Traffic Pollution May Cause Long-Term Lung Damage to Children
-- by Alexia Severson
Children who are exposed to traffic-related air pollution during infancy, particularly those with allergies, could suffer diminished lung function later in life, according to a recent study published in the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.
While earlier studies have shown that long-term exposure to ambient air pollution is associated with reduced lung function in children, the role of timing of exposure, as well as the possible effects of this long-term exposure, remained unknown. But in this prospective birth cohort study, researchers found that early-life exposure to traffic-related air pollution could have long-term respiratory consequences in susceptible children up to 8 years of age, with stronger effects indicated in boys, children with asthma, and children sensitized to allergens.
The Expert Take
In order to assess the effects of long-term exposure to air pollution on lung function in school-age children, Göran Pershagen, professor at the Karolinska Institute of Environmental Medicine in Stockholm, Sweden, and his colleagues followed more than 1,900 children from birth through age eight with repeated questionnaires, spirometry, and immunoglobulin E measurements.
Outdoor concentrations of particulate matter from road traffic were estimated for residential, daycare, and school addresses using dispersion modeling, which is a mathematical simulation of how air pollutants disperse in the atmosphere.
Researchers associated a 5th to 95th percentile difference in time-weighted exposure to outdoor concentrations of particulate matter from road traffic during the first year of life with a reduced forced expiratory volume in one second at age eight. This negative association was particularly pronounced in boys and children with allergies or asthma. After the first year of life, however, exposure to traffic-related air pollution had less of an impact on future lung function in children.
"These results add to a large body of evidence demonstrating the detrimental effects of air pollution on human health," Pershagen said.
Keeping your infant away from all traffic pollution is nearly impossible, but there are a few things you can do to minimize their exposure to harmful environmental particles.
The March of Dimes Foundation offers these tips for keeping your child healthy:
- When local health agencies issue air pollution or smog alerts, keep your child indoors. If you must take your baby out on these days, do so early in the morning or after sunset.
- If you know you live close to a source of air pollution, or if your baby has a heart or lung problem (including asthma), ask your child’s healthcare provider how to best protect your child from air pollution.
- Buy efficient cars and trucks that pollute as little as possible. The Environmental Protection Agency has a vehicle emissions guide.
- Use compact, energy-efficient fluorescent light bulbs. When handling the bulbs, try not to break them because they contain mercury.
- Properly dispose of paints, pesticides, and solvents. (Examples of solvents are turpentine, paint thinners, and grease removers.) Your local health department or environmental agency can tell you how to do this. Store these products in airtight containers.
- Avoid using paint sprayers.
- Keep air conditioning units, heaters, furnaces, wood stoves, and fireplaces in good working order.
- If the air inside your home is stagnant and doesn't get replaced very often, the indoor pollution that results could worsen symptoms of allergies, asthma, or other chronic lung problems.
Source and Method
From 1994 to 1996, 4,089 newborn infants were recruited to the prospective cohort study from four municipalities in Stockholm, Sweden. The response rates were from 96 percent to 84 percent, for the one- and eight-year questionnaires. In addition, 2,630 children (64 percent of the original cohort) attended a clinical examination at age eight, including maximum expiratory flow volume tests and blood sampling. Moving out of the study area and unwillingness to participate were the main reasons for dropout from the clinical follow-up.
Time-weighted average outdoor levels for the different time windows were calculated using emission inventories and a Gaussian air dispersion model. Short-term exposure was estimated using daily air quality measurements and meteorological data from urban background and rural monitoring stations.
This study had a few limitations. Calculations of particulate matter concentrations were only performed for the year 2004 and were extended into to the other years of follow-up, and some miscalculation of individual exposure levels was likely.
A number of studies have shown the negative effects of long-term exposure to ambient air pollution on children’s respiratory health. However, little research has looked at lung function and traffic air pollution in this particular context, and many of the previous studies exhibit inconsistent or imprecise results.
A children’s health study conducted in California showed associations between community-average pollutant concentrations and diminished lung function development in children aged 10 to 18 years old. The observed effect remained statistically significant in the subgroup of non-asthmatics, but the asthmatic children were too few for precise risk estimation.
Similarly, a birth cohort study conducted in Oslo, Norway indicated stronger air pollution effects in asthmatic children compared with nonasthmatics.