The lead is a heavy metal bluish gray and toxic to humans. When ingested, its most severe 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 lungs. The degree of assimilation of lead varies from one person to another, depending on the state of health.
The toxicity of lead contamination must be clearly distinguished . It is a question of contamination with lead when an exposure to this metal generates in the blood a lead level higher than normal, without causing symptoms. If the contamination is large enough to cause symptoms, then it is called lead poisoning .
The adults are the main victims of contamination and lead poisoning. But when young children are affected, their health is particularly at risk . Very small amounts of lead can hinder their cognitive development and cause attention problems. The concern is even greater that young children absorb from 5 to 10 times more lead than adults. Their habit of bringing everything to their mouths could partly explain this phenomenon. In addition, a significant proportion of the metal introduced into their bodies, about 25%, remains in circulation and exerts its neurotoxic effects. In comparison, in adults, only 5% to 10% of absorbed lead remains in circulation. The rest is fixed in the bones and teeth.
Poisoning may be acute, resulting from brief exposure to very high levels of lead or chronic , due to prolonged exposure to small amounts of lead. Lead poisoning, whether acute or chronic, is also known as lead poisoning.
|Where is the lead?
Once assimilated, lead is quickly found in the bloodstream. Then, it settles in the bones and teeth. A small amount of the lead accumulated in the bones will be released and gradually eliminated in the urine. This process is spread over dozens of years.
Diagnostic of Lead intoxication
The lead poisoning is often diagnosed after a screening conducted 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 passed to the relatives of the patient who could also be victims of lead poisoning.
To carry out the test, a blood test is performed which detects the level of lead in the blood (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 mainly reflect recent exposure to lead. Nevertheless, studies indicate that old exposure slightly raises blood lead levels.
Blood lead levels, estimated to be safe for health, have been steadily decreasing in recent decades. Currently, if an individual has a blood lead level 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 the Quebec public health authorities. Exceeding this threshold does not always cause symptoms of toxicity.
Some experts believe that mild cognitive impairment may occur below this limit and that there may be no safe threshold of exposure, especially in children. In fact, a study of 1,987 American adults aged 20 to 39 indicated that subjects with the highest lead (2.1 μg / dl) were twice as likely to suffer from depression and 5 times more panic disorder than those with the lowest rate (0.7 μg / dl or less).
Note . The presence of lead can also be measured in the urine or in the hair . However, the analysis of a urine sample is little used because the results are difficult to interpret. As for hair analysis , it is not recommended as a diagnostic method because the results are too variable.
Magnitude of the problem
Tetraethyl lead has long been used as an additive for automotive gasoline to reduce engine clatter. Due in particular to the risks of toxicity that it presented, the lead was progressively removed from automobile gasoline sold in North America . It was totally banned in 1986 in the United States and in 1990 in Canada. Lead is still found in gasoline sold in developing countries.
In North America and most industrialized countries, the presence of lead in the environment has dropped since the 1970s. Many countries have restricted the use of lead, particularly in gasoline, because of its harmful effects on health.
In the US, the blood lead has steadily decreased in children from 1 year to 5 years during the last 30 years . The average blood lead level was around 15 μg / dl in the late 1970s and around 4 μg / dl in the late 1980s. At the end of the 1990s, it was around 2 μg / dl and 1, 5 μg / dl in 2005. This decline is also observed in Canada in the general population. In 2007-2008, Canadians aged 6 to 79 years had an average blood lead levels of 1.37 mg / dl.
In Quebec, 200 to 500 cases of lead contamination are reported each year, mainly in exposed adults in their workplace(including metal processing plants or recycling of lead-acid automobile batteries). These people are not all intoxicated, that is, they do not all have symptoms.
According to Health Canada, lead poisoning is very rare in children . In these, it would occur mainly near existing or old foundries.
