Spatial variability of volatile organic compound concentrations in Sarnia, Ontario, Canada.

As part of a community health study, an air quality investigation was carried out in Sarnia, Ontario, Canada, which is located within a government-designated "Area of Concern". The Sarnia area, also known as Chemical Valley, has been known to have an abundance of air quality problems that are frequently attributed to the large number of chemical companies located in the area, which are among the largest industrial sources of criteria air pollutants in Canada. Ambient volatile organic compounds (VOC) were monitored during a 2-wk period in October 2005 at 37 sites across the city of Sarnia, using 3M organic vapor monitors. The spatial variability was investigated using ranking and mapping techniques to identify spatial patterns of the VOC across the city. The results show a large spatial variability of most of the VOC investigated. Furthermore, most of the VOC were highly correlated, suggesting common sources in Sarnia. The results also indicate that the industrial and chemical facilities strongly influence the concentrations of VOC in Sarnia, with higher outdoor VOC levels found closer to industrial facilities. The measured VOC and those obtained from a long-term government monitoring station were compared. It was determined that the exposure gradients observed during the study period are relatively representative of the long-term pattern. The results of this study will be used for the community health study.