults and 16 deaths for children).     

Air quality modeling for health risk assessment of ambient PM10, PM2.5 and SO2 in Iran

In this study, we have estimated the number of total mortality (T-mortality), cardiovascular morbidity (CV-mortality), respiratory mortality (R-mortality), hospital admissions due to cardiovascular diseases (HA-CVD), respiratory diseases (HA-RD), chronic obstructive pulmonary diseases (COPD) and acute myocardial infarction (AMI) due to exposure to particulate matter less than 10 µm (PM₁₀), 2.5 µm (PM_2.5) and sulfur dioxide (SO₂) in western Iran in 2016. The World Health Organization (WHO) method was used to assess the mortality and morbidity among the exposed people. The results showed that about 3.9% CM (95% CI: 2.9–7.8%), 3.9% HA-RD (95% CI: 2.4–7.8%) and 4.4% HA-CVD (95% CI: 3.0–6.8%) for ambient PM₁₀ and about 7.3% TM (95% CI: 4.2–9.7%), 12.1% CM (95% CI: 3.5–14.6%) and 3.0% RM (95% CI: 0–6.3%) for PM_2.5 are respectively attributed to concentrations exceeding 10 µg/m³. Furthermore, 3.2% HA-COPD (95% CI: 0–5.04%) and 4.2% AMI (95% CI: 1.6–4.3%) can be attributed to SO₂ concentrations greater than 10 µg/m³, respectively. To reduce the adverse health effect of PM, health advices provided by health authorities should be given to general population especially vulnerable people such as people with chronic lung and heart pathologies, elderly and children during the dusty days.     

Heavy Metal Content in PM2.5 Air Samples Collected in the Metropolitan Area of Monterrey,México

The air PM_2.5 concentration and its heavy metal content (Fe, Pb, Mn, Ni, As) were measured in the Metropolitan Area of Monterrey, Méxicoin Mexico, an area that is characterized by both very active and diverse industrial activity and intense highway traffic and industrial activity. The 24-h PM_2.5 samples were collected in two different zones during a 1-year-long measurement program (February 2008–February 2009). The year PM_2.5 average was above 15 μg/m³ exceeding Mexican and international standards. The difference of PM_2.5 in each zone was not statistically significant. The greatest metal content was for iron, followed by lead, manganese, nickel and arsenic. The difference in metal content for Pb, Mn, and As was statistically significant.     

Elemental composition of ambient air particles in Taiyuan,China: evaluation of lifetime cancer and non-cancer risks

Abstract

Shanxi is a heavily polluted area in China. Our aim was to analyze the elemental concentration (71 elements) in ambient air in Taiyuan and evaluate cancer and non-cancer risks. Air was sampled in four urban sites and one rural site in the heating season (winter/spring) and summer season (totally 118?days sampling time). Mean total suspended particles (TSP) across all sampling sites were 248 µg/m³ in summer and 478 µg/m³ in winter. The heating season had higher levels of S, Pb, Br, Mn, Se, As, Ni, Cd, and Hg (23.3 µg/m³, 821?ng/m³, 725?ng/m³, 460?ng/m³, 79?ng/m³, 65?ng/m³, 34?ng/m³, 17?ng/m³, and 3.5?ng/m³, respectively) than the summer season (9.6 µg/m³, 276?ng/m³, 138?ng/m³, 283?ng/m³, 0?ng/m³, 21?ng/m³, 21?ng/m³, 6.8?ng/m³, and 0?ng/m³, respectively), except for Cr and Co, of which the levels were higher in summer. Many elements had a high correlation with the TSP level (r?=?0.70–0.96) and S (r?=?0.61–0.95). A health risk assessment demonstrated that Mn and Cr could have a risk of non-cancer effects. Estimated lifetime cancer risks (R_i>10^?6) were observed for As, Cd, Co, Cr, and Ni, indicating that cancer risks from air pollution were relatively high in Taiyuan.     