On the other hand, people born before the 1970s, when lead was used more often in industry, could be negatively affected. Indeed, exposure to lead could contribute to the onset of diseases usually associated with aging(hypertension , kidney problems , cataracts, and memory problems). For now, this is still a hypothesis. It is also not known whether these effects are reversible. Osteoporosis could cause lead accumulated in the bones during childhood to be released later into the bloodstream. Indeed, it is known that from 90% to 95% of absorbed lead is fixed in the bones, in the same way as calcium.
Lead exposure sources
|In Canada, industries reported a total release of approximately 54 million pounds of lead into the environment in 2006. A little less was recycled: about 46 million kilos.|
Some industrial sectors still use lead. For example, it is still involved in the production of steel and brass, as well as in the manufacture of electronic products and accumulators for automobiles. In addition, some thermal power plants, particularly coal-fired, continue to release lead into the ground, into the air and into the water. Remember that the lead emitted into the environment in the past does not deteriorate.
Note. Amalgam used in dentistry, commonly known as ” fillings “, does not contain lead, but 50% mercury and an alloy of metals (silver, tin, zinc and copper).
Here are the sources of lead that can lead to lead contamination or poisoning:
- Drinking water. Tap water may contain lead. This may be the case for houses where piping includes lead solder or an old connecting pipe to the municipal aqueduct made of lead (generally installed before the 1970s). According to Health Canada, the lead content of tap water in the general population is below the acceptable limit of 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 lead per liter of water at the first outflow of water in the morning. If in 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 absorbed by crops. In some countries, lead solder from cans is another source. In Canada, canned food manufacturers have not used lead for more than 20 years, but instead use electrical soldering. No cases of lead contamination by containing foods have been reported in Canada for several years. Lead solders are easy to recognize: they form a large uneven line on the side of the box;
- The air. The presence of lead in the air has been greatly reduced by the elimination of lead additives in automotive gasoline. Unleaded gasoline entered Canada in 1975. Since 1990, leaded gasoline has been banned in Canada;
- Floor. Especially near roads, bridges and lead smelters, soil and dust sometimes contain enough lead to be toxic to a young child. Soil contamination also comes from the widespread use of lead in industry in the past;
- The cigarette and the secondhand smoke. 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, particularly in white shades and pastel colors, according to Health Canada and the Canada Mortgage and Housing Corporation (CMHC). The lead content of these paints could then represent up to half the total weight;
In a home, if the painting is in good condition, it poses little risk. But lead-containing dust can be inhaled when the lead-based paint is peeled off, when it is stripped or sanded, or when painted wood is burned. From the 1960s, the lead content of paints gradually decreased. In 1991, Canadian paint manufacturers voluntarily stopped using lead, says CMHC. Today, lead paint is still used to paint commercial and industrial buildings, as well as in the military and naval industries;
- Artisanal productions. Imported 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 to serve drinks or foods, especially if they are acidic and hot;
- The manufacture of ammunition containing lead or fishing sinkers and the use of firing halls withinadequate ventilation systems have resulted in several cases of intoxication in recent years;
- Some traditional remedies. Some non-registered Ayurvedic medicine products contain high levels of lead and other heavy metals, such as mercury and arsenic. Consult the advice issued by Health Canada;
- Some traditional cosmetics. The kohl is a powdery substance dark traditionally used as eye shadow in the Middle East, North Africa and Asia. Some have a high content of lead and cases of poisoning have been reported in young children. Despite the fact that Health Canada prohibits the presence of lead in cosmetics, some contain it;
- The manufacture or renovation of stained glass windows. Especially when lead has to be melted, these activities can lead to significant exposure;
- The jewels of bad quality. Wearing jewelry does not cause harm. Only children who regularly suck or chew poor quality jewelry can poison. As mentioned by Health Canada, jewelry that contains lead can be recognized by its rather greyish color. In addition, they can leave a gray mark when rubbed on a white paper (if the lead is not covered with a paint).
