Agenda Index City of Vancouver

ADMINISTRATIVE REPORT

Date: November 23, 2000
Author/Local:D.Losito/714-5677
RTS No. 1583
CC File No. 3752
Council: December 5, 2000

TO: Vancouver City Council

FROM: Director of Environmental Health in consultation with the General Manager of Engineering Services

SUBJECT: Diesel Exhaust Particulate - Health Effects Research Reports

RECOMMENDATION

GENERAL MANAGER'S COMMENTS:

COUNCIL POLICY

On November 16, 1998 Council endorsed the following recommendations of the Medical Health Officer with respect to Air Quality Impacts of the Major Road Network:

PURPOSE

This report provides Council with the results of the GVRD-sponsored report on Diesel Particulate Health and Environmental impacts and the subsequent review by a Scientific Review Panel commissioned by the Vancouver/Richmond Health Board.

BACKGROUND

Health concerns have been raised around the continued choice of diesel-powered transit buses for use on Vancouver streets and the Major Road Network. As a result a number of recommendations were approved on November 16, 1998. At that time Council was advised by the Medical Health Officer that scientific knowledge about the health effects of exposure to diesel particulate matter was incomplete, with a number of gaps in the data. Recommendations dealing with continuation of the use of trolley buses and increasing the number of PM2.5 monitoring sites have been followed up on.

In response to Recommendation A of the 1998 report, the G.V.R.D. Air Quality Department sponsored a review by Levelton & Associates on the Health and Environmental Impacts of Diesel Exhaust Particulate (DEP). Funding was also provided by Environment Canada and the project was guided by a Steering Committee consisting of representatives from BC Ministry of Environment, Lands and Parks, BC Ministry of Health, Environment Canada, Greater Vancouver Regional District, Health Canada, TransLink, and the Vancouver/Richmond Health Board.

The final Levelton report was then reviewed by a Scientific Review Panel consisting of Dr. Ray Copes, Dr. Sverre Vedal and Dr. Michael Brauer, all of the University of B.C., with funding provided by the Vancouver/Richmond Health Board.

DISCUSSION

The Levelton report arrived at the following conclusions:

… Diesel particulate emissions from heavy duty on-road trucks and buses are forecast to decrease by about 45% over the period from 2000 to 2010-2015 as a result of fleet turn-over, which introduces newer lower-emitting vehicles into the fleet, and the inspection and maintenance program for heavy duty vehicles (AirCare On-Road Program). Emissions of diesel particulate matter from heavy duty on-road vehicles is forecast to trend upward again after 2015, assuming emission standards stay at their current levels.

… Preliminary "screening-level" air quality modeling indicates that a resident livingadjacent to a road with a large amount of heavy duty diesel truck and bus traffic may be exposed to a maximum 24-hour average diesel PM2.5 concentration of about 2.4 micrograms/m3 at the roadside and about 0.7 micrograms/m3 at 20 m away from the road centreline. This excludes the potential contribution of diesel particulate emissions from other nearby roads. Maximum 24-hour average PM2.5 concentrations were predicted to decrease to below 0.25 micrograms/m3 at distances of 150 m or more from the road centreline. More in-depth analysis would be required to verify these preliminary findings.

… Insufficient data are presently available to make any conclusions about the potential significance from a health effects perspective of suggestions from very limited engine dynamometer testing that higher particle number concentrations are produced with current diesel engines than pre-1990 diesel engines.

… Implementation of a continuous monitoring program for PM10 or, preferably, PM2.5, together with chemical analysis of particulate matter samples, is recommended for at least a one year period to determine ambient diesel particulate matter concentrations in the region. It is suggested that sampling be done within a road transportation corridor having a high level of heavy duty truck traffic and at a site expected to be representative of regional average concentrations. (Section 4.4 provides an outline of the recommended program.)

… Information on the health impacts of diesel particulate matter should be monitored periodically to keep abreast of the latest science, including the comprehensive health impact assessment for diesel particulate matter being conducted by the US EPA that is expected to be finalized in 2000.

… The GVRD should work together with other agencies and levels of government to encourage programs that will reduce future diesel particulate matter emissions from heavy duty vehicles in the region, including, for example, consideration of alternative fuel and future diesel heavy duty vehicle technologies reviewed in this study.

