An association between fine particles and asthma emergency department visits for children in Seattle.
Asthma is the most common chronic illness of childhood and its prevalence is increasing, causing much concern for identification of risk factors such as air pollution. We previously conducted a study showing a relationship between asthma visits in all persons < 65 years of age to emergency departments (EDs) and air pollution in Seattle, Washington. In that study the most frequent zip codes of the visits were in the inner city. The Seattle-King County Department of Public Health (Seattle, WA) subsequently published a report which showed that the hospitalization rate for children in the inner city was over 600/100,000, whereas it was < 100/100,000 for children living in the suburbs. Therefore, we conducted the present study to evaluate whether asthma visits to hospital emergency departments in the inner city of Seattle were associated with outdoor air pollution levels. ED visits to six hospitals for asthma and daily air pollution data were obtained for 15 months during 1995 and 1996. The association between air pollution and childhood ED visits for asthma from the inner city area with high asthma hospitalization rates were compared with those from lower hospital utilization areas. Daily ED counts were regressed against fine particulate matter (PM), carbon monoxide (CO), sulfur dioxide, and nitrogen dioxide using a semiparametric Poisson regression model. Significant associations were found between ED visits for asthma in children and fine PM and CO. A change of 11 microg/m3 in fine PM was associated with a relative rate of 1.15 [95% confidence interval (CI), 1.08-1.23]. There was no stronger association between ED visits for asthma and air pollution in the higher hospital utilization area than in the lower utilization area. These findings were seen when estimated PM2.5 concentrations were below the newly adopted annual National Ambient Air Quality Standard of 15 microg/m3. (+info)
Effects of temperature and snowfall on mortality in Pennsylvania.
The relation between exposure to severe cold weather and mortality is examined in a retrospective study of deaths occurring during the month of January from 1991 to 1996 in Pennsylvania. Using division-days as units of observation (n = 1,560) aggregated from death certificates and geographic divisions, the authors estimated mortality rates for total deaths and deaths due to ischemic heart disease, cerebrovascular diseases, and respiratory diseases by analyses based on generalized estimating equations. Total mortality increased on days of "extreme" climatic conditions, that is, when snowfall was greater than 3 cm and when temperatures were below -7 degrees C (rate ratio (RR) = 1.27, 95 percent confidence interval (CI) 1.12-1.44). On days of extreme conditions, mortality due to ischemic heart diseases tripled among males aged 35-49 years (RR = 3.54, 95 percent CI 2.35-5.35), increased for men aged 50-64 years (RR = 1.77, 95 percent CI 1.32-2.38), and rose for males aged 65 years and older (RR = 1.58, 95 percent CI 1.37-1.82), when compared with milder conditions. Among females, mortality for those aged 65 years and older increased for respiratory causes (RR = 1.68, 95 percent CI 1.28-2.21) and cerebrovascular causes (RR = 1.47, 95 percent CI 1.13-1.91). Cold and snow exposure may be hazardous among men as young as 35 years. (+info)
Particulate air pollution and daily mortality on Utah's Wasatch Front.
Reviews of daily time-series mortality studies from many cities throughout the world suggest that daily mortality counts are associated with short-term changes in particulate matter (PM) air pollution. One U.S. city, however, with conspicuously weak PM-mortality associations was Salt Lake City, Utah; however, relatively robust PM-mortality associations have been observed in a neighboring metropolitan area (Provo/Orem, Utah). The present study explored this apparent discrepancy by collecting, comparing, and analyzing mortality, pollution, and weather data for all three metropolitan areas on Utah's Wasatch Front region of the Wasatch Mountain Range (Ogden, Salt Lake City, and Provo/Orem) for approximately 10 years (1985-1995). Generalized additive Poisson regression models were used to estimate PM-mortality associations while controlling for seasonality, temperature, humidity, and barometric pressure. Salt Lake City experienced substantially more episodes of high PM that were dominated by windblown dust. When the data were screened to exclude obvious windblown dust episodes and when PM data from multiple monitors were used to construct an estimate of mean exposure for the area, comparable PM-mortality effects were estimated. After screening and by using constructed mean PM [less than/equal to] 10 microm in aerodynamic diameter (PM10) data, the estimated percent change in mortality associated with a 10-mg/m3 increase in PM10 (and 95% confidence intervals) for the three Wasatch Front metropolitan areas equaled approximately 1. 6% (0.3-2.9), 0.8% (0.3-1.3), and 1.0% (0.2-1.8) for the Ogden, Salt Lake City, and Provo/Orem areas, respectively. We conclude that stagnant air pollution episodes with higher concentrations of primary and secondary combustion-source particles were more associated with elevated mortality than windblown dust episodes with relatively higher concentrations of coarse crustal-derived particles. (+info)
Climate and satellite indicators to forecast Rift Valley fever epidemics in Kenya.
All known Rift Valley fever virus outbreaks in East Africa from 1950 to May 1998, and probably earlier, followed periods of abnormally high rainfall. Analysis of this record and Pacific and Indian Ocean sea surface temperature anomalies, coupled with satellite normalized difference vegetation index data, shows that prediction of Rift Valley fever outbreaks may be made up to 5 months in advance of outbreaks in East Africa. Concurrent near-real-time monitoring with satellite normalized difference vegetation data may identify actual affected areas. (+info)
Repeatability of cough-related variables during fog challenges at threshold and suprathreshold stimulus intensity in humans.
