Kitimat SO2 Alert Pilot Project

In 2018, the Ministry of Environment and Climate Change Strategy (the ministry) began a pilot project to alert the Kitimat public of periods when sulphur dioxide (SO2) levels are elevated. The Ministry is now testing a second approach to provide such information, through an updated Air Quality Health Index (AQHI) that includes SO2 concentrations.

See below for details. 

SO2 is a colourless gas with a strong odour at higher concentrations. It is produced during the combustion of sulphur-containing fuels and industrial operations involving sulphur-containing materials. Major sources of SO2 in BC include: the upstream oil and gas industry, metal smelting facilities, pulp and paper mills and marine vessels.

Short-term exposures to elevated SO2 levels can cause the air passages in the lungs to constrict or tighten, leading to breathing difficulties and tightening in the chest. Those most sensitive to the effects of SO2 include persons with chronic respiratory disease, especially persons with asthma. Symptoms may worsen during vigorous exercise or hard physical labour.

In general, persons with asthma may experience effects at much lower concentrations than the general public. In their Human Health Risk Assessment for Sulphur Dioxide, Health Canada identified a 10-min Reference Concentration (RfC) of 67 ppb – a level that is expected to be protective of human health, including sensitive groups such as those with asthma, when exposed continuously over a lifetime. This level is comparable to a 1-hour concentration of about 35 ppb based on SO2 data evaluated for Kitimat. It is expected that 1-hour SO2 levels of 35 ppb and lower will pose little or no additional health risk to even sensitive individuals.

The SO2 alert system was started as a pilot project in Kitimat in response to local concerns about increasing SO2 emissions and recommendations from the Environmental Appeal Board regarding the Rio Tinto permit amendment.

Beginning January 1, 2018, alerts have been generated whenever 1-hour SO­2 concentrations reach 36 ppb or higher at any of three community monitoring sites in Kitimat (Whitesail, Riverlodge or Haisla Village). Alerts are posted at http://www.env.gov.bc.ca/epd/bcairquality/aqo/csv/alerts/so2.html. Members of the public can be directly e-mailed these alerts by signing up for the provincial Air Quality Subscription Service at https://aqss.nrs.gov.bc.ca/subscription.html (select "Kitimat"). 

Each alert message includes information on 1-hour SO2 concentrations over the past hour and associated health guidance, focusing on advice for those most sensitive to SO2 exposure. Table 1 summarizes the threshold values used and the updated health messages. 

Table 1. Summary of updated health messages for specific SO2 alert levels.

SO2 Levels

SO2 Alert Health Messages

0-35 ppb

None (no alert issued)

36-184 ppb

Persons with chronic respiratory conditions such as asthma should consider reducing or rescheduling strenuous outdoor activities if experiencing symptoms. No effects are expected for the general population.

185+ ppb

Persons with chronic respiratory conditions such as asthma should reduce or reschedule strenuous activities outdoors. Others, especially children and the elderly, should also consider avoiding outdoor physical exertion.

The Air Quality Health Index (AQHI) is the most widely used tool in Canada to communicate with the public about air pollution. It is a scale from 1 to 10+ that reflects the level of health risk associated with air quality. It is based on the observed relationship between daily mortality and concentrations of three pollutants averaged over three hours: nitrogen dioxide (NO2), ozone (O3) and fine particulate matter (PM2.5). This is referred to as the “three-pollutant AQHI”. For additional information on the three-pollutant AQHI, see: https://www2.gov.bc.ca/gov/content/environment/air-land-water/air/air-quality/aqhi

The AQHI-Plus provides a way to include pollutants such as SO2 and PM2.5 that may cause short-term health impacts not otherwise captured by the AQHI. The ministry is testing the AQHI-Plus for PM2.5 at all AQHI sites in the province, to better reflect the variable conditions during the wildfire season and other smoky periods of the year. The ministry is also testing the AQHI-Plus for SO2 in Kitimat to alert the public to those levels of SO2 that may affect the general population as well as persons with chronic respiratory conditions like asthma.

Under this approach, the AQHI-Plus for SO2 is determined each hour by comparing the highest SO2 concentrations among the three community monitoring sites in Kitimat to various pre-defined thresholds summarized in Table 2. The higher of the three-pollutant AQHI, the AQHI-Plus for PM2.5 and the AQHI-Plus for SO2 is reported as the “AQHI” value. This value is available at:  http://www.env.gov.bc.ca/epd/bcairquality/data/aqhi.html?id=AQHI-Kitimat.

When SO2 levels warrant additional guidance beyond the standard AQHI messages, a special note is attached to the AQHI value. For example, a reported AQHI value of “2*” means that the health risk posed by air quality is low for the general population, but that due to elevated SO2 concentrations, persons with chronic respiratory conditions such as asthma should take additional care if experiencing symptoms. An AQHI value of “7*” means that the AQHI has been adjusted upward to reflect an increased health risk for both sensitive populations and the general population due to elevated SO2 concentrations.    

Table 2. Approach for calculating AQHI-Plus for SO2, along with updated SO2 alert messages.

AQHI (based on PM2.5, NO2 and O­3)

1-hour SO2

(ppb)

AQHI-Plus (based on 1-hour SO2)

Reported AQHI Value

Special Note

1-10+

0-35

N/A

AQHI

None

1-3

36-184

N/A

AQHI

*

4-10+

36-184

N/A

AQHI

None

1-6

 ≥185

7

7

**

7-10+

≥185

7

AQHI

None

The special notes referred to in Table 4 are as follows: 

 *Elevated levels of sulphur dioxide have been reported. Persons with chronic respiratory conditions such as asthma should consider reducing or rescheduling strenuous outdoor activities if experiencing symptoms. No effects are expected for the general population. For more information, visit B.C.’s Ministry of Environment and Climate Change Strategy.

