* WHAT. The South Coast AQMD has issued an air quality alert due to harmful levels of fine particle pollution. * WHERE. Smoke from Independence Day Fireworks in most of Los Angeles and Orange Counties and the Inland Empire, and wildfire smoke in Santa Clarita and the San Gabriel and San Bernardino Mountains. Levels of particle pollution can vary by time and location depending on emissions and local weather conditions. * WHEN. Smoke from Fireworks from 5 PM July 4th through 11:59 PM July 5th, and wildfire smoke from midnight Thursday to 10 PM Friday. * IMPACTS. Particle pollution can get deep into the lungs and cause serious health problems such as heart attacks, bronchitis, asthma attacks, and difficulty breathing. Everyone can be affected, but sensitive groups such as people with lung or heart disease, older adults, people who are pregnant, children, and those who spend a lot of time outdoors are at greater risk.