2 National Spill Statistics and Trends
2.8 Summary Findings for Spills by Material Categories
Analysis of the data for this section was carried out by grouping substances into three broad categories: oils, non-oils and wastes/effluents.
The key findings are:
- Oils account for 58% of the total number of spills reported, non-oils 24% and wastes 18%.
- Wastes and effluents account for 89% of the total quantity reported, non-oils account for 8% and oils 3%.
- The number of spills in the three material categories increases in 1988 and remains elevated since that time.
- Fuel oils and gasoline, subsets of the broad ‘oil’ category, account for 30% of the spill events reported.
The following charts and observations refer to all spills, regardless of the sector or source. Broad material categories are examined first, and more specific categories follow.
2.8.1 Reported Number of Spills by Material Category
The distribution of spill events by the broad types of materials spilled is presented in figure 2.8.1a. A distinction between oils and non-oils is used throughout the report, in an effort to maintain consistency with the previous spill trends report (Environment Canada, 1987). This distinction between oils and non-oils was first used in the initial years of spill management in Canada. Oil spills, particularly from large tankers, were at the forefront of public and political concern at that time. Through the years, chemical spills have gained equal importance in spill-prevention efforts.
Oil spills make up 58% of reported spills. The prevalent use of fossil fuels for powering vehicles, heating buildings, generating energy, and a myriad of industrial uses underlines the importance of oils as an independent category. Spill frequency is directly proportional to material usage. It is therefore not surprising to find that the highest spill rate is in the oils category.
Twenty-four percent of the remaining spills are composed of non-oils, and 18% are wastes and effluents.
Figure 2.8.1b looks at the spill quantities for the three categories. The tonnage spilled is dominated by the wastes and effluents category. A survey of the largest spills reported (Section 2.9) indicates that the majority of the largest spills are in this category. Most of these spills are municipal sewage releases, often due to storm or floods that result in the overflow or bypass of storm and sanitary sewage systems. Some incidents in this category are spills of industrial effluents; releases of ‘mine water’, ‘mill water’, ‘white water’, mine tailings, and other dilute solutions.*
Oils, including the range from bunker fuel to natural gas, and crude oil to gasoline, comprise 3% of the quantity reported, while all other substances, the ‘non-oils’ comprise 8% of the total tonnage of spills.
Figure 2.8.1c shows the year by year progression of the breakdown of oils, non-oils, and wastes and effluents by number of spills reported. From 1984 to 1987, the proportion of waste spills ranges from 5% to 7%, while from 1988 on, the proportion of waste spills steadily increases to reach a plateau of about 25% of spills. The percentage of oil spills for the first six years (1984-1989) is 69%; for the last six years (1990-1995) it is 55%. Similarly, for ‘non-oils’, the proportion of reported spills remain fairly steady, going from 24% to 22%.
2.8.2 Percent of Spills by Material Category
Figure 2.8.2 shows a more detailed view of material categories, looking at the distribution by number of spills.
Fuel oils and gasoline, the most common fossil fuels currently used in Canada, account for 30% of the spill events in Canada. Crude oil, the source of these fuels, accounts for only 9% of the spills; with other oils and other hydrocarbons accounting for another 19%. Saltwater, a component of the mixture that comes out of the oil well, mixed with the crude, has always been reported as a separate substance (e.g. a two-tonne spill might be registered as one tonne of crude oil and one tonne of saltwater); it accounts for 7% of the spills. This indicates that the majority of crude oil spills occur at the stage where the crude is still in a mixture with saltwater. Acids and bases (among the most common in use in Canada are sulphuric acid and sodium hydroxide) comprise 3% of spills in the country. Corrosive gases (the most common being chlorine and ammonia) account for 1% of the total. The category called ‘other chemicals and substances’, which includes pesticides, plastic precursors, paints, salts, and a myriad of industrial chemicals, comprises 13% of spills.
* As the concentration values of diluted effluents are usually not available when a spill is reported, the actual quantity of contaminant being discharged is often not known. In those cases where the concentration is known, the values are usually in the parts per million range. This means that the quantity spilled, in terms of contaminant release, may be smaller than it first appears.
