Lower Mainland Region EPD

Ambient PM₁₀ Monitoring, Sechelt BC: 1999 - 2001

In 1999, the Ministry of Water, Land and Air Protection (WLAP) set up a PM₁₀ sampler in Sechelt, BC. PM₁₀ is particulate matter under 10 micrometres in diameter and occurs both naturally and anthropogenically (i.e., caused by humans). Natural sources include windblown soil, pollen, spores and marine aerosols; anthropogenic sources include industrial processing, transportation, and wood smoke from home heating. PM₁₀ has been identified as the most important ambient air pollutant in British Columbia with studies suggesting an association between increased ambient PM₁₀ concentrations and negative health effects, including mortality. More information on PM₁₀ is available at: http://www.bcairquality.ca/reports/pollutant_PM.html.

PM₁₀ sampling in Sechelt commenced on June 11, 1999 and continues to date. A Sierra-Anderson HiVol PM₁₀ sampler was set up on the roof of the Trail Bay Centre Mall (civic address 5755 Cowrie Street) in Sechelt, BC. The Trail Bay Centre Mall location was chosen as it allows for representative ambient air samples to be obtained while providing a secure location requisite for a long-term monitoring program. The sampler is operated according to the National Air Pollution Surveillance (NAPS) network 6-day sampling cycle (i.e., sampling every 6th day). The NAPS 6-day cycle allows for each day of the week to be equally sampled over the duration of a long-term monitoring program. On the designated sample date, the HiVol sampler runs continuously for 24 hours (midnight to midnight). Sample results were compared to the Federal / Provincial Working Group 24-hour PM₁₀ Reference Level of 25µg/m³ and the Provincial Ambient Air Quality 24-hour PM₁₀ Objective of 50µg/m³.

Between June 1999 and December 2001, 143 PM₁₀ samples were collected, 30 in 1999, 57 in 2000, and 56 in 2001. Ambient 24-hour PM₁₀ concentrations during this 31 month period ranged between 3 and 69µg/m³ with a mean 24-hour PM₁₀ concentration of 9.8µg/m³. The Federal / Provincial Working Group 24-hour PM₁₀ Reference Level of 25µg/m³ was exceeded for 2 percent of all samples, and the Provincial Ambient Air Quality 24-hour PM₁₀ Objective of 50µg/m³ was exceeded for less than 1 percent of all samples. The above noted exceedances occurred in July and August 1999, but are not likely representative of ambient PM₁₀ concentrations due to nearby re-roofing activities likely resulting in elevated levels of particulate matter in close proximity to the sampler. Suspect results aside, the Ambient Air Quality Objectives have not been exceeded in Sechelt since commencement of the sampling program. PM₁₀ sampling results also indicate ambient PM₁₀ concentrations are generally lower in Sechelt relative to other areas such as Squamish, Langdale, Vancouver, and Chilliwack.