UNITED NATIONS, July 30 (Xinhua) -- Lead poisoning is affecting children on a massive and previously unknown scale, up to 800 million globally, said a study released on Thursday by the UN Childrens Fund (UNICEF) and Pure Earth. With few early symptoms, lead silently wreaks havoc on childrens health and development, with possibly fatal consequences, said Henrietta Fore, the UNICEF executive director, in a press release. Knowing how widespread lead pollution is and understanding the destruction it causes to individual lives and communities must inspire urgent action to protect children once and for all. About one-third of children in the world have blood lead levels at or above 5 micrograms per deciliter, the level at which requires action. Nearly half of these children live in South Asia, according to the study. Lead is a potent neurotoxin that causes irreparable harm to childrens brains and is particularly destructive to babies and children under the age of 5. It damages their brains before they have had the opportunity to fully develop, causing them life-long neurological, cognitive and physical impairment. Childhood lead exposure has also been linked to mental health and behavioral problems, and to an increase in crime and violence, the study showed. Older children suffer severe consequences, including increased risk of kidney damage and cardiovascular diseases in later life. Blood lead levels for children in low- and middle-income countries have remained elevated and, in many cases, dangerously high even a decade after the global phase-out of leaded gasoline. Blood lead levels have declined dramatically in most high-income countries. Childhood lead exposure is estimated to cost lower- and middle-income countries almost 1 trillion U.S. dollars due to lost economic potential of these children over their lifetime, according to the study. Increased informal and substandard recycling of lead-acid batteries, due to increased vehicle ownership, is a leading contributor to lead poisoning in children living in low and middle-income countries, it said. The good news is that lead can be recycled safely without exposing workers, their children, and surrounding neighborhoods. Lead-contaminated sites can be remediated and restored, said Pure Earth President Richard Fuller. People can be educated about the dangers of lead and empowered to protect themselves and their children. The return on the investment is enormous: improved health, increased productivity, higher IQs, less violence, and brighter futures for millions of children across the planet.