Le lead is a heavy metal of a bluish gray and toxic for humans. When ingested, its most serious effects are on the central nervous system but it can also reach red blood cells and the digestive system.

Lead can enter the body through the mouth or the lungs. The degree of lead assimilation varies from person to person, depending in particular on the state of health.

We must distinguish the intoxication of contamination lead. It is a question of lead contamination when exposure to this metal causes lead levels in the blood above normal levels without causing symptoms. If the contamination is large enough to cause symptoms, it is calledlead poisoning.

The adults are the main victims of lead contamination or poisoning. But when the young children are affected, their health is particularly in danger. Very low amounts of lead can hinder their cognitive development and cause attention problems. The concern is all the greater as young children absorb 5 to 10 times more lead than adults²². Their habit of putting everything in their mouths could partly explain this phenomenon. In addition, a significant proportion of the metal introduced into their body, around 25%, remains in circulation and exerts its neurotoxic effects. By comparison, in adults, only 5% to 10% of the lead absorbed remains in circulation. The rest gets fixed in the bones and teeth.

Intoxication can be acute therefore result from brief exposure to very high amounts of lead or chronic, due to prolonged exposure to small amounts of lead. We also give the name of saturnism lead poisoning, whether acute or chronic.

Diagnostic

THElead poisoning is often diagnosed following a screening led in the Workplace. The attending physician may also suspect lead poisoning based on the symptoms and possible sources of lead to which the patient is exposed. In this case, a test is also taken to the relatives of the patient who could also be victims of lead poisoning.

To carry out the test, a blood analyse which detects the level of lead in the blood (the blood lead). The result is given in micrograms of lead per deciliter of blood (µg / dl) or in micromoles of lead per liter of blood (µmol / l). Blood lead levels primarily reflect recent exposure to lead. However, studies indicate that long-term exposure slightly elevates blood lead levels.

Blood lead levels considered safe for health have steadily declined over the past decades. Currently, if an individual has blood lead levels equal to or greater than 10 µg / dl (or 0,5 µmol / l), his doctor is obliged to notify the public health authorities. This mandatory reporting threshold was proposed by the US Centers for Disease Control in 1991 and was subsequently adopted by public health authorities in Quebec. Exceeding this threshold does not always cause symptoms of toxicity.

Some experts believe that cognitive disorders mild may appear below this limit and that there may not be a safe threshold of exposure, especially in children^2,3. In fact, a study of 1 American adults aged 987 to 20 years indicated that subjects with the highest level of lead (39 µg / dl) were twice as likely to suffer from depression and 2,1 times more panic disorder than those with the lowest level (2 µg / dl or less)²⁹.

Remark. The presence of lead can also be measured inurine or in hair. However, the analysis of a urine sample is little used because the results are very difficult to interpret.¹⁹. As for the analysis of hair, it is not recommended as a diagnostic method because the results are too variable.

Magnitude of the problem

In North America and in most industrialized countries, the presence lead in the environment has fallen since the 1970s. Indeed, many countries have restricted the use of lead, especially in gasoline, because of its harmful effects on health.

In the United States, blood lead has steadily declined in children 1 to 5 years of age over the past 30 years^5,6. The mean blood lead level was around 15 µg / dl at the end of the 1970s and around 4 µg / dl at the end of the 1980s. At the end of the 1990s, it was around 2 µg / dl and 1,5 µg / dl in 2005⁶. This decline is also observed in Canada for the general population. In 2007-2008, Canadians aged 6 to 79 had an average blood lead level of 1,37 µg / dl^27,28.

In Quebec, 200 to 500 cases of lead contamination are reported each year, mainly in adults exposed in their workplace²⁰ (including factories for the treatment of metals or the recycling of automotive batteries containing lead). Not all of these people are intoxicated, that is, not all of them have symptoms.

According to Health Canada, lead poisoning is very rare in children. In these, it would occur mainly near current or old foundries.

On the other hand, people born before the 1970s, when lead was more commonly used in industry, could be adversely affected. Indeed, a past lead exposure could contribute to the development of diseases usually associated with aging⁴ (hypertension^12-14 kidney problems¹¹cataracts¹⁰memory impairment¹⁵). For now, this is still a hypothesis. It is also not known whether these effects are reversible. Osteoporosis may cause lead accumulated in bones during childhood to be released into the bloodstream later. In fact, we know that 90% to 95% of the lead absorbed is fixed in the bones, in the same way as calcium.

