Asthma in the vicinity of power stations: II. Outdoor air quality and symptoms

Methodological issues in descriptive environmental epidemiology. The example of study Sentieri

BACKGROUND

Descriptive epidemiology identifies associations between environmental exposures and health effects that require results from methodologically stronger studies before causation can be considered.

OBJECTIVE

To critically review the methodology and results of Sentieri, a descripitive study on residence in areas with one or more industrial source of pollution.

METHODS

We systematically reviewed the literature quoted by Sentieri for the selection of health effects of nine types of pollution sources of a-priori interest. We also reviewed and meta-analyzed the results of the first report of Sentieri, that analyzed mortality in 44 polluted sites (PS), and 17 causes of deaths during 1995-2002.

RESULTS

Among 159 study results quoted by Sentieri, 23.9 % were supportive of an association between residence near a pollution source and a health effect, 30.2 % were partially supportive, 10.7 % were not supportive, and 35.2 % were not relevant. Among 653 standardized mortality ratios for associations between PS-specific pollution sources and causes of death, 14.4% were significantly above 1.02, and 9.0% were significantly below 0.98. Among 48 meta-analysis, seven were significantly above 1.0, including five on exposure to asbestos.

CONCLUSIONS

Sentieri exemplifies the limitations of descriptive environmental epidemiology studies, in which most hypotheses have limited prior support, most results do not show associations, data on potential confounders and other sources of bias are not available. Such studies tend to replicate well-known associations and occasionally can identify critical situations requiring more investigation, but cannot be used to infer causality either in general or in specific circumstances.

The Australian Child Health and Air Pollution Study (ACHAPS): A national population-based cross-sectional study of long-term exposure to outdoor air pollution, asthma, and lung function

Most studies of long-term air pollution exposure and children's respiratory health have been performed in urban locations with moderate pollution levels. We assessed the effect of outdoor nitrogen dioxide (NO₂), as a proxy for urban air pollution, on current asthma and lung function in Australia, a low-pollution setting. We undertook a national population-based cross-sectional study of children aged 7-11 years living in 12 Australian cities. We collected information on asthma symptoms from parents via questionnaire and measured children's lung function (forced expiratory volume in 1 s [FEV₁], forced vital capacity [FVC]) and fractional exhaled nitric oxide [Fe_NO]). We estimated recent NO₂ exposure (last 12 months) using monitors near each child's school, and used a satellite-based land-use regression (LUR) model to estimate NO₂ at each child's school and home. Our analysis comprised 2630 children, among whom the prevalence of current asthma was 14.9%. Mean (±SD) NO₂ exposure was 8.8 ppb (±3.2) and 8.8 ppb (±2.3) for monitor- and LUR-based estimates, respectively. Mean percent predicted post-bronchodilator FEV₁ and FVC were 101.7% (±10.5) and 98.8% (±10.5), respectively. The geometric mean Fe_NO concentration was 9.4 ppb (±7.1). An IQR increase in NO₂ (4.0 ppb) was significantly associated with increased odds of having current asthma; odds ratios (ORs) were 1.24 (95% CI: 1.08, 1.43) and 1.54 (95% CI: 1.26, 1.87) for monitor- and LUR-based estimates, respectively. Increased NO₂ exposure was significantly associated with decreased percent predicted FEV₁ (-1.35 percentage points [95% CI: -2.21, -0.49]) and FVC (-1.19 percentage points [95% CI: -2.04, -0.35], and an increase in Fe_NO of 71% (95% CI: 38%, 112%). Exposure to outdoor NO₂ was associated with adverse respiratory health effects in this population-based sample of Australian children. The relatively low NO₂ levels at which these effects were observed highlight the potential benefits of continuous exposure reduction.

Contribution of nitrogen oxide and sulfur dioxide exposure from power plant emissions on respiratory symptom and disease prevalence

This study investigates the association between exposure to ambient NOx and SO2 originating from power plant emissions and prevalence of obstructive pulmonary disease and related symptoms. The Orot Rabin coal-fired power plant is the largest power generating facility in the Eastern Mediterranean. Two novel methods assessing exposure to power plant-specific emissions were estimated for 2244 participants who completed the European Community Respiratory Health Survey. The "source approach" modeled emissions traced back to the power plant while the "event approach" identified peak exposures from power plant plume events. Respiratory symptoms, but not prevalence of asthma and COPD, were associated with estimates of power plant NOx emissions. The "source approach" yielded a better estimate of exposure to power plant emissions and showed a stronger dose-response relationship with outcomes. Calculating the portion of ambient pollution attributed to power plants emissions can be useful for air quality management purposes and targeted abatement programs.

