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PubMed1991

Commuter exposures to VOCs in Boston, Massachusetts.

This study examines the commuter's exposure to six gasoline-related volatile organic compounds (VOCs): benzene, toluene, ethylbenzene, m-/p-xylene, o-xylene, and formaldehyde. The VOC concentrations to which commuters were exposed in four different commuting modes (driving, subway, walking, and biking) in Boston, Massachusetts, are compared. The VOC concentrations in participants' homes and offices were also measured. Factors that could influence in-vehicle VOC concentrations, such as different traffic patterns, car model and vehicle ventilation conditions, were also evaluated. Driving a private car was associated with higher VOC concentrations and commuting on urban roadways resulted in the highest VOC concentrations. The use of car heaters resulted in higher in-vehicle VOC concentrations. The longer the subway commuters stayed underground, the higher their VOC exposures. The home-to-work car or subway commute represented about 10 to 20 percent of an individual's total VOC exposure for these compounds.

Air Pollutants↗

PubMedDate not supplied

Environmental exposure of commuters in Mexico City to volatile organic compounds as assessed by blood concentrations, 1998.

OBJECTIVE: To assess the extent of exposure for Volatile Organic Compounds (VOCs) among nonoccupationally exposed commuters in Mexico City. MATERIAL AND METHODS: Blood concentrations of benzene, toluene, ethylbenzene, m-/p-xylene, o-xylene and methyl tert-butyl ether were determined on samples collected from participants after the morning commute. RESULTS: Median blood concentrations of benzene (0.11 microg/l), ethylbenzene (0.081 microg/l), m-/p-xylene (0.32 microg/l) and toluene (0.56 microg/l) in the Mexico City participants were all approximately two times higher than in a nonsmoking subset of the Third National Health and Nutrition Examination Survey population of the United States. On the other hand, median VOC blood levels were similar to medians observed in other studies involving commuters in specific U.S. cities, despite the fact that only half the Mexico City study participants commuted by personal vehicles compared with all U.S. commuters. CONCLUSIONS: These results reflect the extent of the air pollution problem in Mexico City. The surrounding topography exacerbates the problems caused by heavy vehicular traffic, poor emission-control devices on older vehicles, and poor maintenance practices. Elevated levels of gasoline components in the blood of nonoccupationally exposed commuters emphasize the need for regulatory initiatives and mass-transit options to reduce hydrocarbon emissions and thus reduce the risk for nonoccupational exposure for the residents of Mexico City.

Adult↗

PubMed1998

Commuting in multi-nodal urban systems: an empirical comparison of three alternative models.

"This paper analyses whether the basic monocentric model of urban structure and commuting explains actual commuting in Europe, i.e. The Netherlands. As in the USA much wasteful commuting is established. The basic model has a low degree of explanatory power. In order to get more in line with actual commuting, the paper elaborates two alternatives to the basic model. Besides a deconcentrated model, a cross-traffic model is developed. Particularly the latter is quite successful in explaining actual commuting. The paper pleads for endogenising employment and stresses heterogeneity in labour demand and supply."

Behavior↗

PubMed1990

Objective and subjective dimensions of travel impedance as determinants of commuting stress.

The stressful characteristics of commuting constraints are conceptualized in terms of both physical and perceptual conditions of travel impedance. This study develops and operationalizes the concept of subjective impedance, as a complement to our previously developed concept of impedance as a physically defined condition of commuting stress. The stress impacts of high-impedance commuting were examined in a study of 79 employees of two companies in the follow-up testing of a longitudinal study. Subjective impedance was overlapping but not isomorphic with physical impedance, and these two dimensions have differential relationships with health and well-being outcomes. The physical impedance construct received further confirmation in validational analyses and in predicted effects on various illness measures and job satisfaction. The newly constructed subjective impedance index was significantly related to evening home mood, residential satisfaction, and chest pain. Job change was also influenced primarily by commuting satisfaction. The results are discussed within an ecological framework emphasizing interdomain transfer effects and situational moderators of commuting stress.

Adult↗

PubMed1996

Vehicle occupants' exposure to aromatic volatile organic compounds while commuting on an urban-suburban route in Korea.

This study identified in-auto and in-bus exposures to six selected aromatic volatile organic compounds (VOCs) for commutes on an urban-suburban route in Korea. A bus-service route was selected to include three segments of Taegu and one suburban segment (Hayang) to satisfy the criteria specified for this study. This study indicates that motor vehicle exhaust and evaporative emissions are major sources of both auto and bus occupants' exposures to aromatic VOCs in both Taegu and Hayang. A nonparametric statistical test (Wilcoxon test) showed that in-auto benzene levels were significantly different from in-bus benzene levels for both urban-segment and suburban-segment commutes. The test also showed that the benzene-level difference between urban-segment and suburban-segment commutes was significant for both autos and buses. An F-test showed the same statistical results for the comparison of the summed in-vehicle concentration of the six target VOCs (benzene, toluene, ethylbenzene, and o,m,p-xylenes) as those for the comparison of the in-vehicle benzene concentration. On the other hand, the in-vehicle benzene level only and the sum were not significantly different among the three urban-segment commutes and between the morning and evening commutes. The in-auto VOC concentrations were intermediate between the results for the Los Angeles and Boston. The in-bus VOC concentrations were about one-tenth of the Taipei, Taiwan results.

