Associations between short/medium-term variations in black smoke air pollution and mortality in the Glasgow conurbation, UK.

OBJECTIVES: To examine associations between short/medium-term variations in black smoke air pollution and mortality in the population of Glasgow and the adjacent towns of Renfrew and Paisley over a 25-year period at different time lags (0-30 days). METHODS: Generalised linear (Poisson) models were used to investigate the relationship between lagged black smoke concentrations and daily mortality, with allowance for confounding by cold temperature, between 1974 and 1998. RESULTS: When a range of lag periods were investigated significant associations were noted between temperature-adjusted black smoke exposure and all-cause mortality at lag periods of 13-18 and 19-24 days, and respiratory mortality at lag periods of 1-6, 7-12, and 13-18 days. Significant associations between cardiovascular mortality and temperature-adjusted black smoke were not observed. After adjusting for the effects of temperature a 10 µg m(-3) increase in black smoke concentration on a given day was associated with a 0.9% [95% Confidence Interval (CI): 0.3-1.5%] increase in all cause mortality and a 3.1% [95% CI: 1.4-4.9%] increase in respiratory mortality over the ensuing 30-day period. In contrast for a 10 µg m(-3) increase in black smoke concentration over 0-3 day lag period, the temperature adjusted exposure mortality associations were substantially lower (0.2% [95% CI: − 0.0-0.4%] and 0.3% [95% CI: − 0.2-0.8%] increases for all-cause and respiratory mortality respectively). CONCLUSIONS: This study has provided evidence of association between black smoke exposure and mortality at longer lag periods than have been investigated in the majority of time series analyses.

Associations between short/medium-term variations in black smoke air pollution and mortality in the Glasgow conurbation, UK.

OBJECTIVES: To examine associations between short/medium-term variations in black smoke air pollution and mortality in the population of Glasgow and the adjacent towns of Renfrew and Paisley over a 25-year period at different time lags (0-30 days). METHODS: Generalised linear (Poisson) models were used to investigate the relationship between lagged black smoke concentrations and daily mortality, with allowance for confounding by cold temperature, between 1974 and 1998. RESULTS: When a range of lag periods were investigated significant associations were noted between temperature-adjusted black smoke exposure and all-cause mortality at lag periods of 13-18 and 19-24 days, and respiratory mortality at lag periods of 1-6, 7-12, and 13-18 days. Significant associations between cardiovascular mortality and temperature-adjusted black smoke were not observed. After adjusting for the effects of temperature a 10 µgm(-3) increase in black smoke concentration on a given day was associated with a 0.9% [95% Confidence Interval (CI): 0.3-1.5%] increase in all cause mortality and a 3.1% [95% CI: 1.4-4.9%] increase in respiratory mortality over the ensuing 30-day period. In contrast for a 10 µgm(-3) increase in black smoke concentration over 0-3 day lag period, the temperature adjusted exposure mortality associations were substantially lower (0.2% [95% CI: -0.0-0.4%] and 0.3% [95% CI: -0.2-0.8%] increases for all-cause and respiratory mortality respectively). CONCLUSIONS: This study has provided evidence of association between black smoke exposure and mortality at longer lag periods than have been investigated in the majority of time series analyses.

Does deprivation index modify the acute effect of black smoke on cardiorespiratory mortality?

OBJECTIVES: To investigate whether deprivation index modifies the acute effect of black smoke on cardiorespiratory mortality. METHODS: Generalised linear Poisson regression models were used to investigate whether deprivation index (as measured by the Carstairs deprivation index) modified the acute effect of black smoke on mortality in two largest Scottish cities (Glasgow and Edinburgh) between January 1981 and December 2001. Lag periods of up to 1 month were assumed for the effects of black smoke. RESULTS: Deprivation index significantly modified the effect of black smoke on mortality, with black smoke effects generally increasing as level of deprivation increased. The interaction coefficient from a parametric model assuming a linear interaction between black smoke (microg/m(-3)) and deprivation in their effect on mortality--equivalent to a test of 'linear trend' across Carstairs categories--was significant for all mortality outcomes. In a model where black smoke effects were estimated independently for each deprivation category, the estimated increase in respiratory mortality over the ensuing 1-month period associated with a 10 microg/m(3) increase in the mean black smoke concentration was 8.0% (95% CI 5.1 to 10.9) for subjects residing in the 'most' deprived category (Carstairs category 7) compared to 3.7% (95% CI -0.7 to 8.4) for subjects residing in the 'least' deprived category (Carstairs category 1). CONCLUSIONS: The results suggest a stronger effect of black smoke on mortality among people living in more deprived areas. The effect was greatest for respiratory mortality, although significant trends were also seen for other groups. If corroborated, these findings could have important public health implications.

