Nucleon Transversity Distribution in the Continuum and Physical Mass Limit from Lattice QCD.

We report a state-of-the-art lattice QCD calculation of the isovector quark transversity distribution of the proton in the continuum and physical mass limit using large-momentum effective theory. The calculation is done at four lattice spacings a={0.098,0.085,0.064,0.049} fm and various pion masses ranging between 220 and 350 MeV, with proton momenta up to 2.8 GeV. The result is nonperturbatively renormalized in the hybrid scheme with self-renormalization, which treats the infrared physics at large correlation distance properly, and extrapolated to the continuum, physical mass, and infinite momentum limit. We also compare with recent global analyses for the nucleon isovector quark transversity distribution.

Pion and Kaon Distribution Amplitudes from Lattice QCD.

We present a state-of-the-art lattice QCD calculation of the pion and kaon light-cone distribution amplitudes (DAs) using large-momentum effective theory. The calculation is done at three lattice spacings a≈{0.06,0.09,0.12} fm and physical pion and kaon masses, with the meson momenta P_{z}={1.29,1.72,2.15} GeV. The result is nonperturbatively renormalized in a recently proposed hybrid scheme with self-renormalization, and extrapolated reliably to the continuum as well as the infinite momentum limit. We find a significant deviation of the pion and kaon DAs from the asymptotic form, and a large SU(3) flavor breaking effect in the kaon DA.

Lack of social touch alters anxiety-like and social behaviors in male mice.

The importance of social interactions has been reported in a variety of animal species. In human and rodent models, social isolation is known to alter social behaviors and change anxiety or depression levels. During the coronavirus pandemic, although people could communicate with each other through other sensory cues, social touch was mostly prohibited under different levels of physical distancing policies. These social restrictions inspired us to explore the necessity of physical contact, which has rarely been investigated in previous studies on mouse social interactions. We first conducted a long-term observation to show that pair-housed mice in a standard laboratory cage spent nearly half the day in direct physical contact with each other. Furthermore, we designed a split-housing condition to demonstrate that even with free access to visual, auditory, and olfactory social signals, the lack of social touch significantly increased anxiety-like behaviors and changed social behaviors. There were correspondingly higher levels of the pro-inflammatory cytokine interleukin-6 in the hippocampus in mice with no access to physical contact. Our study demonstrated the necessity of social touch for the maintenance of mental health in mice and could have important implications for human social interactions.

Association between long-term exposure to ambient air pollution and COVID-19 severity: a prospective cohort study.

BACKGROUND: The tremendous global health burden related to COVID-19 means that identifying determinants of COVID-19 severity is important for prevention and intervention. We aimed to explore long-term exposure to ambient air pollution as a potential contributor to COVID-19 severity, given its known impact on the respiratory system. METHODS: We used a cohort of all people with confirmed SARS-CoV-2 infection, aged 20 years and older and not residing in a long-term care facility in Ontario, Canada, during 2020. We evaluated the association between long-term exposure to fine particulate matter (PM2.5), nitrogen dioxide (NO2) and ground-level ozone (O3), and risk of COVID-19-related hospital admission, intensive care unit (ICU) admission and death. We ascertained individuals' long-term exposures to each air pollutant based on their residence from 2015 to 2019. We used logistic regression and adjusted for confounders and selection bias using various individual and contextual covariates obtained through data linkage. RESULTS: Among the 151 105 people with confirmed SARS-CoV-2 infection in Ontario in 2020, we observed 8630 hospital admissions, 1912 ICU admissions and 2137 deaths related to COVID-19. For each interquartile range increase in exposure to PM2.5 (1.70 µg/m3), we estimated odds ratios of 1.06 (95% confidence interval [CI] 1.01-1.12), 1.09 (95% CI 0.98-1.21) and 1.00 (95% CI 0.90-1.11) for hospital admission, ICU admission and death, respectively. Estimates were smaller for NO2. We also estimated odds ratios of 1.15 (95% CI 1.06-1.23), 1.30 (95% CI 1.12-1.50) and 1.18 (95% CI 1.02-1.36) per interquartile range increase of 5.14 ppb in O3 for hospital admission, ICU admission and death, respectively. INTERPRETATION: Chronic exposure to air pollution may contribute to severe outcomes after SARS-CoV-2 infection, particularly exposure to O3.

