Dr. Hessel cautions, however that the relationship between air quality and health can be difficult to determine, because common symptoms caused by poor air quality could be triggered by many factors. More studies are needed to obtain a better understanding of air quality in Canadian schools, and its relationship to health, he says. Meanwhile, some parents and school boards are taking action.

One Alberta mother is home schooling her two sons, who have allergies and asthma, after identifying allergy triggers at their schools.

Edmonton's Capital Health Authority is running a pilot project with two school boards in the County of Strathcona to develop an environmental auditing system.

"But can the quality of air in schools be improved?" "Absolutely, and in many cases without a tremendous increase in costs," according to Holden, a mother of four and a long-time advocate for healthy schools in Halton, Ontario.