Thorax 1994;49:133-140 133 Temporal association between hospital admissions for asthma in Birmingham and Thorax: first published as 10.1136/thx.49.2.133 on 1 February 1994. Downloaded from ambient levels of sulphur dioxide and smoke Sarah Walters, R K Griffiths, J G Ayres Abstract (0 to 7) more asthma admissions and 15 5 Background - A study was performed to (6 to 25) more respiratory admissions determine whether daily and weekly var- each day. Independent associations were iations in the levels of smoke and sulphur also found between weekly mean smoke dioxide (SO2) in Birmingham are related and SO2 levels and all respiratory admis- to hospital admissions for asthma and sions during autumn and winter. During acute respiratory diseases. summer, daily mean smoke and SO2 Methods - Daily numbers of hospital ad- levels were significantly associated with missions for asthma (ICD code 493) and non-lagged daily admissions for all res- acute respiratory conditions (ICD 466, piratory diseases (p < 002). There was no 480-486, 490-496) for residents of Birm- association between air pollution and ingham between 1988 and 1990 were hospital admissions during spring. obtained from West Midlands RHA Conclusions - Daily variations in smoke Korner inpatient data. Average daily and SO2 levels are significantly associ- levels of sulphur dioxide and smoke were ated with hospital admissions for asthma obtained from Birmingham City Council and respiratory disease during winter in for the same period, together with daily Birmingham at levels of air pollutants meteorological summaries from the De- within the EC guide levels. This associ- partment of Geography, University of ation was independent of potential con- Birmingham. With the exception of one founding effects of weather (temperat- day, all air pollution measurements ure, pressure, humidity) and suggests remained within current EC guide levels. that current levels of air pollution can Data were divided into seasons and the still produce significant health effects. relation between hospital admissions and http://thorax.bmj.com/ pollutant levels were explored by step- (Thorax 1994;49:133-140) wise least squares regression models. Meteorological variables (temperature, The effects of air pollution on public health pressure, humidity) were entered into have been studied for many years. Studies of the model if they showed significant asso- both short term health effects of temporal ciation with hospital admissions during changes in air pollution levels, and long term the season in Analysis was effects on prevalence of disease and mortality, question. on September 25, 2021 by guest. Protected copyright. undertaken for daily (same day and have been undertaken. Study methods used lagged by two days) and weekly pollutant have included epidemiological studies - both levels. Admissions were lagged behind ecological and planned observations - and con- pollution levels to allow for delayed trolled exposure experiments. Epidemiological effects of pollutants. studies have addressed a wide range of poten- Results - The mean daily level of smoke tial health outcomes including mortality, hos- was 12-7 tg/m3 and of SO2 was 39-1 tg/m3, pital attendances and admissions, and changes with maxima of 188-3 gg/m3 and 126-3 tg/ in symptoms and respiratory function. Despite Institute of Public and Environmental mi3, respectively. Significant associations all this work the exact nature and scale of the Health, University of were found between hospital admissions public health effects of air pollution, and the Birmingham Medical for respiratory disease lagged by two levels of pollutants at which health effects School, Birmingham B15 2TT days, and smoke and SO2 levels during occur, remain unclear. S Walters winter. Associations between admissions In 1952 a severe smog in London with R K Griffiths for asthma and smoke and SO2 levels exceptionally high levels of sulphur dioxide Chest Research were significant at the 5% level. These (SO2) (4000 gig/m3) and smoke (estimated Institute, were independent of temperature, pres- 7000-8000 pg/m3) resulted in more than 4000 Birmingham sure, and humidity. Stepwise regression deaths from respiratory and cardiovascular Heartlands Hospital, Bordesley Green East, including both pollutants showed that disease.' Following this episode, clean air Birmingham B9 5ST smoke, but not SO2, was a significant legislation successfully reduced SO2 and J G Ayres independent predictor of hospital admis- smoke levels throughout the UK.2 With falling Reprint requests to: sions for both asthma and all respiratory levels of these pollutants, interest and research Dr S Walters. conditions. During winter a rise of 100 tg/ into their effects on health waned in the UK. Received 25 February 1993 m3 smoke might result in five (95% CI 0-6 Studies from the USA suggest that current Returned to authors 20 April 1993 to 9) more asthma admissions and 21P5 lower levels of particulates are still associated Revised version received (95% CI 10 to 33) more acute respiratory with mortality. A consistent independent re- 9 