Lead exposure

Lead, a heavy metal with the symbol Pb and atomic number 82 in the Periodic Table of Chemical Elements, has played a significant role in the history of mankind. It is the heaviest of the stable elements. Under Normal Conditions of Temperature and Pressure (NTCTP), lead is a malleable, bluish-grey metal that turns white on oxidation.

Easily extractable and relatively abundant on Earth, it has been one of the most widely used metals since prehistoric times. It has a rich history as a material used by different cultures throughout the ages. From the Sumerians to the Romans, lead has been used in a variety of applications, from pipes to cooking utensils. However, it was in the Middle Ages that the term "lead poisoning" was coined, linking lead to health problems, an association reinforced by the alchemical belief of the time associating lead with the planet Saturn.

It was not until the 19th century, following the death of a child in Australia, that recommendations and screening for lead poisoning were introduced:

• 1914: Ban on the use of lead in the manufacture of drinking water pipes in Switzerland
• 1948: Ban on lead paint in France
• 1995: Total ban on lead pipes in France

The 2 main routes of poisoning are inhalation and ingestion.

Lead poisoning, also known as lead poisoning, is one of the oldest occupational diseases on record. It is listed in Table 1 of the French Social Security system (Affections dues au plomb et à ses composés) and Table 18 of the French Agricultural system (Maladies causées par le plomb et ses composés).

The 2 main routes of intoxication are inhalation and ingestion. Lead enters the body through the nose (smoke or dust, particularly when lead oxide particles are released) or through the mouth as a result of poor hand and face hygiene.

The effects of lead are :

• on the nervous system: mood and memory disorders, deterioration in intellectual capacity, damage to peripheral motor nerves;
• on the kidneys: disruption of elimination functions, chronic renal failure;
• in the blood: reduced number of red blood cells (anaemia);
• in the digestive system: lead colic (abdominal pain);
• others: hepatic, endocrine, etc.

Lead can also be responsible for reproductive abnormalities:

• in women: effects on pregnancy (abortion, premature delivery, etc.) ;
• in men: impaired sperm production.

Children are particularly sensitive to lead poisoning, which can have an impact on the central nervous system, particularly in young children, with potentially serious clinical signs (convulsive coma, behavioural problems, mental retardation, etc.).

As far as the environment is concerned, lead is naturally present in the environment, but it is human activity that has led to an increase in the concentration of lead in the air, water and food. For example, the use of lead in petrol has led to the release of car exhaust fumes. These particles fall back to earth and pollute the soil, surface water and our food.

For lead and its compounds, the French Labour Code sets :

• A binding regulatory occupational exposure limit value (VLEP) of 0.1 mg/m, not to be exceeded as an 8-hour average in the atmosphere of workplaces (Article R. 4412-149).
• The binding regulatory biological limit values (BLV) not to be exceeded are set at 400 μg of lead per litre of blood for men and 300 μg/l of blood for women (article R. 4412-152).
• Specific medical surveillance of workers is required if exposure to a concentration of lead in the air is greater than 0.05 mg/m3, calculated as a time-weighted average on an eight-hour basis, or if a blood lead level greater than 200 micro g/l of blood for men or 100 micro g/l of blood for women is measured in a worker (article R4412-160).
• A ban on employing young workers under the age of 18 in work exposing them to lead and its compounds (article D4153-27).
• A ban on assigning women who have declared themselves pregnant or women who are breastfeeding to work exposing them to metallic lead and its compounds. A pregnant or breast-feeding employee must be offered a change of workstation if she is exposed to metallic lead or its compounds (decree no. 96-364 of 30 April 1996 on the protection of pregnant or breast-feeding workers against chemical, biological and physical risks).