AUGUSTA — A cloud cover that loomed over Maine for stretches at a time this summer helped keep ozone levels low for the second summer running, environmental officials say.

But ozone, which causes irritation of the lungs, remained a problem in some areas, notably Kennebunkport, where President Bush has a summer home.

An ozone monitoring station in that southern Maine coastal town showed the highest single reading and the highest number of violations of government standards of any of Maine’s seven stations this summer.

“Maine’s been euphemistically referred to as the geographical exhaust pipe of the country,” said Andy Johnson of the Department of Environmental Protection.

He described as “the classic example of a high ozone day” one in which a high pressure system forces winds from the southwest, which “pumps up all the air that’s been sitting in the northeast corridor.”

The result is the movement of ozone-creating compounds into Maine from the New York City area and the Midwest.