Are we exposed to too much lead?
by Suzanne Orme
Lead is a highly potent nerve toxin that has been known for decades to have devastating effects on human health and wildlife as well as strong links with violent crime.
While the phase out of lead in petrol has been an outstanding success globally, there is still a long way to go. Technical innovation, stricter controls of industrial emissions, a ban on certain imports and exports together with the enforcement of more stringent air quality standards are required to protect people in all towns and cities.
Whether you and your family are exposed to too much lead depends largely on what job you do and where you happen to live.
Like other heavy metals, lead is hazardous to animals and dangerous to humans as it accumulates in soil, livestock, fish, mammal, human tissue and blood. At all levels of exposure it can cause adverse and often irreversible health impacts to the nervous, immune, reproductive and cardiovascular systems.
Even very low levels of lead in infants can have serious and permanent effects on IQ, a link that is well documented. Lead impairs the development of parts of the brain that regulate behaviour and mood – the anterior cortex and prefrontal cortex.
As early as 1943 studies showed that infants that had chewed lead off the side of their cots were highly predisposed to aggression and violence, years after the exposure. Some interesting studies indicate that 20 years after lead had been banned in many cities there was a noticable reduction in violent crime.
A 2011 article in Journal of Environmental Health by authors Tsai and Hatfield estimated the economic benefits of the phase out of leaded petrol and consequent reduced health risks to be worth US$2.5trillion/year, or roughly 4% of global GDP.
The bad news is that lead is ubiquitous in our society. It is still commonly used in pigments, dyes, some paints, coatings, batteries, ammunition, metal products and devices to shield X-rays. Lead compounds are used in the manufacture of matches, ammunition, fireworks, explosives, pottery glazes, ceramics, brake shoes, flame retardants, electronic parts, plastics, rubbers and as catalysts for industrial production and epoxy curing agents.
People who work in industries that manufacture or use these components may be at greater risk of exposure as are those living near large point sources of lead emissions. At Port Pirie, 250km north of Adelaide 25% of children aged under 5 were found to have blood levels in excess of 10 micrograms per decilitre of blood.
Despite all the research highlighting the dangers, Australian exposure levels for children aged 3 – 14 years remains at the level set in 1993 by the National Health and Medical Research Council (NHMRC). This is 10 micrograms per decilitre of blood, well above the USA of less than 5 micrograms and Germany, less than 3.5 micrograms.
I support the recommendation made in the Medical Journal of Australia for a standard of one microgram per decilitre of blood together with improvements in how lead sources are identified and controlled.
The problem of toxic air emissions is more acute in developing countries. For example, fewer than 1 percent of the 500 Chinese cities studied by the Asian Development Bank and Tsinghua University met the air quality standards recommended by the World Health Organisation (WHO). Poor air quality is caused by coal fired power plants, other industrial sources and vehicles exhaust.
To ensure that the world develops on a sustainable path, research, innovation and technology transfer are now urgently required to phase out toxic substances. Substitutes for lead must be found if we are to protect the air we breath, our wildlife and the world’s children from the devastating effects of lead poisoning.