Study of PM10, PM2.5, and PM1 levels in during dust storms and local air pollution events in urban and rural sites in Tehran

The aim of this study is to survey the PM₁₀, PM_2.5, and PM₁ concentrations in rural and urban areas in Tehran province during cold, warm and dust storm days from December 22, 2016 to June 5, 2017 using Grimm Model aerosol spectrometer. During the study period, daily PM₁₀, PM_2.5, and PM₁ concentrations ranged from 27.2 to 244.96, 8.4 to 77.9, and 6.5 to 56.8 μg/m³ in urban sites, and 22.8 to 286.4, 6 to 41.1, and 2.1 to 20.2 μg/m³ in rural parts, respectively. Particularly, both daily WHO limits for outdoor PM₁₀ (50.0 μg/m³) and PM_2.5 (25.0 μg/m³) exceeded in 95% and 83% of the outdoor measurements in winter and 82% and 58% in total sampled days in urban site, respectively. The 24-h average PM₁₀ and PM_2.5 concentrations also exceeded by 59% and 18% in winter and by 36% and 14% of all sampling days in rural site, respectively. During the dust storm, the 24-h average PM₁₀, PM_2.5, and PM₁ concentrations were, respectively 4.7, 2, and 1.96 times higher than those in urban site and 2, 1.7, and 1.3 times more than those in rural site in all sampled days.     

In-Field Ambient Fine Particle Monitoring of an Outdoor Wood Boiler: Public Health Concerns

Outdoor wood boilers (OWBs) are detached wood-fired units that heat water used for domestic consumption and heating. The increasing use of OWBs has prompted regulatory concern because of escalating public complaints. Few field studies of OWB ambient emissions have been conducted, limiting efforts to assess this air quality problem. A screening level evaluation was conducted to characterize ambient fine particle (PM_2.5) levels nearby an OWB device and to overview operating and design factors that could influence PM_2.5 levels. High hourly (186 μ g/m³ 4.3 h mean, 665 μg/m³ 95th percentile) and peak continuous (8,880 μg/m³ 15 s avg) PM_2.5 concentrations were found within 50–150 ft of an OWB relative to background levels throughout the course of nearly routine operating conditions. Values were highest during air intake within 1 h of fuel loading (416 μg/m³ 1 h mean) compared to air-starved 22–24 h after loading (115 μg/m³ 3.3 h mean). OWB features that could affect PM_2.5 levels include exemption from federal wood stove standards, poor combustion design, large firebox capacity, trash burning use, low stack height, and four-season utility. In view of cardiac and respiratory health risks associated with transient exposure to ambient PM_2.5 at levels well below those reported here, this pilot study contributes to the risk assessment field by identifying an emerging problem of potential public health significance.     

Platinum concentration in PM2.5 in the Mexico City Metropolitan Area: relationship to meteorological conditions

Abstract

Platinum (Pt) concentrations in PM_2.5 were evaluated by means of inductively coupled plasma mass spectrometry (ICP-MS) to evaluate the spatial and temporal behavior and to assess trends. Samples were taken from five representative sites in the Mexico City Metropolitan Area (MCMA): Tlalnepantla-northwest (NW), San Agustin-northeast (NE), La Merced -center (C), Coyoacan-southwest (SW), and Universidad Autonoma Metropolitana Iztapalapa-southeast (SE). Under three weather conditions: dry warm (DW-April), rainy (R-August), and dry cold (DC-November) in 2013. We found that the PM_2.5 median mass concentration was 24?μg m^?3?±?15?μg m^?3 while Pt concentration was 55?pg m^?3?±?15?pg m^?3 (median, interquartile range). Seasonal trend was identified: the concentrations decreased significantly in the following order DC?>?R>DW. No spatial distribution was observed. Interestingly, among other meteorically parameters, wind intensity resulted to be the major factor for the dispersion of Pt in PM2.5 in MCMA. Furthermore, we found that Pt concentrations increased significantly by 19.6% between 2011 and 2013. Regardless of the increase in Pt, carbon monoxide (CO) levels decreased opposite to a rise in vehicular fleet. These results urge for environment public policies that address the upward tendency of Pt levels especially in urban areas.     

