Elemental and organic carbon exposure in highway tollbooths: A study of Taiwanese toll station workers

doi:10.1016/j.scitotenv.2008.04.051

Science of The Total Environment

Volume 402, Issues 2–3, 1 September 2008, Pages 163-170

https://doi.org/10.1016/j.scitotenv.2008.04.051 Get rights and content

Abstract

The carbon composition of fine particles (PM_2.5) from traffic exhausts may play a role in adverse health effects. The objective of this study was to assess the concentrations of elemental and organic carbon in PM_2.5 in traffic exhausts from different types of vehicles in the booths of Taiwanese toll station workers and estimate the relations between traffic density and carbon concentrations. Tollbooth indoor monitoring samples were collected for 10 days to assess the 8 h integrated PM_2.5 concentration. Particle samples were analyzed for the content of total carbon, and elemental, and organic carbon. The mean carbon concentrations in the bus and truck lanes were [total: 167.7 µg/m³ (SD 79.8 µg/m³); elemental: 131.7 (66.2); organic: 36.0 (25.8)], substantially higher compared with the car lanes with cash payment [39.2 (29.5); 20.2 (19.5); 19.2 (14.6)] and the car lanes with ticket payment [34.1 (26.1); 15.8 (17.6); 18.5 (12.2)]. The increase in elemental carbon concentration per vehicle in the bus and truck lane was 14 and 9 times greater than that of car lanes of ticket payment and car lanes of cash payment. The mass fraction of carbonaceous species in PM_2.5 accounted for 54% in bus and truck lanes, whereas the corresponding figure was 30–31% for car lanes. Elemental carbon is an important component of diesel exhaust. Workers in toll stations are exposed to high levels of both elemental and organic carbon.

Introduction

The majority of particulate matter emissions in urban environments originate from traffic exhausts (Wijnen and Zee, 1998, Schwela, 2000). Particulate emissions from diesel engines are composed predominantly of elemental carbon and organic carbon (Lena et al., 2002, Lee et al., 2005). Elemental carbon is essentially a primary pollutant, emitted directly during combustion process. It is the dominant light absorbing species, which scatters solar radiation and contributes to global warming. Organic carbon has the primary origin of adsorbed mutagenic and/or carcinogenic compounds, such as benzene, toluene, ethylbenzene, xylene, and polycyclic aromatic hydrocarbons, PCBs and PCDFs, which are detrimental to human health (Lee et al., 2002, Tsai et al., 2004, He et al., 2006). Secondary organic carbon is formed from volatile organic compound gas-to-particle conversion processes in the atmosphere (Rohr et al., 2003). Total carbon is the sum of these fractions.

Traffic emissions including diesel exhaust particles or their extracts have potential toxicologic effects. These particles contain solid carbon cores that aggregate redox active organics and inorganics and can lead to generation of reactive oxygen species (ROS) (Ma and Ma, 2002). Epidemiologic studies have provided strong and consistent evidence that exposure to atmospheric particulate matter is associated with an increased risk of morbidity and mortality from cardiovascular diseases (Donaldson et al., 2001, Frampton, 2001). There is also evidence that long-term exposure to particles increases the risk of lung cancer (Nafstad et al., 2003) and organic carbon exposure influences heart rate variability (Henneberger et al., 2005). Oxidative stress has been found to be associated with exposure to carbon black (Ma and Ma, 2002, Sorensen et al., 2003).

To date several studies on carbonaceous particles in PM_2.5 were reported from different environmental settings. We have previously shown that highway toll station workers in Taipei may be exposed to daily mean concentrations of PM_2.5 reaching over 350 µg/m³ when collecting toll from the drivers. The exposure concentrations are substantially higher in lanes used by buses and trucks compared with lanes used by cars (Lai et al., 2003/4). A study conducted in Baltimore, MD, showed that tollbooth workers are potentially exposed to elevated levels of toxic mobile source emissions (e.g., PAHs, 1,3-Butadiene, Benzene) as well (Sapkota and Buckley, 2003, Sapkota et al., 2005). Furthermore, to the best of our knowledge, elemental and organic carbon exposure levels for highway toll station workers have never been assessed.

In the present study, we assessed the content of elemental and organic carbon in traffic exhausts from different types of vehicles in the booths of toll station workers. Particulate matter sampling and analysis of particulate carbon content requires substantial resources and therefore our second objective was to calculate estimates for the elemental and organic carbon exposure levels under various traffic and environmental conditions based traffic density.

Section snippets

Study location

The selected toll station was located on the First Highway, 10 km south from Taipei City. According to the Bureau of Highway Records, this toll station has the highest traffic density among all toll stations in Taiwan. There are 20 tollbooths, 10 used to collect the toll from traffic from Taipei City to Taipei County (from north to south), and the remaining 10 booths collect toll from the opposite traffic flow. Of the 20 booths, 2 to 3 in each direction were designed to accommodate bus and

Meteorological and traffic density data

Table 1 shows the meteorological data during the study period provided by the Central Weather Bureau. During the period of sampling, wind velocity, temperature, and humidity ranged from 1.8 to 5.6 m/s, 17.5 °C to 20.6 °C and 83.6% to 94.0%, respectively. The average traffic density in the car lanes with ticket payment, 661 per hour (SD 221), was significantly higher compared with 390 vehicles per hour (SD 105) in the cash payment line (P < 0.001) and with 274 vehicles per hour (SD 85) in the

Discussion

Our results showed that concentrations of both elemental and organic carbon were high, from 22 to 200 µg/m³, in the breathing zone of toll station workers. In bus and truck exhausts elemental carbon dominated whereas in car exhausts elemental and organic carbon were evenly distributed. Consequently, elemental carbon levels were 7–8 fold higher and organic carbon levels 2 fold higher in bus and truck lanes compared with car lanes. Fine particles from bus and truck exhausts contained 54% of

Acknowledgement

This research was supported by the National Science Council in Taiwan (NSC 94-2314-B-016-061).

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Elemental and organic carbon exposure in highway tollbooths: A study of Taiwanese toll station workers

Abstract

Introduction

Section snippets

Study location

Meteorological and traffic density data

Discussion

Acknowledgement

Atmos Environ

Atmos Environ

Atmos Environ

Sci Total Environ

Atmos Environ

Chemosphere

Atmos Environ

Atmos Environ

Atmos Environ

Atmos Environ

Atmos Environ

Comparison between different traffic-related particle indicators: Elemental carbon (EC), PM2.5 mass, and absorbance

J Expo Anal Environ Epidemiol

Ambient particles inhalation and the cardiovascular system: potential mechanisms

Environ Health Perspect

Systemic and cardiovascular effects of airway injury and inflammation: Ultrafine particle exposure in humans

Environ Health Perspect

Evaluations of the chemical mass balance method for determining contributions of gasoline and diesel exhaust to ambient carbonaceous aerosols

J Air Waste Manage Assoc

Chemical characterization of fine particles from on-road vehicles in the Wutong tunnel in Shenzhen, China

Chemosphere