The Scientific Review Panel commented as follows:

"There is considerable qualitative and quantitative uncertainty surrounding the health effects of exposure to DEP. While this may appear to present policy makers with a dilemma, it should be appreciated that, in practice, most environmental policy and regulatory decisions are made under conditions of substantial scientific uncertainty, whether this is explicitly recognized at the time of decision making or not. Depending on the circumstances, it may be quite reasonable for policy makers to defer a decision until `more science' is available.

However, waiting until science can provide all the answers would result in failure to take action on risks that result in substantial death and illness, tobacco and asbestos being but two examples. In the case of asbestos and some other environmental hazards, failure to take appropriate risk reduction measures based on early evidence may not only have failed to prevent death and illness but may have resulted in an `overreaction' when regulators were finally forced to take action. Such an approach is neither effective nor efficient.

Sources of Uncertainty Surrounding the Health Effects of DEP in the Lower Mainland

In the case of DEP it is certain virtually everyone is exposed to relatively low concentrations in ambient air and that a portion of this may also end up indoors. In the Lower Mainland, there is relatively little information to accurately quantify exposures of residents to DEP. One can apply results obtained elsewhere but this may or may not be a valid reflection of average levels for the lower mainland. Results from other urban areas are of even less use in characterizing the spatial variation to exposure to DEP that may occur within the lower mainland. The recent European work discussed above indicates that proximity to roadways may be important in the risk of acute non-cancer outcomes in children. Action to better characterize the exposures to DEP in the Lower Mainland is one step that can be taken by policy makers within the region. A better characterization of DEP exposure in the Lower Mainland would reduce the current uncertainty regarding this variable any assessment of health risks.

There is still some uncertainty as to whether DEP is truly carcinogenic. Most evaluations of DEP's carcinogenicity have concluded that it is `probably' or `likely' carcinogenic. This falls one step short of `proven'. If it is accepted that DEP is carcinogenic, there is still substantial uncertainty regarding its potency or the degree of risk for a given exposure to DEP. This uncertainty is related to accuracy of exposure assessment in studies of DEP workers, high to low dose extrapolation and assumed mechanism of effect. As is the case with many other substances, some of this uncertainty may be reduced by additional scientific studies. However, taking action to reduce this source of uncertainty is not something generally viewed as being within the powers of local or regional authorities. Furthermore, it should be appreciated that regardless of the state of scientific knowledge on DEP carcinogenicity, the estimates of individual risks and the estimates of the number of potential DEP related cancers in the lower mainland will remain estimates rather than observations.

It is unlikely that one could devise any type of an epidemiologic study that would directly confirm or refute the current estimates.

The risk of acute non-cancer effects is largely ignored by the report. Again, the currently available scientific information leaves one with some uncertainty as to whether these effects occur in general or in the lower mainland specifically. However, unlike the estimates of cancer risk, risk of acute respiratory effects from exposure to DEP are amenable to direct investigation. It is possible to conduct a study in the lower mainland that would investigate whether there is a discernable relationship between proximity to major roadways and acute effects on respiratory health. As these effects may be most pronounced in children, this might be the best sub-population to study. This work could be carried out within the lower mainland and deals with a question related to local and regional public health. It would provide additional information to local decision makers on the presence of health effects in the lower mainland, it would reduce the current scientific uncertainty regarding the existence of health impacts and could provide useful local information on the need for local and regional measures to reduce exposure to DEP.

Action now or later?

The scientific evidence on the effects of DEP with its attendant uncertainties may be viewed differently by people holding different world-views. Adherents of the `precautionary principle' may well see enough evidence to warrant substantial action to reduce (or even desire to eliminate) exposure to DEP. Others recognizing the difficulties inherent in taking action on a substance as widespread and useful as diesel fuel may feel that watching and waiting represents a preferable course of action.

The debate between these viewpoints is frequently played out in policy discussions at the local, provincial, national and international levels and represents one of the dynamic tensions in democratic societies. Frequently positions may be coloured by equity questions. Who bears the potential risks from failure to take prompt effective actions to mitigate risks and who bears the costs of any actions that are taken?

