As roads in urban areas get busier and more crowded, parents should be aware of the health implications of living in high traffic areas on their kids.

Fumes coming from cars and trucks are already known to be harmful but a new report from the U.S. Centers for Disease Control and Prevention (CDC) suggests that vehicle exhaust is particularly harmful to children.

The report, which is based on a review of seven earlier studies that involved more than 8,000 children, says that young kids exposed to high levels of vehicle emission apparently have increased risks of childhood leukemia, with researchers noting that kids who are diagnosed with the disease more likely live near busy roads where they are exposed to high levels of harmful vehicle exhaust.

The study, published in the American Journal of Preventive Medicine sought to find a link between residential traffic exposure and childhood cancer and found that leukemia, the most prevalent type of cancer among children and teens, is associated with residential traffic exposure. "Current evidence suggests that childhood leukemia is associated with residential traffic exposure during the postnatal period, but not during the prenatal period," the researchers wrote.

Lead study author and CDC health scientist Vickie Boothe, however, said that although they found an association between leukemia and living near busy roads, their study does not prove a cause and effect relationship. "While the study found a link, it does not prove that living near a busy road causes leukemia," Boothe said.

Boothe and study co-author Tegan Boehmer, an epidemiologist at CDC, said that more research is required to determine a cause and effect relationship albeit the researchers said that their findings suggest a need to inform the public of the risks of living in busy roads. "As many people reside near busy roads, especially in urban areas, precautionary public health messages and interventions designed to reduce population exposure to traffic might be warranted," they wrote.

The prevalence of childhood cancer in the U.S. has been on the rise since 1975. Leukemia, the cancer of white blood cells, is the most common type of the disease comprising about 33 percent of cancer cases in children 14-years-old and younger.