Air pollution and general practice consultations for respiratory illnesses

Associations between ozone and morbidity using the Spatial Synoptic Classification system

BACKGROUND

Synoptic circulation patterns (large-scale tropospheric motion systems) affect air pollution and, potentially, air-pollution-morbidity associations. We evaluated the effect of synoptic circulation patterns (air masses) on the association between ozone and hospital admissions for asthma and myocardial infarction (MI) among adults in North Carolina.

METHODS

Daily surface meteorology data (including precipitation, wind speed, and dew point) for five selected cities in North Carolina were obtained from the U.S. EPA Air Quality System (AQS), which were in turn based on data from the National Climatic Data Center of the National Oceanic and Atmospheric Administration. We used the Spatial Synoptic Classification system to classify each day of the 9-year period from 1996 through 2004 into one of seven different air mass types: dry polar, dry moderate, dry tropical, moist polar, moist moderate, moist tropical, or transitional. Daily 24-hour maximum 1-hour ambient concentrations of ozone were obtained from the AQS. Asthma and MI hospital admissions data for the 9-year period were obtained from the North Carolina Department of Health and Human Services. Generalized linear models were used to assess the association of the hospitalizations with ozone concentrations and specific air mass types, using pollutant lags of 0 to 5 days. We examined the effect across cities on days with the same air mass type. In all models we adjusted for dew point and day-of-the-week effects related to hospital admissions.

RESULTS

Ozone was associated with asthma under dry tropical (1- to 5-day lags), transitional (3- and 4-day lags), and extreme moist tropical (0-day lag) air masses. Ozone was associated with MI only under the extreme moist tropical (5-day lag) air masses.

CONCLUSIONS

Elevated ozone levels are associated with dry tropical, dry moderate, and moist tropical air masses, with the highest ozone levels being associated with the dry tropical air mass. Certain synoptic circulation patterns/air masses in conjunction with ambient ozone levels were associated with increased asthma and MI hospitalizations.

Daily visibility and mortality: assessment of health benefits from improved visibility in Hong Kong

Visibility in Hong Kong has deteriorated significantly over 40 years with visibility below 8km in the absence of fog, mist, or precipitation, increasing from 6.6 days in 1968 to 54.1 days in 2007. We assessed the short-term mortality effects of daily loss of visibility. During 1996-2006, we obtained mortality data for non-accidental and cardiorespiratory causes, visibility recorded as visual range in kilometers, temperature, and relative humidity from an urban observatory, and concentrations of four criteria pollutants. A generalized additive Poisson regression model with penalized cubic regression splines was fitted to control for time variant covariates. For non-accidental mortality, an interquartile range (IQR) of 6.5km decrease in visibility at lag0-1 days was associated with an excess risk (ER%) [95% CI] of 1.13 [0.49, 1.76] for all ages and 1.37 [0.65, 2.09] for ages 65 years and over; for cardiovascular mortality of 1.31 [0.13, 2.49] for all ages, and 1.72 [0.44, 3.00] for ages 65 years and over; and for respiratory mortality of 1.92 [0.49, 3.35] for all ages and 1.76 [0.28, 3.25] for ages 65 years and over. The estimated ER% for daily mortality derived from both visibility and air pollutant data were comparable in terms of magnitude, lag pattern, and exposure-response relationships especially when using particulate matter with aerodynamic diameter < or = 10 microm to predict the mortality associated with visibility. Visibility provides a useful proxy for the assessment of environmental health risks from ambient air pollutants and a valid approach for the assessment of the public health impacts of air pollution and the benefits of air quality improvement measures in developing countries where pollutant monitoring data are scarce.