Seasonal Variation in Schools’ Indoor Air Environments and Health Symptoms among Students in an Eastern Mediterranean Climate

The indoor air quality (IAQ) in classrooms highly affects the health and productivity of students. This article aims to clarify seasonal variation in indoor environment and sick building syndromes (SBS) symptoms in an Eastern Mediterranean climate. A series of field measurements were conducted during the fall and winter seasons from October 2011 to March 2012 in 12 naturally ventilated schools located in the Gaza Strip. Data on environmental perception and health symptoms were obtained from 724 students by using a validated questionnaire. The results showed that indoor PM₁₀ and PM_2.5 concentrations were 426.3 ± 187.6 μg/m³ and 126.6 ± 94.8 μg/m³, respectively. The CO₂ concentrations and ventilation rate widely exceeded their reference values during the winter season. The prevalence rates of general symptoms were relatively high at baseline assessment in the fall season and increased significantly during follow-up in the winter season. Significant increases in disease symptoms such as mucosal irritation and pre-existing asthma symptoms among students could be related to poor indoor air quality. Five distinct groups of SBS symptoms from factor analysis of students’ related symptoms were significantly correlated with PM₁₀ and PM_2.5, CO₂, ventilation rate, and indoor temperature. As vulnerable children, this situation negatively affects their school performance and health.     

Assessing the Impact of Advected African Dust on Air Quality and Health in the Eastern United States

Large quantities of African dust are carried into the southeastern United States each summer with concentrations typically in the range of 10 to 100?µg m^?3. Because approximately one-third to one-half of the dust mass is in the size range under 2.5?µm diameter, the advection of African dust has implications for the EPA's newly implemented standard for PM_2.5 particulate matter and for the assessment of human health effects. It will be difficult to assess the impact of African dust events on air quality because they occur during the summer (maximum in July) when photochemical pollution events are frequent and intense in the eastern United States. Indeed, the presence of dust could affect the evolution of photochemical dust events. In order to assess the role of African dust in air quality in the United States, it will be necessary to develop a set of diagnostic indicators; it appears that dust mineralogy and elemental composition might be useful for this purpose. Various satellite products can be used to characterize the spatial coverage of dust events and, when coupled with meteorological tools, to predict impact regions.     

Susceptibility of patients with chronic obstructive pulmonary disease to heart rate difference associated with the short-term exposure to metals in ambient fine particles: A panel study in Beijing,China

Susceptibility of patients with chronic obstructive pulmonary disease (COPD) to cardiovascular autonomic dysfunction associated with exposure to metals in ambient fine particles (PM_2.5, particulate matter with aerodynamic diameter ≤2.5 µm) remains poorly evidenced. Based on the COPDB (COPD in Beijing) panel study, we aimed to compare the associations of heart rate (HR, an indicator of cardiovascular autonomic function) and exposure to metals in PM_2.5 between 53 patients with COPD and 82 healthy controls by using linear mixed-effects models. In all participants, the HR levels were significantly associated with interquartile range increases in the average concentrations of Cr, Zn, and Pb, but the strength of the associations differed by exposure time (from 1.4% for an average 9 days (d) Cr exposure to 3.5% for an average 9 d Zn exposure). HR was positively associated with the average concentrations of PM_2.5 and certain metals only in patients with COPD. Associations between HR and exposure to PM_2.5, K, Cr, Mn, Ni, Cu, Zn, As, and Se in patients with COPD significantly differed from those in health controls. Furthermore, association between HR and Cr exposure was robust in COPD patients. In conclusion, our findings indicate that COPD could exacerbate difference in HR following exposure to metals in PM_2.5.

     

Induction of non-protein thiols and phytochelatins by cadmium in Eichhornia crassipes

Abstract

Impact of root Cd concentration on production of cysteine, non-protein thiols (NP-SH), glutathione (GSH), reduced glutathione (GSSG), and phytochelatins (PCs) in Eichhornia crassipes exposed to different dilutions of brass and electroplating industry effluent (25%, 50%, and 75%), and synthetic metal solutions of Cd alone (1, 2.5, and 3.5?ppm) and with Cr (1?ppm Cd + 1?ppm Cr, 2.5?ppm Cd + 3?ppm Cr, and 3.5?ppm Cd + 4?ppm Cr) was assessed in a 45?days study. Different treatments were used to understand and compare differential antioxidant defense response of plant under practical drainage (effluent) and experimental synthetic solutions. The production of NP-SH and cysteine was maximum under 2.5?ppm Cd + 3?ppm Cr treatments i.e., 1.78?µmol/g fw and 288?nmol/g fw, respectively. The content of GSH declined whereas that of GSSG increased progressively with exposure duration in all treatments. HPLC chromatograms revealed that the concentrations of PC2, PC3, and PC4 (248, 250, and 288?nmol-SH equiv.g^?1 fw, respectively) were maximum under 1?ppm Cd, 1?ppm Cd + 1?ppm Cr, and 2.5?ppm Cd + 3?ppm Cr treatments, respectively. PC2, PC3, and PC4 concentrations increased with Cd accumulation in the range 812–1354?µg/g dry wt, 1354–2032?µg/g dry wt and 2032–3200?µg/g dry wt, respectively. Thus, the study establishes a direct proportionality relationship between concentration/length of phytochelatins and root Cd concentrations, upto threshold limits, in E. crassipes.     