Current evidence does raise the question of whether DEP is a particularly noxious component of the mix of air pollutants. Although it may be argued on the basis of esthetics, visual and olfactory, that this is already demonstrated, current scientific evidence falls short of proving this to be the case with respect to health risks. If DEP is truly as bad as some claim, measures to reduce exposures are warranted. It is hoped that this review will help inform the debate on the pace and extent of any such measures deemed necessary by decision-makers in the lower mainland, as well as providing some guidance on how current uncertainties in the science can be addressed at the regional level."

OTHER SOURCES OF RESEARCH:

Recent events in the U.S. also assist in filling in some of the data gaps that existed 2 years ago. These include the finalization of an EPA Risk Assessment of Diesel Exhaust and the development of a Risk Management approach by the California Air Resources Board (CARB). The E.P.A. document came to the following conclusions, tempered with a fair bit of uncertainty:

… On the basis of available human and animal evidence, it is concluded that Diesel Exhaust can cause acute irritation (e.g., eye, throat, bronchial irritation), neurophysiological symptoms (e.g., lightheadedness, nausea), and respiratory symptoms (cough and phlegm).

… Diesel Exhaust may pose a chronic respiratory hazard to humans.

… Diesel Exhaust is likely (downgraded from "highly likely" in the previous draft) to be carcinogenic to humans by inhalation at any exposure condition.

The CARB risk management approach has highlighted some cost-effective ways for the diesel engine industry to significantly reduce the risk from exposure to DPM. With full implementation of the proposed risk reduction plan, coupled with tightened Federal emission standards, CARB predicts a 75% reduction in emissions and cancer risk by 2010, and an 85% reduction by 2020. The good news is that we are likely to benefit from these major reductions in diesel particulate emissions driven by engine re-design and regulatory changes in the U.S.

A recent study sponsored by the Northeast Advanced Vehicle Consortium revealed some promise from hybrid diesel/electric technology:

"The results of this program demonstrate that diesel hybrid-electric vehicles offer reduced drive cycle emissions relative to conventional diesel buses, comparable to that achieved by conventional CNG buses and in most cases setting the in-use benchmark. Only emissions of nitrogen oxides from the hybrids failed to set the performance benchmark. The CNG-like particulate emissions of these diesel hybrid-electric buses were facilitated by the use of low sulfur diesel fuel and catalyzed particulate filters. The project confirmed significant fuel economy benefits of greater than 100 percent over a comparable CNG bus when operated on severe duty cycles such as New York Bus.

A recent study by the Harvard Center for Risk Analysis, released in January of 2000, concluded:
"The choice to use diesel or natural gas fuels in heavy duty trucks is not straightforward. These fuels have different effects on environmental quality, health, safety, truck performance, and economics. Decision-makers should recognize that fuel choice involves trade-offs between competing policy goals. The table below summarizes the relative advantages of the fuels withrespect to different criteria considered in this qualitative assessment. "

DIESEL VS.NATURAL GAS IN HEAVY DUTY TRUCKS
Criterion Relative Advantage

Pollution    

    Fine particulates

   X

    Ultra-fine particulates

 ? ?

    Nitrogen Oxides

   X

    Greenhouse gases

 X  
Safety X  
Performance X  
Economics    

    Short Run Costs

 X  

    Long Run Costs

 ? ?

The authors of this study did not compare diesel and natural gas against electric power (e.g. trolleys) which is an alternative Council strongly favoured in the 1998 report. From what we already know about electric-powered buses, it would be safe to conclude that they are superior to both diesel and natural gas on every criterion except Short Run (capital) costs and perhaps Performance. Staff is recommending that Council's strong stance on the replacement (and extension) of the trolley fleet with trolley buses be once again communicated to TransLink.

CONCLUSION

The Levelton report has shed some additional light on the relative risks of diesel particulate matter and the choice of diesel as an urban fuel for buses and heavy duty vehicles. The Scientific Review Panel report has pointed out some gaps in our knowledge that still need to be addressed. Both reports have suggested that additional studies should be undertaken to gather data on actual DEP levels next to major roads and to better understand the relationship between acute respiratory health effects and vicinity to major roads. In the interim, staff recommends that decision-makers adopt a "precautionary" approach with respect to fuel and engine technology options, and that public health and environmental impacts be taken into account when making "traditional accounting" decisions around these options. Adoption of the recommendations in this report should lead to further enhancements in our knowledge about the health effects of diesel particulate matter and assist policy makers in making difficult trade-offs and risk management decisions.

