Studies conducted both in the UK and World-wide have consistently reported an association between exposure to ambient air pollutants and ill health, most notably respiratory and cardiovascular disease. Although respiratory disease is one of the major causes of death in the City of Manchester, with mortality rates in some areas of the City approximately twice the national average, the possible relationship between air pollutant exposure and the observed health effects has not previously been assessed for the Manchester population. To assess the short-term health effects of air pollutants the study used a time series design where daily variations in selected causes of mortality and morbidity in the City of Manchester were compared with daily variations in air pollutants. To assess the longer-term (chronic) effects of pollutants on health the approach adopted was to map standardised mortality ratios (SMRs) and standardised hospitalisation ratios (8HRs) for specific diseases in Manchester and to examine the relationship between these and the air pollutants. In both methods, the relationship between the two variables was assessed using Poisson regression techniques whilst adjusting for the potential confounding effects of other environmental and social variables. The results of the time series study indicated that there was small, but significant associations between exposure to air pollutants and acute adverse health effects in the Manchester population. With respect to mortality, the most significant finding was an association between ozone (03) concentrations and both all cause mortality and cardiovascular mortality (warm season only) with an increase of 10ppb in the 1-hour or 8-hour maximum 0 3 concentration associated with an increase in the number of deaths of approximately 3-4%. In both cases, the association persisted after adjustment for the effects of meteorology and other potential confounding variables and appeared to be independent of the other air pollutants. A significant association between mortality (all cause and disease specific) and the other air pollutants: particulate matter (PM1o), black smoke (88), nitrogen dioxide (N02) and sulphur dioxide (802) was not observed. The results of the time series study also indicated a significant association between a number of the measured air pollutants and both total respiratory hospital admissions and asthma admissions. For both disease groups, the stronger predictor was the daily mean BS concentration (lagged by three days) although associations were also observed between these groups and the daily mean N02, PM10 and S02 concentrations. For these two disease groups, an increase in the daily mean BS concentration of 1 O~gm3 was associated with an approximate 3-5% increase in hospital admissions. The main finding of the cross-sectional study was a significant association between ill health (as measured by the age-sex SMR and SHR) and socioeconomic deprivation (as measured by the IMD2000 or the DOE Index). In pollutant only models (Le. no adjustment for the effects of deprivation) a significant association (p<O.05) was observed between all cause mortality SMR and N02, PM10 and carbon monoxide (CO), with PM10 being the stronger predictor. A significant association was also observed between the SHR for COPD and PM10 levels. However, after adjusting for the effects of confounding by deprivation, a significant association between the air pollutants and the standardised mortality ratios (SMR) or standardised hospitalisation ratios (SHR) was not observed. In conclusion, this study has presented evidence that exposure to relatively low levels of air pollutants are associated with small but significant acute adverse health effects. The strongest relationships were observed between 0 3 and mortality (all cause and cardiovascular) and between BS and both total respiratory admissions and asthma admissions. However, associations between respiratory admissions (total and asthma) and a number of other pollutants were also observed. In view of this, it would be imprudent to conclusively assign the observed effects to any single pollutant. In contrast, the study found no evidence of an association between long-term exposure to air pollutants and chronic respiratory or cardiovascular disease, although a strong association between socio-economic deprivation and ill health was observed. However, due to the lack of data at the individual level, the ecological study design is limited in its power to detect small pollutantlhealth associations. Thus, the lack of a significant association between the air pollutants and ill health, as observed in this study, should not be viewed as conclusive evidence against such an association.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:392566 |
| Date | January 2002 |
| Creators | Carder, Melanie |
| Publisher | Manchester Metropolitan University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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