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PubMed2006

Fluoride excretion of adults living in border regions with either water or salt fluoridation.

The canton of Basel-Stadt was the only canton in Switzerland which introduced drinking water fluoridation (DWF) at 1 ppm (mg/l). All other cantons have relied on fluoridated domestic salt at 250 ppm F as the main vehicle for basic fluoride exposure. It has been suggested that persons living and working in the DWF areas or persons commuting to the DWF areas may be exposed to higher than optimal doses of fluoride. The objective of this present study was to determine the urinary fluoride excretion of adults living and or working in neighboring areas of either salt or water fluoridation. In this study, 24-hour urine was collected from 69 healthy subjects and tested for fluoride concentration. The mean fluoride concentration for all participants was 0.55 +/- 0.25 ppm (mg/l) ranging from 1.14 to 0.09 ppm. The mean fluoride excretion was 0.95 +/- 0.47 mg F/d ranging from 0.18 to 2.12 mg F/d. The 33 subjects living in a DWF region showed a mean urine fluoride concentration of 0.64 +/- 0.24 ppm (mg/l) and a mean fluoride excretion of 1.14 +/- 0.48 mg F/d. Those 36 subjects living in a region without DWF showed a mean urine fluoride concentration of 0.47 +/- 0.24 ppm (mg/l) and a mean fluoride excretion of 0.78 +/- 0.40 mg F/d. A significant difference between the two means of the groups living in regions with or without DWF was detected when the Mann-Whitney statistical test was applied (p < 0.005). The combined intake of fluoridated drinking water and fluoridated table salt in the sub-group of 11 subjects who commuted showed an overall increase in fluoride urine concentration. The measured values, however, were not significantly different from the other sub-groups.

Adult↗
PubMed1991

The reference method value.

The basis for the achievement and the control of accuracy in routine testing is represented by a hierarchy of methods. Different materials are used for transferring accuracy and for monitoring traceability. In these two operations, unreliable results may be obtained by using different materials (e.g. clinical specimens and reference materials) when matrix-sensitive methods are being used, as is frequently the case with routine methods. Intermediate-level (reference) methods may help to bridge the gap between the highest and the lowest levels, by using clinical specimens for method comparisons. If non-commutable materials are used for calibration and control of routine methods, these should have system specific values, assigned with an appropriate experimental design, including appropriate use of clinical specimens. Setting up networks of reference laboratories to implement and run reference systems on an ongoing basis, appears to be the practical pathway to accuracy. Improvements should be directed to lowering the matrix-sensitivity of routine methods and increasing the commutability of reference materials.

Calibration↗
PubMed1995

Evaluating lyophilized human serum preparations for suitability as proficiency testing materials for high-density lipoprotein cholesterol measurement.

OBJECTIVE: To evaluate the suitability of various commercial preparations for use by the College of American Pathologists as survey materials in assessing high-density lipoprotein cholesterol measurement performance. DESIGN: Lyophilized human serum preparations from six vendors (vendors A through F) were evaluated to determine which material(s) best mimicked the commutability of fresh human serum. Two freshly collected unfrozen pools prepared from donor specimens were analyzed concurrently with the vendor materials to identify sources of variation and possible matrix bias. Each material was evaluated using 5 common precipitation reagents (phosphotungstate-magnesium, phosphotungstic acid, dextran sulfate [50K and 500K], and heparin-manganese). To evaluate how each reagent separates lipoproteins in each material, the lipoprotein separation patterns were profiled using high-pressure liquid chromatography and compared with separation patterns observed for the fresh human serum pools. MAIN OUTCOME MEASURES: Similarities in performance characteristics of vendor material(s) were compared with fresh human serum. RESULTS: Two of the six materials gave separation profiles for the lipoproteins similar to the typical patterns observed for human serum. Material from vendor B showed the best commutability across all of the precipitation reagents and had the best combination of low overall variability (10% for level 1 and 9.4% for level 2) and minimal concentration differences among reagents. CONCLUSIONS: Vendor B was selected by the College of American Pathologists to provide materials for use in assessing performance of lipid and lipoprotein testing in the 1994 Comprehensive Chemistry Surveys. This study demonstrates the great variability that different vendor preparations introduce into the measurement of high-density lipoprotein cholesterol. It also emphasizes the effort required to evaluate the suitability of processed materials for use in proficiency testing.

Analysis of Variance↗
PubMed1995

Pilots involved in multiple crashes: "accident proneness" revisited.