Air pollution: a tale of two countries

The fast growing economies and continued urbanization in Asian countries have increased the demand for mobility and energy in the region, resulting in high levels of air pollution in cities from mobile and stationary sources. In contrast, low level of urbanization in Australia produces low level of urban air pollution. The World Health Organization estimates that about 500,000 premature deaths per year are caused by air pollution, leaving the urban poor particularly vulnerable since they live in air pollution hotspots, have low respiratory resistance due to bad nutrition, and lack access to quality health care. Identifying the differences and similarities of air pollution levels and its impacts, between Indonesia and Australia, will provide best lesson learned to tackle air pollution problems for Pacific Basin Rim countries.

Risk of asthmatic episodes in children exposed to sulfur dioxide stack emissions from a refinery point source in Montreal, Canada

BACKGROUND

Little is known about the respiratory effects of short-term exposures to petroleum refinery emissions in young children. This study is an extension of an ecologic study that found an increased rate of hospitalizations for respiratory conditions among children living near petroleum refineries in Montreal (Canada).

METHODS

We used a time-stratified case-crossover design to assess the risk of asthma episodes in relation to short-term variations in sulfur dioxide levels among children 2-4 years of age living within 0.5-7.5 km of the refinery stacks. Health data used to measure asthma episodes included emergency department (ED) visits and hospital admissions from 1996 to 2004. We estimated daily levels of SO2 at the residence of children using a) two fixed-site SO2 monitors located near the refineries and b) the AERMOD (American Meteorological Society/Environmental Protection Agency Regulatory Model) atmospheric dispersion model. We used conditional logistic regression to estimate odds ratios associated with an increase in the interquartile range of daily SO2 mean and peak exposures (31.2 ppb for AERMOD peaks). We adjusted for temperature, relative humidity, and regional/urban background air pollutant levels.

RESULTS

The risks of asthma ED visits and hospitalizations were more pronounced for same-day (lag 0) SO2 peak levels than for mean levels on the same day, or for other lags: the adjusted odds ratios estimated for same-day SO2 peak levels from AERMOD were 1.10 [95% confidence interval (CI), 1.00-1.22] and 1.42 (95% CI, 1.10-1.82), over the interquartile range, for ED visits and hospital admissions, respectively.

CONCLUSIONS

Short-term episodes of increased SO2 exposures from refinery stack emissions were associated with a higher number of asthma episodes in nearby children.

Acute effects of urban ambient air pollution on respiratory symptoms, asthma medication use, and doctor visits for asthma in a cohort of Australian children

We enrolled a cohort of primary school children with a history of wheeze (n=148) in an 11-month longitudinal study to examine the relationship between ambient air pollution and respiratory morbidity. We obtained daily air pollution (ozone, particulate matter less than 10 microm, and nitrogen dioxide), meteorological, and pollen data. One hundred twenty-five children remained in the final analysis. We used logistic regression models to determine associations between air pollution and respiratory symptoms, asthma medication use, and doctor visits for asthma. There were no associations between ambient ozone concentrations and respiratory symptoms, asthma medication use, and doctor visits for asthma. There was, however, an association between PM(10) concentrations and doctor visits for asthma (RR=1.11, 95% CI=1.04-1.19) and between NO(2) concentration and wet cough (RR=1.05, 95% CI=1.003-1.10) in single-pollutant models. The associations remained significant in multipollutant models. There was no consistent evidence that children with wheeze, positive histamine challenge, and doctor diagnosis of asthma reacted differently to air pollution from children with wheeze and doctor diagnosis of asthma and children with wheeze only. There were significant associations between PM(10) levels and doctor visits for asthma and an association between NO(2) levels and the prevalence of wet cough. We were, however, unable to demonstrate that current levels of ambient air pollution in western Sydney have a coherent range of adverse health effects on children with a history of wheezing.

[Respiratory allergy and environmental pollution in pediatrics]

Allergic disease and pollution effects on children are a subject of worldwide concern. Outdoor pollution is the sum of acid particle (SO2, NO2, PM) and photochemical (ozone) pollution. Experimental studies demonstrated correlation between animals and humans concerning inhalation of pollutants and inflammatory and functional effects. Several studies among children confirmed with variable odds ratios the interaction between air pollution and respiratory health, but other studies showed no clear effect. Physicians should inform parents with children experiencing respiratory disease.

Mortality among residents near cokeworks in Great Britain

OBJECTIVES

To investigate whether residents near cokeworks have a higher standardised mortality than those further away, particularly from cardiovascular and respiratory causes, which may be associated with pollution from cokeworks.

