The real-world impact of the COVID-19 pandemic on patients with cancer: a multidisciplinary cross-sectional survey.

INTRODUCTION: The coronavirus disease 2019 (COVID-19) pandemic has caused unprecedented disruptions to cancer care worldwide. We conducted a multidisciplinary survey of the real-world impact of the pandemic, as perceived by patients with cancer. METHODS: A total of 424 patients with cancer were surveyed using a 64-item questionnaire constructed by a multidisciplinary panel. The questionnaire examined patient perspectives regarding COVID-19-related effects (eg, social distancing measures) on cancer care delivery, resources, and healthcare-seeking behaviour, along with the physical and psychosocial aspects of patient well-being and pandemic-related psychological repercussions. RESULTS: Overall, 82.8% of respondents believed that patients with cancer are more susceptible to COVID-19; 65.6% expected that COVID-19 would delay anti-cancer drug development. Although only 30.9% of respondents felt that hospital attendance was safe, 73.1% expressed unaltered willingness to attend scheduled appointments; 70.3% of respondents preferred to receive chemotherapy as planned, and 46.5% were willing to accept changes in efficacy or side-effect profile to allow an outpatient regimen. A survey of oncologists revealed significant underestimation of patient motivation to avoid treatment interruptions. Most surveyed patients felt that there was an insufficient amount of information available concerning the impact of COVID-19 on cancer care, and most patients reported social distancing-related declines in physical, psychological, and dietary wellness. Sex, age, education level, socio-economic status, and psychological risk were significantly associated with patient perceptions and preferences. CONCLUSION: This multidisciplinary survey concerning the effects of the COVID-19 pandemic revealed key patient care priorities and unmet needs. These findings should be considered when delivering cancer care during and after the pandemic.

Spatiotemporal characteristics of ozone and the formation sensitivity over the Fenwei Plain.

High surface ozone (O3) levels affect human and environmental health. The Fenwei Plain (FWP), one of the critical regions for China's "Blue Sky Protection Campaign", has reported severe O3 pollution. This study investigates the spatiotemporal properties and the causes of O3 pollution over the FWP using high-resolution data from the TROPOspheric Monitoring Instrument (TROPOMI) from 2019 to 2021. This study characterizes spatial and temporal variations in O3 concentration by linking O3 columns and surface monitoring using a trained deep forest machine learning model. O3 concentrations in summer were 2-3 times higher than those found in winter due to higher temperatures and greater solar irradiation. The spatial distributions of O3 correlate with the solar radiation showing decreased trends from the northeastern to the southwestern FWP, with the highest O3 values in Shanxi Province and the lowest in Shaanxi Province. For urban areas, croplands and grasslands, the O3 photochemistry in summer is NOx-limited or in the transitional regime, while it is VOC-limited in winter and other seasons. Reducing NOx emissions would be effective for decreasing O3 levels in summer, while VOC reductions are necessary for winter. The annual cycle in vegetated areas included both NOx-limited and transitional regimes, indicating the importance of NOx controls to protect ecosystems. The O3 response to limiting precursors shown here is of importance for optimizing control strategies and is illustrated by emission changes during the 2020 COVID-19 outbreak.

A patient-specific measurement technique to model shoulder joint kinematics.