Air Pollutants↗

PubMed1998

Long commuting time, extensive overtime, and sympathodominant state assessed in terms of short-term heart rate variability among male white-collar workers in the Tokyo megalopolis.

To investigate the possible effects of long commuting time and extensive overtime on daytime cardiac autonomic activity, the short-term heart rate variability (HRV) both at supine rest and at standing rest of 223 male white-collar workers in the Tokyo Megalopolis was examined. Workers with a one-way commute of 90 min or more exhibited decreased vagal activity at supine rest and increased sympathetic activity regardless of posture, and those doing overtime of 60 h/month or more exhibited decreased vagal activity and increased sympathetic activity at standing rest. These findings suggest that chronic stress or fatigue resulting from long commuting time or extensive overtime caused these individuals to be in a sympathodominant state. Although these shifts in autonomic activities are not direct indicators of disease, it can be hypothesized that they can induce cardiovascular abnormalities or dysfunctions related to the onset of heart disease. Assessment of the daily and weekly variations in HRV as a function of daily life activities (such as working, commuting, sleeping, and exercising) among workers in Asia-Pacific urban areas might be one way of studying the possible effects of long commuting time, and extensive overtime, on health.

Adult↗

PubMed1994

Uptake of carbon monoxide in Los Angeles commuters.

The uptake of carbon monoxide in Los Angeles commuters was measured by determining carbon monoxide concentrations in expired air before and after commuting. Estimates of exposure were made by determining carbon monoxide concentration in air collected within each car during each trip. There was a definite increase in expired air carbon monoxide concentration during the morning commute trip, but not during the afternoon trip. No consistent differences by geographic area were noted. Multiple correlation analysis showed that the post-commuting values depended more upon precommuting expired air values than upon carbon monoxide measured within the car. Smokers showed consistently higher values of carbon monoxide than nonsmokers, and the effect of smoking was several times greater than that of exposure to carbon monoxide levels experienced during commuting.

Adolescent↗

PubMedDate not supplied

Longer distance commuting as a substitute for migration in Britain: a review of trends, issues and implications.

"Drawing on analyses of commuting data from secondary sources as well as on selected results from a research project on long-distance commuting in Britain, this article investigates the extent to which, and why, households may choose to substitute longer distance commuting for migration. Reasons for long-distance weekly commuting, and associated advantages and disadvantages from individual, household and employer perspectives, are outlined. The evidence points to increasing complexity in home and working lives, with important implications for housing, transport and human resource management policies, as well as for family life."

Behavior↗

PubMed1987

Long-distance commuting and population change in Georgia, 1960-80.

The authors investigate counter-urbanization and population change in Georgia between 1960 and 1980 by examining commuting patterns. "The immediate objective is to construct the entire set of commuting fields of both large metropolitan areas to metropolitan and nonmetropolitan employment centers. We then proceed to the relationship between commuting from nonmetropolitan areas to all levels of Georgia's urban hierarchy and population change in these nonmetropolitan settings. By matching population growth and decline areas with explicit employment ties...the nature of the population changes is much better understood." Data from the 1960, 1970, and 1980 censuses for 581 Census County Divisions (CCDs) in Georgia are analyzed. It is concluded that "most nonmetropolitan growth taking place in Georgia is associated with intensification of metropolitan commuting fields along with growth of nonmetropolitan centers and their influence along the very periphery of metropolitan spheres of employment influence. However, a significant share of Georgia's nonmetropolitan population revitalization is explained by growth independent of direct metropolitan influence. It would appear then that nonmetropolitan growth centers are an important part of the basis for population decentralization in Georgia. Metropolitan spill-over alone cannot account for counterurbanization on this portion of the American economic landscape."

Americas↗

PubMed2001

Kindergartners' understanding of additive commutativity within the context of word problems.

Baroody and Gannon (1984) proposed that children's understanding of additive commutativity progresses through several levels of understanding based on a unary view of addition (change meaning) before developing a "true" level of understanding based on a binary conception (part-whole meaning). Resnick (1992) implied that children have both a unary and a binary conception of additive commutativity from the earliest stages of development. Fifty-three 5- and 6-year-old (M = 6-0) kindergartners' unary and binary understanding of additive commutativity was investigated using performance on tasks involving change-add-to and part-part-whole word problems, respectively. The data were inconsistent with the predictions of both models and suggest three alternate theoretical explanations. Moreover, the data indicate that success on a task involving change-add-to problems may be a more rigorous test of understanding of additive commutativity than that involving part-part-whole problems.

