* WHAT. The South Coast AQMD has updated an air quality alert due to harmful levels of ozone pollution. * WHERE. In Metropolitan Los Angeles, the San Fernando Valley, Santa Clarita, and the San Gabriel Mountains. Levels of ozone pollution can vary by time and location depending on emissions and air pollution transport. * WHEN. Until Thursday at 800 PM PDT. The highest ozone levels typically occur in the afternoon and early-evening hours. * IMPACTS. Ozone air pollution can cause serious health problems, including trouble breathing, asthma attacks, and lung damage. Everyone can be affected, but sensitive groups such as people with lung disease, older adults, people who are pregnant, children, and those who spend a lot of time outdoors are at greater risk. * ADDITIONAL DETAILS. To help keep indoor air clean when air quality is poor: * Keep windows and doors closed * Run your air conditioner and/or an air purifier * Do not use whole house fans or swamp coolers that bring in outside air if you have other methods to stay cool * Avoid other sources of pollution such as fireplaces, candles, incense, and grilling To help minimize outdoor ozone air pollution levels: * Limit the use of gasoline powered lawn and garden equipment until evening hours * Try to delay trips to the gas station and the use of household chemicals until the evening