BACKGROUND: Measuring dynamic in vivo shoulder kinematics is crucial to better understanding numerous pathologies. Motion capture systems using skin-mounted markers offer good solutions for non-invasive assessment of shoulder kinematics during dynamic movement. However, none of the current motion capture techniques have been used to study translation values at the joint, which is crucial to assess shoulder instability. The aim of the present study was to develop a dedicated patient-specific measurement technique based on motion capture and magnetic resonance imaging (MRI) to determine shoulder kinematics accurately. HYPOTHESIS: Estimation of both rotations and translations at the shoulder joint using motion capture is feasible thanks to a patient-specific kinematic chain of the shoulder complex reconstructed from MRI data. MATERIALS AND METHODS: We implemented a patient-specific kinematic chain model of the shoulder complex with loose constraints on joint translation. To assess the effectiveness of the technique, six subjects underwent data acquisition simultaneously with fluoroscopy and motion capture during flexion and empty-can abduction. The reference 3D shoulder kinematics was reconstructed from fluoroscopy and compared to that obtained from the new technique using skin markers. RESULTS: Root mean square errors (RMSE) for shoulder orientation were within 4° (mean range: 2.0°-3.4°) for each anatomical axis and each motion. For glenohumeral translations, maximum RMSE for flexion was 3.7mm and 3.5mm for empty-can abduction (mean range: 1.9-3.3mm). Although the translation errors were significant, the computed patterns of humeral translation showed good agreement with published data. DISCUSSION: To our knowledge, this study is the first attempt to calculate both rotations and translations at the shoulder joint based on skin-mounted markers. Results were encouraging and can serve as reference for future developments. The proposed technique could provide valuable kinematic data for the study of shoulder pathologies. LEVEL OF EVIDENCE: Basic Science Study.

Concentrations and source contributions of particulate organic matter before and after implementation of a low emission zone in Munich, Germany.

Within the Munich low emission zone (LEZ), samples of PM(2.5) were collected before (2006/2007) and after (2009/2010) the implementation of the LEZ. The samples were analyzed for carbon fraction (EC/OC) and particulate organic compounds (POC). Significant lower concentrations were noticed for elemental carbon (EC) and some of the POC like vanillic acid, acetosyringone, syringylacetone and syringic acid after the implementation of the LEZ. Higher concentrations of levoglucosan, retene and O-PAH were detected in the second sampling period. Positive matrix factorization (PMF) was used to identify the main sources of POC. Emissions from traffic, solid fuels combustion, cooking and mixed source were separated. The contribution of traffic source factor was decreased about 60% after the implementation of the LEZ. Thus the average concentration of EC from traffic factor decreased from 1.1 to 0.5 µg/m(3) after the implementation of the LEZ.

Characteristics and source apportionment of PM1 emissions at a roadside station.

The mass concentrations of PM(1) (particles less than 1.0 µm in aerodynamic diameter), organic carbon (OC), elemental carbon (EC), water-soluble ions, and up to 25 elements were reported for 24h aerosol samples collected every sixth day at a roadside sampling station in Hong Kong from October 2004 to September 2005. Annual average PM(1) mass concentration was 44.5 ± 19.5 µg m(-3). EC, OM (organic matter, OC × 1.2), and SO(4)(=) were the dominant components, accounting for ∼ 36%, ∼ 26%, and ∼ 24% of PM(1), respectively. Other components, i.e., NO(3)(-), NH(4)(+), geological material, trace elements and unidentified material, comprised the remaining ∼ 14%. Annual average OC/EC ratio (0.6 ± 0.3) was low, indicating that primary vehicle exhaust was the major source of carbonaceous aerosols. The seasonal variations of pollutants were due to gas-particle partitioning processes or a change in air mass rather than secondary aerosol produced locally. Vehicle exhaust, secondary aerosols, and waste incinerator/biomass burning were dominant air pollution sources, accounting for ∼ 38%, ∼ 22% and ∼ 16% of PM(1), respectively. Pollution episodes during summer (May-August) which were frequently accompanied by tropical storms or typhoons were dominated by vehicle emissions. During winter (November-February) pollution episodes coincided with northeasterly monsoons were characterized by secondary aerosols and incinerator/biomass burning emissions.

Enzyme replacement therapy for mucopolysaccharidosis VI (Maroteaux-Lamy syndrome): experience in Hong Kong.