A time-series study of the health effects of water-soluble and total-extractable metal content of airborne particulate matter.

OBJECTIVES: To assess whether adverse acute cardiopulmonary health outcomes are associated with concentration of trace metals in airborne particulate matter. METHODS: Daily PM(10) and PM(2.5) were collected for 1 year in Edinburgh, UK, and the water-soluble and total-extractable content of 11 trace metals determined in each sample. Time series were analysed using generalised additive Poisson regression models, including adjustment for minimum temperature and less smoothing of trends. Methods were explored of extending the time series of metal concentration in daily PM(10) for the previous 7 years using multiple regression of the variation in metal content for the 1 year of measurements and the associated variation in air mass source region and other concurrently-measured potential predictor variables. RESULTS: The 1 year of direct measurements showed no evidence of significant associations of particle-bound metal concentration with health outcomes beyond that expected by chance. Analysis of the extended time series showed significant positive associations with cardiovascular admissions both for total PM(10) and for a number of the metals (eg, Cu, Fe, Ni, V, Zn) but the metal effects were no longer significant after adjusting for PM(10). CONCLUSIONS: Within the limitations of the study power, the epidemiological results have not provided evidence for associations between particle-bound metal concentrations and adverse health outcomes that are substantially greater than for total PM. The generally strong correlations between metal and total PM suggest that quantifying independent effects of PM metal exposure on health will be difficult, even using more powerful time series of direct measurements.

Interacting effects of particulate pollution and cold temperature on cardiorespiratory mortality in Scotland.

OBJECTIVES: To determine whether the effect of black smoke on cardiorespiratory mortality is modified by cold temperatures. METHODS: Poisson regression models were used to investigate the relationship between lagged black smoke concentration and daily mortality, and whether the effect of black smoke on mortality was modified by cold temperature for three Scottish cities from January 1981 to December 2001. MAIN RESULTS: For all-cause respiratory and non-cardiorespiratory mortality, there was a significant association between mortality and lagged black smoke concentration. Generally the maximum black smoke effect occurred at lag 0, although these estimates were not statistically significant. A 10 mugm(-3) increase in the daily mean black smoke concentration on any given day was associated with a 1.68% (95% CI 0.72 to 2.65) increase in all-cause mortality and a 0.43% (95% CI -0.97 to 1.86), 5.36% (95% CI 2.93 to 7.84) and 2.13% (95% CI 0.82 to 3.47) increase in cardiovascular, respiratory and non-cardiorespiratory mortality, respectively, over the ensuing 30-day period. The effect of black smoke on mortality did not vary significantly between seasons (cool and warm periods). For all-cause, cardiovascular and non-cardiorespiratory mortality the inclusion of interaction terms did not improve the models, although for all-cause and non-cardiorespiratory mortality there was a suggestion for interaction between temperature and recent black smoke exposure. CONCLUSIONS: The results of this study suggested a greater effect of black smoke on mortality at low temperatures. Since extremes of cold and particulate pollution may coexist, for example during temperature inversion, these results may have important public health implications.

The lagged effect of cold temperature and wind chill on cardiorespiratory mortality in Scotland.

AIMS: To investigate the lagged effects of cold temperature on cardiorespiratory mortality and to determine whether "wind chill" is a better predictor of these effects than "dry bulb" temperature. METHODS: Generalised linear Poisson regression models were used to investigate the relation between mortality and "dry bulb" and "wind chill" temperatures in the three largest Scottish cities (Glasgow, Edinburgh, and Aberdeen) between January 1981 and December 2001. Effects of temperature on mortality (lags up to one month) were quantified. Analyses were conducted for the whole year and by season (cool and warm seasons). MAIN RESULTS: Temperature was a significant predictor of mortality with the strongest association observed between temperature and respiratory mortality. There was a non-linear association between mortality and temperature. Mortality increased as temperatures fell throughout the range, but the rate of increase was steeper at temperatures below 11 degrees C. The association between temperature and mortality persisted at lag periods beyond two weeks but the effect size generally decreased with increasing lag. For temperatures below 11 degrees C, a 1 degrees C drop in the daytime mean temperature on any one day was associated with an increase in mortality of 2.9% (95% CI 2.5 to 3.4), 3.4% (95% CI 2.6 to 4.1), 4.8% (95% CI 3.5 to 6.2) and 1.7% (95% CI 1.0 to 2.4) over the following month for all cause, cardiovascular, respiratory, and "other" cause mortality respectively. The effect of temperature on mortality was not observed to be significantly modified by season. There was little indication that "wind chill" temperature was a better predictor of mortality than "dry bulb" temperature. CONCLUSIONS: Exposure to cold temperature is an important public health problem in Scotland, particularly for those dying from respiratory disease.