Analysis of crashes of air taxi and commuter flights explored the controversial issue of "accident proneness." There were 20 pilots who had 2 or more crashes during 1983-88. These pilots (repeaters) and their 42 crashes were compared with 534 pilots who were each involved in a single air taxi or commuter crash during the same period (nonrepeaters). Unexpectedly, repeaters were more experienced pilots with a mean total flight time of 7016 h vs. 5321 for nonrepeaters. Repeaters did not differ from nonrepeaters in the overall proportion of crashes in which pilot performance appeared to be a major factor. Repeaters differed significantly from nonrepeaters as to flight hours during the past 90 d (mean 215 vs. 183 h) and the proportion of their crashes that occurred in Alaska (48% vs. 24%). Alaska repeaters differed from non-Alaska repeaters with regard to the proportion of crashes on takeoff (40% vs 14%) and airport conditions as a factor (50% vs. 18%). The high proportion of repeaters involved in crashes in Alaska, where environmental conditions make flying more hazardous, and the substantially greater recent flight time suggest that the intensity and amount of occupational exposure are major determinants of pilot involvement in more than one crash.

Accident Proneness↗
PubMed1995

Multienzyme control serum (Seraclear-HE) containing human enzymes from established cell lines and other sources. 2: Evaluation as candidate working enzyme Reference Material for alanine and aspartate aminotransferases.

Seraclear-HE, containing seven enzyme analytes from human sources, was evaluated as an intermethod calibrator for aspartate aminotransferase (AST) and alanine aminotransferase (ALT) to transfer Reference Method values to seven routine methods, including one based on hydrogen peroxide detection for possible unification of values (interlaboratory comparability of data). The commutabilities of AST from erythrocytes and ALT from a hepatoma cell line were studied between the consensus methods of Japan Society of Clinical Chemistry (chosen as the Reference Methods) and each of the automated routine methods at reaction temperatures of 30 degrees C and 37 degrees C. For AST, calibration of patients' sera with Seraclear-HE decreased average intermethod variation (CV) from 12% to 2%; for ALT, the decrease was from 20% to 3%. For both enzymes, Seraclear-HE was judged to be commutable between the Reference Methods and each of the methods investigated. The limitations for such use are discussed.

Alanine Transaminase↗
PubMed1994

Reference materials in clinical enzymology: preparation, requirements and practical interests.

Five enzyme materials (gamma-glutamyltransferase, alkaline phosphatase, creatine kinase, alanine aminotransferase and prostatic acid phosphatase) are currently certified using a reference method. Furthermore, feasibility studies have been performed for four other enzymes (aspartate aminotransferase, lactate dehydrogenase, amylase and lipase). They indicated that these enzymes can be purified and stabilized, but the materials have not yet been certified. This shows that the most important enzymes in clinical laboratories can be purified, and stabilized, without significant alteration of their catalytic properties. By carefully choosing a matrix, the commutability of these enzyme preparations and patients' samples between some methods, including routine methods, may be preserved. Thus, these materials can be used to calibrate the routine methods in terms of the corresponding reference methods after commutability has been verified. Current studies suggest that this objective can be reached, provided three criteria are satisfied: i) the calibrated and reference methods must be of equal specificity; ii) the enzyme calibrator should be, as closely as possible, identical to the human analyte enzyme in its native matrix (eg serum); iii) and the inter-method ratio should be constant (within the limits of experimental error) for the enzyme calibrator and for all patients' samples.

Calibration↗
PubMedDate not supplied

Long-term trends in United States highway emissions, ambient concentrations, and in-vehicle exposure to carbon monoxide in traffic.

This paper reviews 16 published studies conducted between 1965 and 1992 of in-vehicle exposure to carbon monoxide (CO) in traffic on urban roadways in the United States. Analysis of these studies shows a downward trend in CO exposure, which corresponds to similar trends for CO in motor vehicle emission factors and ambient concentrations. The analysis demonstrates that emission controls on motor vehicles sold in the United States have been very effective in reducing commuter CO exposure. It is recommended that future studies of this kind be done routinely in cities nationwide to provide a more robust database for accurate estimates of commuter exposure. Such studies should relate human exposure measurements to estimates of emissions at study sites to document the progress of motor vehicle emission control programs. In addition, future studies should use standard protocols to enable comparisons of results in time and space. Previous studies have shown that typical in-vehicle exposures vary by study approach (direct versus indirect), city, season, roadway type and location, travel mode, and vehicular ventilation. Future studies should carefully account for these factors.