Analysis of Variance↗

PubMed1991

Exposure of commuters to volatile aromatic hydrocarbons from petrol exhaust.

Twenty-two volatile aromatic hydrocarbons were determined in the air of an automobile during commuting. Sampling was made on Tenax cartridges and laboratory determinations were carried out using thermal desorption combined with temperature-programmed capillary gas chromatography. Selected hydrocarbons representative of petrol exhaust were determined in the automobile and in an electric commuter train during eight parallel commuter trips. In the automobile, the concentrations of benzene were 35-70 micrograms/m3 and those of total aromatic hydrocarbons 200-400 micrograms/m3. The petrol exhaust levels were 5-10 times higher in the automobile than in the compartment of the commuter train.

Air Pollution↗

PubMed1999

Risky behavior of bus commuters and bus drivers in Karachi, Pakistan.

Buses account for a disproportionate number of road traffic accident fatalities in Karachi, Pakistan and other developing countries. Potentially dangerous bus driving and commuting practices that increase risk of road accidents and the effect of traffic police on bus behavior are evaluated. A total of 250 episodes each of disembarking and embarking commuters, buses stopping and moving on the road at ten of Karachi's highest risk intersections for traffic injuries were observed. Of the disembarking passengers, 33% did not wait for the bus to stop; 54% stepped off in the center of the road and 84% did not look out for traffic. Among the embarking commuters, 38% got on moving buses; 73% climbed on buses filled to their outer foot boards and 83% waited for buses on the street. Males were more likely than females to jump off a moving bus (43% versus 1.6%, P < 0.001), get on a moving bus (49% versus 12%, P < 0.001), and run to catch a bus (45% versus 8%, P < 0.001). At the bus stops, 30% of the buses did not stop completely; 46% stopped away from the stop and 79% stopped in the center of the road. Where traffic police were present buses were more likely to race (9% versus 3%, P = 0.05) and to cut off other vehicles (13% versus 2%, P = 0.001) than where police were absent. Risky behavior is common among both Karachi bus drivers and bus commuters. The traditional efforts to regulate bus traffic through traffic police is ineffective.

Accidents, Traffic↗

PubMed2003

Specimen materials, target values and commutability for external quality assessment (proficiency testing) schemes.

BACKGROUND: The objective of external quality assessment is to evaluate clinical acceptability of laboratory results. It is desirable to evaluate intermethod harmonization and traceability to a reference system. METHODS: Conventional matrix-modified processed materials are used in most programs, because they can be produced in large quantities, can have multiple abnormal analytes in the same vial and have excellent stability. The principal limitation of these materials is non-commutability which makes them unsuitable for traceability or harmonization evaluation. Peer group evaluation is used which allows an individual laboratory to confirm appropriate use of a measurement technology and a manufacturer to monitor uniformity in their calibration transfer process. Authentic clinical specimen pools provide commutability but are limited by the quantity available and number of analytes at pathologic levels in the same vial. Hybrid approaches have used authentic clinical specimen pools in conjunction with non-commutable processed materials to determine method-specific matrix-corrected target values which have enabled evaluation of traceability to reference methods. CONCLUSIONS: Conventional processed materials are limited by non-commutability. Pooled clinical specimens are limited by availability. When used together, external quality assessment can evaluate traceability to reference systems and harmonization between test procedures.

Clinical Laboratory Techniques↗

PubMed2003

Commuter exposure to aromatic VOCs in public transportation modes in Hong Kong.

This study investigated commuter exposure to aromatic volatile organic compounds (VOCs) in different commuting microenvironments. In Hong Kong, more than 90% of the local citizens rely on public transport facilities in their daily commutes. During five winter months in late 2001 and early 2002, in-vehicle monitoring was performed in nine popular public transportation modes: tram, public light bus, air-conditioned bus, non-air-conditioned bus, taxi, ferry and three railway systems (Mass Transit Railway-MTR, Kowloon-Canton Railway-KCR and Light Rail Transit-LRT). These transports were grouped into three categories: railway transport, roadway transport and marine transport. Air samples of benzene, toluene, ethylbenzene and m/p/o-xylene were collected by canisters and analysed by gas chromatography and mass selective detector technique. Results indicated that the in-vehicle VOC exposure levels were greatly influenced by the mode of transport. For benzene, mean concentration ranged from 4.8 to 6.1 microg x m(-3) in roadway transports, 3.0-3.8 microg x m(-3) in railway transports and it was 2.1 microg x m(-3) in ferry. Regardless of the results in MTR and air-conditioned buses, the VOC levels in roadway transport were the highest and was followed by railway transport. The exposure levels in marine transport were the lowest. The TEX concentrations were found to be substantially higher in air-conditioned buses and MTR trains than in other transports, suggesting the existence of additional solvent-related sources in their vehicle interiors. Measurements in non-air-conditioned double deck vehicles indicate that there was slightly higher VOC levels in the lower deck than in the upper deck microenvironment. The average upper to lower deck exposure ratio ranged from 0.79 to 0.87 in trams and 0.78-0.83 in non-air-conditioned buses, depending on the compound of concern. The VOC exposure levels of public transport commuters in Hong Kong are far lower than those in most oversea cities. The experimental concentrations obtained in this study are within the relevant health-protecting limits as stated in the Hong Kong Indoor Air Quality Objective. Influences of recent VOC pollution control measures and local traffic characteristics on in-vehicle level are discussed.