UV, ozone, and COVID-19 transmission in Ontario, Canada using generalised linear models.

BACKGROUND: Quantifying the impact of environmental factors on COVID-19 transmission is crucial in preventing more cases. Ultraviolet (UV) radiation and ozone (O3) have reported antimicrobial properties but few studies have examined associations with community infectivity of COVID-19. Research suggests UV light can be preventative while the effect of O3 is contested. We sought to determine the relationship between UV, O3, and COVID-19 incidence in Ontario, Canada. METHODS: In our time series analyses, we calculated daily incidence rates and reproductive number (Rt) from 34,975 cases between January and June 2020 across 34 Ontario Public Health Units. We used generalised linear models, adjusting for potential confounders, to calculate point estimates (PE) and 95% confidence intervals (CI) for UV and O3. Analyses were further stratified by age groups and outbreaks at institutions versus community. RESULTS: We found that 1-week averaged UV was significantly associated with a 13% decrease (95% CI: 0.80-0.96) in overall COVID-19 Rt, per unit increase. A negative association with UV was also significant among community outbreaks (PE: 0.88, 95% CI: 0.81-0.96) but not institutional outbreaks (PE: 0.94, 95% CI: 0.85-1.03). A positive association of O3 with COVID-19 incidence is strongly suggested among institutional outbreak cases (PE: 1.06, 95% CI: 1.00-1.13). CONCLUSION: Our study found evidence to support the hypothesis that higher UV reduced transmission of COVID-19 and some evidence that ground-level O3 positively influenced COVID-19 transmission. Setting of infection should be strongly considered as a factor in future research. UV and O3 may explain some of COVID-19's seasonal behaviour.

Evaluation of a Passive Sampling Method for Long-Term Continuous Monitoring of Volatile Organic Compounds in Urban Environments.

Environmental Protection Agency Method 325 was developed for continuous passive monitoring of volatile organic compounds (VOCs), particularly benzene, at petroleum refinery fencelines. In this work, a modified version of the method was evaluated at an Ontario near-road research station in winter to assess its suitability for urban air quality monitoring. Samples were collected at 24 hour and 14 day resolution to investigate accuracy for different exposure times. Tubes were analyzed by thermal desorption-gas chromatography-mass spectrometry, and 11 VOCs were quantified, including aromatic air toxics. The same VOCs were simultaneously monitored using traditional canister sampling for comparison, and a subset of four were also monitored using a novel miniature gas chromatograph. Good agreement (within 10%) was observed between the 14 day passive tube samples and the canister samples for benzene. However, field-calibrated uptake rates were required to correct passive tube concentrations for less volatile aromatics. Passive tube deployment and analysis is inexpensive; sampling does not require power, and accurate measurements of benzene are demonstrated here for an urban environment. The method is expected to be advantageous for the generation of long-term continuous benzene datasets suitable for epidemiological research with greater spatial coverage than is currently available using traditional monitoring techniques.

Near-Road Air Pollutant Measurements: Accounting for Inter-Site Variability Using Emission Factors.

A daily integrated emission factor (EF) method was applied to data from three near-road monitoring sites to identify variables that impact traffic related pollutant concentrations in the near-road environment. The sites were operated for 20 months in 2015-2017, with each site differing in terms of design, local meteorology, and fleet compositions. Measurement distance from the roadway and local meteorology were found to affect pollutant concentrations irrespective of background subtraction. However, using emission factors mostly accounted for the effects of dilution and dispersion, allowing intersite differences in emissions to be resolved. A multiple linear regression model that included predictor variables such as fraction of larger vehicles (>7.6 m in length; i.e., heavy-duty vehicles), vehicle speed, and ambient temperature accounted for intersite variability of the fleet average NO, NO x, and particle number EFs (R2:0.50-0.75), with lower model performance for CO and black carbon (BC) EFs (R2:0.28-0.46). NO x and BC EFs were affected more than CO and particle number EFs by the fraction of larger vehicles, which also resulted in measurable weekday/weekend differences. Pollutant EFs also varied with ambient temperature and because there were little seasonal changes in fleet composition, this was attributed to changes in fuel composition and/or post-tailpipe transformation of pollutants.

Progression from Asthma to Chronic Obstructive Pulmonary Disease. Is Air Pollution a Risk Factor?