Mucopolysaccharidosis VI (Maroteaux-Lamy syndrome) is a very rare inherited lysosomal storage disease. We evaluated the efficacy and safety of weekly infusions of recombinant human arylsulfatase B as enzyme replacement therapy for two patients in whom this condition was advanced. The primary outcome variables were the distance walked in a 6-minute walk test, forced vital capacity, and ejection fraction. The secondary outcome variables were the number of stairs climbed in a 3-minute stair climbing test, joint mobility, urinary glycosaminoglycan excretion, auto-continuous positive airway pressure study and liver size. After 24 weeks of treatment, patient A walked 40 m (36%) and patient B walked 66 m (58%) more in the walk test than at baseline. After 48 weeks, in patient A the corresponding improvements were 142 m (129%) in the walk test and 33 stairs (60%) in the 3-minute stair climbing test, and in patient B the respective improvements were 198 m (174%) and 77 stairs (140%). There was a significant decline in urinary glycosaminoglycan excretion and improvement in range of motion of joints in both patients. The auto-continuous positive airway pressure study revealed improvements in patient A, while other efficacy variables remained static. There were no drug-related adverse events or allergic reactions reported during and after the infusions of recombinant human arylsulfatase B. Recombinant human arylsulfatase B significantly improves endurance and reduces urinary glycosaminoglycan excretion. The drug is generally safe and well tolerated.

Chemically-speciated on-road PM(2.5) motor vehicle emission factors in Hong Kong.

PM(2.5) (particle with an aerodynamic diameter less than 2.5microm) was measured in different microenvironments of Hong Kong (including one urban tunnel, one Hong Kong/Mainland boundary roadside site, two urban roadside sites, and one urban ambient site) in 2003. The concentrations of organic carbon (OC), elemental carbon (EC), water-soluble ions, and up to 40 elements (Na to U) were determined. The average PM(2.5) mass concentrations were 229+/-90, 129+/-95, 69+/-12, 49+/-18microg m(-3) in the urban tunnel, cross boundary roadside, urban roadside, and urban ambient environments, respectively. Carbonaceous particles (sum of organic material [OM] and EC) were the dominant constituents, on average, accounting for approximately 82% of PM(2.5) emissions in the tunnel, approximately 70% at the three roadside sites, and approximately 48% at the ambient site, respectively. The OC/EC ratios were 0.6+/-0.2 and 0.8+/-0.1 at the tunnel and roadside sites, respectively, suggesting carbonaceous aerosols were mainly from vehicle exhausts. Higher OC/EC ratio (1.9+/-0.7) occurred at the ambient site, indicating contributions from secondary organic aerosols. The PM(2.5) emission factor for on-road diesel-fueled vehicles in the urban area of Hong Kong was 257+/-31mg veh(-1) km(-1), with a composition of approximately 51% EC, approximately 26% OC, and approximately 9% SO(4)(=). The other inorganic ions and elements made up approximately 11% of the total PM(2.5) emissions. OC composed the largest fraction (approximately 51%) in gasoline and liquid petroleum gas (LPG) emissions, followed by EC (approximately 19%). Diesel engines showed higher emission rates than did gasoline and LPG engines for most pollutants, except for V, Br, Sb, and Ba.

The effect of acidification on the determination of elemental carbon, char-, and soot-elemental carbon in soils and sediments.

We studied the influence of acid pretreatment on the effective distinction between elemental carbon (EC) and organic carbon (OC), and between char-EC and soot-EC. Though widely employed in the pretreatment of soils and sediments for EC quantification, the use of HCl, HF, and HNO(3) could decrease soot thermal stability as acid remains, leading to an underestimation of soot-EC by thermal methods. We compared thermal optical reflectance (TOR) measurements of EC concentrations in char reference materials and in lacustrine and marine sediments following pretreatment with various acids. The results showed that pretreatment with 2M HCl, concentrated HNO(3), 7 M HNO(3), and 1 M HNO(3) did not result in EC oxidation. However, hot concentrated HNO(3) oxidized EC significantly, leading to lower concentrations of EC, char-EC and soot-EC. By comparing the removal of potentially interfering materials, which contain little fire-derived carbon, with different acid pretreatments, we recommend the HCl-HF-HCl and concentrated (not hot) HNO(3)-HF-HCl pretreatments for the determination of EC, char-EC, and soot-EC in soils and sediments using the TOR method.

