Agenda Index City of Vancouver

MEMORANDUM

Date: December 1, 1998

To: Vancouver City Council

cc: City Manager

From: Domenic Losito, Director of Environmental Health

Re: Report Back on Air Quality Impacts of Major Road Network

In response to Council’s request for “conversion of information contained on page 11 of the Policy Report dated October 20, 1998 and entitled “Air Quality Impacts of Major Road Network” which expressed emissions in grams per vehicle kilometre for older diesel buses, “clean” diesel buses, and cars, to measurement in fine particles (PM2.5)”, the Director of Environmental Health has endeavoured to provide this conversion. The following table is provided with some caveats:

· The original PM numbers in the report are based on “emission factors” calculated and utilized in the PART5 emissions model out of the U.S. These numbers may not be reflective of in-use conditions in Canada nor of actual trip cycles for in-use buses.

· They suffer similar drawbacks to those stated in the Policy Report, specifically that they are based on engine certification data rather than exhaust pipe measurements.

· A strong caution is expressed in the report about relying on “mass” of air pollutants emitted as a basis for comparison of the relative toxicity of fine particulate matter. The scientific evidence clearly points to the smaller particles (which make up the smallest fraction of the total mass), which have the largest surface area and which penetrate deepest into the lung, as being the fraction of greatest public health concern. That caution is re-emphasized in responding to Council’s request to view the particulate emission data on a PM2.5 basis by weight/km.

Emissions in
g/km

Older diesel bus

“Clean”diesel bus

Natural Gas Bus

Car

PM (from report)

.30

.06

N/A

.03

PM (from Atlanta study of in-use buses)#

.40

.2

.02

N/A

PM 2.5 *

.25 - .30

.05 - .18

~.02

No data

* Estimates, based on ~75% of “old” diesel particulate being PM2.5 and 90% of “clean” diesel being PM2.5.
# Results derived from actual measurements in “Natural Gas and Diesel Transit Bus Emissions: Review and Recent Data” utilizing Detroit Diesel 50 New Flyer buses (1994=Old; 1996=Clean) and Detroit Diesel 50G CNG buses.

Staff would be pleased to update Council on any advancement in knowledge of PM2.5 sources and impacts relative to fuel and engine choice, as new information becomes available.

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