RATIONALE: Individuals with asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS), have more rapid decline in lung function, more frequent exacerbations, and poorer quality of life than those with asthma or COPD alone. Air pollution exposure is a known risk factor for asthma and COPD; however, its role in ACOS is not as well understood. OBJECTIVES: To determine if individuals with asthma exposed to higher levels of air pollution have an increased risk of ACOS. METHODS: Individuals who resided in Ontario, Canada, aged 18 years or older in 1996 with incident asthma between 1996 and 2009 who participated in the Canadian Community Health Survey were identified and followed until 2014 to determine the development of ACOS. Data on exposures to fine particulate matter (PM2.5) and ozone (O3) were obtained from fixed monitoring sites. Associations between air pollutants and ACOS were evaluated using Cox regression models. MEASUREMENTS AND MAIN RESULTS: Of the 6,040 adults with incident asthma who completed the Canadian Community Health Survey, 630 were identified as ACOS cases. Compared with those without ACOS, the ACOS population had later onset of asthma, higher proportion of mortality, and more frequent emergency department visits before COPD diagnosis. The adjusted hazard ratios of ACOS and cumulative exposures to PM2.5 (per 10 µg/m(3)) and O3 (per 10 ppb) were 2.78 (95% confidence interval, 1.62-4.78) and 1.31 (95% confidence interval, 0.71-2.39), respectively. CONCLUSIONS: Individuals exposed to higher levels of air pollution had nearly threefold greater odds of developing ACOS. Minimizing exposure to high levels of air pollution may decrease the risk of ACOS.

Improving the correlations of ambient tapered element oscillating microbalance PM2.5 data and SHARP 5030 Federal Equivalent Method in Ontario: a multiple linear regression analysis.

UNLABELLED: Tapered element oscillating microbalances equipped with sample equilibration system (TEOM-SES) used by the province of Ontario for the ambient monitoring of PM2.5 (particulate matter with an aerodynamic diameter < or = 2.5 microm) in its air quality index (AQI) network were collocated with the Synchronized Hybrid Ambient Real-time Particulate monitor (SHARP 5030) at two monitoring sites for a period spanning approximately 2 years to determine the similarities and differences between the measurement outputs of both instrumental systems. Due mainly to mass loss observed with the TEOM-SES in cooler months, the province has recently switched its PM2.5 instrumentation at all stations in its monitoring network from the TEOM-SES to the SHARP 5030, which has the U.S. Environmental Protection Agency (EPA) Federal Equivalent Method (FEM) Class III designation. Thus, it has become imperative to develop corrections for historical and future TEOM measurements for the purpose of making them more agreeable to the new FEM method. This work details the authors' multiple linear regression analyses (MLRAs) of particulate matter data from both instrumental monitors, with the inclusion of operational parameters of physicochemical relevance for both cases of transformations of historical TEOM and TEOM measurements to be made in the future. For historical TEOM data, it was observed that the transformations only benefited winter and fall months. Furthermore, comparisons of the transformed historical TEOM data with PM2.5 concentrations determined from the Federal Reference Method (FRM) sampler at seven locations within the province showed marked improvements over the observed TEOM-FRM comparisons. IMPLICATIONS: This work provides a path to correcting the historically observed underreporting of particulate mass in winter and fall in Ontario by making the TEOM-based continuous data resemble the new FEM outputs (in this case, more SHARP-like). It is possible that the transformation of mainly winter TEOM data as detailed in this work may potentially lead to revisions in historical annual composite mean PM2.5 concentrations and total annual number of days PM2.5 exceeded the Canada-wide Standard (CWS) metric across the province.

Uptake and mobilization of organic chemicals with clouds: evidence from a hail sample.

Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were measured in hail samples collected during a storm that occurred on a spring morning in Toronto, Canada. The presence of these organic chemicals in hail suggests that clouds likely provide an atmospheric transport pathway for these substances in the free atmosphere. Results reported here may carry significant implications for atmospheric transport, mass balance, tropospheric cold trapping, and environmental fate of organic chemicals. Backward trajectories along with measured and modeled cloud cover show that clouds causing the hail event were formed and advected from the midwestern and southeastern United States. After being emitted to the atmosphere, the organic chemicals were likely lifted by atmospheric ascending motions to a higher atmospheric elevation and partitioned onto clouds. These clouds then carry the organic chemicals to a downwind location where they are deposited to the ground surface via precipitation. We found that the organic chemicals with high solubility and vapor pressure tend to partition into clouds through sorption to cloudwater droplets and ice particles. It was found that approximately 7-30% of pyrene could be sorbed into cloudwater droplets and ice particles in this hail event at the expense of reduced gas-phase concentrations.