Elevated levels of urinary 17-ketosteroids in central Indian children residing near sewage treatment plant and solid waste disposal plant: A preliminary study

Urinary excretion of 17-ketosteroid (17-KS) was assessed in male pre-pubertal subjects aged (8–11 years; n = 90). Children living near sewage treatment plant and solid waste disposal plant (Group P) showed significantly higher levels of urinary 17-KS (Group P: 3.27 ± 1.63 µg/mL/CRE; p < 0.01) than children living in cleaner area (0.50 ± 0.53 µg/mL/CRE; Group C). Occurrence of urinary dibutyl phthalate in representative subjects of Group P (odds ratio: 9; p < 0.05; 95% of Confidence interval (CI) 1.93–72.99) was higher compared to Group C. Urinary concentrations of Cd (0.85 µg/g CRE ± 0.11), Mn (24.25 µg/g CRE ± 6.11) and Pb (12.39 µg/g CRE ± 2.86) in Group P were significantly (p < 0.01) higher than those found in Group C (Cd (0.28 µg/g CRE ± 0.03), Mn (13.33 µg/g CRE ± 3.20) and Pb (5.67 µg/g CRE ± 0.53)). Analyses of ambient air samples (PM₁₀) in polluted area revealed major occurrence of phthalates, whereas derivatives of trifluoromethyl, dione, etc. were identified in PM_2.5 fraction. Metal (Cd, Co, Mn and Pb) concentrations in ambient air (24 h, PM₁₀) were higher in polluted area compared to cleaner area. We conclude that elevated levels of urinary 17-KS in Group P could be attributed to higher exposure of these subjects to Endocrine disrupting chemicals (EDCs) compared to Group C.     

大庆市6种绿化树种对SO2、NO2的消减及滞尘效应

城市森林在吸收、滞留大气污染物,改善城市生态环境方面具有重要意义。以大庆市6种常见绿化树种为研究对象,采用水洗-滤膜法和熏气试验探究不同树种对总悬浮颗粒物(TSP)、大颗粒物(PM_>10)、粗颗粒物(PM_3—10)和细颗粒物(PM_1—3)的滞留规律以及对大气中SO₂、NO₂的消减效果。研究结果表明：(1)不同树种的滞尘能力差异显著(P<0.05),对TSP的滞留量从大到小依次为：油松(3.82±0.40)g/m²>红瑞木(1.45±0.12)g/m²>紫丁香(1.22±0.17)g/m²>梣叶槭(1.21±0.13)g/m²>大叶杨(0.93±0.17)g/m²>旱柳(0.54±0.14)g/m²;(2)树种间对不同颗粒物的滞留量具有显著差异(P<0.05),供试树种对不同粒径颗粒物滞留的质量占比表现...     

Concentration Levels of Essential and Non-essential Metals in Ethiopian Khat (Catha edulis Forsk)

The levels of essential (Ca, Mg, Mn, Fe, Zn, Cr, Cu, and Co) and non-essential (Cd and Pb) metal in six different varieties of Ethiopian khat (Catha edulis Forsk, an evergreen stimulant plant) commonly consumed in the country and exported to the neighboring countries were determined by flame atomic absorption spectrometry. Known weight of oven-dried khat samples were wet-digested using 2 mL of (69–72%) HNO₃ and 2 mL of (70%) HClO₄ for 2 h and 30 min at variable temperature (120–270°C). The mineral contents in the digests were analyzed using flame atomic absorption spectrometer. The following concentrations ranges in fresh-weight basis were recorded in decreasing order: Ca (1,038–2,173 µg/g)?>?Mg (478.2–812.3 µg/g)?>?Fe (53.95–82.83 µg/g)?>?Zn (5.18–9.40 µg/g)?>?Mn (6.98–8.66 µg/g)?>?Cu (1.85–5.53 µg/g)?>?Cr (0.66–3.47 µg/g)?>?Co (0.41–0.80 µg/g). A wide variation in the mineral contents of khat from different region of Ethiopia was noticed. The toxic metals (Pb and Cd) were not detected in all the samples analyzed.     

