|LEAD Action News Vol
1 no 2 Winter 1993 ISSN 1324-6011
Incorporating Lead Aware Times ( ISSN 1440-4966) and Lead Advisory Service News ( ISSN 1440-0561)
The journal of The LEAD (Lead Education and Abatement Design) Group Inc.
Lead pollution and the human environment
by Ted Floyd
Ted Floyd has been an environmentalist for 20 years and a campaigner with Friends of the Earth for the last five years. Can you tell when he wrote this article?
One of the by-products of the industrial and technological revolutions that have occurred in the last couple of hundred years has been the increase of chemicals in the environment. Many of these chemicals are dangerous to human and animal health.
Many thinking people were shocked when Rachel Carson published her book "Silent Spring" in 1962. This book clearly showed the hazards of the continual use of pesticides. Because of the initial work of Rachel Carson most people are now aware of the dangers of pesticides, but pesticides are still being used indiscriminately.
There is one chemical, lead, which is being continually released into the environment and which is potentially more dangerous to humans than the total impact of pesticides. Studies on lead are showing that it is very toxic and is affecting many people especially in motorised, urban environments.
The toxicity of lead to humans has been a problem for many years. For example, some historians partially attribute the downfall of the ruling classes of Rome to lead poisoning. Lead was used in plumbing, for wine storage, in drinking and eating utensils and cosmetics. Even today, cases of lead poisoning have been attributed to improperly lead glazed pottery. One possible cause of lead poisoning, is pica, or the eating of non-food items, which occurs as a normal phase in a young child's development and becomes abnormal if it persists beyond the age of around 18 months. Children or adults can be lead poisoned by eating chips of paint containing lead (which often occurs in old houses), contaminated soil, bullets, fishing sinkers, lead shot, etc.
Industries where lead is used were a common source of lead poisoning. However, in most countries regulations are now in force which control lead in paint and help protect workers in industry, but cases of industrial lead poisoning still occur.
Health hazards of lead
Lead poisoning occurs when a human being absorbs, through the air he breathes or the food or other material he ingests, 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. The foetus, infant and child are especially vulnerable. Lead is a cumulative poison and once absorbed it remains in the body for months or years.
At high blood lead levels, obvious clinical symptoms often occur, but recent research has found that at lower levels less obvious, hard to detect, i.e. subclinical symptoms can occur.
Lead has an adverse effect on many enzyme systems causing metabolic disturbances. Lead can disrupt the orderly function of some trace elements such as copper and zinc. Metabolic disturbances occur above about 20 micrograms. Subclinical lead exposure can have effects on behaviour and intelligence. Evidence is accumulating that prolonged low-grade exposure to lead may cause hyperactivity in children, learning difficulties and impaired brain function.
Lead poisoning in children occurs at lower blood lead levels than in adults. The age range of 1-5 years is the most critical. The pregnant woman and her foetus are highly susceptible to lead poisoning. Chronic exposure to lead can cause miscarriages and stillbirths. During conditions of abnormally high calcium metabolism such as fever or cortisone therapy, lead can be mobilised from bones and then transported via the blood to other organs to wreak damage once again.
Lead, petrol and pollution
Lead is added to petrol in the form of tetra ethyl and tetra methyl lead. These compounds increase the octane rating of the petrol.
Many studies have shown that the lead content of air increases in areas close to roads, and falls dramatically with distance from a road. Usually within 50m of a road over 50% of the lead has settled out. More lead is found on the downwind side of a road and the lead content of the air or the soil near a road increases with traffic density. In cities with tall buildings there can be a problem of poor ventilation which can result in very high lead content in both street dusts and air at street level.
Lead is transferred from the atmosphere to the soil and vegetation by sedimentation and precipitation. Most lead that enters the soil forms insoluble compounds and this results in most soil lead being found in the surface soil. Soils near roadsides can contain 30 times as much lead as virgin soils.
Plants growing near roads are contaminated with lead, mainly on their above-ground external surfaces. Vegetables near roads contain 5-20 times more lead than other vegetables.
Though the most serious levels of petrol lead pollution are in the vicinity of roads, studies of lead levels in areas remote from pollution sources, such as Northern Greenland and Cape Grim in Tasmania, demonstrate that lead from petrol is polluting the whole earth.
The lead and petrol industries claim that general air lead levels have little effect, while recent overseas studies show that lead levels once thought to be safe can be detrimental to health.
Current legislation in NSW restricts petrol content of lead (in Sydney, Newcastle and Wollongong) to 0.45 grams per litre (g/L). This restriction is to be lowered to 0.40 g/L by 1st Jan 1980. Is this legislation sufficient? Are children who live near expressways safe from lead?
This article was written over 14 years ago and lists all the reasons that every other OECD country has legislated nationally to curb lead pollution from petrol and other sources. Australia is the only developed country with different legislated petrol lead limits for each state and Greece is the only other OECD country which, like Australia, allows more lead in country petrol than in city petrol. Australian country lead in petrol limits and the lead limits for three of our capital cities remain higher than in any other OECD city or country.
system lead poisoning |
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