Sources of lead exposure

Some industrial sectors still use lead. For example, it always goes into the production ofacier and brass as well as in the manufacture of electronic products and D’Accumulators for automobiles. In addition, some thermal power plants, especially coal-fired ones, continue to release lead into the ground, air and water. Remember that the lead emitted into the environment in the past does not degrade.

Note. Amalgams used in dentistry, commonly called ” seals », Do not contain lead, but 50% mercury and a metal alloy (silver, tin, zinc and copper).

Here are the sources of lead that can cause lead contamination or poisoning:

• Drinking water. Tap water may contain lead. This can be the case for houses where the piping includes lead solder or an old lead connecting to the municipal waterworks (generally installed before the 1970s). According to Health Canada, the lead content in tap water for the general population is below the acceptable limit, i.e. 10 micrograms (µg) of lead per liter of water after 5 minutes of flow (which corresponds to 0,010 ppm of lead). In the United States, the standard is set at 15 micrograms of lead per liter of water, when the water is first taken out in the morning. In case of doubt, it is possible to have your water tested in an accredited laboratory (see Sites of interest). See also Basic preventive measures;
• Food. According to Health Canada, traces of lead are found in almost all foods. Lead in the air returns to the soil and is taken up by crops. Another source is lead solder in cans in some countries. In Canada, canned food manufacturers have stopped using lead for the last XNUMX years, but instead have used electric soldering. There have been no reported cases of lead contamination from the food container in Canada for several years²³. Lead solders are easily recognized: they form a wide, uneven line on the side of the box;
• The air. The presence of lead in the air has been greatly reduced thanks to the elimination of lead additives in motor gasoline. Unleaded gasoline entered Canada in 1975. Since 1990, leaded gasoline has been banned in the country;
• You sun. Particularly near roads, bridges and lead smelters, soil and dust sometimes contain amounts of lead sufficient to be toxic to a young child. Soil contamination also stems from the widespread use of lead in industry in the past;
• Cigarettes and second-hand smoke. The lead naturally contained in tobacco leaves is released into the air during combustion;
• The painting. Until the 1960s, lead was used as a pigment in paints, especially in shades of white and pastel colors, according to Health Canada and the Canada Mortgage and Housing Corporation (CMHC).²⁵. The lead content of these paints could then represent up to half of the total weight;

  In a home, if the paint is in good condition, it poses little risk. However, dust containing lead can be inhaled when lead-based paint peels off, when stripping or sanding it, or when painted wood is burned. From the 1960s, the lead content in paints gradually decreased. In 1991, Canadian paint manufacturers voluntarily stopped using lead, recalls CMHC. Nowadays, lead paint is still used to paint commercial or industrial buildings, as well as in the military and naval industries;

• Handicrafts. Imported artisanal pottery and ceramics are sometimes covered with a lead glaze. Crystal, a variety of glass, can be made with lead. The problem arises if these types of containers are used for serving drinks or food, especially if they are acidic and hot;
• The manufacture of munitions containing lead or lead fishing as well as the frequentation of shooting rooms whose ventilation systems are inadequate have caused several cases of poisoning in recent years;
• Some traditional remedies. Some unauthorized Ayurvedic medicine products contain high levels of lead and other heavy metals, such as mercury and arsenic. Consult the advice issued by Health Canada⁸;
• Some traditional cosmetics. Le kohl is a dark-colored powdery substance traditionally used as an eye shadow in the Middle East, North Africa and Asia. Some are high in lead and cases of poisoning have been reported in young children²¹. Despite the fact that Health Canada prohibits any presence of lead in cosmetics, some do contain it;
• The manufacture or renovation of stained glass. Especially when the lead needs to be melted, these activities can result in significant exposure;
• Poor quality jewelry. Wearing jewelry does no harm. Only children who regularly suck or chew low-quality jewelry can become poisoned.²⁴. As Health Canada mentions, jewelry that contains lead can be recognized by its rather grayish color. Additionally, they can leave a gray mark when rubbed onto white paper (if the lead is not coated with paint).