Air pollution during pregnancy and cord blood immune system biomarkers (Lay summary)

Ashley-Martin J, Lavigne E, Arbuckle TE, Johnson M, Hystad P, Crouse DL, Marshall JS, Dodds L. Journal of Occupational and Environmental Medicine. 2016 Oct;58(10):979-986. doi:  [10.1097/JOM.0000000000000841]

Exposure to elevated levels of outdoor air pollutants such as fine particulate matter (PM2.5) or nitrogen dioxide (NO2) may be associated with a wide variety of harmful health effects, especially in the very young and the elderly. These effects range from minor breathing difficulties, coughing, and wheezing to the exacerbation of respiratory diseases such as asthma, bronchitis, and emphysema.

Fine particulate matter (PM2.5) is primarily formed from chemical reactions in the atmosphere and through fuel combustion (e.g., motor vehicles, power generation, industrial facilities, residential fire places, wood stoves and agricultural burning).  NO2 is also produced from combustion, with most of it coming from the transportation sectors.

Little is known about the possible effects of exposure to air pollution during pregnancy on the newborn’s immune system.  We do know that some studies have found links between exposure to specific air pollutants and both low birthweight and premature birth.

The current study was designed to explore potential associations between prenatal exposure to NO2 and PM2.5 and the immune system of newborn infants.  Three immune system biomarkers were measured in the umbilical cord blood of MIREC singleton infants born at term: immunoglobulin E (or IgE, an antibody) and interleukin-33 (IL-33) and thymic stromal lymphopoietin (TSLP).  IL-33 and TSLP are small proteins which interact with cells in the body and influence immune system responses to environmental exposures, such as air pollutants.  Researchers estimated prenatal exposure to air pollution using the first three letters of the postal code for residences of MIREC women during the 1st and 3rd trimesters and air pollution data from across Canada.  Data were available for 1253 mothers and their infants.

The study found significant associations between higher maternal NO2 exposure and elevated cord blood concentrations of both IL-33 and TSLP among girls but not boys.  These findings suggest that exposure to elevated levels of the air pollutant NO2 during pregnancy may affect development of the newborn infant’s immune system as measured by these two markers.

Further research is needed to see whether other studies will also observe this association.  This work was led by researchers at Dalhousie University.