Indoor/outdoor relationships for PM2.5 and associated carbonaceous pollutants at residential homes in Hong Kong - case study.

UNLABELLED: Six residences were selected (two roadside, two urban, and two rural) to evaluate the indoor-outdoor characteristics of PM(2.5) (aerodynamic diameter <2.5 microm) carbonaceous species in Hong Kong during March and April 2004. Twenty-minute-averaged indoor and outdoor PM(2.5) concentrations were recorded by DustTrak samplers simultaneously at each site for 3 days to examine diurnal variability of PM(2.5) mass concentrations and their indoor-to-outdoor (I/O) ratios. Daily (24-h average) indoor/outdoor PM(2.5) samples were collected on pre-fired quartz-fiber filters with battery-powered portable mini-volume samplers and analyzed for organic and elemental carbon (OC, EC) by thermal/optical reflectance (TOR) following the Interagency Monitoring of Protected Visual Environments (IMPROVE) protocol. The average indoor and outdoor concentrations of 24 h PM(2.5) were 56.7 and 43.8 microg/m(3), respectively. The short-term PM(2.5) profiles indicated that the penetration of outdoor particles was an important contributor to indoor PM(2.5), and a household survey indicated that daily activities were also sources of episodic peaks in indoor PM(2.5). The average indoor OC and EC concentrations of 17.1 and 2.8 microg/m(3), respectively, accounted for an average of 29.5 and 5.2%, respectively, of indoor PM(2.5) mass. The average indoor OC/EC ratios were 5.8, 9.1, and 5.0 in roadside, urban, and rural areas, respectively; while average outdoor OC/EC ratios were 4.0, 4.3, and 4.0, respectively. The average I/O ratios of 24 h PM(2.5), OC, and EC were 1.4, 1.8, and 1.2, respectively. High indoor-outdoor correlations (r(2)) were found for PM(2.5) EC (0.96) and mass (0.81), and low correlations were found for OC (0.55), indicative of different organic carbon sources indoors. A simple model implied that about two-thirds of carbonaceous particles in indoor air are originated from outdoor sources. PRACTICAL IMPLICATIONS: Indoor particulate pollution has received more attentions in Asia. This study presents a case study regarding the fine particulate matter and its carbonaceous compositions at six residential homes in Hong Kong. The characteristics and relationship of atmospheric organic and elemental carbon were discussed indoors and outdoors. The distribution of eight carbon fractions was first reported in indoor samples to interpret potential sources of indoor carbonaceous particles. The data set can provide significant scientific basis for indoor air quality and epidemiology study in Hong Kong and China.

Forming facultative heterochromatin: silencing of an X chromosome in mammalian females.

Compensating for the dosage difference in X-linked genes between male and female mammals involves the formation of an extremely stable heterochromatin structure on one of the two X chromosomes in females. The inactive X acquires numerous features of silent chromatin, including the expression of a noncoding RNA, a switch to late replication, histone modifications, recruitment of the histone variant macroH2A and DNA hypermethylation. Although the induction of inactivation in differentiating mouse embryonic stem cells suggests that the onset of each of these features appears to occur in a sequential manner, it is likely that there is a much more complex interplay between the different features which leads to the extremely stable silencing observed in female somatic cells. Expression of the untranslated RNA, XIST, is required in cis for the establishment of the heterochromatic state. Recent results have started to elucidate how expression of Xist is controlled, including the role of the antisense transcript Tsix.

Ectopic XIST transcripts in human somatic cells show variable expression and localization.

