Greetings from the National Library of Medicine and MedlinePlus.gov

I’m Rob Logan, PhD. Senior Staff, US. National Library of Medicine substituting this week for Donald Lindberg, M.D, the Director of the U.S. National Library of Medicine.

Here is what’s new in MedlinePlus this week.

A study recently published in the online version of The Lancet reports that children who live near a highway experience lung impairments, which could result in life long health problems.  

The report is the first to note a statistical association between reduced lung capacity in children and air pollution from nearby motorway traffic. The authors note that previous research from Europe suggested that declining lung function was associated with a resident’s exposure to traffic exhaust. However, this is one of the first epidemiological studies of the impact of traffic exhaust on the health of children, as they age from 8 through 18.

The study of more than 3,600 Southern California children noted that significant lung impairment occurred when kids lived within 500 meters (or about a quarter of a mile) from a motorway. In addition, a child’s proximity to traffic pollution seemed to be associated with reduced lung capacity regardless of the air quality in the neighborhood where he or she lived. 

The study found that by age 18, children who lived near a motorway had a three percent deficit in the amount of air they could exhale compared to a control group of kids who lived 1,500 meters from the same highway. These results occurred regardless of the air quality within the neighborhood where either group lived. The study reported no differences between boys and girls.

Moreover, the study’s 11 researchers, primarily based in the Keck School of Medicine at the University of Southern California, found that children, who moved away from a highway during the study - but stayed within the same community - experienced a higher lung capacity.

The worst lung capacity reduction occurred when a child lived both within 500 meters of a highway and in a neighborhood with higher air pollution.

The authors explain that a person’s lung capacity is medically established before adulthood. As a result, a teenager with reduced lung capacity may carry it for the rest of his or her life. Reduced lung capacity is a known risk factor for cardiovascular and respiratory diseases, such as emphysema.  

The study began by selecting volunteer, fourth grade students, averaging age 10, from 12 communities in Southern California, including the Los Angeles metropolitan area in 1993 and 1996. The study’s geographic dispersion (from San Luis Obispo through San Diego County in Southern California) is important since air quality levels vary within these areas. Both San Luis Obispo and San Diego counties, for instance, are outside of the Los Angeles basin where smog has a tendency to hang in the summer months.

In this prospective study, each group or cohort of students (one who lived within 500 meters of a highway and those who lived farther away) were carefully monitored for eight years.

The researchers conducted 22,686 pulmonary-function tests from all participants during the study’s eight year period, and an average of about six tests were done for each child.

Besides interesting findings, the study also demonstrates how researchers weed out confounding influences to posit an association between traffic pollution and lung damage.  For example, besides distance from a highway, the researchers also investigated whether there were a gas stove and pets in each child’s house, if each child experienced in utero exposure to maternal smoking or second hand smoke. The association between distance from a highway and lung impairment was significant even after controlling for these and other variables.

We emphasize that the study reports an association between traffic exhaust, location near a freeway and lung damage in children. The study does not demonstrate that living near a freeway is a direct cause of lung impairment -  nor does it provide a biomedical explanation how reduced lung capacity occurs. To investigate the latter, the authors suggest further research about the biomedical links between diesel emissions and impaired lung function.

In terms of the study’s social implications, the authors note their findings suggest that civic planning and zoning officials should consider whether it is appropriate to build parks and residential housing within a quarter mile of a highway.

Dr. W. James Gauderman, the study’s first author, told the Los Angeles Times he estimates that in some Southern California cities, such as Long Beach, as many as 17 percent of the population lives within a quarter of a mile (or 500 meters) of a highway.

In an accompanying commentary in the Lancet, two European scientists who were not involved in the study, write the findings are important, “because it shows that within communities, some children are at higher risk than others.”

The commentary also explains the study suggests that environmental health risks may be more localized than has been previously appreciated. Environmental health risks are often perceived to occur regionally, or within certain neighborhoods rather than contiguous areas next to highways.
A Health Day news story about the study is currently available in MedlinePlus. To find it just type ‘air pollution’ within the search box on MedlinePlus’ home page, then, click on ‘Air pollution (National Library of Medicine).’ The link is in the ‘Latest News’ section at the top of the page.

The same page also contains links to learn more about the impact of air pollution on your health. It includes a section about air pollution and children. This contains a website designed for kids that explains how air quality is determined, which is provided by the U.S. Environmental Protection Agency.

To learn more about environmental health, we highly recommend you visit ‘Tox Town,’ which has a prominent link on the ‘Air pollution (National Library of Medicine)’ page. Tox Town, which is a National Library of Medicine website, introduces you to toxic chemicals and environmental health risks you might encounter in everyday life, in everyday places.

The gateway pages on Tox Town include a cartoon of a city, town, port, farm and border area. From there, you are automatically linked to information about commonly found environmental health risks within each area. The information provided is derived from highly reliable and carefully screened sources of information, so you can be assured of its accuracy and currency.

We hope you will find Tox Town easy to use and I think you will be surprised how much information about environmental health is at your fingertips.

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It was nice to be with you.

Dr. Lindberg returns in the near future.