Written by Dr Adrian Hyzler, Chief Medical Officer and Head of Medical Communications
Updated: August 2019
Lead is a highly toxic metallic element that occurs naturally in the earth’s crust and has many industrial uses. Man has been mining and using this heavy metal for thousands of years, poisoning himself in the process. Being very soft and pliable and highly resistant to corrosion, it was ideal for use in plumbing as well as for the manufacture of pewter. It has been extensively used in modern industry to manufacture products such as lead-acid batteries, radiation shields, gasoline, paint, etc.
Although lead poisoning is one of the oldest known work and environmental hazards, the modern understanding of the small amount of lead necessary to cause harm did not come about until the latter half of the 20th century. No safe threshold for lead exposure has been discovered – that is, there is no known sufficiently small amount of lead that will not cause harm to the body.
SOURCES | What are the sources of lead poisoning?
1. Air pollution – from the polluted atmosphere
Lead is considered to be one of six major air pollutants that are harmful to public health and the environment – the other pollutants are ozone, particulate matter, nitrogen oxides, carbon monoxide, and sulphur dioxide.
In the past, motor vehicles were the major contributor of lead emissions to the air. Environment Protection Agencies (EPAs) around the world have targeted the reduction of lead in on-road motor vehicle petrol, and in air emissions of lead from the transportation sector, and particularly the automotive sector.
Consequently, lead pollution has greatly declined around the world over the past two decades. Batteries remain the main modern usage of lead, and Metals Processing is the major source of lead emissions in the air today. The highest air concentrations of lead are usually found near lead smelters. The other major source of lead pollution is the emissions produced by piston-engine aircraft operating on leaded aviation gasoline.
2. Direct ingestion – from food / water / occupational exposure
Lead is persistent in the environment and accumulates in soils and sediments through deposition from air sources, direct discharge of waste streams to bodies of water, mining and erosion. Ecosystems near point sources of lead demonstrate a wide range of adverse effects including losses in biodiversity, changes in community composition, decreased growth and reproductive rates in plants and animals, and neurological effects in vertebrates.
This leads to the other major exposure pathways that include ingestion of lead in drinking water and lead-contaminated food. Lead-based paint remains a major source of toxicity in older homes, especially in children. The most common cause of lead poisoning in adults is occupational exposure.
Primary stationary sources of lead today include:
- Lead smelters
- Waste incinerators
- Power stations
- Lead-acid battery (LAB) manufacturers and recyclers.
Other industrial sources of lead emissions can include:
- Metal processing
- Iron and steel foundries
- Copper smelters
- Industrial, commercial and institutional boilers
- Glass manufacturers
- Cement manufacturers
EFFECTS | How is lead poisoning harmful and how is lead contamination measured?
Lead poisoning occurs when a human being absorbs substantially more lead than his body can excrete. Absorbed lead enters the blood stream and accumulates in body tissue, particularly the kidneys, bones and nervous system. Lead poisoning also affects the oxygen carrying capacity of the blood. Lead is a cumulative poison and once absorbed it remains in the body for months or years.
The effects of lead most commonly encountered in current populations are neurological effects in children, and cardiovascular effects (e.g. high blood pressure and heart disease) in adults. Infants and young children are especially sensitive to even low levels of lead, which may contribute to behavioural problems, learning deficits and lowered IQ. Symptoms of lead poisoning include abdominal pain, confusion, headache, anaemia, irritability and in severe cases, seizures, coma and death.
Elevated levels of lead in the body can be detected by microscopic analysis of blood samples and also by dense lines seen on X-ray in the bones of children. Children are especially prone to the health effects of lead and, as a result, safe blood lead levels are set lower than adults and closely monitored if contamination is suspected. If high levels of lead are found they can be removed by the administration of agents that bind to the lead in the body so that it can be excreted.
PREVENTION | How is the environment kept clean?
It is important that individual countries/states develop and implement strategies to maintain a safe and clean environment for the population. This involves a number of programs, including:
- A monitoring programme to measure actual air pollutants
- Air quality calculations and computer models to predict the effects of different strategies to reduce emissions
- A database that lists the amount and source of pollutants
- Proven control strategies to reduce emissions
- Formal adoption of measures to reduce emissions
- Periodic review to evaluate progress in reduction of emissions.