Soluble transition metals in welding fumes cause inflammation via activation of NF-kappaB and AP-1.

We previously reported that the molecular pro-inflammatory effects of welding fumes in vitro were caused by soluble transition metals via an oxidative stress-mediated mechanism. Herein, we tested the hypothesis that transition metals in welding fume drive the in vivo inflammatory response caused by welding fume. Rats were instilled with either whole, soluble extract or washed welding fume particulates or soluble extracts pre-treated with a transition metal chelator. Markers of pulmonary inflammation were measured in the bronchoalveolar lavage fluid (BALF) and nuclear translocation of transcription factor was assessed in BAL cells by electrophoretic mobility shift assay. Instillation of either whole or soluble fractions of welding fume caused a significant influx of inflammatory cells and other markers of inflammation in the BALF 24 h later. MIP-2 protein in BALF and nuclear translocation of NF-kappaB and AP-1 were significantly greater following instillation of whole and soluble fractions than in saline-instilled lungs. Chelation of the soluble fraction, to remove transition metals, abolished the ability to cause inflammation, MIP-2 increase or transcription factor translocation to the nucleus. Instillation of washed particulates alone caused no significant change in any end-point compared to saline. This study demonstrates that soluble transition metals present in welding fumes cause inflammation via activation of the redox-sensitive transcription factors NF-kappaB and AP-1 and confirms the validity of utilising in vitro models to assess inflammatory responses to such particles.

Intercomparison of five PM10 monitoring devices and the implications for exposure measurement in epidemiological research.

Five different instruments for the determination of the mass concentration of PM10 in air were compared side-by-side for up to 33 days in an undisturbed indoor environment: a tripod mounted BGI Inc. PQ100 gravimetric sampler with a US EPA certified Graseby Andersen PM10 inlet; an Airmetrics Minivol static gravimetric sampler; a Casella cyclone gravimetric personal sampler; an Institute of Occupational Medicine gravimetric PM10 personal sampler; and two TSI Inc. Dustrak real-time optical scattering personal samplers. For 24 h sampling of ambient PM10 concentrations around 10 microg m(-3), the estimated measurement uncertainty for the two gravimetric personal samplers was larger (approximately +/- 20%) compared with estimated measurement uncertainty for the PQ100/Graseby Andersen sampler (< +/- 5%). Measurement uncertainty for the Dustraks was lower (approximately +/- 15% on average) but calibration of the optical response against a reference PM10 method is essential since the Dustraks systematically over-read PM10 determined gravimetrically by a factor approximately 2.2. However, once calibrated, the Dustrak devices demonstrated excellent functionality in terms of ease of portability and real-time data acquisition. Estimated measurement uncertainty for PM10 concentrations determined with the Minivol were +/- 5%. The Minivol data correlated well with PQ100/Graseby Andersen data (r= 0.97, n = 18) but were, on average, 23% greater. The reason for the systematic discrepancy could not be traced. Intercomparison experiments such as these are essential for assessing measurement error and revealing systematic bias. Application of two Dustraks demonstrated the spatial and temporal variability of exposure to PM10 in different walking and transport microenvironments in the city of Edinburgh, UK. For example, very large exposures to PM10 were identified for the lower deck of a double-decker tour bus compared with the open upper deck of the same vehicle. The variability observed emphasises the need to determine truly personal exposure profiles of PM10 for quantifying exposure response relationships for epidemiological studies.

On the interpretation of event and sub-event rainfall chemistry.

Variations in precipitation chemistry between and within rain events have been examined in order to identify possible relationships with synoptic, mesoscale and micrometeorological processes. A microprocessor-based acid rain monitor was used to provide high resolution meteorological and rain chemistry data from which two case study events have been selected to illustrate event and sub-event rainfall chemistry characteristics. Event rainfall chemistry is strongly influenced by the history of the prevailing air mass and the synoptic situation. From back trajectories calculated at the 950 mbar level it is clear that air mass history can change markedly within a few hours. These observations emphasise the value of high resolution rainfall chemistry measurements. Pollutant concentrations in rainwater have been shown to fluctuate markedly within the course of individual events as a result of both advective and scavenging processes. Advective effects may result from: (a) air mass discontinuities at frontal zones; and/or (b) variable rainfall interception of the air mass prior to arrival at the site. A simple mathematical model has been developed to describe the scavenging mechanisms and it shows good agreement with field observations. Theoretical considerations suggest that in-cloud processes give rise to most of the observed decline in concentrations.