Cough-related variables such as cough frequency, time to onset (i.e. the time until the first cough occurs) and the cough index (i.e. the ratio between the cough frequency and the time to onset) may be important when interpreting results of cough challenges for therapeutic interventions or for comparative research purposes. Nevertheless, repeatability (or reproducibility) for these widely used variables has been poorly studied. In thirty normal subjects, coughing was induced by inhalation of threshold (T) and suprathreshold (1.6 x T) concentrations of ultrasonically nebulized distilled water (fog). Cough threshold was taken as the lowest fog concentration that evoked at least one cough effort during two challenges separated by a 30-min interval. During challenges performed at both threshold and suprathreshold stimulus intensity, cough frequency, time to onset, and the cough index were assessed; within-subject repeatability for these variables was subsequently evaluated. Median +/- interquartile range cough threshold value was 0.9+/-0.5 mL x min(-1). During the two challenges performed to assess cough threshold, the mean +/-SD values of cough frequency, time to onset, and cough index were similar (5.0+/-2.7 and 5.3+/-3.1 coughs x min(-1), 32.4+/-13.3 and 32.9+/-13.6 s, and 0.2+/-0.2 and 0.2+/-0.2, respectively). However, none of these cough-related variables proved to be sufficiently repeatable. During the two challenges performed at suprathreshold stimulus intensity, mean values of cough frequency, time to onset, and cough index were also similar (20.0+/-9.0 and 18.2+/-10.2 coughs x min(-1), 13.5+/-5.8 and 12.0+/-4.62 s, and 1.7+/-1.0 and 1.8+/-1.2); furthermore, all considered variable of suprathreshold challenge turned out to be reproducible. In conclusion, during fog challenges at threshold stimulus intensity, cough frequency, time to onset and cough index cannot reliably be used for evaluating cough responses. However, these cough-related variables may represent useful and reliable research tools in the evaluation of suprathreshold cough responses. (+info)
Epidemiology of respiratory syncytial virus infection among paediatric patients in Hong Kong: seasonality and disease impact.
In a 5-year retrospective survey of respiratory syncytial virus (RSV) infections among hospitalized children, 1340 cases were identified of which, 98.4% were children < 5 years old with a male:female ratio of 1.5: 1. Most cases occurred from April to September showing a significant positive correlation with temperature and relative humidity. Community-acquired infections accounted for 92.5% of the cases with a mean hospital stay of 5 days. The estimated annual incidence of RSV infection requiring hospitalization was 2.5/1000 children < 5 years old with a mortality of 0.15% among hospitalized cases. On average, 248 children were admitted each year to the 1400-bed acute regional hospital accounting for an expenditure of HK S1.94 ((approximately US +/-0.25) million for hospitalization costs which equates to an annual cost in excess of HK $6.67 (approximately US $0.86) million for the whole of Hong Kong. An RSV vaccine should be a priority. (+info)
Residual delay maps unveil global patterns of atmospheric nonlinearity and produce improved local forecasts.
We use residual-delay maps of observational field data for barometric pressure to demonstrate the structure of latitudinal gradients in nonlinearity in the atmosphere. Nonlinearity is weak and largely lacking in tropical and subtropical sites and increases rapidly into the temperate regions where the time series also appear to be much noisier. The degree of nonlinearity closely follows the meridional variation of midlatitude storm track frequency. We extract the specific functional form of this nonlinearity, a V shape in the lagged residuals that appears to be a basic feature of midlatitude synoptic weather systems associated with frontal passages. We present evidence that this form arises from the relative time scales of high-pressure versus low-pressure events. Finally, we show that this nonlinear feature is weaker in a well regarded numerical forecast model (European Centre for Medium-Range Forecasts) because small-scale temporal and spatial variation is smoothed out in the grided inputs. This is significant, in that it allows us to demonstrate how application of statistical corrections based on the residual-delay map may provide marked increases in local forecast accuracy, especially for severe weather systems. (+info)
Determination of acrylamide monomer in polyacrylamide degradation studies by high-performance liquid chromatography.
A high-performance liquid chromatography method using C18 and ion-exchange columns in series is developed for the determination of acrylamide and acrylic acid monomers in polymeric samples. The C18 column acts as a guard column, trapping surfactants and impurities and retaining the nonionic species. The ion-exchange column then separates the monomers according to their respective ionic strengths. This method has been proven in the laboratory to work successfully for all types of acrylamide/acrylic acid polymers and matrices. Detection limits for both monomers can be achieved in the parts-per-billion range. The method is used to study the possible degradation of polyacrylamide to acrylamide monomer in the presence of glyphosate (a herbicide) and sunlight. Polyacrylamide is used as a spray drift reduction aid in combination with glyphosate. In normal applications, the polymer and herbicide are in contact with each other in the presence of sunlight. The results show that the polymer does not degrade to acrylamide in the presence of glyphosate or sunlight or any combination of the two. It is also observed that glyphosate influences the solubility of polyacrylamide, and care must be used when combining the two. (+info)