 ** Elevated levels of sulphur dioxide have been reported and the AQHI has been adjusted to reflect an increased health risk for both sensitive populations and the general population. Consider reducing or rescheduling strenuous outdoor activities if experiencing symptoms. For more information, visit B.C.’s Ministry of Environment and Climate Change Strategy.

Kitimat AQHI values are updated hourly and made available by the ministry at http://www.env.gov.bc.ca/epd/bcairquality/data/aqhi.html?id=AQHI-Kitimat. SO2 is included in these calculations. Pending final system upgrades, Kitimat AQHI values will also be reported by Environment and Climate Change Canada at: https://weather.gc.ca/airquality/pages/provincial_summary/bc_e.html. Until then, only forecast AQHI values will be available for Kitimat.

The SO2 alert system is based on the highest SO2­ concentrations measured at the Kitimat Whitesail, Riverlodge and Haisla Village monitoring sites. The AQHI reflects a more holistic measure of air quality and what it means for an individual’s health. Under the Kitimat pilot, the publicly reported AQHI value is the higher of (1) the three-pollutant AQHI determined for the Whitesail station, (2) the AQHI-Plus based on 1-hour PM2.5 levels at the Whitesail station, and (3) the AQHI-Plus based on the highest 1-hour SO2 concentrations measured at the Kitimat Whitesail, Riverlodge and Haisla Village stations.

Some updates have been made to the SO2 alert system, as summarized in Table 3, to ensure that its health messages are both consistent with those associated with the AQHI and appropriate based on the health evidence. These changes were reviewed by health experts at the BC Centre for Disease Control. The special notes associated with the AQHI-Plus for SO2 are applied when additional guidance beyond the standard AQHI message is warranted to reflect elevated SO2 concentrations.

As shown in Figure 1, each SO2 alert describes:

  • the time, location and 1-hour SO2 concentration that was reached over the past hour,
  • health advice appropriate for the SO2 concentration, to help sensitive individuals, including persons with asthma, to adjust their activities to protect their health,
  • the time that the next alert may be issued if concentrations remain elevated, and
  • a web link to additional information on the website of the BC Ministry of Environment & Climate Change Strategy.

Figure 1. Example of SO2 alert

Figure 1. Example of SO2 alert

 

Where is SO2 monitored in Kitimat?

SO2 is monitored immediately north of the smelter, at the Haul Rd site, and at three community sites in Whitesail, Riverlodge and Kitamaat Village.

SO2 levels in Kitimat are generally low, with the highest concentrations observed at the Haul Rd site located in an industrial area near the smelter. The Haul Rd site is considered an industrial fence line monitoring site, and not generally reflective of community air quality. In 2018, SO2 concentrations at the community monitoring sites averaged below 1 ppb and 1-hour SO2 concentrations did not exceed 36 ppb. Data from 2019 have yet to be fully validated, but based on preliminary information, the 1-hour SO2 levels of 36 ppb was reached or exceeded on 7 different days at the three community monitoring sites to the end of September 2019. The highest value of 73 ppb was recorded at the Haisla Village monitoring site on August 19, 2019.   

On a seasonal basis, the highest SO2 levels tend to occur in the spring through fall periods, when winds are mostly from the south. In general, SO2 levels can change quickly with the weather conditions.

The SO2 alert system is a public information tool only.  Emissions from the RT smelter are regulated under a permit issued by the Ministry of Environment & Climate Change Strategy. Criteria for triggering a reduction in emissions and/or other mitigation are described in the Environmental Effects Monitoring (EEM) program plan that is a requirement of the permit amendment. 

 

What are the Canadian Ambient Air Quality Standards for SO2?

Canadian Ambient Air Quality Standards (CAAQS) for SO2 were endorsed by the Canadian Council of Ministers of the Environment in 2016. These include standards based on one-hour and annually-averaged data for 2020 and 2025 (see Table 4). The 1-hour CAAQS is primarily intended to protect human health, whereas the annual CAAQS is intended to protect ecosystems.

Table 4. Summary of 2020 and 2025 CAAQS for SO2.
Averaging Period 2020 CAAQS 2025 CAAQS Statistical Form
1-hour 70 ppb 65 ppb Annual 99th percentile of daily 1-hour maximum; averaged over three years
Annual 5 ppb 4 ppb Annual average over calendar year of all 1-hour values

When SO2 concentrations are elevated, consider reducing or rescheduling activities outdoors, remaining indoors, and reducing indoor sources of SO2 including tobacco smoke, wooden matches, and unvented gas stoves. Persons with asthma should follow a management plan developed with their health care provider. If you are having trouble in breathing, chest pain or discomfort, or a severe cough, contact your health care provider, walk-in clinic, or emergency department. See HealthLinkBC for summary health recommendations and Heath Canada’s Human Health Risk Assessment for Sulphur Dioxide for more detailed information.

 

How long will the Kitimat pilot run?             

The AQHI-Plus for SO2 will be piloted in Kitimat through 2020 and then re-assessed for further application. During this period, the Ministry will continue to operate the SO2 alert system, and a decision on the next steps will follow the project review.

 

For additional information, please see: