What can DNA tell us about the damaging effects of air pollution?

By now, we have heard of at least some of the health effects of air pollution. The severe air pollution in Beijing has been associated with a reduction in life expectancy of up to 16 years, with women and young adults particularly susceptible. A recent article published online in JAMA Pediatrics demonstrates that particulate matter air pollution exposure during pregnancy is associated with shorter telomers at birth. This is a well-designed study that carries great significance because it demonstrates that air pollution may affect individuals from the beginning of life and have long lasting impactful effects on survival.

The term "telomers" requires some explanation. Telomers are DNA sequences that occur at the end of chromosomes. They can initially be thousands of base-pairs in length and consist of repeated motifs of a six DNA base-pair sequence. Each time the cell divides, a portion of the telomer is lost, and so after repeated cell divisions, the length of the telomer shortens. Shorter telomers have been associated with mortality and diseases related to aging. They have also been associated with oxidative stress and inflammatory disease states. Telomers were discovered in 1984 by Elizabeth Blackburn and Carol Greider, who were awarded the 2009 Nobel Prize in Medicine and Physiology for this discovery.

The study itself looked at prenatal exposure to air pollutants, in this case maternal residential PM2.5, which means particulate air pollution of average aerodynamic diameter of 2.5 microns (invisible to the naked eye), in 730 mothers from the Flanders region of Belgium, and found that newborns born to mothers with higher exposures had shorter telomers at birth. What does this mean?

In other studies, telomer length has been associated with shorter life expectancy, and with various disease states including bone marrow failure, acquired aplastic anemia, cancer, liver disease and pulmonary fibrosis. Previous studies have found that telomer length is shorter in adults exposed to particulate air pollution. The fact that this study demonstrates that same finding in neonates born to mothers exposed to particulates suggests that the damage occurs early in life, before birth, and that these neonates may begin life at a serious disadvantage when it comes to their future health.

There are limitations to the study. It was done in a small geographical area, there is no information on the parents' telomer length, and there may be other unknown factors that can affect telomer length. These limitations were mentioned in the article.

It should be noted that telomer length in newborns is inherently very variable, and that there are many factors throughout life that can affect the length of telomers as we age. So just because one may start with a shorter telomer does not mean that they will die early. Someone with a longer telomer length at birth who exposes themselves to a large number of stressors or toxins may in fact "catch-up" and these exposures may impact their longevity as well.

Industrialization and modernization has greatly increased our quality of life, but it has also been associated with many unforeseen consequences, including air pollution, population redistribution, and subsequent climate change. What this paper does demonstrate is that air pollution is a serious problem that can affect our health from the beginning of life. This study suggests that there should be a greater urgency to the mitigation of air pollution, whether through innovation in the development of green technology, or by clean air legislation and regulation.

In addition, we can all do our part to decrease air pollution. Some of this may involve lifestyle changes, such as conserving energy, using energy efficient light bulbs, installing solar roofs, carpooling to decrease the amount of exhaust from automobiles, using electric rather than gas driven lawn care equipment, or combining errands to decrease car usage. These are only a few of the measures we can take to reduce our carbon footprint and limit our exposure to the harmful effects of air pollution, benefiting not just us but future generations to come.