Asthma and the atmosphere - Europe PMC

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Britain by the recent hot weather, the advent of warnings about air quality, and the ... in the long term and whether they may lead to healthy peo- ple developing ...
LONDON, SATURDAY 10 SEPTEMBER 1994

Asthma and the atmosphere Patients should be given practical advice on how to deal with episodes ofsevere air pollution Journalists and the public have become increasingly concerned about the possible effects of the weather and air pollution on health. This anxiety has been exacerbated in Britain by the recent hot weather, the advent of warnings about air quality, and the availability of measurements of air quality on Ceefax. What sensible advice can be given to people about their response to episodes of air pollution? The first challenge is to identify just who is at risk during these episodes. Most of the relevant research has come from two types of study. Panel studies take a group of people and follow up symptoms and lung function for a period during which air quality is thought likely to become poor. Event studies report effects of unusual episodes of pollution on a group of patients already recording symptoms or peak flow, or both, daily. Most of the studies conducted in North America have been of children attending summer camps, where the exposures were to ozone, acid aerosols, and particulates-the acid summer haze effect.' European studies, by contrast, have largely reported the effects of winter pollution with particulates, nitrogen oxides, and sulphur dioxide. In the summer in both Europe and North America ozone is the most important pollutant. The standard for ozone in Britain has recently been reset at 50 ppb as an eight hour running average.2 During ozone "events" the concentration may peak at over 110 ppb, when some patients with asthma and some non-asthmatic people will show a slight fall in lung function.' Symptoms do not develop until much higher concentrations are reached. Patients with more severe asthma or increased bronchial reactivity show a greater response, and this may explain the range of reported results.45 Children seem to be more sensitive than adults. Invariably, however, the effects are small: a fall in the forced expiratory volume in one second of 0A4-2-5 ml for each ppb rise in ozone concentration.6 The ozone studies have only rarely taken account of pollen counts, but the finding that ozone can enhance the bronchial response to challenge with an allergen complicates the interpretation of the effects of lower concentrations of ozone.7 Episodes of pollution during the winter show similar sized but sometimes more prolonged effects; up to three weeks may elapse before lung function returns to normal.8 The effects of repeated exposures to such episodes on patients with asthma remains unknown-let alone the BMJ VOLUME 309

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effects on those without pre-existing lung disease. High concentrations of particulates (38% of which in British air come from diesel emissions9) can undoubtedly contribute to symptoms of asthma,'0 and the recent finding from a series of studies in the United States of an association between particulates and mortality has rightly caused concern."1 If a link is found in Europe exposures to episodes of severe air pollution might then acquire more importance. The questions that need to be answered are whether repeated exposures will make patients with asthma worse in the long term and whether they may lead to healthy people developing asthma. Both questions will require the establishment of formal longitudinal studies. It would be unwise to support these beliefs by reliance on selected data culled from studies that were not designed specifically for the purpose. Meanwhile, what can we do for our patients today? We should advise those with asthma to double their inhaled prophylactic treatment as soon as warnings about air quality are given out. There may be some logic in suggesting to those taking twice daily prophylaxis that they should add a midday dose-ozone concentrations are highest in the afternoon. Some patients who are not taking any prophylactic treatment should start inhaled anti-inflammatory drugs-much as they might do with a cold-and continue them until a few days after the episode. All patients should be encouraged to modify their behaviour and activity. They might be told, for example, to wait for the next bus rather than to run for one and not to jog in the afternoon. Paradoxically, patients with asthma may have to use their cars (worsening the pollution) rather than walk during these episodes. The suggestion that patients with asthma should stay indoors and shut doors and windows during such spells is unnecessarily stringent, though severely asthmatic people may believe that this is the right thing to do. Without doubt, episodes of air pollution may affect the health of many patients with asthma or chronic airflow limitation in the short term. Patients should be warned when air quality is going to be poor and told what they may be able to do to reduce any ill effect, but the advice should be balanced. We are only just beginning to unpick the effects of air pollution on public health both in the long and the short term. Today we can advise on what change in treat-

ment is needed during episodes. Tomorrow we may be able to advise on how to avoid what is as yet an unquantified health load from the air we breathe. JON AYRES Consultant respiratory physician Chest Research Institute, Birmingham Heartlands Hospital, Birmingham B9 5SS 1 Bates DV, Sizto R. Air pollution and hospital admissions in southem Ontario: the acid summer haze effect. Environ Res 1987;43:317-31. 2 Expert Panel on Air Quality Standards. Ozone. London: HMSO, 1994. 3 Lippmann M, Lioy PL, Leikauf G, et al. Effects of ozone on the pulmonary function of children. Adv Mod Environ Toxicol 1983;31:423-46.