METHOD

Cross sectional small area study with routinely collected postcoded mortality data and small area census statistics. Populations within 7.5 km of 22 cokeworks in Great Britain, 1981-92. Expected numbers of deaths within 2 and 7.5 km of cokeworks, and in eight distance bands up to 7.5 km of cokeworks, were calculated by indirect standardisation from national rates stratified for age and sex and a small area deprivation index, and adjusted for region. Age groups examined were all ages, 1-14, 15-64, 65-74, > or = 75. Only the 1-14 and 15-44 age groups were examined for asthma mortality.

RESULTS

There was a 3% (95% confidence interval (95% CI) 1% to 4%) excess of all deaths within 2 km of cokeworks, and a significant decline in mortality with distance from cokeworks. The excess of deaths within 2 km was slightly higher for females and elderly people, but excesses within 2 km and declines in risk with distance were significant for all adult age groups and both sexes. The size of the excess within 2 km was 5% (95% CI 3% to 7%) for cardiovascular causes, 6% (95% CI 3% to 9%) for ischaemic heart disease, and 2% (95% CI -2% to 6%) for respiratory deaths, with significant declines in risk with distance for all these causes. There was a non-significant 15% (95% CI -1% to 101%) excess in asthma mortality in the 15-44 age group. There were no significant excesses in mortality among children but 95% CIs were wide. Within 2 km of cokeworks, the estimated additional excess all cause mortality for all ages combined related to region and mainly to the greater deprivation of the population over national levels was 12%.

CONCLUSIONS

A small excess mortality near cokeworks as found in this study is plausible in the light of current evidence about the health impact of air pollution. However, in this study the effects of pollution from cokeworks, if any, are outweighed by the effects of deprivation on weighed by the effects of deprivation on mortality near cokeworks. It is not possible to confidently exclude socioeconomic confounding or biases resulting from inexact population estimation as explanations for the excess found.

Outdoor air pollution and children's respiratory symptoms in the steel cities of New South Wales

OBJECTIVE

To investigate the relationship between outdoor air pollution and the respiratory health of children aged 8 to 10 years.

DESIGN

A cross-sectional survey (between October 1993 and December 1993) of children's health and home environment. Summary measures of particulate pollution (levels of particles with an aerodynamic diameter less than 10 microns [PM10] each 6th day) and SO2 (daily mean and maximum hourly values) were estimated for each area (using air quality monitoring station data from July 1993 to June 1994). SETTING AND SURVEY PARTICIPANTS: Parents of 3023 primary school children (Years 3, 4 and 5) from industrial and non-industrial areas with air quality monitoring stations in the Hunter and Illawarra regions of New South Wales.

MAIN OUTCOME MEASURES

Reported occurrence of four or more chest colds, four or more attacks of wheezing, and night-time cough without a cold for more than two weeks, all within the previous 12 months.

RESULTS

77% response rate, ranging by area from 66% to 88%. The average annual outdoor air pollution for the nine areas was 18.6-43.7 micrograms/m3 for PM10 and 0.16-0.90 parts per hundred million for SO2. The proportion of children reported to have the main outcome symptoms were: chest colds, 3.0%-9.7%; night cough, 12.3%-30.5%; and wheeze, 3.4%-11.3%. There was no significant association with SO2, but a significant increase in the odds of symptoms per 10 micrograms/m3 increase in PM10 on chest colds (odds ratio [OR], 1.43; 95% confidence interval [CI], 1.12-1.82) and night-time cough (OR, 1.34; 95% CI, 1.19-1.53), but not wheeze. Passive smoking was significantly associated with chest colds but not with the other symptoms. Maternal allergy was associated with all three respiratory symptoms, most strongly with wheeze.

CONCLUSION

These results provide evidence of health effects at lower than expected levels of outdoor air pollution in the Australian setting. They also suggest differences in contributions of environmental and hereditary factors to cough and chest colds compared with wheeze.

Effects of air pollution on symptoms and peak expiratory flow measurements in subjects with obstructive airways disease

BACKGROUND

Evidence from laboratory studies suggests that air pollution can produce bronchoconstriction and respiratory symptoms in selected subjects, but the relevance of these findings to exposure to natural pollution is unclear. This study was performed to determine whether air pollution at typical levels found in the UK has demonstrable effects on respiratory function and symptoms in subjects with airways disease.