Air Pollution, Indoor↗
PubMedDate not supplied

Recent advances in the estimation of population exposure to mobile source pollutants.

The U.S. Environmental Protection Agency (EPA) has developed several computer-based exposure models applicable to pollutants which are directly or indirectly linked to mobile sources. Probabilistic versions of the National Ambient Air Quality Standards (NAAQS) Exposure Model (pNEM) have been used to estimate the exposures of urban populations to carbon monoxide and ozone. An enhanced version of the Hazardous Air Pollutant Exposure Model (HAPEM-MS) has been used to develop city-specific estimates of exposure to benzene and other volatile organic compounds emitted by mobile sources. These models are similar in that each contains algorithms that simulate microenvironmental pollutant levels, time/activity patterns, and commuting patterns. The pNEM models also provide estimates of equivalent ventilation rate (EVR), defined as ventilation rate divided by body surface area. This paper summarizes the methods and results of selected research projects conducted since 1991 with the goal of improving pNEM, HAPEM-MS, and similar exposure models applicable to mobile source pollutants. The studies include: (1) the development of an improved algorithm for estimating EVR, (2) a field study to measure ozone levels near roadways and inside vehicles, (3) the development of an algorithm for estimating school commuting patterns, and (4) the construction of a comprehensive database containing time/activity data from ten activity diary studies.

Adult↗
PubMed1996

Multienzyme control serum (Seraclear-HE) containing human enzymes from established cell lines and other sources. 3: Evaluation as candidate working enzyme reference material for gamma-glutamyltransferase.

Seraclear-HE, containing gamma-glutamyltransferase (GGT, EC 2.3.2.2) derived from the cell culture of a human macrophage cell line, was evaluated as a candidate enzyme reference material (ERM) to calibrate routine methods in terms of a Reference Method for GGT. We have compared this preparation with commercially available materials, including Certified Reference Material 319, at 30 degrees C and 37 degrees C with respect to kinetic properties and with respect to commutability between the Reference Method and each of 15 analytical procedures involving five structurally different donor substrates. GGTs of human origin are far more commutable with reagents of varied types than are GGTs derived from animals. Calibration of 44 patients' sera with Seraclear-HE decreased average intermethod variation from 20% to approximately 4%, whereas GGTs of animal origin showed intermethod variations of approximately 30% with no benefit from calibration. Seraclear-HE is promising as a secondary or working ERM to be used as an intermethod calibrator.

Animals↗
PubMedDate not supplied

Exposure to carbon monoxide, methyl-tertiary butyl ether (MTBE), and benzene levels inside vehicles traveling on an urban area in Korea.

This study was designed to allow systematic comparison of exposure on public (40-seater buses) and private (four passengers cars) transport modes for carbon monoxide (CO), methyl-tertiary butyl ether (MTBE), and benzene by carrying out simultaneous measurements along the same routes. There were statistically significant differences (p < 0.05) in the concentrations of all target compounds among the three microenvironments; inside autos; inside buses; and in ambient air. The target compounds were significantly correlated for all the three environments, with at least p < 0.05. The in-vehicle concentrations of MTBE and benzene were significantly higher (p < 0.0001), on the average 3.5 times higher, in the car with a carbureted engine than in the other three electronic fuel-injected cars. On the other hand, the CO concentrations were not significantly different among the four cars. The in-auto MTBE levels (48.5 micrograms/m3 as a median) measured during commutes in this study was 2-3 times higher than the New Jersey and Connecticut's results. The in-auto concentration of CO (4.8 ppm as a median) in this study was comparable with those in later studies in some American cities, but much lower than those in earlier studies in other American cities. The in-bus CO concentration was 3.6 ppm as a median. As a median, the in-auto concentration of benzene was 44.9 micrograms/m3, while the in-bus concentration 17.0 micrograms/m3. The in-auto/in-bus exposure ratios for all the target compounds was 31-40% higher than the corresponding concentration ratios, due to the higher travel speed on buses in the specified commute route as compared to the autos.

Air Pollutants↗
PubMed1994

Opening the frontier: recent spatial impacts in the former inner-German border zone.