4 Walters SM, Miles J, Archer G, Ayres JG. Effect of an air pollution episode on respiratory finction of patients with asthma. Thorax 1993;48:1063. 5 Raizenne M, Bumett RT, Stem B, Franklin CA, Spengler JD. Acute lung function responses to ambient acid aerosol exposures in children. Environ Health Perspect 1989;79:179-85. 6 Spektor DM, Thurston GD, Mao J, He D, Hayes C, Lippmann M. Effects of single and multi-day ozone exposures on respiratory function in active healthy children. Environ Res 1991;54: 135-50. 7 Molfino NA, Wright SC, Katz I, Tarlo S, Silverman F, McClean PA, et al. Effect of low concentrations of ozone on inhaled allergen responses in asthmatic subjects. Lancet 1991;338: 199-203. 8 Hoek G, Brunekreef B, Hofschreuder P, Lumens M. Effects of air pollution episodes on pulmonary function and respiratory symptoms. Toxicol Ind Health 1990;6:189-97. 9 Quality of Urban Air Review Group. Second report: diesel vehicle emissions and urban air quality. London: Department of the Environment, 1993. 10 Pope CA, Dockery DW. Acute health effects of PM. pollution on symptomatic and asymptomatic children. Am Rev Respir Dis 1992;145:1 123-8. 11 Dockery DW, Pope CA. Acute respiratory effects of particulate air pollution. Annu Rev Public Health 1994;15:107-32.

Surgical removal of third molars Prophylactic surgery should be abandoned The surgical removal of teeth is one of the four surgical operations included in both top 10 day case and inpatient NHS procedures for England and Wales.' The other three procedures, for 1989-90, were endoscopic operations on the upper gastrointestinal tract and bladder and evacuation of the contents of the uterus. Surprisingly, in the last year for which statistics are available (1989-90) more than twice as many people (60 000) were admitted for the surgical removal of teeth as were treated as day cases (28 000). For inpatient procedures, the surgical removal of teeth was ninth in frequency behind vasectomy. The surgical removal of third molars (wisdom teeth) accounted for 70% of these procedures in 1989-90. In addition, 67 000 people had their third molars removed by dental practitioners in the general dental service and 22 000 had their third molars removed in the private sector. The total cost of third molar removal in the NHS in 1989-90 was estimated as £23-3m and in the year ended 30 June 1992 was £22m in the private sector.2 In the hospital service, patients waiting for third molar removal account for up to 90% of patients on waiting lists in oral and maxillofacial surgery.' Although patient throughput has increased year on year since 1985, in 1990 the oral and maxillofacial surgery waiting lists remained among the longest of any surgical specialty. Despite the very large number of third molars that are being removed, audit suggests that rates of surgical intervention could be reduced and that more rational decision making is needed.24 Although prophylactic removal has previously been criticised5 and the cost-benefit ratio of this procedure is very poor,6 little evidence exists of a link between levels of morbidity and intervention. Wide small area variation in operation rates for the South West Regional Health Authority has been reported,' and recent comparisons of treatment decisions with National Institutes of Health consensus criteria for intervention have shown that about a fifth of patients not meeting these criteria were nevertheless scheduled for surgery.4 A recent literature review concluded that "prophylactic surgery is not an appropriate management strategy for third molars."6 The wholesale removal of unerupted teeth seems as inappropriate as the wholesale removal of tonsils and adenoids. In terms of health gain, the scales are loaded against intervention even in the presence of mild pericoronitis (inflammation around the crown).6 Previously, prophylactic surgery has been justified on 620

the basis that third molars have no role in the mouth, notwithstanding that few people would contemplate the prophylactic removal of their appendix, which, unlike many unerupted third molars, communicates with the alimentary tract throughout life. Prophylactic removal has also been justified on the basis that unerupted teeth contributed to facial pain and even that the presence of an unerupted tooth weakens the lower jaw such that it is likely to fracture; no objective evidence exists to substantiate these assertions. No reliable evidence is available on trends in the incidence and severity of infections associated with the eruption of third molars, but the number of third molars surgically removed by family dental practitioners has increased by 30% since 1988. Good reasons exist why the number of impacted unerupted teeth are increasing, including improved dental health leading to fewer extractions of standing teeth and therefore decreased space for third molars to erupt. Surveillance has also improved, as more people now attend for dental treatment; payment by capitation has been introduced into dentistry, and the use of panoral x ray machines is increasing. The indications for removing third molars was the subject of a National Institutes of Health consensus conference held in the United States in 1979.' The consensus criteria for surgical intervention were recurrent pericoronitis, caries not amenable to restorative measures, dentigerous cyst, internal or external resorption, and periodontal disease to which the third molar was contributing. Overall, pericoronitis is the reason for intervention in about one fifth of removals,8 though a study of more than 16 000 lower third molars showed that only 8% had been removed for this problem.9 Recent evidence suggests that the teeth at most risk are partially erupted, vertically placed mandibular third molars. The prevalence of periodontitis associated with third molars is also low-reportedly about 5% in studies of 1200 and 1800 impacted third molars.10 In relation to resorption of the adjacent second molar, prevalence has been estimated at about 2%. Crowding of anterior teeth has previously been attributed, at least in part, to the eruption of third molars, but recent findings and reviews all strongly suggest no causal link.1' The prevalence of cystic change has been found to be about 2-4%. There are many reports of an association between facial pain and the presence of BMJ VOLUME 309

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