METHODS

Seventy five adult patients with diagnoses of asthma or chronic obstructive pulmonary disease (COPD) were studied for a period of four weeks during which they kept records of their peak expiratory flow (PEF) rates, symptoms (wheeze, dyspnoea, cough, throat and eye irritation), and bronchodilator use. Thirty six patients in whom the provocative dose of methacholine causing a 20% fall in FEV1 was below 12.25 mumol were classified as reactors. Ambient air pollution was measured with absorption spectroscopy.

RESULTS

There were modest but significant increases in PEF variability, bronchodilator use, and wheeze with increasing sulphur dioxide levels; bronchodilator use, dyspnoea, eye irritation, and minimum PEF readings were related to ozone levels. In the subgroup of reactors falls in mean and minimum peak flow and increases in wheeze, dyspnoea, and bronchodilator use were associated with increases in levels of both sulphur dioxide and ozone. Some associations were seen with pollution levels on the same day, but for others the pollution effects appeared to be delayed by 24 or 48 hours. Pollution levels did not breach the WHO guide levels during the course of the study.

CONCLUSIONS

Increases in environmental levels of ozone and sulphur dioxide are associated with adverse changes in peak flow measurements and both ocular and respiratory symptoms in subjects with obstructive airways disease. Although the peak flow and symptom changes were modest, they occurred at pollution levels below current WHO guide levels.

Increased wheeze but not bronchial hyperreactivity near power stations

STUDY OBJECTIVE

In a previous study a higher than expected prevalence of asthma was found in Lake Munmorah, a coastal town near two power stations, compared with another coastal control town. This study aimed to compare atopy, bronchial hyperreactivity, and reported symptoms of asthma in the power station town and a second control area with greater socioeconomic similarity.

DESIGN

A cross sectional survey was undertaken.

SETTINGS

Lake Munmorah, a coastal town near two power stations, and Dungog, a country town in the Hunter Valley, NSW, Australia.

PARTICIPANTS

All children attending kindergarten to year 6 at all schools in the two towns were invited to participate in 1990. The response rates for the questionnaire for reported symptoms and associated demographic data were 92% in Lake Munmorah and 93% in Dungog, with 84% and 90% of children respectively being measured for lung function, atopy, and bronchial reactivity. There were 419 boys and 432 girls aged 5 to 12 years.

MEASUREMENTS AND MAIN RESULTS

Main outcome measures were current wheeze and bronchial hyper-reactivity, defined as a fall in forced expiratory volume in 1 second (FEV1) or peak expiratory flow (PEF) of 20% or more. Current wheeze was reported in 24.8% of the Lake Munmorah children compared with 14.6% of the Dungog children. Bronchial hyper-reactivity was similar for both groups--25.2% in Lake Munmorah and 22.3% in Dungog. The mean baseline FEV1 was lower in Lake Munmorah than in Dungog (p < 0.001). Dungog children were more likely to have positive skin test to house dust mite (Dungog 27.0%, Lake Munmorah 20.2%, p = 0.028) but there were no other differences in skin test atopy in the two towns. After adjusting for age, gender, any smoker in the house, and positive dust mite skin test, the odds of current wheeze in Lake Munmorah compared with Dungog was 2.16 (95% confidence interval 1.45, 3.15).

CONCLUSIONS

Baseline lung function was lower and reported symptoms of asthma were higher in the power station town, but bronchial hyper-reactivity and skin test defined atopy were similar in the two communities. These results are consistent with the previous study and confirm the increased presence of reported symptomatic illness in the town near power stations.

Asthma in the vicinity of power stations: I. A prevalence study

Respiratory symptoms, atopy, and bronchial reactivity were measured in primary school children living in Lake Munmorah (LM), a coastal town near two power stations, and in Nelson Bay (NB), a coastal town free from any possible major sources of outdoor air pollution. A prevalence survey and longitudinal follow-up study were performed 1 year apart. In both studies, the prevalence of ever wheezed, current wheezing, breathlessness, wheezing with exercise, diagnosed asthma, and use of drugs for asthma at LM were all approximately double the prevalence at NB (all P values less than 0.01). The prevalence of bronchial reactivity was significantly greater at LM than NB (P less than 0.01) at the first but not the second survey. By contrast, no significant differences were found between the two areas for skin test atopy or for parental history of allergic disease. Multivariate analysis supported the conclusion from the univariate analysis that there was more wheezing at LM compared to NB at both studies, when adjusted for atopy, smoking in the home, age, and sex. As expected, a positive skin test reaction to house dust mite was the predominant explanatory variable. Asthma was more common in the community near power stations (LM) than in the NB area. The absence of significant differences in skin test atopy and parental history of allergic disease argued against major genetic differences between the two groups. By contrast, the more common reporting of siblings' chest disease and asthma in Lake Munmorah supported an environmental cause.