Dechloranes in a river in northeastern China: spatial trends in multi-matrices and bioaccumulation in fish (Enchelyopus elongatus).

Dechloranes (Decs), including Dechlorane Plus (DP) and Dechlorane (Dec) 602, 603, 604, are used as flame retardants. Fifty four samples were collected in a river in northeastern China and analyzed for Decs by gas chromatography/mass spectrometry. The average concentrations of total DP (syn- and anti-) in water, sediment, air, reed (Phragmites australis), and fish (E. elongatus) were 0.30±0.24 (mean±SD) ng L(-1), 1.3±0.69 ng g(-1) dry weight (dw), 0.25±0.18 ng m(-3), 0.63±0.18 ng g(-1) wet weight (ww), and 29±20 ng g(-1) lipid weight (lw), respectively. While Dec 602 and Dec 603 were detected in most of sediment and fish samples, no Dec 604 was found in any of the investigated environmental matrices. The mean ratio of syn-DP to total DP (fsyn) in water, sediment, reed, and fish were 0.28, 0.25, 0.27 and 0.47, suggesting depletion in abiota and enrichment in biota for syn-DP. It was found that biota-sediment accumulation factor (BSAF) was 4.7 for Dec 602, 0.88 for syn-DP, and 0.33 for anti-DP.

Long-term measurements of ground-level ozone in Windsor, Canada and surrounding areas.

This study investigated temporal variability of ground-level ozone (O3) during smog season in Windsor, Canada and surrounding states of the US during 1996-2015. Cluster analysis classified six sites into two groups with similar features of O3 concentrations. The first group consists of four urban/suburban sites, Windsor, Allen Park and Lansing in Michigan, and Erie in Ohio, and the second group includes two rural sites, Delaware and National Trail School in Ohio. The similarities among all six sites include (1) diurnal and seasonal variability of O3 concentrations owing to similar weather conditions, and (2) decreasing peak O3 (95th percentile) concentrations due to reduced emissions of precursors, thus less photochemical O3 formation. However, how O3 levels changed with reduced NOX emissions during the study period and on weekends differed between the two groups. Lower O3 concentrations were recorded at urban/suburban sites (30 ppb) than at rural sites (34 ppb). At urban sites, annual smog season O3 concentrations increased by 0.12-3.2 ppb/year. The increasing trends occurred at all percentile levels except for 95th percentile and in most months, due to weakened NO titration effect. At the rural sites, smog-season O3 concentrations decreased by 0.01-2.71 ppb/year. The decreasing trends were observed at 50-95th percentile levels and in most months. Between the two groups, the urban/suburban group had a greater increment in weekend O3 concentrations (3.3 vs. 1.6 ppb) due to a greater reduction of local NO emissions on weekend, thus, weakened NO titration effect. Overall, O3 formation was more sensitive to VOCs during the study period; however, the O3 formation regime gradually shifted toward more sensitive to NOX during 1996-2007 then became more sensitive to VOCs during 2008-2015. Therefore, controlling anthropogenic VOC emissions is needed to effectively mitigate O3 pollution in the study region.

Design and Optimization of a New Anti-reflux Biliary Stent With Retractable Bionic Valve Based on Fluid-Structure Interaction Analysis.

Duodenal biliary reflux has been a challenging common problem which could cause dreadful complications after biliary stent implantation. A novel anti-reflux biliary stent with a retractable bionic valve was proposed according to the concertina motion characteristics of annelids. A 2D equivalent fluid-structure interaction (FSI) model based on the axial section was established to analyze and evaluate the mechanical performances of the anti-reflux biliary stent. Based on this model, four key parameters (initial shear modulus of material, thickness, pitch, and width) were selected to investigate the influence of design parameters on anti-reflux performance via an orthogonal design to optimize the stent. The results of FSI analysis showed that the retrograde closure ratio of the retractable valve primarily depended on initial shear modulus of material (p < 0.05) but not mainly depended on the thickness, pitch, and width of the valve (p > 0.05). The optimal structure of the valve was finally proposed with a high retrograde closing ratio of 95.89%. The finite element model revealed that the optimized anti-reflux stent possessed improved radial mechanical performance and nearly equal flexibility compared with the ordinary stent without a valve. Both the FSI model and experimental measurement indicated that the newly designed stent had superior anti-reflux performance, effectively preventing the duodenobiliary reflux while enabling the bile to pass smoothly. In addition, the developed 2D equivalent FSI model provides tremendous significance for resolving the fluid-structure coupled problem of evolution solid with large deformation and markedly shortens the calculation time.

