Muiris Houston: Lead linked to adverse health in 250 BC

Long-term exposure can damage reproductive and nervous systems

Lead was first linked to adverse health as far back as 250 BC and has been the subject of environmental controls since the late 20th century, when lead in paint and petrol was banned.

However, the metal was used for pipework and watertanks before the 1970s in many homes, schools and hospitals. Lead from these pipes leeches into water, leading to the discovery of lead contamination levels of up to 80 times the legal limit in drinking water in parts of Dublin.

Lead is a metal with no known biological benefit to humans. Too much lead can damage various systems of the body including the nervous and reproductive systems and the kidneys. It accumulates slowly in the body and even low doses can eventually result in poisoning.

Some 95 per cent of lead in the body is deposited in the bones and teeth while lead in blood is found within the red blood cells. Because it shortens the life span of these cells it can cause anaemia.


Developing brains

Lead is especially harmful to the developing brains of foetuses and young children and to pregnant women. Exposure to lead through water is generally low in comparison with exposure through air or food.

The amount of lead that may dissolve in water depends on its acidity, temperature, hardness and how long it has been standing in the lead pipe. The legal level of lead in drinking water in Ireland is now 10 micrograms per litre.

However, in babies who are formula-fed, drinking water can form a significant proportion of the total daily intake of lead where lead pipework is present, leading to concerns that lead levels below the legal limit may be harmful.

Chronic exposure to lower levels of lead is more common than acute poisoning. In children, who absorb a greater percentage of lead in food and water than adults, exposure to lead in drinking water can result in physical and mental developmental delay; deficits in attention span and learning ability have also been noted.

The symptoms of chronic lead poisoning include mild abdominal pain, constipation, hearing loss, a drop in fertility and headaches. Acute high blood levels of lead cause more severe abdominal pain, vomiting and jaundice.

Muiris Houston

Dr Muiris Houston

Dr Muiris Houston is medical journalist, health analyst and Irish Times contributor