A U.S. study suggests that women who breathe polluted air, while pregnant, could lead to health problems in children, including high blood pressure.
Researchers for the study focused on pollution that was created by fine particulate matter, or PM 2.5. It is a mixture of solid particles and droplets of liquid smaller than 2.5 micrometers around. It is found in traffic dust and includes dirt, dust, smoke, and soot.
One-thousand-two-hundred-ninety-three pairs of mothers and children were part of the study. The children’s blood pressure was assessed between the ages of 3 and 9. They were divided into three groups by exposure to pollution PM 2.5 while in the womb. Those in the highest-exposure group were 61 percent more likely to have high blood pressure than the children in the lowest-exposure group.
Co-author, Noel Mueller, of Johns Hopkins Bloomberg School of Public Health in Baltimore stated:
We believe that when pregnant women breathe air with high levels of fine particulate matter, it causes an inflammatory response that alters genetic expression and fetal growth and development, on the pathway to high blood pressure in childhood.
The message to pregnant women is to avoid high-pollution areas while pregnant. This is particularly important during intense physical activity, which is important to maintain during pregnancy, according to Mueller.
Hypertension is a major risk factor for heart disease. It contributes to 7.5 million deaths annually worldwide.
Previous research linked air pollution exposure in the womb to an increased risk of birth defects. Some possible birth defects include hypospadias, which are abdominal malformations and an abnormality in boys that occurs when the urethra does not develop properly. It causes the opening of the penis to form on the shaft or scrotum instead of the tip of the penis.
In the current study, children exposed to PM 2.5 levels of a minimum of 13 micrograms per cubic meter of air (ug/m3), during the final trimester, have an increased risk of high blood pressure. This is slightly higher than the limit set by the Environmental Protection Agency (EPA), which is 12 ug/m3.
The group with the highest exposure to air pollution while in the womb were exposed to PM 2.5 levels of 11.80 to 28.81 ug/m3.
The children in the group with the lowest exposure in the third trimester experienced PM 2.5 levels of 3.79 to 9.57 ug/m3, which is within the range permitted by the EPA.
Each 5 ug/m3 increase in exposure to pollution PM 2.5 in the womb was associated with a 3.39 percentile increase in systolic blood pressure. (This is the top number.) This number represents the pressure blood exerts against the artery walls when the heart beats. If the systolic blood pressure was in the top 10 percent for children the same age, they were identified with hypertension.
The study was not a controlled experiment designed to prove exposure to air pollution in the womb could directly cause high blood pressure. There is also data missing on how much time these mothers spent breathing polluted air outside or at work.
Nevertheless, the study provides fresh evidence that links air pollution to hypertension in children. The connection appeared for children of varying birth weights. Previous research found the same connection in babies who were overweight.
If early exposure to pollution increases the risk of hypertension, it is important to reduce early-life exposure to pollution through regulation and local, and regional efforts to help protect children from developing higher blood pressure in childhood. This could also improve long-term cardiovascular health, according to Diane Gold, author of the accompanying editorial and a professor at the Harvard T.H. Chan School of Public Health in Boston.
By Jeanette Smith
Reuters: Air pollution during pregnancy tied to high blood pressure in kids
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