XIST encodes a functional RNA that is expressed exclusively from the inactive X in female mammals and is required for the silencing of most of the genes on the chromosome. XIST transcripts remain in the nucleus, and their specific localization to the inactive X is important for silencing; however, it is not known how these transcripts localize to the inactive X chromosome. Expression of mouse and human XIST from ectopic sites has suggested that localization to the chromosome from which the gene is expressed may be dependent upon either the copy number of the integrated constructs or the level of ectopic XIST expression. To further examine the behavior of XIST transgenes when expressed from ectopic sites, we introduced an XIST-containing PAC into the human male somatic cell line HT-1080. In five different transformant clones, the degree of localization and associated DNA condensation of the surrounding chromatin varied within nuclei of the same clone, as well as among different clones. Comparing the number of integrated transgenes and the levels of XIST expression revealed that neither factor was sufficient for a tight localization of the XIST signal. Therefore, the extent of expression and localization of XIST transcripts from ectopic transgenes is likely dependent upon many interacting factors, including the number of integrated transgenes, the level of XIST expression, and the site of integration.

A Critical Evaluation of Interlaboratory Data on Total, Elemental, and Isotopic Carbon in the Carbonaceous Particle Reference Material, NIST SRM 1649a.

Because of increased interest in the marine and atmospheric sciences in elemental carbon (EC), or black carbon (BC) or soot carbon (SC), and because of the difficulties in analyzing or even defining this pervasive component of particulate carbon, it has become quite important to have appropriate reference materials for intercomparison and quality control. The NIST "urban dust" Standard Reference Material(®) SRM 1649a is useful in this respect, in part because it comprises a considerable array of inorganic and organic species, and because it exhibits a large degree of ((14)C) isotopic heterogeneity, with biomass carbon source contributions ranging from about 2 % (essentially fossil aliphatic fraction) to about 32 % (polar fraction). A primary purpose of this report is to provide documentation for the new isotopic and chemical particulate carbon data for the most recent (31 Jan. 2001) SRM 1649a Certificate of Analysis. Supporting this is a critical review of underlying international intercomparison data and methodologies, provided by 18 teams of analytical experts from 11 institutions. Key results of the intercomparison are: (1) a new, Certified Value for total carbon (TC) in SRM 1649a; (2) (14)C Reference Values for total carbon and a number of organic species, including for the first time 8 individual PAHs; and (3) elemental carbon (EC) Information Values derived from 13 analytical methods applied to this component. Results for elemental carbon, which comprised a special focus of the intercomparison, were quite diverse, reflecting the confounding of methodological-matrix artifacts, and methods that tended to probe more or less refractory regions of this universal, but ill-defined product of incomplete combustion. Availability of both chemical and (14)C speciation data for SRM 1649a holds great promise for improved analytical insight through comparative analysis (e.g., fossil/biomass partition in EC compared to PAH), and through application of the principle of isotopic mass balance.

A confirmatory factor analysis of the BASIS-32 in racial and ethnic samples.

The present study performed confirmatory factor analysis across major racial and ethnic groups of the BASIS-32, a measure of functional status of persons receiving mental health treatment and suitable for routine assessment mental health care. The purpose was to perform a preliminary investigation of cross-cultural equivalence in a county-level mental health program in a major metropolitan area. The results indicated a factor structure similar to that reported in the literature, and they suggested acceptable levels of agreement in structure between racial and ethnic minority groups and whites. The study revealed little reason to believe that the BASIS-32 varied in underlying structure across racial and ethnic boundaries, although further research is indicated.

Estimating middle-, neighborhood-, and urban-scale contributions to elemental carbon in Mexico City with a rapid response aethalometer.

