| HOME | HELP | CONTACT US | SUBSCRIPTIONS | CME | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
||||||||
|
||||||||||
AAP Grand Rounds 18:67-68 (2007)
© 2007 American Academy of Pediatrics
Previously published studies have found associations between residence in high air pollution areas within the Los Angeles area and decreased lung development.1–3 Investigators from the University of Southern California, Los Angeles, the University of California, Berkeley, and their collaborators from Petaluma, California and Barcelona, Spain, sought to assess whether proximity to major roadways adversely affects lung-function growth in children between ages 10 and 18, a period of rapid growth and rapid lung development.
Study participants were part of the Children’s Health Study that recruited two cohorts of fourth-grade children from 12 southern California communities with a wide range in regional air quality. Children in both cohorts were prospectively followed up for eight years. Children had yearly lung-function measurements. A yearly questionnaire was used to update information on asthma status, personal smoking, and exposure to environmental tobacco smoke.
The exposure of every study participant to traffic-related pollutants was characterized by two types of measures — proximity of the child’s residence to the nearest freeway or to the nearest major nonfreeway road, and model-based estimates of traffic-related air pollution at the residence, derived from dispersion models that incorporated distance to roadways, vehicle counts, vehicle emission rates, and meteorological conditions. Regional air pollution was continuously monitored at one central site location within each study community over the course of the investigation.
A total of 3,677 children with a mean age of 10 years (SD=0.44) were enrolled (cohort 1, n=1,718; cohort 2, n=1,959). There were equal proportions of male and female participants. Most children were of nonHispanic white or Hispanic ethnic origin; 440 (12%) children lived within 500 m of a freeway.
An average of 6.2 pulmonary function tests were done per child. Eight-year growth in forced expiratory volume (FEV1), and maximum midexpiratory flow rate (MMEF) averaged 1316 mL and 1402 mL/s, respectively, in girls, and 2406 mL and 2476 mL/s, respectively, in boys. Reduced lung-function growth was independently associated with both freeway distance and regional air pollution. Children living within 500 m of a freeway (–81 mL; 95% CI, –143 had deficits in eight-year growth of FEV1 to –18) and MMEF (–127 mL/s; 95% CI, –243 to –11) compared with those living at least 1500 m from a freeway. Even children in low air pollution regions had negative effects when living <500 m from freeways. For children living within 500 m of freeways, the average deficits in attained mean-percent-predicted lung function at age 18, relative to children living >1500 m from freeways, were 97.0% for FEV1 (P=.013; 95% CI, 94.6–99.4) and 93.4% for MMEF (P=.006; 95% CI, 89.1–97.7).
Nonstatistically significant decreases also were found among children living at intermediate ranges from a freeway suggesting a dose response relationship. Such effects were not found for other large roads. There were significant independent negative effects of individual combustion-related pollutants such as nitrogen dioxide, acid vapor, particulate matter less than 2.5 and 10 microns, and elemental carbon (soot), but not with concentrations of ozone. The authors conclude that local exposure to freeway traffic emissions has adverse effects on development of lung function of children, independent of regional air quality and perhaps resulting in decreased attained lung function in adulthood.
|
Commentary by
|
|---|
| Bloomberg School of Public Health, Baltimore, MD |
This publication is one in a long series from this group studying environmental effects of air quality. As the authors point out, it has some limitations, primarily related to study design. Prospective cohort studies attempt to look at all reasonable confounding variables for other explanations for the effects noted, but it is always possible that other factors not measured may explain or contribute to the observed outcomes. Study participants, particularly in a multi-year study such as this one, will drop out or be lost to follow-up. Gauderman’s study experienced an 11% attrition rate per year.
Another minor issue with the study is that only population means were reported, and it would have been useful to know information about individuals. For example, how many children in the various freeway distance groups had pulmonary function testing below a level likely to cause symptoms in everyday activity?
The absence of this information does not lessen the warning that impaired lung growth may have ramifications for the overall health of these children in future decades, even if they are able to lessen their exposure to environmental pollutants subsequently, because lung growth is essentially completed by age 18.
This study has important policy implications. A 2004 policy statement by the AAP identified numerous adverse health consequences from traffic-related pollution.4 The AAP has recognized that air pollution exacerbates preexisting lung disease in children, and many clinicians are well aware of "ozone alert days;" "orange alerts," during which children with asthma and other respiratory diseases are at risk; and "red alerts," when everyone may be exposed to unhealthy levels of pollutants.
The advice given is to avoid heavy and prolonged exertion especially during afternoons on such days. In terms of freeway-related pollution, the AAP recommended that schools and child-care facilities be located away from freeways and other major air pollution sources.4
However, in addition to generalized pollution, many children live in areas that are air pollution "hot spots" due to residential proximity to freeway traffic. Recognition of this hazard highlights the need for previously recommended policy steps, such as development of lower emissions, more efficient alternatives to current diesel and gasoline engines, and more stringent air pollution standards.4 In addition, it needs to be recognized that, by design, the federal air pollution monitoring system measures regional averages and does not collect measurements in high pollution areas. Approaches need to be developed to assure that all children, including those living in close proximity to freeways, are protected under federal air pollution standards.
| Editors’ Note |
|---|
| References |
|---|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | CONTACT US | SUBSCRIPTIONS | CME | ARCHIVE | SEARCH | TABLE OF CONTENTS |