The authors examine the 1989 removal of the frontier region (Zonenrandgebiet) along the eastern border of the former Federal Republic of Germany. "The paper examines the socio-economic impacts on the North Bavarian section of the Zonenrandgebiet, which is characterized by its dispersed industrial base and lack of higher-order urban centres. Evidence is presented of rapid upturns in population growth and economic activity, together with a large inflow of commuters from the former East Germany and Czechoslovakia, following frontier opening. Traffic, environmental pressures and living costs have also increased. Both positive and negative impacts are strongest in districts contiguous with the former frontier. Long-term development prospects hinge on its newly-gained centrality within Germany. Substantial local benefits are anticipated...,but they are unlikely to induce a major reshaping of the German space-economy; this will be dominated by the rivalry between the largest metropolitan centres." (SUMMARY IN FRE AND GER)

Behavior↗
PubMed1994

Estimating temporary populations.

The difficulty of tracking temporary short-term population movements (commuting, seasonal visitation, convention and business travel) is examined, with a focus on Hawaiian statistician Robert Schmitt's work. The author finds that "Schmitt's contributions toward a methodology for estimating daytime populations were important because this approach utilized data sources that were widely available for small areas on at least an annual basis. Consequently, this approach could be used for frequent updates of the estimates, for many areas and at relatively little cost.... The major drawback of the approach is the lack of solid data on temporary residents to serve as larger-area control totals and as a historical base for small-area estimates." The geographical focus is on the United States, particularly Hawaii.

Americas↗
PubMed1986

[The migration of the rural population of Central Java].

"The objectives of this study are to examine the migration, circulation, and commuting dimensions of population mobility in rural areas of Central Java. An analysis was made to gauge a relationship between the population mobility dimensions and the agricultural modernization in the different villages." The data were collected by means of systematic random sampling from nine villages in 1981. (SUMMARY IN ENG)

Agriculture↗
PubMed1992

[Some demographic aspects of urban sprawl in Montreal from 1971 to 1991 and the implications for metropolitan management].

"Urban sprawl over the last two decades has changed the relationships between the central city and its suburb, as the urban character of the suburb asserts itself. Data on migrations and commuting inside Montreal show diminishing contracts between the suburbanites and the central city, indicating that Montreal...is experiencing this process of 'urbanization' of its suburb as well. However, the downtown area keeps a large part of its attractiveness: it is still visited by many suburbanites who nevertheless live in a different environment." (SUMMARY IN ENG AND SPA)

Americas↗
PubMed1986

Modelling population changes in small English urban areas.

The authors examine processes underlying the growth of small urban areas in England. "There is evidence of 'people-led' growth in environmentally attractive locations (for example, through retirement migration). However, growth of small- and medium-sized towns also reflects employment decentralisation and deconcentration to freestanding or satellite towns, and the extension of commuter hinterlands.... Government policies encouraging growth are also demonstrated to be significant." The processes resulting in population decline in some small towns are identified. "The impact on modelling growth in urban areas of a diversity of causal processes and locational contexts for growth is considered."

Behavior↗
PubMed2005

Characterizing the general surgery workforce in rural America.

BACKGROUND: General surgeons form a crucial component of the medical workforce in rural areas of the United States. Any decline in their numbers could have profound effects on access to adequate health care in such areas. HYPOTHESIS: We hypothesize that the rural areas of the United States are relatively undersupplied with general surgeons. DESIGN AND SETTING: The American Medical Association's Physician Masterfile was used to identify all clinically active general surgeons as well as their locations and characteristics. Their geographic distribution was examined using the ZIP code version of the Rural-Urban Commuting Areas. Surgeons were classified as practicing in urban areas, large rural areas, or small/isolated rural areas. RESULTS: There are currently 17 243 general surgeons practicing in the United States. Nationally, the number of general surgeons per population of 100 000 varies from 6.53 in urban areas to 7.71 in large rural areas and 4.67 in small/isolated rural areas. Only 10.6% of the nation's general surgeons are female. Wide variations in numbers of general surgeons were found between and within individual states. General surgeons in the smallest rural areas are more likely than those in urban areas to be male (92.7% vs 88.3%, P<.001), 50 years of age or older (51.6% vs 42.1%, P<.001), or international medical graduates (25.2% vs 20.1%, P<.001). CONCLUSIONS: The overall size of the rural general surgical workforce has remained static over the last decade, but its demographic characteristics suggest that numbers will decline. Many rural residents have limited access to surgical services. Steps to reverse this trend are needed to preserve the viability of health care in many parts of rural America.