- - - - -

APPENDIX A
Executive Summary - LEVELTON REPORT

Diesel particulate matter emissions from on-road diesel vehicles and their potential impact on human health in the Lower Fraser Valley are the focus of this study. The major findings from the study are summarized below.

Potential Health Impacts from Exposure to Diesel Particulate Matter

- The California Air Resources Board (CARB) has reviewed all of the epidemiological studies involving exposure to diesel particulate matter and concluded that diesel particulate is carcinogenic, and that a reasonable estimate of the cancer risk factor for continuous exposure to diesel particulate matter over a 70 year lifetime is about 300 cases of cancer per million population per 1 microgram/m3 average concentration of diesel PM2.5 in the ambient air. Based on the scientific data, a threshold diesel particulate concentration for carcinogenic effects has not been identified.

- The CARB review also concluded that chronic non-cancer health effects (i.e. non-lethal) are unlikely to result from a lifetime exposure to below an average ambient air concentration of 5 micrograms/m3 of diesel PM2.5.

- The US EPA is presently preparing a health assessment for diesel particulate emissions that is expected to be finalized in 2000 following review by the Clean Air Scientific Advisory Committee of the Science Advisory Board.

- Insufficient data are presently available to make any conclusions about the potential significance from a health effects perspective of suggestions from very limited engine dynamometer testing that higher particle number concentrations are produced with current diesel engines than pre-1990 diesel engines.

Diesel Particulate Emissions and Ambient Air Concentrations in the Lower Fraser Valley

- From the 1998 emission inventory, it is estimated that the emissions of PM10 and PM2.5 in the Lower Fraser Valley are as follows:

- Diesel particulate emissions from heavy duty on-road trucks and buses are forecast to decrease by about 45% over the period from 2000 to 2010-2015 as a result of fleet turn-over, which introduces newer lower-emitting vehicles into the fleet, and the inspection and maintenance program for heavy duty vehicles (AirCare On-Road Program). Emissions of diesel particulate matter from heavy duty on-road vehicles is forecast to trend upward again after 2015, assuming emission standards stay at their current levels.

- The average ambient regional PM10 concentration is currently about 13-15 micrograms/m3 and is forecast to remain approximately within this range to 2020 with implementation of the 1994 Air Quality Management Plan.

- The current regional average concentration of diesel PM10 and PM2.5 from on-road diesel vehicle emissions is estimated to be about 1 microgram/m3, based on the annual diesel particulate emissions from on-road vehicles, and on the assumption that these emissions disperse to the same extent as observed regionally for carbon monoxide emissions from on-road vehicles.

- Average ambient concentrations of diesel PM2.5 from all on-road and off-road sources in several Eastern U.S. urban areas range from 0.5 to 1.6 microgram/m3. The average diesel particulate concentration in Los Angeles is about 1.5 microgram/m3. While there is no ambient air monitoring data for total diesel PM2.5 in the GVRD, estimates in this study suggest that average diesel particulate concentration in the Lower Fraser Valley is similar in magnitude to that observed in some large U.S. cities.

- Preliminary "screening-level" air quality modeling indicates that a resident living adjacent to a road with a large amount of heavy duty diesel truck and bus traffic may be exposed to a maximum 24-hour average diesel PM2.5 concentration of about 2.4 micrograms/m3 at the roadside and about 0.7 micrograms/m3 at 20 m away from the road centreline. This excludes the potential contribution of diesel particulate emissions from other nearby roads. Maximum 24-hour average PM2.5 concentrations were predicted to decrease to below 0.25 micrograms/m3 at distances of 150 m or more from the road centreline. More in-depth analysis would be required to verify these preliminary findings.

Risk Assessment for Diesel Particulate Matter from On-road Vehicles

- Applying the CARB cancer risk factor to the estimated regional ambient average diesel PM2.5 concentration of 1 microgram/m3 from on-road vehicles yields a cancer risk factor of 300 per million population over a 70 year lifetime exposure. This equates to a probability of about 8 excess cases of cancer per year in the approximately 2 million population of the GVRD (300 per million x 2 million population/70 year lifetime). This cancer risk is projected to decrease by about half by the 2010 to 2015 period as a result of replacement of the older existing trucks and buses in the on-road fleet with vehicles meeting current, lower engine emission standards.