Air Pollution, Indoor↗

PubMed1999

Daily time budgets of long-distance commuting workers in Tokyo megalopolis.

In Tokyo Megalopolis, long-distance commuting between residences in the suburbs and work places in the centre of the city was examined. Using a questionnaire, heads of household in two suburbs were asked about the influences of long commuting hours on their daily time budgets. The results showed that on workdays, the workers who spent longer commuting rose and left home for work earlier, and came back home and retired later; accordingly, both time spent on in-home activities on workdays and hours slept on the day before a workday were shorter. Comparison of time budgets between the subjects who work 5 and 6 days per week revealed more vulnerable influences of long commuting hours in the former than the latter. The expected health consequences of these findings are discussed from a biosocial/human ecological viewpoint.

Adult↗

PubMed2026

CAKR: commutative algebra k-mer representations for genomics.

Despite the availability of various sequence analysis models, comparative genomic analysis remains a challenge in genomics, genetics, and phylogenetics. Commutative algebra, a fundamental tool in algebraic geometry and number theory, has rarely been used in data and biological sciences. In this study, we introduce commutative algebra k-mer representations as a nonlinear algebraic framework for analyzing genomic sequences. This representation bridges commutative algebra, algebraic topology, combinatorics, and machine learning to establish a mathematical framework for comparative genomic analysis. We evaluate its effectiveness on three tasks including genetic variant classification, phylogenetic tree reconstruction, and viral classification, typically requiring alignment-based, alignment-free, and machine-learning approaches, respectively. In this work, we show that commutative algebra k-mer representations outperform five state-of-the-art sequence analysis methods across twelve primary datasets, with two additional supplementary fragment-placement benchmarks, especially in viral classification, and maintain relatively stable predictive accuracy as dataset size increases, underscoring scalability and robustness.

Genomics↗

PubMed1993

Commutability of control materials in cholesterol measurement.

The 'commutability' is the property of a material to show inter-assay changes comparable to those of patients' sera. In order to assess the commutability, the cholesterol concentration was measured in 107 patients' sera and in 24 lyophilized control materials by a direct enzymatic method and by a reference-class procedure. The distance from the regression line of patients' sera results, expressed in SD units (normalized residual), was calculated and used to assess the commutability of each material. Out of 24 materials tested one had a normalized residual outside the +/- 3 interval (-4.4), and was considered as non-commutable. However, the distribution of the normalized residuals from the remaining 23 materials suggested a different behaviour in comparison with patients' sera, in the specific pair of methods. The relevance of this finding to the control of accuracy is discussed.

Animals↗

PubMed2000

Effect of commuter cycling on physical performance of male and female employees.

PURPOSE: The purpose of this study was to determine the effect of commuter cycling on physical performance. Eighty-seven male and 35 female employees volunteered to cycle regularly to their work. METHODS: Sixty-one participants went commuter cycling for 1 yr (cycling group); the others cycled only in the second half year (control group). A maximal exercise test on a cycle ergometer was carried out at the start of the study, after 6 months, and after 1 yr to measure maximal external power (Wmax) and maximal oxygen uptake (VO2max). RESULTS: After the first 6 months of commuter cycling, with a mean single trip distance of 8.5 km and a mean frequency of more than three times a week, a significant increase of 13% was found in the Wmax per kilogram body weight (Wmax x kg(-1)) in both sexes of the cycling group. The improvement in VO2max x kg(-1) was significant for the male participants (6%) but not for the female participants (-2%). At the end of the second half year, the control group also showed a mean gain in Wmax x kg(-1) of 13%. Their VO2max x kg(-1) declined in the first half year, but this was counteracted in the second half year. A dose-response relationship was found between two independent variables and the physical performance; the lower the physical performance at the start of the study and the higher the total amount of kilometers cycled, the higher the gain in Wmax. For subjects with a low initial fitness level, a single trip distance of only 3 km turned out to be enough to improve physical performance. CONCLUSION: Commuter cycling can yield much the same improvement in physical performance as specific training programs.

Adult↗