China burns more coal than anywhere else in the world, and it is used to generate roughly 70% of all the country’s electricity needs. Unfortunately, coal doesn’t burn very cleanly and produces scores of toxic pollutants as byproducts, including polycyclic aromatic hydrocarbons (PAH). After a coal-burning power plant in Tongliang, China closed in 2004, researchers began examining health of children before and after the closure in an attempt to explore a possible link between air pollution and child health. Children born after the plant’s closure did better in developmental tests than those born before. The research was led by Dr. Deliang Tang from Columbia University Medical Center and the paper was published in PLOS ONE.
When DNA is exposed to carcinogenic molecules such as PAH, the two can become covalently bonded and form what is known as a DNA adduct. These adducts act as biomarkers for researchers in order to determine exposure levels. Unfortunately, these DNA adducts can form during prenatal development and can have harmful effects. Previous research has shown correlations between PAH exposure and lower IQ and developmental delays. Tang’s group hypothesized that with the power plant closing in Tongliang, reduced airborne PAH levels would lead to future children scoring higher in developmental tests and have increased levels of brain-derived neurotrophic factor (BDNF), a protein critical to fetal brain development.
For the study, the researchers examined umbilical cord blood samples from newborns whose mothers were non-smokers who lived within 2.5 km of the plant. The first cohort consisted of 150 newborns from March-June 2002 while the plant was still opened. The second cohort consisted of 158 children born between March and May of 2005.
The cord blood samples were examined for PAH-DNA adducts, other toxins, and plasma levels of BDNF. Statistical tests were completed in order to compare levels between the two cohorts. The researchers discovered that the 2005 cohort had significantly higher levels of BDNF as well as significantly fewer PAH-DNA adducts, implying an inverse correlation. The newborns from the 2005 cohort also had larger head circumferences than those born in 2002.
After the children in each cohort turned two, the researchers used the Gesell Developmental Schedule in order to identify development of language, motor skills, learned behavior, and social function. The researchers were able to identify a positive association between higher BDNF levels and higher scores on the developmental exams, though the results were not statistically significant.
“The key to limiting the health impacts of environmental exposures is policy change supported by scientific evidence. These findings indicate that regulation can rapidly decrease exposure and improve health outcomes among the most sensitive populations, providing support for implementing additional measures such as the closure of the Tongliang coal-fired power plant,” said Tang in a press release.
The researchers state that the next challenge is to identify environmental enrichment techniques to offset deficiencies caused by prenatal PAH damage. Additionally, it would be interesting to see how future cohorts, born long after the plant’s closure, would fare in comparison to the original two.