ALBANY-The state Department of Environmental Conservation often issues air-quality alerts during the summer. High temperatures may lead to the formation of ground-level ozone, a major component of smog. Automobile exhaust and out-of-state emission sources are the primary causes of ground-level ozone and are the most serious air pollution problems in the northeast. This surface pollutant should not be confused with the protective layer of ozone in the upper atmosphere. People should consider limiting strenuous outdoor physical activity when ozone levels are the highest, generally afternoon to early evening. Ozone levels generally decrease at night. The state's toll-free Air Quality Hotline (1-800-535-1345) gives information on air quality and current alerts. Information is also available at www.dec.state.ny.us and www.health.state.ny.us.