Prenatal Exposure to Air Pollution Might Affect Cognitive Development Among Children (New Study)

A recent study conducted in China revealed that in the first trimester of pregnancy, mothers’ exposure to fine inhalable particles, also called PM2.5, in the form of air pollutants leads to lower IQ scores among six-year-old children. This relationship was more noticeable in boys, children who engaged in less outdoor physical activity, and children who were breastfed for a shorter period of time. 

PM2.5, or particulate matter with a diameter of 2.5 micrometers or less, is made up of microscopic particles that are airborne and can enter the respiratory system through inhalation. These particles come from a variety of sources, including natural occurrences like wildfires, industrial processes, car emissions, and combustion processes, and make up a sizable portion of air pollution.

Among the over 50 known chemical components that compose PM2.5 particles, the most common ones include ammonium, sulfate, nitrate, organic carbon, soil dust, and black carbon.

Given their small size, PM2.5 particles can penetrate the lungs and evade the body’s defenses, which may lead to or exacerbate respiratory and cardiovascular health problems. Exposure to PM2.5 can have detrimental impacts on one’s health, such as heart disease, worsened asthma, respiratory disorders, and other cardiovascular or respiratory illnesses.

Research has shown that prenatal exposure to PM2.5, particularly black carbon, can increase oxidative stress and inflammation, which can have a detrimental effect on a child’s nervous system development.

The study, which was published by the Environmental Safety and Ecotoxicology journal, investigated the relationship between prenatal exposure to PM2.5 particles and their six main components, and the intelligence levels of children at six years of age. The study also examined whether the child’s sex, breastfeeding, and physical activity had an impact on this relationship. 

Previous research indicated that longer breastfeeding sessions and higher physical activity levels are beneficial for the nervous system’s development. The researchers therefore postulated that these variables could alter the effects of PM2.5 exposure.

The participants in this study were a part of the Shanghai-Minhang birth cohort, a longitudinal investigation that gathered data on PM2.5 exposure during pregnancy and its constituent parts. The research comprised 1292 expectant mothers who were enrolled in the study at their initial prenatal checkup at the Minhang Maternal and Child Health Hospital in 2012, between the 12th and 16th week of pregnancy. Most of these mothers resided within 20 kilometers of the hospital in the districts of Minhang, Songjiang, and Xuhui, and gave birth to 1225 singleton live babies.

Based on aerosol optical depth data from satellites, statistical modeling was used to predict the participants’ exposure levels to PM2.5 particles. The data from the satellites was cross-validated by the researchers using information from a thousand ground measuring stations. Nevertheless, only five hundred and twelve mothers’ accurate PM2.5 exposure data was available, therefore these findings served as the foundation for the final analyses.

The study indicated that children’s perceptual reasoning scores were often higher in cases where the mothers had less exposure to PM2.5 particles during the first trimester. The mothers exposed to higher levels of ammonium and sulfate particles were associated with poorer overall intellect scores among their children. Yet, there was no discernible correlation found between the children’s IQ and exposure to PM2.5 particles in the second and third trimesters of pregnancy.

Gender-specific examination of the data revealed more negative correlations between mother exposure to PM2.5 particles and the IQ of male children during the first trimester. In the third trimester of the mothers’ pregnancies, there were discernible links among girls with overall PM2.5, ammonium, nitrate, organic carbon, and black carbon exposure.

This study, entitled “Prenatal Exposure to Ambient PM2.5 and its Chemical Constituents and Child Intelligence Quotient at 6 Years of Age”, significantly contributes to the scientific knowledge of the effects of air pollution on human health. Yet, the study also has limitations that must be taken into consideration. Particularly, some participants dropped out during the study, resulting in the final sample being more or less more educated than the initial sample. The assessment of mothers’ exposure to PM2.5 particles was based on concentrations at their residences during pregnancy, not accounting for exposure in other locations.

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