Symptoms of lead poisoning
Children and adults
- A metallic taste in the mouth;
- Abdominal pain;
- Vomiting and diarrhea;
- Convulsions, coma and sometimes death.
The following damages, if any, usually occur at school age:
- Fatigue and irritability;
- Low attention span
- Learning difficulties;
- Aggressive behavior
At a higher degree of exposure, the following symptoms may also occur:
- A pallor caused by anemia;
- Hearing problems;
- Language and speech disorders;
- Motor coordination problems;
- Abdominal pain;
- A loss of appetite and weight.
|According to one study, for every 10 micrograms of lead per deciliter of blood (10 μg / dl), there is a loss of about 4 points of intelligence quotient (IQ). It is unclear for the moment whether this effect is sustained in the medium and long term.|
Chronic exposure to lead does not result in easily detectable symptoms. But it could increase the following risks:
- Fertility problems (men and women);
- For pregnant women: miscarriage, premature birth or stillbirth;
- Potentially chronic health problems ;
People at risk for Lead intoxication
- The infants and children aged 6 and under ;
- The pregnant women and their fetuses . The lead trapped in the bones can be released in the body, cross the placenta and reach the fetus;
- Possibly seniors , especially women, who have been exposed to significant amounts of lead in the past. Osteoporosis, which affects more postmenopausal women, could cause lead accumulated in bones to be released into the organism.e. Elderly people are more likely to have high blood lead levels with fewer symptoms than children;
- Children who suffer from pica . This is a compulsive eating disorder that involves the systematic ingestion of certain inedible substances (earth, chalk, sand, paper, paint chips, etc.).
- Work in a metal processing plant or recycling of automotive batteries or electronic products containing lead;
- Live near factories that release lead into the environment;
- Living in a house built before 1980, due to the risks associated with exposure to tap water (piping with lead solder) and old lead paint;
- A nutritional deficiency in calcium, vitamin D, protein, zinc and iron facilitates the absorption of lead by the body.
Prevention of lead intoxication
|In case of intoxication , since the symptoms have already declared themselves, it is too late to prevent. However, in case of contamination , the symptoms are not always detectable. The contamination must then be confirmed by a blood sample.
Recommendations vary from country to country. In Canada, screening for blood lead is recommended only for infants and children at high risk. The Centers for Disease Control and Prevention and the American Academy of Pediatrics recommend systematic screening for all children aged 1 to 2 years, as well as screening for at-risk adults.
According to Canadian experts, if the blood leads level is between 6 μg / dl and 10 μg / dl (which are higher than the Canadian average), the doctor should question the individual about his environment and try to reduce exposure to lead. , as a precautionary measure.
From 10 μg / dl, the monitoring of blood lead levels and concrete actions to reduce the sources of lead are important.
|Basic preventive measures|
|In general, the aim is to limit exposure to the various sources of lead as much as possible.
In the House
Medical treatment of lead intoxication
In the majority of cases, no medical treatment is indicated. The most important intervention is to detect and avoid further exposure to lead. This may require the home inspection by a professional. Medical follow-up is usually undertaken every 3 to 6 months.
In cases of severe acute intoxication , chelating agents such as succimer or EDTA(ethylenediaminetetraacetic acid) are used. They are injected into the veins where they bind to the lead molecules in the blood, and then are excreted in the urine. They can reduce blood lead from 40% to 50%. The number of treatments depends on the severity of the intoxication. With EDTA, the treatment lasts on average 5 days. It should not be unduly prolonged as the chelating agent also binds to minerals beneficial to the body, such as iron and zinc.
Note that chelation may involve risks important because lead is recirculated in the body. In addition, allergic reactions may occur. Few studies have evaluated the effectiveness of this treatment in reducing immediate symptoms and preventing the long-term effects of lead poisoning. The decision to use this type of treatment should always be made by talking to a doctor experienced in this area.
In parallel, the doctor recommends a healthy and nutritious food and if need supplements of calcium or iron.