5. Environmental and Health Effects of Reducing Sulphur in Fuel Oils

When fuel oils are combusted, the sulphur in them is emitted into the air as sulphur dioxide (SO2) and sulphate particles (SO4).

Emissions of SO2 are a primary cause, along with emissions of nitrogen oxides, of acidic deposition27 which has a significant effect on the Canadian environment, particularly in central and eastern Canada. Once in the air, SO2 undergoes chemical reactions to form acids or acidifying sulphates that may be carried hundreds of kilometres before eventually falling to earth in rain, fog, or snow (these forms are often referred to as wet deposition). Sulphate particles and gases also fall to the land and vegetative surfaces (e.g., leaves) during periods without precipitation (dry deposition).

High levels of acid rain can result in the acidification of lakes, rivers and streams which causes the nutrients and metals to leach form the soil into the water. The acidification of lakes means that they cannot support the same variety of life - the fish, frogs, insects and micro-organisms gradually disappear from these waters. Acidic deposition contributes to declining growth rates and increased death rates in trees. It also accelerates the erosion of buildings.

Furthermore, SO2 in the air can combine with other pollutants and water to form fine particles (i.e., PM2.5), that may potentially affect the health for people with heart and respiratory disease. The haze that these particles forms also contributes to visibility reductions.

Some work has been done to better define the benefits to the environment and health of Canadians of reducing sulphur in fuel oils. The findings of these scoping studies are summarized below (see Appendix 1 for complete listing of the studies which are available on request).

ARM Consultants undertook a study to investigate the impact of lowering sulphur levels in HFO and LFO to 1.0% wt. and 0.1% wt., respectively on changes in acid deposition and SO2 and SO4 air concentrations on an annual basis. The study also assessed the impact on critical load exceedances (Critical loads are estimates of the amount of acid deposition that a particular region can receive without significant damage to its ecosystems).

Estimates of critical loads for wet sulphate deposition range from more than 20 kilograms of sulphate per hectare per year in the most tolerant areas to less than 8 kilograms per hectare per year in the most sensitive. These highly sensitive areas are found mostly in the Canadian Shield areas of central Ontario, eastern Quebec, and the Atlantic provinces.

The Acid Deposition and Oxidant Model (ADOM) was used to simulate the impact of reducing sulphur in fuel oils in year 2010 compared to a reference scenario corresponding to the actual provincial SO2 caps expected in 2010 with voluntary over-compliance from some major point sources agreed to under the Eastern Canada Acid Rain Control Program. In the context of this study, concentration of sulphate was used as a surrogate for PM2.5 over eastern Canada.

The study found:

Table 5.1: Eastern Canadian Land Area in Exceedance of Wet SO4 Critical Load for Reference and Fuel Oils Emission Scenarios
Area (x 1000 km2)
Scenario Name Nominal Year Ontario Quebec New Brunswick Nova Scotia Nfld. & Lab. All Eastern Canada
Reference 2010 204 406 95 82 4 791
Fuel oils 2010 204 399 95 82 0 780

The size of the area of eastern Canada in exceedance for different threshold levels of critical load is summarized in Table 5.2 for the reference and the fuel oil scenarios.

Table 5.2: Eastern Canadian Land Area (in 1000 km2) in Exceedance of Wet SO4 Critical Load for the Reference and Fuel Oils Emission Scenarios for Different Thresholds
Scenario Name Nominal Year Exceedance threshold
(kg SO4 ha-1 yr-1)
0-2 2-4 4-6 6-8 >8
Reference 2010 290 246 125 81 50
Fuel oils 2010 308 229 122 73 48

In examining particulate emission reductions, the study used ambient sulphate concentration as a surrogate for fine particulate matter (i.e., it was assumed that a reduction in ambient sulphur concentration will result in a reduction in concentration of fine particulate matter). The estimated reduction in ambient sulphate concentration was on the order of 2% in southern Ontario, 6% around Montreal, and about 28% in Atlantic Canada.

The changes in the Atlantic Canada are dominated by the local emission reductions and a small decrease in long-range transport from Ontario and Quebec. The decrease in ambient SO4 concentrations would also result in a decrease in fine particulate matter (PM2.5), of which sulphate particles are a significant fraction in eastern Canada (up to 40%).

Environment Canada used the resulting changes in concentrations of pollutant as estimated by the ADOM model to estimate order of magnitude health and environmental benefits28. The estimated avoided physical impacts in 2010 for the fuel oil scenario were calculated29.

In the interim, new developments in the United States have put into question some of the research underlying on estimated health benefits. It is not yet clear whether, in resolving the uncertainty, the estimates of health benefits will become smaller or larger than the current estimates. Consequently, Environment Canada has decided not to finalize its estimates of health benefits due to reducing sulphur in fuel oils at this time.

Nevertheless, Environment Canada expects that reducing sulphur in fuel oils will result in improvements to air quality, which in turn will result in health benefits for Canadians. However the magnitude of these health benefits is unknown at this time.




Footnotes

27 Because rain is only one of the means by which the acid reached the earth's surface, scientists often prefer to speak of acid deposition rather than acid rain. However for convenience, the wellknown, often-used term "acid rain" is often used in this paper, but always in the broader sense of all forms of acid deposition.
28 The general methodology used in this analysis was the damage-function approach. The damagefunction approach uses available scientific and economic information to determine how changes in pollution emissions affect things of value to society. It refers to a quantitative relationship between pollution concentrations and damage to human health and the environment. When pollution is reduced, this approach is used to estimate benefits (i.e., the reduction in damages). The damage function approach was implemented in this process using the Air Quality Valuation Model (AQVM). Changes in the ambient air quality as a result of reducing sulphur in fuel oils were used as input into the AQVM computer model. The model computes changes in physical impacts such as health events using concentration-response relationships, applying economic values to physical impacts, and aggregating benefits across all affected individuals and all relevant time periods. It should be noted that AQVM currently only includes one environmental endpoint for SO2 (i.e. material damage) and one environmental endpoint for wet sulphate deposition (i.e., impacts on recreational fishing). It includes many endpoints for particulate matter.
29 To give readers a point of comparison, these preliminary estimates using the old methodology were found to be about one-quarter of the benefits estimated for the reduction of sulphur in gasoline.

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