Lead poisoning in children is a well-known safety threat which has severe negative consequences for developing brain. A recent research shows that lead poisoning affects about 800 million children globally, or one out of three.
The report titled "The Toxic Truth: Children's exposure to lead pollution undermines a generation of potential" says that the majority of these affected children live in South Asia. India is one of the worst affected countries with more than 275 million children suffering from lead poisoning.
The study is a collaboration between UNICEF and Pure Earth, a nonprofit organisation that seeks to help poor countries threatened by toxic pollutants.
"With few early symptoms, lead silently wreaks havoc on children's health and development, with possibly fatal consequences," said UNICEF Executive Director Henrietta Fore in a UN statement.
Lead poisoning causes symptoms such as abdominal pain, kidney failure and infertility, among others. Children with a blood lead level above 5 micrograms per decilitre need immediate treatment to prevent life-long consequences from the powerful neurotoxin.
The New York Times reported that lead in dust and fumes from smelters, fires, car batteries, old peeling paint and water pipes, electronics junkyards, and even cosmetics and lead-infused spices pose a huge risk to a generation of children's mental and physical development.
The authors of the study claim car batteries are the prime culprit of exposure to lead. They based their conclusions on data from the University of Washington's Institute of Health Measurements and Evaluation (IHME), which collected blood test results from hundreds of thousands of children worldwide, the BBC reported.
"Vehicles in low and middle-income countries have tripled since 2000 and that has led to a graphic rise in lead acid battery recycling, often in an unsafe way," Dr Nicholas Rees, one of the report's authors, told the BBC.
The BBC reported that about 85 percent of the world's lead goes into producing lead-acid batteries, with the vast majority coming from recycled car batteries.
However, lead poisoning is rare in more developed countries, suggesting that the problem is solvable with decisive action.
In another study published in the journal Environmental Science, scientists at Hokkaido University partnered with the University of Zambia to examine blood lead rates in 140 children aged 2 to 10 years in Kabwe, Zambia for more than half a decade.
Children from towns near and far from an old, highly polluted lead-zinc mine were chosen. Because of this mine, Kabwe was considered as one of the 10 most polluted places on Earth in 2013, according to a survey conducted by the Blacksmith Institute (now, Pure Earth).
The research found that children living closer to the mine had three times higher lead level in blood than those living further away.
These scientists used a technique called methylation-specific polymerase chain reaction (MSP) to determine the methylation of the DNA sequences. Methylation is a process by which methyl (CH3) groups are added to DNA; this modification generally causes the activity of genes to reduce.
Increased blood lead levels correlated positively with aberrant, increased methylation of DNA responsible for the expression of genes. The genes affected were ALAD, which synthesises a key compound in the development of red blood cells; and p16, a tumour suppressor gene, which is frequently inactivated in different types of cancer.