August 1993 Accepted for publication admissions each day in Birmingham. A lation has been shown between both total sus- 4 November 1993 100 jg/m3 rise in SO might result in four pended particulates34 and particulates below 134 Walters, Griffiths, Ayres 10 gm in diameter (PM10)56 and daily morta- Other pollutants, alone or in combination lity; the relation is strongest in patients with with SO2 and particulates, have also been respiratory and cardiovascular conditions. associated with health effects. In a panel study Thorax: first published as 10.1136/thx.49.2.133 on 1 February 1994. Downloaded from The effect of SO2 and particulates on hos- in Denver hydrogen ion concentration was pital admissions or attendances has also been significantly associated with several sympto- studied. A series of Canadian studies showed matic indices of asthmatic status, as were fine significant relations between hospital admis- particulates and sulphate.22 In Los Angeles, sions for asthma and respiratory diseases and risk of asthma attacks was increased on days air pollution. Admissions were significantly with high oxidant and particulate pollution.23 associated with levels of SO2, coefficient of Several studies in summer camps have con- haze, and a composite air pollution index in firmed that ozone levels can affect pulmonary southern Ontario.7 Bates and Sizto showed a function.2425 relation between hospital admissions for There is good experimental evidence to back asthma and respiratory diseases and levels of up these epidemiological findings. SO2 can SO2, ozone, oxides of nitrogen and sulphate cause bronchoconstriction at high levels in during summer.8 In Vancouver, SO2 was sig- normal subjects,26 but asthmatic subjects ap- nificantly associated with attendances at the pear to react at one tenth of the concentra- emergency department for asthma and respira- tion.27 The effect is increased by exercise2829 tory diseases during both summer and winter.9 and may occur after exposure of five minutes This study also showed a significant associ- or less.30 Ozone3132 and N02 have also been ation during summer between hospital attend- shown to cause bronchoconstriction, either ances and sulphate and ozone levels. A recent directly or via their effects on bronchial sensit- study from Barcelona showed significant, ivity.34 though weak, relations between SO2, smoke As well as studies of acute effects, there is and carbon monoxide levels and hospital at- some evidence that exposure to air pollution tendances in patients with chronic obstructive can produce longer term effects on symptom pulmonary disease (COPD).'0 prevalence. The Harvard Six Cities study An important series of recent studies from reported an association between prevalence of Utah on the effects of PM10 pollution on cough, bronchitis, and chest illness in children various health outcomes has confirmed health and ambient particulate and S02 levels.3 This effects of relatively low levels of particulates. was subsequently confirmed in a second study Hospital admissions rose by 89% in children which showed symptom prevalence to be more and by 47% in adults when PM10 levels strongly associated with particulate levels than exceeded 50 gg/m3." In a later study hospitali- SO2 or NO2.36 Associations were stronger in sation rates for Utah Valley were compared children with asthma, and for fine particulates http://thorax.bmj.com/ with those in two other valleys during a period (PM15). of steel mill closure. Hospital admission rates Thus there is a substantial amount of pub- were high in the polluted Utah Valley, but fell lished literature to show that particulate pollu- almost to those in the comparison valleys dur- tion and S02 is associated with acute health ing closure of the mill, and rose again rapidly effects. However, there are no recent studies after reopening.'2 A study from Seattle con- from the UK of health effects at current levels firmed the association between hospital at- of particulate and S02 pollution. Hospital ad- tendances for asthma and PM10 levels.'3 missions for asthma are rising in the West on September 25, 2021 by guest. Protected copyright. Further studies from Utah have shown PM10 Midlands, particularly in children.37 This to be associated with school absences, even study sought to determine whether SO2 and when corrected for weather.'4 Peak expiratory smoke (the only available measure of particu- flow (PEF) in panels of children is significantly lates) were associated with hospital admissions associated with PM10, even when days above for asthma and respiratory disease in Birm- the air quality standard of 150 gg/m3 were ingham, to determine the size and potential excluded.'5 The association was stronger for public health importance of any association children with respiratory symptoms. seen, and to establish whether these health Early panel studies showed a relation effects could be detected using routinely col- between daily smoke and S02 levels in London lected data. and symptoms in patients with COPD'6; how- ever, pollution levels were considerably higher than at present.