A successive moving average subtraction method is developed and applied to black carbon measured over 5-min intervals at a downtown location near many small emitters and at a suburban residential site within the urban plume but distant from specific emitters. Short-duration pulses assumed to originate from nearby sources are subtracted from the concentrations at each site and are summed to estimate middle-scale (approximately 0.1-1 km) contributions. The difference of the remaining baselines at the urban and suburban monitors is interpreted as the contribution to the downtown monitor from source emissions mixed over a neighborhood scale (1-5 km). The baseline at the suburban site is interpreted as the contribution of the mixture of black carbon sources for the entire city. When applied to a 24-day period from February and March 1997 in Mexico City, the analysis showed that 65% of the 24-hr black carbon was part of the urban mixture, 23% originated in the neighborhood surrounding the monitor, and only 12% was contributed from nearby sources. These analyses indicate that a fixed-site monitor can reasonably represent exposures in its surrounding neighborhood even when many local sources, such as exhaust from diesel buses and trucks, affect the monitor.

Sources of PM10 and sulfate aerosol at McMurdo Station, Antarctica.

Source contributions to PM10 and sulfate aerosol at McMurdo Station, Antarctica during the austral summers of 1995-1996 and 1996-1997 were estimated using Chemical Mass Balance (CMB) receptor modeling. The average PM10 (particles with aerodynamic diameters less than 10 microm) concentration at Hut Point, located less than 1 km downwind of downtown McMurdo, was 3.4 microg/m3. Emissions profiles were determined for potentially important aerosol source types in McMurdo: exposed soil, power generation, space heating, and surface vehicles. Soil dust, sea salt, combustion emissions, sulfates, marine biogenic emissions as methanesulfonate, and nitrates contributed 57%, 15%, 14%, 10%, 3%, and 1%, respectively, of average estimated PM10 at Hut Point (3.2 microg/m3). Soil dust, sea salt, and combustion sources contributed 12%, 8%, and 20%, respectively, of the average PM10 sulfate concentration of 0.46 microg/m3. Marine biogenic sources contributed 0.17 microg/m3 (37%). The remaining sulfate is thought to have come from emissions from Mt. Erebus or hemispheric pollution sources.

Arthroscopic osteochondral transplantation: Histologic results.

PURPOSE: Localized, full-thickness articular cartilage defects of the femoral condyle are challenging. This report presents the histology of clinical cases obtained at intervals from 2 to 12 months after arthroscopic osteochondral transplantation. TYPE OF STUDY: Longitudinal cohort study. METHODS: Patients found at arthroscopy to have full-thickness femoral condyle defects between 1 and 3.5 cm in diameter underwent arthroscopic osteochondral transplantation. Exclusion criteria were associated tibial defects, patellar defects, or generalized arthritic change. The grafts taken from the superior and lateral intercondylar femoral notch were press-fit into holes drilled into the defect starting adjacent to the articular cartilage margin. Cancellous bone bridges were maintained between grafts. At various time intervals from 2 to 12 months after the osteochondral transplantation, arthroscopic biopsy specimens of the recipient sites were obtained. RESULTS: Ten patients (5 male, 5 female) enrolled at 2 centers were evaluated arthroscopically at various intervals up to 13 months after osteochondral transplantation. The average patient age was 40 years (range, 17 to 65 years). One to 3 plugs had been harvested and inserted. Seven patients underwent biopsy at intervals ranging up to 12 months postoperatively. All showed maintenance of the integrity of the grafts with living chondrocytes and osteocytes. Donor sites filled without grafting and were covered with fibrocartilagenous scar. No complications occurred in this group. CONCLUSIONS: These histologic results suggest that arthroscopic osteochondral transplantation is a viable alternative for treating full-thickness chondral defects, with the grafts retaining their integrity and living chondrocytes and osteocytes observed in the grafts for up to 12 months after implantation.

Source characterization of major emission sources in the imperial and Mexicali Valleys along the US/Mexico border.