In addition, regulations can be enforced to remove lead-containing items such as piping or blinds from homes. Children in older housing with chipping paint, or lead dust from moveable window frames with lead paint, are at greater risk of lead poisoning and thus incentives may be made available to replace the contaminant.
The lead pollution problem facing China
Despite China’s leaded gasoline phase-out in 2000, the continued high rates of lead poisoning found in children’s blood samples reflect the need for identifying and controlling other sources of lead pollution. From 2001 to 2007, 25% of nearly 100,000 children studied in China were found to be lead poisoned, with blood concentration levels exceeding 100 μg/L ([the mean level in developed countries is 30μg/L – in May 2012 the U.S. Centers for Disease Control lowered the reference value for identifying exposed children from 100 μg/L to 50 μg/L). These trends reveal that China still faces significant public health challenges, with millions of children currently at risk of lead poisoning.
The unprecedented growth of China’s lead-acid battery (LAB) industry from the electric bike, automotive, and photovoltaic industries, may explain these persistently high levels – as China remains the world’s leading producer, refiner, and consumer of both lead and lead-acid batteries. The vast majority of lead in global commerce (about 80%) is used to produce LABs and 97% of these batteries are recycled and reprocessed, primarily in developing low-income countries. At least two thirds of this takes place in China. The remaining uses of lead in China include the production of glass, household items, lead alloys, cables, paint additives, and anti-corrosion materials.
Fueled by consumer demand for inexpensive and convenient transportation, China’s electric bike market is the largest in the world. The relatively low cost of electricity compared with gasoline, as well as the convenience of recharging e-bike batteries with a standard electrical outlet, make e-bikes one of China’s fastest growing modes of transportation. Moreover, many local governments promote the use of e-bikes in urban centers due to their zero tail-pipe emissions and ability to cut down on traffic congestion. These factors have contributed to well over 100 million e-bikes being purchased and on the road in the past decade.
Due to their relatively low-costs and high power surge capabilities, LABs are used to fuel this growing demand. Other applications include powering photography devices, uninterruptible power supplies, cell-phones, and electric power systems. With the rapid development of each of these industries in China, the production of LABs is poised to increase dramatically, as is the concomitant rise in lead pollution.
The United Nations Environment Programme labels lead a ‘potent neurotoxin’ and a ‘nerve poison’ that globally threatens the health and intellectual development of millions of children and adults. It can inflict brain damage, mental retardation, nervous system disorders, and a host of other neurological disorders. Until the toxin is eradicated, it will continue to impair sensory and cognitive functions, cause serious kidney and cardiovascular damage, and disrupt overall organ development. Gastrointestinal, cardiovascular, reproductive, and nervous systems can all be impacted even if only small doses infiltrate the body. Moreover, the cumulative and degenerative characteristics of lead can seemingly generate adverse health effects in every individual exposed, particularly in children.
According to the U.S. CDC, “no level of lead in a child’s blood can be specified as safe”. With no safe threshold of exposure to lead, the number of children in China at risk of lead poisoning is in the tens of millions. China faces a public health and social stability challenge with regard to lead poisoning. Scores of mass lead poisoning incidents involving children have directly fueled large-scale protests, resulting in factory damage and violent riots.
This highlights the need to mitigate the health hazards driven by the rapid growth of the LAB industry. It also demonstrates that despite extensive knowledge of lead’s adverse health effects, lead continues to cause serious public health concerns. China’s LAB industry is spread over many provinces and production is poised to increase dramatically and will continue to do so for many years. Thus, there is a clear urgency for immediate regulatory action to prevent further poisoning of millions of children in China.
US Environmental Protection Agency – http://www.epa.gov/oaqps001/lead/
US Center for Disease Prevention – http://www.cdc.gov/air/pollutants.htm
Environment Canada, Government of Canada – http://www.ec.gc.ca/toxiques-toxics/Default.asp?lang=En&n=D048E4B9-16
Health hazards of China’s lead-acid battery industry: a review of its market drivers, production processes, and health impacts – Published online 2013 Aug 3. PMCID: PMC3750646 – http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3750646/