NRDC: No Breathing in the Aisles: Diesel Exhaust Inside School ...

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• Driving uphill increased the level of diesel exhaust inside the bus; • Driving downhill sometimes resulted in higher levels of diesel exhaust than did driving on the flats—this may be because the drivers shifted into a lower gear and used the engine to slow the bus on steep hills or because smoke lingered in the bus from a recent uphill ascent. • Levels of diesel exhaust in the bus did not rise when the bus stopped and idled—in fact, the levels often decreased on idling; • There was significant variability among individual buses sampled. Even two buses from the same model year had different levels of diesel exhaust. • A child sitting in the back of the bus with the windows closed would receive an average exposure to diesel exhaust that is up to 4 times greater than a child riding in a passenger car immediately ahead of the same bus. In addition, the extra exposure to a child inside the bus was between one and 14 micrograms per cubic meter (mcg/m 3 ) higher than the exposure that same child would get from walking or riding in a car on those same streets. Indeed, the California Air Resources Board estimated that the average outdoor concentration of diesel exhaust in California in 1995 was 2.2 mcg/m 3 . Thus, for the time a child is in a school bus, his or her exposure to diesel exhaust may be up to 8-1/2 times the average statewide air levels. Figure 1 illustrates, as an example, the average readings we obtained inside one 1986 school bus compared with simultaneous measurements inside a passenger car driving directly ahead of the bus. FIGURE 1 Diesel Particulate (mcg/m 3 ) Driving Conditions Figure 2 shows an example of minute-by-minute measurements of black carbon simultaneously inside the back of a 1986 bus and inside a passenger car driving immediately ahead of the bus. Some of the sources of variability are marked. The only times when the levels of diesel exhaust particles in the car briefly exceeded the levels in the bus were when the car was behind the bus for a few minutes idling at a school, and when four windows in the bus were opened to ventilate the interior of the bus. 8 30 25 20 15 10 5 0 Simultaneous Bus and Car Diesel Levels: 1986 Bus Idling Uphill Dow nhill Overall BUS CAR
FIGURE 2 Diesel Exhaust Particulate (mcg/m 3 ) 35.0 30.0 25.0 20.0 15.0 10.0 5.0 0.0 9:29 There was also clear evidence of variability between buses, whereas the levels of diesel exhaust measured in the car or outdoors was consistently lower and somewhat less variable. For example, two 1986 buses rented from the same bus company were found to have very different average levels of diesel exhaust inside the buses (see Figure 3). Thus, age alone does not necessarily predict a “smoky” bus. FIGURE 3 Diesel Exhaust Particulate (mcg/m 3 ) 20 18 16 14 12 10 8 6 4 2 0 Bus average Car average 9:48 9:53 9:58 10:03 10:08 10:22 10:27 Real-Time Bus and Car Comparisons Uphill Downhill Car behind bus, idling 10:32 10:37 11:00 11:05 Variability Among Buses 11:10 11:15 Time 1986a 1986b 1987 1988 11:20 11:40 12:04 12:09 Congested street, stop and go Bus 12:29 13:02 Bus windows open 13:16 “Background” 13:21 13:26 Idling 13:31 13:36 Windows closed stop & go 13:41 9 BUS CAR
Page 1 and 2: NO BREATHING IN THE AISLES Diesel E
Page 3 and 4: TABLE OF CONTENTS Introduction 1 Hi
Page 5 and 6: INTRODUCTION t’s a common occurre
Page 7 and 8: advance of 2006 so that school buse
Page 9 and 10: • A growing number of states have
Page 11: with children. We were unable to ac
Page 15 and 16: INTERPRETATION OF THE RESULTS Diese
Page 17 and 18: according to the SCAQMD study, 71 p
Page 19 and 20: espiratory diseases, chronic obstru
Page 21 and 22: Studies have also shown that the pr
Page 23 and 24: y 2002. In addition, there is overw
Page 25 and 26: to be as cost-effective as CNG. Nev
Page 27 and 28: CHAPTER 4 CLEAN FUEL SCHOOL BUS SUC
Page 29 and 30: well trained in-house mechanics con
Page 31 and 32: complaints. Maintenance costs are l
Page 33 and 34: TABLE 4 Certified Emissions Levels
Page 35 and 36: using historical data on in-use die
Page 37 and 38: CHAPTER 6 AFTERTREATMENT, REPOWERS,
Page 39 and 40: CHAPTER 7 FUNDING IS AVAILABLE TO H
Page 41 and 42: Georgia—Clean Fuels Grant Program
Page 43 and 44: CHAPTER 8 LOCAL AIR QUALITY AGENCIE
Page 45 and 46: APPENDIX A SCHOOL BUS MONITORING ST
Page 47 and 48: 2. Load secon d A ethalo m eter in
Page 49 and 50: APPENDIX B POTENTIAL CANCER RISK TO
Page 51 and 52: APPENDIX C Magee Scientific Company
Page 53 and 54: APPENDIX D PORTABLE MONITOR/DATA LO
Page 55 and 56: • Alarm averaging time : real tim
Page 57 and 58: APPENDIX F Examples of Available Fu
Page 59 and 60: APPENDIX G Sample Letter to Air Boa
Page 61 and 62: Sample Letter to Elected Officials
Page 63 and 64:
ENDNOTES 1 State and Territorial Ai
Page 65 and 66:
54 Wiley, J., J. Robinson, T. Piazz
Page 67:
123 Department of Energy, Clean Cit
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