An integrated tool to assess the role of new planting in PM10 capture and the human health benefits: a case study in London

The role of vegetation in mitigating the effects of PM(10) pollution has been highlighted as one potential benefit of urban greenspace. An integrated modelling approach is presented which utilises air dispersion (ADMS-Urban) and particulate interception (UFORE) to predict the PM(10) concentrations both before and after greenspace establishment, using a 10 x 10 km area of East London Green Grid (ELGG) as a case study. The corresponding health benefits, in terms of premature mortality and respiratory hospital admissions, as a result of the reduced exposure of the local population are also modelled. PM(10) capture from the scenario comprising 75% grassland, 20% sycamore maple (Acer pseudoplatanus L.) and 5% Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) was estimated to be 90.41 t yr(-1), equating to 0.009 t ha(-1) yr(-1) over the whole study area. The human health modelling estimated that 2 deaths and 2 hospital admissions would be averted per year.

Social disadvantage, air pollution, and asthma physician visits in Toronto, Canada

BACKGROUND

Previous research demonstrates that ambient air pollution exacerbates asthma. Asthma morbidity also varies with socioeconomic position (SEP). Few studies have examined if ambient air pollution has a differential impact on income subgroups of the population. This paper investigates socioeconomic variation in ambulatory physician consultations for asthma and assesses possible effect modification of SEP on the association between physician visits and air pollution for children aged 1-17 and adults aged 18-64 in Toronto, Canada, between 1992 and 2001.

METHODS

Generalized additive models and generalized linear models were used to estimate the adjusted risk of asthma physician visits associated with an interquartile range increase in sulfur dioxide (SO2), nitrogen dioxide (NO2), particulate matter (PM2.5), and ozone (O3).

RESULTS

A socioeconomic gradient in the number of physician visits was observed among children and adults and both sexes. SO2, NO2, and PM2.5 had positive associations with physician visits. The risk ratios for the low socioeconomic group were significantly greater than those for the high socioeconomic group in several of the models of SO2 and PM2.5.

CONCLUSIONS

These findings suggest increased ambulatory physician visits represent another component of the public health impact of urban air pollution. The burden of this impact may be borne disproportionately by those with lower SEP. Clarifying the role of SEP in altering susceptibility to the effects of air pollution is essential not only to inform revisions of ambient air quality standards, but also to design public health interventions to reduce health impacts on sensitive subgroups of the population.

Air pollution: costs and paths to a solution in Hong Kong--understanding the connections among visibility, air pollution, and health costs in pursuit of accountability, environmental justice, and health protection

Air quality has deteriorated in Hong Kong over more than 15 yr. As part of a program of public accountability, photographs on Poor and Better visibility days were used as representations of the relationships among visibility, air pollution, adverse health effects, and community costs for health care and lost productivity. Coefficients from time-series models and gazetted costs were used to estimate the health and economic impacts of different levels of pollution. In this population of 6.9 million, air quality improvement from the annual average to the lowest pollutant levels of Better visibility days, comparable to the World Health Organization air quality guidelines, would avoid 1335 deaths, 60,587 hospital bed days, and 6.7 million doctor visits for respiratory complaints each year. Direct costs and productivity losses avoided would be over US$240 million a year. The dissemination of these findings led to increased demands for pollution controls from the public and legislators, but denials of the need for urgent action arose from the government. The outcome demonstrates the need for more effective translation of the scientific evidence base into risk communication and public policy.

Association between air pollution and general practitioner visits for respiratory diseases in Hong Kong

BACKGROUND

Few studies have explored the relation between air pollution and general practitioner (GP) consultations in Asia. Clinic attendance data from a network of GPs were studied, and the relationship between daily GP consultations for upper respiratory tract infections (URTI) and non-URTI respiratory diseases and daily air pollutant concentrations measured in their respective districts was examined.

METHODS

A time series study was performed in 2000-2002 using data on daily patient consultations in 13 GP clinics distributed over eight districts. A Poisson regression model was constructed using the generalised additive model approach for each GP clinic, and associations with daily numbers of first visits for URTI were sought for daily concentrations of the following air pollutants: SO(2), NO(2), O(3), PM(10,) and PM(2.5). A summary relative risk of first visits to the GP for URTI per unit increase in concentration for each air pollutant was derived using a random effect model. First visits for non-URTI respiratory diseases were analysed in three GP clinics.