Chemical profiles for particle emissions are needed for source apportionment studies using the chemical mass balance (CMB) receptor model. Source measurements of geological sources, motor vehicle exhaust, vegetative burning (e.g. asparagus, field burning, charbroil cooking), and industrial sources (e.g. oil-fueled glass plant, manure-fueled power plants) were acquired as part of the Imperial/Mexicali Valley Cross Border PM10 Transport Study in 1992. Six different source sampling techniques (i.e. hot- and diluted-exhaust sampling, ground-based source sampling, particle sweeping/grab sampling, vacuum sampling, and laboratory resuspension sampling) were applied to acquire filter samples of PM 2.5 and PM10 (particulate matter with aerodynamic diameters < 2.5 and 10 microm, respectively). Filter samples were analyzed for mass by gravimetry, elements (Na to U) by X-ray fluorescence, anions (Cl(-), NO3(-), SO4(=)) by ion chromatography, ammonium (NH4(+)) by automated colorimetry, soluble sodium (Na+) and potassium (K+) by atomic absorption spectrophotometry, and organic and elemental carbon (OC, EC) by thermal/optical reflectance. Concentration data were acquired for a total of approximately 50 chemical species. Elevated abundances of crustal components (Al, Si, K, Ca, Fe) from geological material, carbon (OC, EC) and trace elements (Br, Pb) from vehicle exhausts, carbon (OC, EC) and ions (K(+), Cl(-)) from vegetative burning, ions (SO4(=), NH4(+), Na(+), K(+), Cl(-)) and elements (Cl, Se) from a manure-fueled power plants, and sulfur and trace elements (Na(+), Pb, Se, Ni, V) from an oil-fueled glass plant were found in the resulting source profiles. Abundances of crustal species (e.g. Al, Si, Ca) in the Imperial/Mexicali Valley geological profiles are more than twice those found in central and southern California. Abundances of lead in motor vehicle exhausts indicate different vehicle fleets in border cities. Emission profiles from field burning and charbroil cooking specific to the border area show that a majority (>60%) of emissions are comprised of carbon, with high organic to total carbon ratios (0.93 to 0.97). Abundances of sulfate and ammonium account for nearly 60% of the manure-fueled power plant's emissions. Elevated levels of metals (Na(+), Pb, Cd, Se) and byproducts of petroleum combustion (S, Ni, V) were found in the oil-fueled glass plant's emissions.

Zones of representation for PM10 measurements along the US/Mexico border.

The 'Imperial/Mexicali Valley Cross-Border PM10 Transport Study' acquired a database of meteorological and air quality measurements to determine source contributions to elevated PM10 concentrations and to estimate transport of PM10 between the US and Mexico. The study was conducted from 13 March 1992 to 29 August 1993, in a 80-km long by 20-km wide area spanning the US/Mexico border approximately 200 km inland from the coast of the Pacific Ocean, with monitoring sites located in the Imperial Valley on the US side and in the Mexicali Valley on the Mexico side. Measurements of PM 10 (particles with aerodynamic diameters less than 10 microm) mass, elements, water-soluble cations (i.e. sodium, potassium, ammonium) and anions (i.e. chloride, nitrate, sulfate), organic and elemental carbon and particle light absorption were acquired at two base sites on an every-sixth-day schedule supplemented by daily monitoring during winter and 4 times per day monitoring during intensive periods. Measurements were also taken at as many as 30 neighborhood (satellite) sites during week-long intensive monitoring periods in spring, summer and winter. This paper examines the zones of representation of long-term PM10 monitors by comparing their measurements with those from a spatially dense network of satellite sites. PM10 concentrations at the Mexicali site were consistently 30 to 50% higher than those observed at the Calexico site, even though the two sites were only 12 km apart. Distinct diurnal variations were found, with 6-h average PM10 concentrations often varying by a factor of 2 throughout the day - lowest during afternoon (12.00-18.00 h PST) and highest during night time (18.00-24.00 h PST). On average, crustal material accounted for 32-35% of annual-average PM10, carbonaceous aerosol for 20-30%, and ionic species for 8-10%. Levels of trace elements and sea salt were in the range of 1-4% of PM10. Significant concentration variations were found within the study area. PM10 concentrations in Mexico were double those in the US, decreasing with increasing northerly distance.