Lead in the spotlight

Lead in old paint (Photo: Cookiemonster)

Lead has again come into the spotlight, this time in Australia. Although not really new since it has been highlighted as a concern for decades in the USA in particular, Australian environmental scientists in November 2012 pointed out the danger of lead pigments in old paint when renovating houses. Lead was previously added to paint to speed up drying, increase durability, maintain a fresh appearance, and resist moisture that causes corrosion. To be fair the Australian government had previously issued warnings about old lead paint in 2009.

Due to its natural occurrence in the environment and long history of global use, lead is everywhere and can be found in air, water and soil as well as in food, drinking water and household dust. The source of lead in household dust is often old peeling lead-containing paint, but a nearby lead smelter can make the situation many times worse. Fortunately, levels of lead in most environmental media have declined significantly over the past few decades due to the discontinued use of lead in paint, petrol and the solder used in food cans in many countries. However, the problem is far from disappearing.

Lead affects virtually every system in the body, including the blood, the cardiovascular, renal, endocrine, gastrointestinal, immune and reproductive systems. The most critical target for lead appears to be the central nervous system, particularly the developing brain, where it has the potential to cause impaired learning abilities and intellectual performance in children even at low exposure levels. Thus lead exposure is a particular problem for infants and young children.

Lead in crystal glass (Photo: Peter Q)

A recent reminder is the sad Australian case of lead poisoning recorded in an infant fed mothers milk stored in an old lead-containing crystal glass decanter. The mother wanted to use the best equipment possible for the child, which resulted in blood lead levels over recommended levels. After removing the lead source the infants blood lead levels decreased, but it has not yet been possible to assess potential long-term negative effects.

Acceptable blood levels of lead for children have been revised downwards several times. The frightening fact is that they have often been set at what can be achieved rather than what is toxicologically acceptable. Currently a level of 100 µg of lead/L of blood (in many countries expressed as 10 µg per decilitre since medicos for some reason prefer to express blood measurements per decilitre) is considered the cut off point. However, scientists now consider that this should be at least halved or maybe even reduced to 10 µg of lead/L of blood to be fully protective.

In one of the first blogs on this site we covered lead exposure in detail. The blog provided references to the latest risk assessments performed by the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives (JECFA) and the European Food Safety Authority (EFSA). Both organisations concluded that there is no safe threshold levels of lead exposure and that even at the reduced levels of lead seen today harmful effects cannot be excluded. Continued vigilance will be necessary.