AIR QUALITY MONITORING
Although air pollution in the Sea-to-Sky air shed has not reached levels experienced in some of the more polluted regions of British Columbia, trends for growth in the Sea-to-Sky region indicate that air quality may deteriorate without preventative action.
Vehicle based pollution is currently the most significant factor affecting air quality in the Sea-to-Sky air shed. This source is expected to become even more important in the future as the population of the region and tourism continue to increase. Mobile sources, due to their transient nature, are difficult to quantify (they can not be monitored with the same ease as permanent smoke stacks for example).
In order to monitor air quality in the Sea-to-Sky air shed a number of permanent monitoring stations have been established in communities along the Sea-to-Sky corridor. By installing air pollution monitors near village centres we are able to sample air that is similar to the air experienced by many of the community's residents. Datasets from monitoring stations are used to evaluate air quality events and to determine trends over time. From this information we will be able to ensure that human and ecosystem health are protected, and that villages such as Pemberton experience exceptional air quality. Additionally information from monitoring stations will be used to make management decisions regarding which preventative air quality actions will be most useful to implement.
PARTICULATE MATTER (PM)
One of the main air pollutants in the Sea-to-Sky corridor is particulate matter (PM). This pollutant is classified as a Criteria (or Common) Air Contaminants (CACs). Particulate matter is broken into two main components, PM10 and PM2.5. The term PM10 has been given to atmospheric particles that are less than 10 mm in diameter and the term PM2.5 represents particles that are less than 2.5 mm in diameter. Particulate matter is of concern because of the potential health effects associated with inhaling particles. Further, PM is a constituent of smog and haze.
Fine particles are of particular concern because they can be inhaled and deposited deep within the lungs possibly leading to respiratory irritations. Fine particulates can chronically and/or acutely aggravate cardiovascular or pulmonary diseases and may increase symptoms in asthmatics. Recent studies indicate that there is no safe level for particulate matter meaning that health effects can occur in vulnerable individuals even at low particulate concentrations.
SOURCES OF PM
Fine particulates (PM10 and PM2.5) are directly emitted by a number of sources including industrial, mobile and area sources. Primary sources of PM10 in the Sea-to-Sky airshed are from the pulp and paper industry (40%) as well as mobile sources (including road dust), and area sources (burning, space heating) (33%). The sources of PM2.5 are similar to PM10 except that PM2.5 can also be formed as a secondary particulate through reactions with other air pollutants (such as ammonium nitrate and ammonium sulphate) in the atmosphere. Particulate matter can also arise from natural sources. In the Sea-to-Sky airshed natural sources of PM10 and PM2.5 include mainly sea spray and forest fires.
Particulate matter (PM2.5) has been measured in Pemberton since September, 2005. The PM2.5 monitor is located on the roof of the Signal Hill Elementary School. This is the newest site in the Sea-to-Sky air quality monitoring network. It is often difficult to predict with accuracy where the worst air pollution will occur. The monitor represents one location, and can only be used to give us an approximation of what residents are experiencing. The Pemberton monitor location is an ideal site as it is near the town's center and also in an area that will experience growth in the future.
DETAILS OF THE STATION
A new continuous PM2.5 monitor was added to the station in the summer of 2015, which previously used a non-continuous monitor to measure PM2.5.
Visit the BCairquality.ca website to read how these pieces of equipment function.
To evaluate the quality of the air, data is compared with Provincial and National Air Quality Objectives in order to determine if exceedances have occurred. The National PM2.5 Objective (called the Canada Wide Standard) is 30 mg/m3 over a 24-hour averaging period (based on the annual 98th percentile value, averaged over 3-years). Additionally a Health Reference Level of 15 mg/m3 (over a 24-hour period) for PM2.5 has been set by the Canadian Environmental Protection Act (CEPA). The Health Reference Level represents the concentration at which there is a statistically significant correlation between PM2.5 concentrations and adverse human health affects. Although there is not enough information to calculate the Canada Wide Standard, review of available data indicates that neither the Canada Wide Standard nor the Health Reference Level were likely exceeded at the Pemberton site during the September or October sampling periods.
For PM10 the Provincial PM10 Level B objective (there is no National objective for PM10 at this time) is 50 mg/m3 over a 24-hour rolling average time period (any consecutive 24-hour period). Additionally a Health Reference Level of 25 mg/m3 (over a 24-hour period) has been set by CEPA for PM10. As for PM2.5, the PM10 Health Reference Level represents the concentration at which there is a statistically significant correlation between PM10 concentrations and adverse human health affects. Examination of available data indicates a maximum of 11 mg/m3 for the months of September and October, 2005. This value is much lower than the Health Reference Level.
In addition to comparing results to National and Provincial Objectives a common method used to determine the quality of the air is to convert the PM10 concentration into a unitless index number which can then be compared with the Air Quality Index (AQI) scale (Table 1). Information on the AQI is available on the Ministry of Environment website.
The conversion of PM10 data to the AQI is simple in that the concentrations can be directly translated into the index. For example, a 24-hour PM10 concentration of 14 mg/m3 equals an AQI of 14. An AQI of 14 falls into the 'Good' range on the AQI scale. An air quality warning is issued if the AQI is expected to reach poor, but recently, during the Boulder Creek Wildfire Complex and Elaho Fires (the fire events that took place in our airshed in the summer of 2015) the Ministry of Environment issued a number of air quality advisories for the Sea-to-Sky airshed warning residents of 'Very Poor' conditions.
TABLE 1: AIR QUALITY INDEX (AQI) CATEGORIES
|0 to 25||26 to 50||51 to 100||100+|
OTHER PM MONITORING STATIONS IN THE CORRIDOR
In addition to comparing results to National or Provincial Objective levels, there is interest in comparing data from other sites in the Sea-to-Sky airshed in order to determine which communities have the best or worst air quality.
There is a non-continuous PM10 monitor in Whistler and a non-continuous PM2.5 monitor in Squamish.
The Whistler PM2.5 monitor and the Squamish PM10 monitors are continuous, and utilize a completely different technology than the non-continuous PM monitors. In short, the continuous monitors utilize an oscillating filter that collects particulate matter. The filter oscillation changes as it "loads" particulate and the change in oscillation is correlated to a PM concentration. Although data from continuous and non-continuous monitors should not be compared directly, both types of monitors provide valuable information regarding the ambient concentrations of particulate matter.