- Since emissions from all commercial, public transit and school buses in the region are about 5% of the diesel particulate emissions from on-road vehicles, the cancer risk attributable to these vehicles is currently 15 per million population over a 70 year lifetime exposure, or 1 new cancer case every two years. This risk factor will probably remain roughly constant through to the 2010 to 2015 period if lower vehicle emissions from introduction of cleaner, new diesel buses in the fleet are countered by increases in the number of buses.

- The preliminary air quality modeling results indicate that the CARB reference concentration of 5 micrograms/m3 for adverse non-cancer health effects from long-term exposure would not be exceeded in the Lower Fraser Valley even in the most impacted areas adjacent to major arterial roads with a high volume of diesel truck and bus traffic.

Interpretation of the Acceptability of the Health Risk Estimates for the GVRD

- As the cancer risk associated with exposure to diesel particulate matter from on-road diesel vehicles was predicted to be 300 cases per million population for continuous exposure over a 70 year lifetime, and this is above levels of 1 to 10 cases per million population often deemed to represent a threshold of significance when evaluating environmental public health risks, an appropriate level of priority and risk management should be applied to diesel particulate emissions.

- The cancer risk from exposure to diesel particulate matter predicted in this study appears to be a small component of the current total lifetime risk from cancers of all kinds, which is about 200,000 to 250,000 in a million population over a 70 year lifetime.

- The 45% decline in diesel particulate emissions from current levels forecast to occur by 2010-2015 is relevant to future management as it will result in a corresponding reduction in the cancer risk over that period.

Next Steps

- Implementation of a continuous monitoring program for PM10 or, preferably, PM2.5, together with chemical analysis of particulate matter samples, is recommended for at least a one year period to determine ambient diesel particulate matter concentrations in the region. It is suggested that sampling be done within a road transportation corridor having a high level of heavy duty truck traffic and at a site expected to be representative of regional average concentrations. (Section 4.4 provides an outline of the recommended program.)

- Information on the health impacts of diesel particulate matter should be monitored periodically to keep abreast of the latest science, including the comprehensive health impact assessment for diesel particulate matter being conducted by the US EPA that is expected to be finalized in 2000.

- The GVRD should work together with other agencies and levels of government to encourage programs that will reduce future diesel particulate matter emissions from heavy duty vehicles in the region, including, for example, consideration of alternative fuel and future diesel heavy duty vehicle technologies reviewed in this study.

APPENDIX B

Executive Summary - Scientific Panel Review

A scientific panel consisting of Drs. M. Brauer, R.Copes and S.Vedal from the Faculty of Medicine and the School of Occupational and Environmental Hygiene at the University of British Columbia reviewed the report Diesel Particulate Matter and Associated Environmental Concerns, Health Risks and Tradeoffs prepared for The Onroad Diesel Emissions Evaluation Task Force as well as other relevant scientific literature on the health effects of exposure to diesel exhaust.

While the panel agreed with much of the content of the report there are some points that they feel require emphasis.

1) There is still considerable scientific debate on the carcinogenicity of diesel exhaustparticulate (DEP), particularly with respect to its potency as a carcinogen. This results in appreciable uncertainty in the level of risk to members of the public from exposure to current ambient levels of DEP in North American and European cities.

2) The report does not address any potential for acute effects from DEP. Recent work from the Netherlands appears to implicate exposure to DEP at current ambient levels in producing reduced lung function in children and increased respiratory symptoms, especially in children sensitized to common allergens and children that have bronchial hyperactivity. While the evidence on this is not conclusive, these acute effects rather than cancer may reflect the most important public health consequence of exposure to DEP.

3) There is relatively little data on the levels of DEP around the lower mainland. While the results of monitoring done elsewhere can be extrapolated to the lower mainland, this is not a good substitute for local information. Estimation of exposure through traffic volumes may introduce considerable error. Better quantification of public exposure to DEP in the lower mainland would not be difficult to perform and would help to better characterize the extent of any health risks.

* * * * *

ag001205.htm

Comments or questions? You can send us email.

[City Homepage] [Get In Touch]

(c) 2000 City of Vancouver