Characterization and human health risk assessment of trace metal in PM10 in Bac Giang,short-term study in a developing province in Vietnam

Abstract

This study investigated the airborne concentration of PM₁₀ and 20 trace elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Na, Pb, Ti, V, Zn) in residential, industry, traffic road, coal mining, thermal power plant area of Bac Giang province. The average PM₁₀ concentration was highest at coal site, followed by traffic 1 sites, industrial sites and traffic 2 sites, the residential sites, and lowest at the power plant site located in mountain area. While Al, Ca, Fe, K, Mg, Na were the most abundant elements in all sampling sites, accounting for 73–96% of total obtained elements, the concentration of As, Cd, Cr, Cu, Mn, Ni, Pb, V, and Zn occupied from 2.9 to 23.2%. Noticeably, the concentrations of Cd were from 7 to 65 times higher than the concentration limit for Cd (0.1?ng/m³) according the World Health Organization (WHO). Although, the Hazard Index (HI values) of all metals were found to be within the safe level for both children and adults, the Carcinogenic Risk (CR) of Cr and As in all sites were closed to the acceptable levels for children, implying a potential carcinogenic risks of these metals.     

Spatio-temporal modelling of particulate matter concentrations using satellite derived aerosol optical depth over coastal region of Chennai in India

The present study primarily focuses on describing aerosol optical depth (AOD), its distribution pattern and seasonal variation, and modelling Particulate Matter Concentrations in Chennai. The frequency distribution of AOD and PM_2.5 demonstrates that AOD can be used as a proxy for estimating PM_2.5 in the study region as the occurrence of AOD almost resonates with that of PM_2.5. The seasonal variation of AOD and PM_2.5 revealed that during the winter (October–January) and summer (February–May) seasons, AOD reasonably followed the trend of PM_2.5. However, during the monsoon period, AOD showed random variations. Different models like linear and non-linear regression models and machine learning models such as random forest (RF) have been developed for PM_2.5 estimation. The model's performance in different stations and seasons has been assessed. The effect of meteorology and other factors in the model has also been assessed. From linear and non-linear model analysis, AOD was a significant parameter in estimating PM_2.5. The Random Forest model was the stable model for the study region, with a model R² of 0.53 and an RMSE of 15.89 μg/m³. The inclusion of meteorological parameters like relative humidity, wind speed, and wind direction decreased the error in prediction by 17.45 μg/m³. The seasonal and spatial analysis indicates that the prediction capability of models varies with stations and seasons. The best performing model was found to be Model RF, and the model could explain about 53.14% of the variability in PM_2.5 concentration occurrence in the study region with a prediction error of 15.89 μg/m³.     

An Assessment of Risk from Particulate Released from Outdoor Wood Boilers

Use of outdoor wood boilers (OWB) has increased due to cost of fossil fuels. OWB short stacks release particles close to the breathing level, producing high levels of particulate matter ≤2.5 μm in diameter (PM_2.5). This assessment determines OWB contribution to local cancer risk and estimates thresholds for acute non-cancer risks. Carcinogenic PAHs in wood smoke (PM_2.5) cancer risks range from 2.7 × 10^–3 for the upper bound scenario (95% UCL value of PM_2.5 (665 μg/m³)) to 7.6 × 10^–5 for the lower bound (mean (186 μg/m³)). These risks represent a 7-fold increase of acceptable cancer risk for the lower bound value and 2 orders of magnitude above acceptable levels for the upper bound values. Non-cancer effects such as asthma and cardiopathies include respiratory attacks, hospital emergency room visits, and hospitalizations. Inhaled dose acute risk thresholds of 96, 120, and 250 μg PM 2.5/6 hours are proposed. Operation of an OWB that emits 100 grams PM_2.5/h was modeled and found to increase the exposures that exceed the 120-μg-risk level at and in residences within 500 to 1000 feet. The increases are projected to occur during periods of poor air mixing due to decreased wind speeds or inversions. Our analysis proposes a 6-h PM_2.5 inhaled dose threshold to predict peak periods of unhealthy air quality instead of 24-h and annual averages standards, which mask peak emissions.