Short-Term Hyperuricemia Leads to Structural Retinal Changes That Can be Reversed by Serum Uric Acid Lowering Agents in Mice.

Purpose: Metabolic disorders have been implicated in ocular diseases, such as age-related macular degeneration (AMD) and diabetic retinopathy (DR). Recently, hyperuricemia (HUA) has been proposed as another risk factor for AMD, although no cause-and-effect experimental data have been published. In this study, we investigated whether HUA would initiate AMD or related retinal damages in hyperuricemic mice. Methods: HUA was induced in male ICR mice by dietary supplements of uric acid and oxonic acid potassium salt, with or without treatments by allopurinol or benzbromarone for various durations. Serum uric acid and angiotensin II concentrations were measured by enzyme-linked immunosorbent assay (ELISA) at regular intervals. The retinal damages were assessed by hematoxylin and eosin staining, immunostaining, and TUNEL assay. The cause-and-effect of HUA was compared among the study groups. Results: The results showed that the total thickness of photoreceptor inner and outer segments, as well as the thickness of the photoreceptor outer segment alone, were reduced under HUA. Furthermore, HUA elevated serum angiotensin II, which indicated activation of the renin-angiotensin system (RAS), leading to higher matrix metalloproteinase-2 (MMP-2) expression, and glial activation in the ganglion cell layer. HUA also led to the reduction of retinal pigment epithelium gap junction protein connexin-43 and apoptosis. Uric acid lowering agents, allopurinol or benzbromarone, were effective in ameliorating the impairments. Conclusions: HUA may pose as a causative factor of retinal injuries. The reduction of serum uric acid may reduce the detrimental effects caused by HUA.

Spatial distribution of hexachlorocyclohexanes in agricultural soils in Zhejiang province, China, and correlations with elevation and temperature.

Large quantities of hexachlorocyclohexanes (HCHs) were historically applied to soils in Zhejiang, a hilly province of eastern China, yet very limited information is publicly available for the present levels and residue characteristics of HCHs in the region. In this work, concentrations of HCHs and enantiomeric fractions (EFs) of α-isomer were analyzed in 58 agricultural soil samples (0-20 cm) collected in Zhejiang province. On the basis of the ratio of α-HCH/ß-HCH and the fact that HCHs were banned in 1983 for agricultural use in China, fresh application of technical HCHs in a large quantity was unlikely in this province. Significant correlation was found between soil concentrations and elevation (R = 0.52, P < 0.001) and temperature (R = -0.55, P < 0.0001), but not between soil concentrations and total technical usage (R = -0.24, P = 0.1), suggesting a typical secondary distribution pattern. The soil residue inventories of HCHs derived from the relationship between concentration and elevation indicated 14.2 tons of HCHs left in agricultural soils in plain areas with the average elevation less than 100 m, and 61.6 tons of HCHs left in mountain soils with the average elevation higher than 100 m. It was also found that EFs of α-HCH were significantly negatively correlated with carbon biomass (C(bio)) in soils. This implies that C(bio) might have important impact on orientation and extent of enantioselective degradation of α-HCH in the region, which is, according to our knowledge, the first report of this kind.

Bias from two analytical laboratories involved in a long-term air monitoring program measuring organic pollutants in the Arctic: a quality assurance/quality control assessment.

