There was a time when lead poisoning was feared in canned foods because the solder used during the manufacture of sanitary open top cans contained lead as a component. Lead poisoning also became an issue with marine fish caught from some of the polluted waters. Now comes the news that lead contamination can be more widely prevalent because of the multifarious activities in to day's industrial society, deserving more attention. Lead can come from paints, petrol, food cans and water pipes causing contamination in cereals, vegetables and tap water. The dangers posed by lead are sufficiently documented and most developed countries are taking action to reduce lead exposure by banning substances of daily use known to contain lead.
Lead was discovered more than 8000 years ago and it was one of the widely used heavy metals by the engineering, chemical, paint and gasoline industry. It is found in Lead-acid batteries, lead wires and pipes, metal recycling works, foundries, smelters, soldering compounds, radiation shields, ammunition products, surgical equipments,fetal monitors, circuit boards, jet engines, welding rods, ceramic glazes, rubber products, paints and pigments etc to varying extent. Incorporating lead in gasoline started in 1920 and continued till 2000 when exhaust gases contributed to air pollution with lead extensively. Lead contaminated foods were common in vending kiosks working on road sides and highway routes with high vehicle density during the latter half of the last millennium.
Though it is a fact that lead exposure has come down drastically since the last 50 years. it is an area of concern in some countries, especially amongst children. Lead at even smaller levels in the body can cause irreparable damage in human beings. It interferes with a host of processes in the body, toxic to many organs, tissues, bones, intestines, kidneys and reproductive nervous system. Since it affects development of nervous system, there can be permanent learning and behavioral disorders amongst children. Lead poisoning symptoms include abdominal pain, head ache, anemia, irritability, seizures, coma and death eventually in serious cases. It inhibits the critical delta-aminolevulenic acid dehydratase enzyme (ALAD) and ferrochelatase that influence heme synthesis. The common routes for entry of lead into the human body can be through air we breathe, water we consume. soil we tread on and the food we ingest every day. According WHO guidelines safe limit of Lead in blood is 10 ug per dL, though it rarely exceeds 2 ug under to day's living condition in many countries. At levels beyond 40 ug/dL symptoms of lead poisoning may manifest in some people while
at 50-60 ug many will be affected.
While protected water supplies can deliver potable water with lead concentrations of less than 15 ug per liter, food can be a cause of some concern. Foods, mainly commodities, can contain Lead, between 13 and 80 ug per kg but as per WHO guidelines safe limit of ingestion of lead through food is 200 ug per day for an average adult which is much higher than the present levels of consumption through various foods. Before the advent and overwhelming use of stainless steel utensils for cooking and storing food, copper and brass utensils were routinely tinned and Lead contamination from tin coating was a common occurrence.
More than adults, the effect of Lead on children in the age group 1-5 years is receiving critical attention world over because of its effect on the brain development amongst them. Recently an expert panel on contaminants, which assessed current levels of Lead exposure through food and other sources at the request of the European Commission, could not set a firm level above which Lead in food could trigger health problems. There appears to be considerable evidence demonstrating that the developing brain is more vulnerable to the neurotoxicity of Lead than the mature brain and in children, an elevated blood lead level is inversely associated with a lower intelligence quotient (IQ) score and reduced cognitive functions up to at least seven years of age.
The fact that Lead can pose greater dangers to children during their early stages of brain development causing lower IQ when they grow up to become adults is frightening. Though no consensus is still emerging regarding the safe limit that can be tolerated by children without ill effect, there is an urgent necessity to evolve as low a limit as possible, if not zero level, for Lead content in products that may come in contact with children. Recent Indian ban of toys imported from China was due to high lead content in them but politically GOI found it expedient to lift the ban within a few days, putting Indian children at great risks! Sensitivity regarding the adverse impact of Lead on human health is at a very low level in countries like India and nutritionists, food scientists and policy makers must do some thing to address this dangerous problem. World does not want to create a future generation of population with reduced intelligence and learning abilities due to negligence and unintended activities by the present generation. Continuing decline of Lead levels in the food consumed and dramatic reduction of this heavy metal in the blood amongst most of the population over the last few years, gives hope that lead related disorders may eventually disappear from this planet.