- Pregnant women breathing in polluted air and exposing their babies in utero to high pollution levels may be putting them at increased risk of childhood hypertension.
- Earlier studies have already shown that direct exposure to air pollution is associated with childhood and adult hypertension and is a cause of increased mortality and morbidity worldwide.
- Findings highlight the importance of keeping our environment and air clean and the need for urgent measures to reduce rising pollution levels worldwide.
Unborn babies exposed to increased air pollution, especially during the third trimester of their mother's pregnancy are at an increased risk of developing hypertension in childhood, finds a new study conducted at Johns Hopkins University Bloomberg School of Public Health in Baltimore, Maryland. The findings of the study appear in the American Heart Association's journal Hypertension
"Our 's is one of the first studies to show breathing polluted air during pregnancy may have a direct negative influence on the cardiovascular health of the offspring during childhood," said Noel T. Mueller, Ph.D., M.P.H., senior author of the study and an assistant professor of epidemiology at the Johns Hopkins University Bloomberg School of Public Health in Baltimore, Maryland. " High blood pressure during childhood
often leads to high blood pressure in adulthood and hypertension is the leading cause of Cardiovascular Disease
Details of Study
The study aimed to find an association between exposure to increased pollution levels in utero and risk of childhood hypertension.
‘Keeping our environment and air clean is essential to ensure the health of our children including unborn babies.’
In order to estimate levels of pollution the pregnant woman (and her baby)
were exposed to, in each trimester, the research team used the woman's residential address, as well as data from the nearest U.S. Environmental Protection Agency's (EPA) air quality monitor.
The levels of particulate matter (PM) 2.5
in the highest category in this study (11.8 micrograms per cubic meter or higher) were slightly lesser than the EPA's National Air Quality Standard (12 micrograms per cubic meter).
- The research team examined 1,293 mothers and their children who participated in a large, ongoing Boston Birth Cohort study.
- Blood pressure of the child was measured at each childhood clinic visit from 3- to 9- years old.
Systolic (upper reading) blood pressure was considered increased if it fell within the top 10 percent for children of the same age based on national data. The scientists also adjusted for other factors that could to impact childhood blood pressure, such as maternal smoking and birth weight
Findings of Study
- Babies in the womb who were exposed to higher levels (the top third) of atmospheric fine-particulate pollution during the third trimester were 61 percent more likely to have increased systolic blood pressure in childhood compared to those exposed to the lowest levels (the bottom third).
- Exposure to increased levels of air pollution in the third trimester when weight gain is the most has been shown (in prior studies) to cause low birth weight; however the current study found an association between pollution levels in utero and childhood hypertension regardless of birth weight
- Exposure to fine particulate air pollution before pregnancy was not associated with elevated pressure in her children, thus suggesting the potentially significant impact of in-utero exposure.
"These results reinforce the importance of reducing emissions of PM2.5 in the environment. Not only does exposure increase the risk of illness and death in those directly exposed, but it may also cross the placental barrier in pregnancy and effect fetal growth and increase future risks for high blood pressure," Mueller said.
What Is Fine Particulate Matter and Why is it Important?
Particulate matter refers to all solid and liquid particles suspended in air, many of which are dangerous. This complex mixture consists of both inorganic and organic particles, such as dust, pollen, smoke, soot, and liquid droplets. These particles vastly differ in size, origin and composition.
Based on size, particulate matter are subdivided into coarse with a diameter between 2.5 to 10Ķm and fine particulate matter with a diameter of upto 2.5 microns
Fine particulate matter is produced from motor vehicles and the burning of coal, oil, and biomass. It can enter the circulatory system and negatively affect human health. Suspended fine particles (PM2.5
) are also mainly responsible for reduced visibility (haze) in many cities.
Long term exposure to particulate matter causes the following adverse effects
- Reduced life expectancy in persons with underlying heart or lung disease
- Nonfatal heart attacks
- Aggravation of asthma
- Reduced lung function
- Exacerbation of cough, breathlessness and other respiratory symptoms
Scope of Study
The team state that the study has not established a cause-and-effect relationship, but only established an association. However, the results of the study are strengthened by its size, follow-up and due adjustment for other influencing factors.
Thus, the study reinforces the utmost importance of individual intent, as well as strict governmental regulations to curb the alarming pollution levels in several cities across the world for improving the health of the population.
To conclude with Muller's remarks, "The science on the health effects of air pollution is under review by the EPA. The findings of our study provide additional support for maintaining, if not lowering, the standard of 12 micrograms of PM2.5 per cubic meter set in 2012 by the National Ambient Air Quality Standards under the Clean Air Act. We need regulations to keep our air clean, not only for the health of our planet but also for the health of our children." References:
- In-womb air pollution exposure associated with higher blood pressure in childhood - (https://newsroom.heart.org/news/in-womb-air-pollution-exposure-associated-with-higher-blood-pressure-in-childhood?preview=8ede)
- Health and Environmental Effects of Particulate Matter (PM) - (https://www.epa.gov/pm-pollution/health-and-environmental-effects-particulate-matter-pm)
- Air Pollution Particulate Matter - (https://www.greenfacts.org/en/particulate-matter-pm/level-3/02-health-effects.htm#1p1)