If you're looking for some fresh air you just might want to stay in the city. Why? There's a good chance it could be cleaner than downwind of Toronto, suggests York meteorologist David Sills.

    Sills, a York doctoral student, is studying the lake breeze effect to determine what role it might play in moving air pollutants -- such as ozone -- in the lower atmosphere.

    The link between ozone and lake breezes is relatively simple, explains Sills. "At night a land breeze moves polluted air from the cooler land over the warmer water. The next day the chemical soup is cooked by the sun over the lake, creating smog with high ozone levels. By afternoon, smog is pushed from the lake, a high pressure area, back over the land, a low pressure area," he says. The lake breeze often takes the pollution downwind of Toronto. The result is high ozone levels, or spikes, deep in the countryside.

    Sills, and his thesis supervisor, Earth and Atmospheric Science professor Peter Taylor, are part of a larger group who have studied the problem since 1992. Initially, their focus was on late-day ozone level increases up to 40 km inland in Hastings County that couldn't be explained by air chemistry reactions alone. York researchers now believe the lake breeze plays an important role in transporting polluted air from over the lake far into the countryside.

    The result of the lake breeze effect can be sudden ozone level increases that exceed recommended health levels (no more than 50 parts per billion). Ozone at high atmospheric levels is good because it traps harmful UV radiation, but at lower levels (known as ground-level ozone) it can cause respiratory problems and burn agricultural crops.

    Says Sills, "What we know now is, given the right meterological conditions, the countryside can be more polluted than downtown Toronto."