Did a ban on diesel-fuel reduce emergency respiratory admissions for children?

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Abstract

This paper assesses whether a ban on diesel-powered motor vehicles in Lebanon has reduced emergency respiratory admissions for children less than 17 years of age in Beirut. Monthly admissions for total respiratory complaints, asthma, bronchitis, pneumonia, and upper respiratory tract infections, from October to February, were compared before and after the ban, using Poisson regression models and adjusting for rainfall, humidity and temperature. Analyses were repeated excluding the flu months of January and February. A test of significance of p  0.05 was used. Air pollution is not systematically monitored in Lebanon and no ambient particulate concentration data were available.

A significant drop in admissions for respiratory symptoms (p  0.05) and upper respiratory tract infection (p  0.001) from 1 year pre-ban to 1 year post-ban has been recorded. When flu months are excluded, a significant drop (p  0.001) in admissions for all studied categories, except pneumonia, is observed. The effect of the ban however was negligible in the second year. When 2 year pre-ban versus 2 year post-ban are considered excluding flu months, statistically non-significant reductions are recorded for asthma and upper respiratory tract infection (p  0.1). The study hence suggests an impact of the diesel ban on respiratory health only during the first year after the ban. This finding is weakened by the absence of supporting evidence from air quality monitoring and speciation of particulate matter, which are lacking in Lebanon and most developing countries.

Introduction

Diesel fuel is widely used as a cheaper alternative to gasoline. While often resulting in smaller amounts of CO, hydrocarbons and CO2 emissions per kilometer traveled in comparison with gasoline, its particulate and NOx emissions are significantly higher (Colls, 1997, Cohen and Nikula, 1999). In addition, a large proportion of respirable diesel-emitted particles are 0.1 to 0.5 μm in size, adsorbing heavy metals and organic compounds and penetrating deep into the respiratory system. Epidemiological and toxicological evidence points to a causal relationship between exposure to diesel emissions from mobile sources and the incidence of cancer, respiratory symptoms and respiratory diseases (Garshick et al., 1988, Northridge et al., 1999, Bremner et al., 1999, Hoppin et al., 2004).

Few studies have examined the effects of exposure to diesel-fumes on the respiratory health of children (Northridge et al., 1999, Brunekreef et al., 1997, Timonen and Pekkanen, 1997, van Vliet et al., 1997, Weir, 2002). In a cross-sectional study of schools located near major roads, van Vliet et al. (1997) found that the prevalence of respiratory symptoms among school children in south Holland is proportional to traffic density and inversely proportional to distance from the road. Brunekreef et al. (1997) reported a strong association between the deterioration of the lung function of Dutch school children and the density of road traffic with a stronger association among female students compared to their male counterparts. Miller et al. (2004) found an association between asthma and prenatal exposure to polycyclic aromatic hydrocarbons (a major component of diesel emissions) and environmental tobacco smoke among children under 24 months of age. No study appears to have investigated whether a policy aimed at reducing ambient diesel-related air pollutants has resulted in the expected health gains. However, such studies have been reported for particulate matter. In Utah Valley, hospital children's admission for respiratory illnesses were two to three times lower during the winters when the local steel mill was closed as compared to winters when it was open (Pope 1989). Clancy et al. (2002) investigated the health gains of an immediate ban the sale of coal in the city of Dublin. This policy was associated with a 70% reduction in smoke concentration and a parallel drop in the cardiovascular and respiratory death rates during the 3 year period after the ban as compared to the 3 year period before the ban. Typically, emission reductions are introduced over an extended period of time which makes it difficult to incorporate all covariates in the analysis. Hence, studies investigating rare occasions on which emissions are curtailed on a specific date or over a short period of time are useful because they can yield a more effective assessment of causality than those which analyze the effects of multi-source particulate emissions on respiratory health.

Lebanon, like many developing countries, has become rapidly urbanized over the last century. At the end of the civil war in 1990, economic activity took off, accompanied by a largely unregulated growth of the transportation sector (Chaaban et al., 2001). The average age of the one-million vehicle fleet is believed to be more than 10 years. Particulate concentrations have been found to exceed international standards (El-Fadel and Massoud, 2000, El-Fadel et al., 2000). Fuel is imported, with little effective control by government over its quality. Fuel policy has been anything but consistent. Initially banned, diesel was re-introduced in 1977 for a small category of vehicles. In 1994, laws were passed which allowed diesel mini-vans, buses and trucks to operate in the country. In 1999, custom fees for public vehicles were abolished to encourage their importation. A year later, following a public outcry at diesel-generated outdoor pollution, a new law banned the import of all light- and medium-duty diesel engines. The law met strong resistance from the union of taxi drivers and its implementation was delayed until 15 June 2002. By 15 July 2002, the law had been in effect. Prohibited cars in motion were heavily fined or temporarily confiscated. Some drivers replaced the engine by a gasoline-operated one. However, no program was established to monitor the enforcement of the law or the effect of the ban on air quality and concerns remained about its effectiveness. The only documentation that exists is a single study by one of the co-authors that showed that the mean concentration of particulate matter at major intersections of the city in the summer of 1999 (3 years pre-ban) was 181.3 μg/m3 (SD = 49.3) as compared to 97.1 μg/m3 (SD = 50.3) in the summer of 2002 (post-ban) (El-Fadel et al., 2004). Despite this drop in particulate levels, strong opposition remains to the policy and calls for its reversal are still vocal.

This study assesses whether the diesel ban has had a statistically significant impact on the emergency room respiratory admissions in Beirut of children under the age of 17. Hence, it contributes to knowledge about the causality between diesel emissions and health worldwide, as well as the ongoing debate on the diesel ban in Lebanon.

Section snippets

Data collection

The study was limited to the Greater Beirut Area which hosts 40% of the Lebanese population and 50% of the vehicle fleet. Only accredited hospitals (Class A or B as per the Ministry of Public Health classification) with 50 or more hospitals beds and 24-hour emergency services were approached (The Syndicate of Hsopitals in Lebanon, December 1, 2006, Lebanese Ministry of Public Health, December 1, 2006). Eight hospitals with a total of 1902 hospital beds met the eligibility criteria, of which 5

Results

Fig. 1 shows emergency admissions over the 5 months periods by disease category. A pattern of variability over the five months from October to February can be readily discerned, decreasing for asthma and generally increasing for URTI, pneumonia and bronchitis. Table 1 shows mean admissions before and after the ban, as well as the p value of the paired t-test. A significant decrease in URTI and asthma is observed on the first year after the ban. However, the respiratory gains are lost in year 2

Discussion

A number of studies have found significant associations between exposure to air pollution, including diesel emissions, and respiratory outcomes. Some studies have measured the incidence of respiratory symptoms such as wheezing and coughing (e.g., Timonen and Pekkanen, 1997, Hoppin et al., 2004) while others have focused on respiratory diseases such as asthma (e.g, Stenfors et al., 2004). However, two areas of uncertainty remain. First, most studies assess exposure to a collection of pollutants

Conclusions

The study has highlighted the difficulty of establishing a causal link between a pollution source and specific health impacts. These difficulties range from obstacles to obtaining continuous health data to quantifying potential confounders such as flu incidence, and population trends. These obstacles are compounded in many developing countries by a general absence of air quality data which could provide crucial link in establishing a causal association between pollution source and health effect.

Acknowledgments

This project was conducted with partial funding through a grant from the World Health Organization WHO/EMRO. Dr. Abbas El-Zein was a full-time faculty member of the Faculty of Health Sciences of the American University of Beirut during the study.

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