Summer 2002 smog levels exceed critical threshold three days in four
Levels of potentially harmful ground-level ozone exceeded a critical threshold somewhere in Europe on more than three days out of four this summer, according to preliminary information compiled by the European Environment Agency.
Ozone, the main component of summer smog, can cause serious health problems in humans and damage to ecosystems, agricultural crops and materials. It forms when certain air pollutants emitted by industry and transport react with sunlight. Ozone levels tend to be highest during warm, sunny weather, and are generally higher in southern Europe than in the north.