Estimating Cancer Risk Increment from Air Pollutant Exposure for Sewer Workers Working in an Industrial City

Gui-Xiang Lin,Shu-Hsing Yeh,Hui-Tsung Hsu,Ching-Ho Lin,Chin-Hsing Lai,Yuh-Wen Huang,Ming-Jen Chen,Tzong-Tzeng Lin

doi:10.4209/aaqr.2010.09.0074

Abstract

Sewer construction in Taiwan lags other developed nations, and the authorities are undertaking major sewerage system construction projects in several cities. In Kaohsiung City, sewerage networks pass through residential, commercial and industrial areas. The composition of sewage thus is highly complicated. Eight target monitoring positions are chosen to analyze the compounds and concentrations of hazardous air pollutants. Pollutant concentrations are used to evaluate the cancer risk increment based on inhalation intake for sewer workers under using exhaust ventilation and wearing personal gas filtering equipment. GC/MS analysis confirmed that concentrations of benzene and trichloromethane compounds in sewer air for all the monitoring positions exceeded the minimum risk levels (MRLs) of 0.009 ppm benzene and 0.1 ppm trichloromethane, and the maximum concentrations reached 148.4 and 327.3 ppm, respectively. The cancer risks of benzene and trichloromethane for workers without personal protection approached 2.77-3.98×10^(-3) and 29.74-42.70×10^(-3), respectively. Through ventilation for 15 minutes and the wearing of gas filtering equipment, the cancer risks for benzene and trichloromethane were reduced to 0.0003-0.0004×10^(-3) and 0.0029-0.0041×10^(-3), respectively. The authorities thus must order all workers to follow a strict code of practice for sewer entry before entering sewer systems. This code of practice should include a minimum time for general exhaust ventilation and the use of personal protection equipment.

Highlights

Sanitary sewer system air is influenced by regional environment type and sewage exhaust characteristics (Matos and Aires, 1995; Matthijs et al, 1995; Muezzinoglu, 2003; Paxeus, 1996; Veldkamp and Wiggers, 1997; Gostelow et al, 2001)
Through ventilation for 15 minutes and the wearing of gas filtering equipment, the cancer risks for benzene and trichloromethane were reduced to 0.0003–0.0004 × 10-3 and 0.0029–0.0041 × 10-3, respectively
(1.6–25.3 ppm), propene (0.7–18.9 ppm), 2-methylpentane (0.3–16.8 ppm), 3-methylpentane (0.5–14.1 ppm), 1,1dichloroethylene (2.2–14.2 ppm), 1-butene (0.8–13.7 ppm), butane (1.0–12.4 ppm), cis-2-butene (0.6–3.1 ppm), trans2-butene (0.8–2.3 ppm) and the other trace species. Both of benzene and trichloromethane were identified as major of carcinogenic air pollutants by the Integrated Risk Information System (IRIS) of US EPA, while the other compounds belonged to the non-carcinogenic air pollutants

Summary

Introduction

Sanitary sewer system air is influenced by regional environment type and sewage exhaust characteristics (Matos and Aires, 1995; Matthijs et al, 1995; Muezzinoglu, 2003; Paxeus, 1996; Veldkamp and Wiggers, 1997; Gostelow et al, 2001). Government of Taiwan indicated that the substances of benzene and trichloromethane were detected in sewer air (Environmental Protection Bureau, Kaohsiung City Government, 2009). The impact of hazardous air pollutants on health and cancer risk for sewer workers has recently attracted considerable attention in industrialized countries (Chinery and Gleason, 1993; Kuo et al, 1998; Hinwood et al, 2007). In Kaohsiung City (in the south of Taiwan), the networks of domestic sewerage collection system serve residential, commercial and industrial areas, and are extremely complicated (Lin, 2001; Dong et al, 2002; Environmental Protection Bureau, Kaohsiung City Government, 2009; Wang et al, 2010). Taiwan recently suffered an accident in which sewerage workers were injured after a manhole explosion. This explosion accident might have resulted from high concentrations of VOCs or methane in the sewer system

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Results

Conclusion