Initiated in 1992, air monitoring of organic pollutants in the Canadian Arctic provided spatial and temporal trends in support of Canada's participation in the Stockholm Convention of Persistent Organic Pollutants. The specific analytical laboratory charged with this task was changed in 2002 while field sampling protocols remained unchanged. Three rounds of intensive comparison studies were conducted in 2004, 2005, and 2008 to assess data comparability between the two laboratories. Analysis was compared for organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in standards, blind samples of mixed standards and extracts of real air samples. Good measurement accuracy was achieved for both laboratories when standards were analyzed. Variation of measurement accuracy over time was found for some OCPs and PCBs in standards on a random and non-systematic manner. Relatively low accuracy in analyzing blind samples was likely related to the process of sample purification. Inter-laboratory measurement differences for standards (<30%) and samples (<70%) were generally less than or comparable to those reported in a previous inter-laboratory study with 21 participating laboratories. Regression analysis showed inconsistent data comparability between the two laboratories during the initial stages of the study. These inter-laboratory differences can complicate abilities to discern long-term trends of pollutants in a given sampling site. It is advisable to maintain long-term measurements with minimal changes in sample analysis.

Design and evaluation of a novel anti-reflux biliary stent with cone spiral valve.

Endoscopic placement of biliary stent is a well-established palliative treatment for biliary obstruction. However, duodenobiliary reflux after stent placement has been a common problem which may lead to dreadful complications. This paper designed a novel anti-reflux biliary stent with a cone spiral valve. Fluid-Structure Interaction (FSI) simulations were established to evaluate the efficiency of the anti-reflux stent comparing with a clinically applied standard stent. According to the stress distribution of the valve, the fatigue performance in the stress concentration area was analyzed. The results show that when the antegrade flow through the valve, the cone spiral valve could stretch and open to realize adequate drainage under the normal physiological pressure of biliary tract; When the duodenal reflux through the valve, the valve would be compressed and close with a result of nearly zero at the outlet flow rate. Furthermore, the anti-reflux stent achieved improved radial mechanical performance with 2.7 times higher radial stiffness than standard stent. Finite element analysis (FEA) also indicates that compared with the standard stent, the addition of the anti-reflux valve had little negative effect on flexibility of the stent. Fatigue analysis results showed that the valve was reliable. This research provides the new stent with a cone spiral valve and proves that it is technically feasible and effective for preventing the duodenobiliary reflux while ensuring the antegrade bile flow without compromising the other biomechanical performances.

The decisive role of subordination in social hierarchy in weanling mice and young children.

Social hierarchy plays important roles in maintaining social structures. Despite similarity in concept, frameworks of human hierarchy have seldom been investigated in parallel with other animals. Moreover, the importance of subordination in hierarchical formation has been largely underestimated in previous research. Here we established, compared, and investigated hierarchy in children and weanling mice. Temperament assessments suggested that children who are less persistent, low emotional intensity, and withdrew easily were more likely to be subordinate in competitive scenarios independent of task characteristics and interaction experiences. The tube test further showed that conflicts between mice were not resolved by winner approach but by loser withdrawal, which was mainly determined by intrinsic subordinate status regardless of opponents. Our study presents evolutionary conserved hierarchical relationships in young and a critical role of the intrinsic subordinate characteristics in hierarchical determination. These findings provide a new perspective on social interactions with potential implications for preschool education.

Quantifying metal emissions from vehicular traffic using real world emission factors.

Road traffic emissions are an increasingly important source of particulate matter in urban and non-road environments, where non-tailpipe emissions can contribute substantially to elevated levels of metals associated with adverse health effects. Thus, better characterization and quantification of traffic-emitted metals is warranted. In this study, real-world emission factors for fine particulate metals were determined from hourly x-ray fluorescence measurements over a three-year period (2015-2018) at an urban roadway and busy highway. Inter-site differences and temporal trends in real-world emission factors for metals were explored. The emission factors at both sites were within the range of past studies, and it was found that Ti, Fe, Cu, and Ba emissions were 2.2-3.0 times higher at the highway site, consistent with the higher proportion of heavy-duty vehicles. Weekday emission factors for some metals were also higher by 2.0-3.5 times relative to Sundays for Mn, Zn, Ca, and Fe, illustrating a dependence on fleet composition and roadway activity. Metal emission factors were also inversely related to relative humidity and precipitation, due to reduced road dust resuspension under wetter conditions. Correlation analysis revealed groups of metals that were co-emitted by different traffic activities and sources. Determining emission factors enabled the isolation of traffic-related metal emissions and also revealed that human exposure to metals in ambient air can vary substantially both temporally and spatially depending on fleet composition and traffic volume.