RESULTS

Significant associations were observed between first visits for URTI and an increase in the concentrations of NO(2), O(3), PM(10), and PM(2.5). The excess risk was highest for NO(2) (3.0%), followed by O(3) (2.5%), PM(2.5) (2.1%), and PM(10) (2.0%). Similar associations with these air pollutants were found for non-URTI respiratory diseases.

CONCLUSIONS

These results provide further evidence that air pollution contributes to GP visits for URTI and non-URTI respiratory diseases in the community.

Risks for Heart Disease and Lung Cancer from Passive Smoking by Workers in the Catering Industry

Workers in the catering industry are at greater risk of exposure to secondhand smoke (SHS) when smoke-free workplace policies are not in force. We determined the exposure of catering workers to SHS in Hong Kong and their risk of death from heart disease and lung cancer. Nonsmoking catering workers were provided with screening at their workplaces and at a central clinic. Participants reported workplace, home, and leisure time exposure to SHS. Urinary cotinine was estimated by enzyme immunoassay. Catering facilities were classified into three types: nonsmoking, partially restricted smoking (with nonsmoking areas), and unrestricted smoking. Mean urinary cotinine levels ranged from 3.3 ng/ml in a control group of 16 university staff through 6.4 ng/ml (nonsmoking), 6.1 ng/ml (partially restricted), and 15.9 ng/ml (unrestricted smoking) in 104 workers who had no exposures outside of work. Workers in nonsmoking facilities had exposures to other smoking staff. We modeled workers' mortality risks using average cotinine levels, estimates of workplace respirable particulates, risk data for cancer and heart disease from cohort studies, and national (US) and regional (Hong Kong) mortality for heart disease and lung cancer. We estimated that deaths in the Hong Kong catering workforce of 200,000 occur at the rate of 150 per year for a 40-year working-lifetime exposure to SHS. When compared with the current outdoor air quality standards for particulates in Hong Kong, 30% of workers exceeded the 24-h and 98% exceeded the annual air quality objectives due to workplace SHS exposures.

An enquiry into the respiratory health effects on a rural community of a soil mound erected close to residential property

The health concerns of a rural community were investigated following the erection of a soil mound in close proximity to residential property. Retrospective comparisons were made of respiratory and non-respiratory consultations with general practitioners between the exposed population and a sociodemographically similar comparison population. A 2-year period was examined, 1 year before and 1 year after the mound was erected. In the 1-year period prior to erection of the mound, similar consultation rates for both respiratory and non-respiratory conditions were observed in both populations. In the 1-year period following erection of the mound, the exposed population was more likely to consult for respiratory conditions than the comparison population (OR=4.10, 95% CI 2.26-7.44). No differences were observed for non-respiratory conditions. We identified a significant increase in respiratory consultations in the exposed population following erection of the soil mound. Limitations associated with this type of study should be considered when interpreting the results.

Do environmental pollutants influence the onset of respiratory syncytial virus epidemics or disease severity?

The trigger for annual epidemics of respiratory syncytial virus (RSV) infections and the factors contributing to the disappearance of RSV infections in late winter remain obscure. Similarly, there is no adequate explanation for the higher morbidity and admission rates in industrialised as compared with rural areas. It has been suggested that a variety of environmental factors such as temperature, daylight and humidity may influence the onset and waning of the epidemics. However, the few studies assessing these variables fail to support such a link. In many tropical countries the annual epidemic occurs in the summer or autumn, arguing against temperature having a direct influence. A number of studies have suggested that indoor pollutants, including cigarette smoke, are associated with an increased likelihood of being admitted to hospital with severe lower respiratory tract disease. One study exploring the potential role of outdoor pollutants on the pattern of RSV related illness in infancy was unable to identify a clear link between a variety of pollutants and the timing of the epidemic. Nitric oxide levels were higher in winter than during the summer and much higher winter peaks of NO were observe in industrialised areas as compared with urban and rural areas. Whether this or other environmental pollutants contribute to the higher incidence of severe disease in industrialised areas is unclear. Further work is required to explore the possible influence of NO and other environmental pollutants on both the timing and severity of epidemics.