Smoking is a normal part of life for some adults living in California. But this doesn't mean that it should also be part of their children's lives.

A researcher found that a large number of children are exposed to secondhand smoke from both their surroundings and their family.

When a non-smoker is exposed and breaths in smoke, that's when secondhand smoking or passive smoking happens.

According to Sue Holtby, lead author of the study and senior researcher at the Public Health Institute, which works alongside the University of California, Los Angeles, Center for Health Policy Research, more than 2.5 million children under the age of 12 victims to passive smoke.

Out of this number, authors of the study estimated that over 561,000 children are directly exposed to secondhand smoke in the home, while the other 1.9 million are at risk because they live in a home where a family member is a smoker.

In addition to the number who are exposed and are at risk, the authors also found that 12.6 percent of African American children live in homes where smoking is permitted. That percentage is three times higher than any other racial or ethnic group.

For both African American and white children - 13.4 percent and 12.2 percent respectively - the likelihood of having an adult or a teen smoker in their homes is significantly higher.

Research also suggests that income level also has a relationship as to whether children are exposed to secondhand smoke or not. Those living in households at or above 300% of the federal poverty level are far less likely to be subject to passive smoke than children from lower-income levels.

As for location, researchers found that in rural areas, such as California's Northern or Sierra region, the percentage of smokers at home were higher than those in urban areas, such as the Central Coast.

The authors noted that with their findings, targeted messages concerning the negative health effects of secondhand smoke can be done.

Secondhand smoke has a number of effects on children: asthma, bronchitis or pneumonia, and increased susceptibility to middle ear infection.

Terry Martin, of About.com, reported that children face a higher risk of negative effects from secondhand smoke than adults. This is because adults breathe in and out around 14 to 18 times a minute; in contrast, newborns can breathe 60 times a minute, while children at the age of 5 can breathe around 20 to 60 times a minute.