Adult↗
PubMed2004

Coffee consumption and risk of type 2 diabetes mellitus among middle-aged Finnish men and women.

CONTEXT: Only a few studies of coffee consumption and diabetes mellitus (DM) have been reported, even though coffee is the most consumed beverage in the world. OBJECTIVE: To determine the relationship between coffee consumption and the incidence of type 2 DM among Finnish individuals, who have the highest coffee consumption in the world. DESIGN, SETTING, AND PARTICIPANTS: A prospective study from combined surveys conducted in 1982, 1987, and 1992 of 6974 Finnish men and 7655 women aged 35 to 64 years without history of stroke, coronary heart disease, or DM at baseline, with 175 682 person-years of follow-up. Coffee consumption and other study parameters were determined at baseline using standardized measurements. MAIN OUTCOME MEASURES: Hazard ratios (HRs) for the incidence of type 2 DM were estimated for different levels of daily coffee consumption. RESULTS: During a mean follow-up of 12 years, there were 381 incident cases of type 2 DM. After adjustment for confounding factors (age, study year, body mass index, systolic blood pressure, education, occupational, commuting and leisure-time physical activity, alcohol and tea consumption, and smoking), the HRs of DM associated with the amount of coffee consumed daily (0-2, 3-4, 5-6, 7-9, > or =10 cups) were 1.00, 0.71 (95% confidence interval [CI], 0.48-1.05), 0.39 (95% CI, 0.25-0.60), 0.39 (95% CI, 0.20-0.74), and 0.21 (95% CI, 0.06-0.69) (P for trend<.001) in women, and 1.00, 0.73 (95% CI, 0.47-1.13), 0.70 (95% CI, 0.45-1.05), 0.67 (95% CI, 0.40-1.12), and 0.45 (95% CI, 0.25-0.81) (P for trend =.12) in men, respectively. In both sexes combined, the multivariate-adjusted inverse association was significant (P for trend <.001) and persisted when stratified by younger and older than 50 years; smokers and never smokers; healthy weight, overweight, and obese participants; alcohol drinker and nondrinker; and participants drinking filtered and nonfiltered coffee. CONCLUSION: Coffee drinking has a graded inverse association with the risk of type 2 DM; however, the reasons for this risk reduction associated with coffee remain unclear.

Adult↗
PubMed2006

Extended work duration and the risk of self-reported percutaneous injuries in interns.

CONTEXT: In their first year of postgraduate training, interns commonly work shifts that are longer than 24 hours. Extended-duration work shifts are associated with increased risks of automobile crash, particularly during a commute from work. Interns may be at risk for other occupation-related injuries. OBJECTIVE: To assess the relationship between extended work duration and rates of percutaneous injuries in a diverse population of interns in the United States. DESIGN, SETTING, AND PARTICIPANTS: National prospective cohort study of 2737 of the estimated 18,447 interns in US postgraduate residency programs from July 2002 through May 2003. Each month, comprehensive Web-based surveys that asked about work schedules and the occurrence of percutaneous injuries in the previous month were sent to all participants. Case-crossover within-subjects analyses were performed. MAIN OUTCOME MEASURES: Comparisons of rates of percutaneous injuries during day work (6:30 am to 5:30 pm) after working overnight (extended work) vs day work that was not preceded by working overnight (nonextended work). We also compared injuries during the nighttime (11:30 pm to 7:30 am) vs the daytime (7:30 am to 3:30 pm). RESULTS: From a total of 17,003 monthly surveys, 498 percutaneous injuries were reported (0.029/intern-month). In 448 injuries, at least 1 contributing factor was reported. Lapse in concentration and fatigue were the 2 most commonly reported contributing factors (64% and 31% of injuries, respectively). Percutaneous injuries were more frequent during extended work compared with nonextended work (1.31/1000 opportunities vs 0.76/1000 opportunities, respectively; odds ratio [OR], 1.61; 95% confidence interval [CI], 1.46-1.78). Extended work injuries occurred after a mean of 29.1 consecutive work hours; nonextended work injuries occurred after a mean of 6.1 consecutive work hours. Injuries were more frequent during the nighttime than during the daytime (1.48/1000 opportunities vs 0.70/1000 opportunities, respectively; OR, 2.04; 95% CI, 1.98-2.11). CONCLUSION: Extended work duration and night work were associated with an increased risk of percutaneous injuries in this study population of physicians during their first year of clinical training.

Accidents, Occupational↗