Updated February 2012)
Benzene is part of the large group of chemicals called volatile organic compounds (VOCs) and is a known human carcinogen (cancer-causing substance). Long-term exposure can lead to reproductive effects or birth defects. Short-term exposure to benzene can cause drowsiness, dizziness and headaches. Benzene can also irritate the eyes, skin and respiratory tract.
Besides these serious health effects, benzene can be harmful to the environment. Motor vehicle emissions are the main source of benzene in Alberta, followed by industrial emissions and other combustion sources. Benzene also enters the air through evaporation from handling and storing fuels, the use of solvents, and cigarette smoke. Natural sources include volcanoes and forest fires.
What does the indicator show?
This indicator shows trends in annual average and peak benzene concentrations.
Annual average benzene concentrations have significantly decreased between 1990 and 2010. All annual average trends shown are statistically significant. Overall, concentrations have been reduced by 92 per cent at Edmonton Central, 53 per cent at Edmonton East and 96 per cent at Calgary Central. The reductions in ambient benzene concentrations at these urban locations are mainly the result of regulations to lower the benzene content of gasoline and regulations to improve the emission performance of on-road vehicles in Canada.
Trends in peak concentrations are available below.
Benzene is monitored at the Edmonton Central, Edmonton East, Calgary Central and Syncrude stations. Currently, the Syncrude station does not have adequate data for trend analysis. Only those stations with five or more years of consecutive data are included in the analysis. Trends that are statistically significant (a=0.05) are represented with an asterisk. For a description of the statistical analysis procedure used for trend detection, see the 2009 Statistical Procedure Report.
Benzene data are collected intermittently (every sixth day) according to the National Air Pollution Surveillance (NAPS) system. Monitoring results are 24-hour total concentrations, therefore the data presented here are annual averages of these 24-hour concentrations.
Alberta has a one-hour ambient air quality objective for benzene of 30 micrograms per cubic metre (µg m3).
Peak levels of benzene
Maximum levels of a contaminant are important because of potential health or environmental effects of high concentrations. Scientists often find the "99th percentile" reading more helpful in tracking trends than a single, maximum reading. The annual 99th percentile concentration is the concentration that is higher than 99 per cent of the concentrations recorded throughout the year. In other words, only one per cent of the concentrations observed during the year fall above the 99th percentile concentration.
Annual 99th percentile concentrations of benzene have generally declined between 1990 and 2010 (according to trend analysis). Statistically significant trends were found at Edmonton Central (a decrease of 90 per cent) and at Calgary Central (a decrease of 95 per cent). Peak benzene concentrations at Edmonton East generally decreased from 1991 to 2001 (by 12 per cent); however peak concentrations increased between 2002 and 2008. In 2009, the 99th percentile concentration fell substantially and it continued to decrease in 2010, bringing the level just above those recorded at the other two stations. The main source of benzene at the Edmonton East station is nearby petrochemical refinery and storage facilities.
What actions are being taken?
In June 2000, the Canadian Council of Ministers of the Environment ratified the Canada-Wide Standard for Benzene - Phase 1. This agreement committed the Ministers at the federal, provincial (excluding Quebec) and territorial levels to achieve 30 per cent reductions in national benzene emissions between 1995 and 2000.
Alberta’s implementation of the CWS for Benzene is focused on three industrial sectors, including natural gas dehydrators, petroleum refineries and chemical manufacturing plants. Emission reduction initiatives by the Alberta government have led to an overall 50 percent decrease in benzene emissions from industry and vehicles between 1995 and 1999.
In October 2001, Phase 2 of the CWS for benzene was endorsed by the provinces and territories (excluding Quebec). Phase 2 establishes a six-kilotonne reduction in national benzene emissions (in addition to the 30 per cent reduction proposed for Phase 1) by 2010.
As part of Alberta’s implementation of Phase 2 of the Canada-Wide Standard for Benzene, the goal of the Benzene Technical Advisory Team (Phase 2) is to establish the lowest practicable levels of benzene at facilities in the upstream oil and gas industry.
The Benzene Technical Advisory Team is made up of representatives from provincial governments (Alberta, Saskatchewan and British Columbia), the federal government, industry and non-government organizations.