Early exposure to airborne pollutants could increase the risk of infection in newborn babies.
New parents already have plenty of potential hazards to worry about, from flame-retardants in footed pajamas to hormone-disruptors in breast milk. A new study now adds air to the list of environmental concerns.
Chronic exposure to air pollution, the study found, increases a baby's chance of developing bronchiolitis -- a lung infection that is the most common cause of hospitalizations in the first year of life.
The findings suggest that parents and pediatricians need to work together to reduce infants' exposure to traffic and other sources of dirty air, said study author Catherine Karr, an academic pediatrician at the University of Washington, Seattle.
That's true no matter where families live, she added. Her study, published in the American Journal of Respiratory and Critical Care Medicine, took place in the Pacific Northwest, which is known for its clean air and green living.
"This study adds to our understanding about infants and children as being susceptible to health risks from low-level, day-in, day-out exposure to contaminants," Karr said, "even in regions where we might not think it's a bad air pollution setting."
Bronchiolitis is an inflammation of small passages of the lungs. The condition peaks every fall and winter, and is most common in babies between 3 and 6 months old.
A virus called RSV is the most frequent cause of the infection, but the flu or other viruses can also trigger it.
While adults and most young children who catch RSV usually come down with cold symptoms for about a week, babies can develop complications from bronchiolitis. These include difficulty breathing, severe coughing and blue skin.
Thirteen percent of babies who get bronchiolitis end up going to the doctor or to the hospital for treatment, Karr said. Kids who come down with bronchiolitis in the first year are also at higher risk of developing asthma later, though it's not yet known whether one causes the other or if they're related in another way.
Air pollution has also been linked with asthma and heart problems in older children and adults.
In previous work, Karr had found a connection between air pollution and bronchiolitis in Los Angeles, which has some of the country's worst air quality. To follow up, she wondered how babies might be faring in supposedly "greener" places.
In and around Vancouver and Victoria, British Columbia, she and colleagues compiled information about nearly 12,000 babies that had been hospitalized for bronchiolitis before their first birthdays. For each of those babies, the researchers identified about 10 more infants in the area who were born on the same day but made it to the sick baby's age without developing the illness.
Using maps of traffic density, industry and other pollution generators near where the infants lived, Karr and colleagues found that babies who had been exposed to the most air pollution, day after day, were between 5 and 10 percent more likely to be hospitalized for bronchiolitis than were babies exposed to the fewest air pollutants
The biggest contributors were traffic, wood smoke and industrial sources. Exposure levels were all within recommended guidelines.
Pollutants can assault the immune system, cause inflammation and disturb a barrier of cells in the lungs that normally keep out respiratory viruses, Karr said. But there might be other explanations for her findings, too.
At the Columbia Center for Children's Environmental Health in New York, researchers have been putting air-monitoring backpacks on pregnant women and following their babies through adolescence. The results of that study suggest that urban air pollution is affecting the expression of genes in fetuses, setting kids up to develop asthma later in life.
"There is growing evidence that prenatal and postnatal exposure to air pollution may be playing causal roles in the development of respiratory illnesses and asthma," said Frederica Perera, Director of the Columbia Center. "This study and others are underscoring the importance of preventing environmental risk to children, beginning as early as in the womb."
There are some things parents can do to protect their babies, Karr said. As much as possible, she recommends choosing homes, schools and daycares that aren't on major roads with lots of traffic.
Parents also need to make sure that fireplaces are working properly and shouldlimit wood fires to special or necessary occasions.
"Doctors should educate their patients about thinking about sources of air pollution in their lives and their children's lives," she said, "and reducing those that they have control over."