Air pollution led to genetic changes that may have sapped learning skills in children whose mothers were exposed to a Chinese coal-fired power plant before it was shuttered a decade ago, researchers found.
Babies born in the southwestern Tongliang county just before the plant was shut in 2004 had significantly lower levels of a protein crucial to brain development in their cord blood than those conceived later, a March 19 report in the Plos One journal said. They also had poorer learning and memory skills when tested at age two, the study by Columbia University and Chongqing Medical University found.
“I wasn’t anticipating such a clear difference when we compared the first and second cohorts, and this shows how much of an impact effective policies can have on local populations,” said Columbia’s Deliang Tang, lead author of the report.
The findings add to a growing body of evidence on the health fallouts of China’s pollution crisis, which has sparked public outrage and forced its leaders to pledge stronger efforts to protect the environment. Outdoor air pollution can cause lung cancer and is linked to higher risk of bladder cancer, a World Health Organization agency said in October, ranking it as a carcinogen for the first time.
Officials in Tongliang, a town of 800,000 near Chongqing city, shut down the power plant, based near the town center, in May 2004 and replaced it with the national grid’s electrical system, according to the report. The study analyzed data on the children until they were two.
The old power plant has been replaced by an apartment complex with five towers, amid tree-lined walkways, playgrounds, and an amphitheater. On a day in mid-March, retirees played bridge around a makeshift table, while children skipped rope and rode on bicycles.
Tongliang resident Yang Chuntian, who was pregnant with her first son in 1996, says she wasn’t aware of the ill effects of air pollution. She lived near the coal plant.
As a toddler, her now 18-year-old son fell sick often with headaches that made him dull and unresponsive, said Yang, a store assistant in a bicycle shop. “I don’t know if that’s because of the smoke from the plant, but he’s fine now. And we’re a lot more careful nowadays -- about pollution, about the safety of the food we eat.”
Zhang Mingwei, a retired carpenter who lives in the complex that replaced the plant, still remembers markets selling soot-coated vegetables and neighbors complaining of laundry covered by coal-dust.
“We could hear the sirens whenever the plant started up, and then we’ll see black smoke coming out of the chimney,” said 72-year-old Zhang.
The plant had been the county’s main source of air pollutants when it was shuttered. It spat out 2000 micrograms of particles per cubic meter of air, 8 times U.S. emissions standards at the time, and included particulate matter, carbon dioxide, sulfur dioxide and heavy metals, the report said.
Researchers, informed of the plant’s impending shutdown, in 2002 recruited 150 non-smoking Tongliang mothers and their newborn, and another group of 158 mothers and children in 2005. Umbilical cord and maternal blood were collected at delivery, and the children were evaluated on neurodevelopment when they were two years old.
Evaluators looked at the children’s muscle coordination that dictate activities such as ability to flip pages in a book, stack cubes, or climb steps without help. They were also tested for adaptive and language abilities, such as recognizing their own names and forming at least three word sentences.
An earlier report from the study, published in the Environmental Pollution journal last November, showed the 2002 cohort of babies had smaller head sizes compared with the 2005 group, a condition that persisted into childhood. The Plos One report found average levels of brain-derived neurotrophic factor, BDNF, proteins involved in the growth of nerve cells, were significantly higher in the 2005 group.
Higher levels of the protein are positively associated with neurocognitive development, which “provides further evidence of the direct benefits to children’s health as a result of the coal plant shut down, supporting clean energy and environmental policies in China and elsewhere”, the authors wrote.
Columbia University is currently following up with a larger study of children in Taiyuan, a city of 4 million in northern Shanxi province, Tang said.
Developing fetuses can inherit the harmful effects of environmental pollution as that’s when the cells of organs such as the brain and heart are starting to develop. That warrants further research into the mechanisms, said Liming Bao, a professor of pathology at Dartmouth College’s Geisel School of Medicine in Hanover, New Hampshire, who wasn’t involved in the study.
“Genetic mutations could get passed along and have a long term impact, and when there’s damage to the cells, it’s difficult to reverse,” said Bao, who helped Children’s Hospital of Chongqing Medical University set up a molecular medicine unit in 2007. “It’s not something that you can switch on or switch off.”
— With assistance by Daryl Loo