While the earth’s crust naturally contains lead, it has no effect on the health of the general population. In contrast, human activities cause high levels of lead contamination. The effects of lead contamination on general health, especially among children, are severe.
An association has been observed between elevated blood lead levels in children and decreased IQ after exposure to lead, even at levels below one microgram per deciliter. In adults, an association between blood lead levels and an increased risk of cardiovascular disease and death has been observed, even at low levels.
One of the greatest historical sources of lead exposure was the use of tetraethyl lead in gasoline in the early twentieth century. It is estimated that this led to the release of at least 9 million tons of lead into the environment. The United States was the first country to ban leaded gasoline in 1975. Shortly afterwards, the decision to phase out lead-containing gasoline became universal.
Other high-income countries, such as Sweden and Germany, did the same in the 1980s and 1990s. Thanks to this decision, the average level of lead in the blood of the people in the United States between 1976 and 1991 decreased by nearly 78%. Researchers have seen similar declines in other high-income countries.
Meanwhile, developing countries implemented phasing out, and finally, at the end of 2005, abandoned the use of leaded gasoline in cars. However, the average blood lead level of the general population in low- and middle-income countries is still significantly higher than in developed countries.
In a new study published in the journal Lancet Planet Health, a team of researchers looked at major sources of lead exposure in 49 developing countries. Brett Erickson The University of Macquarie Australia and colleagues estimate that the blood lead levels of 632 million children in 34 developing countries are higher than the reference level of 5 micrograms per deciliter set by the US Centers for Disease Control and Prevention. Researchers explain:
The difference between developing and developed countries is severe. In the United States, for example, data from the 2017 National Children’s Blood Monitoring Program showed that less than 2 percent of children (zero to five years old) had more than 5 micrograms per deciliter.
According to researchers’ analyzes, the four main sources of lead exposure in developing countries are: Irregular production and recycling of acid batteries (lead-acid batteries); ۲. Extraction and processing of metals; 3. Electronic waste; 4. Use of lead as a cheat in food and mainly in spices. “This finding is worrying,” say researchers. “In particular, research continues to show adverse effects of lead, even in very small amounts.”
To further explore how the general population in developing countries is typically exposed to high levels of lead, a group of researchers systematically reviewed 520 studies that reported blood lead levels in people in 49 countries. The study included 1,345,455 people living in low- and middle-income countries. The studies were published from January 1, 2010 to October 31, 2019.
Studies involving at least 30 participants were reviewed for inclusion in the analysis if they contained blood lead data from human populations in low- and middle-income countries. Another criterion for selecting previous studies was that data had been collected since 2005. The largest number of studies (149 studies) included in the analysis was in China. Other countries that had adequate data on blood lead levels were: Mexico, India, Bangladesh, Brazil, Egypt, Iran, Nigeria, Pakistan, South Africa, Thailand, Turkey, Ethiopia, Sudan, Sri Lanka, Nepal, Palestine, Russia. , Vietnam and Myanmar.
Children in Palestine and Pakistan had the highest blood lead concentrations of 30.9 and 27.9 micrograms per deciliter, respectively, which is approximately twice as high as 5 micrograms per deciliter set by the Centers for Disease Control and Prevention as the reference level. Other countries where children were exposed to high levels of lead were: Cameroon (blood lead level 70.8 μg / dl), Egypt (24.8 μg / dl), Senegal (22.8 μg / dl), Serbia (80.7 micrograms per deciliter) and Nigeria (67.7 micrograms per deciliter).
Researchers estimate that of the 1.3 billion children (zero to fourteen years old) living in 34 low- and middle-income countries with sufficient data on their children’s lead levels, approximately 413 million children (31.7%) have lead levels. They have more than 10 micrograms per deciliter of blood. Not to mention that in Pakistan and Egypt, adults had the highest blood lead concentrations at 36.11 and 36.10 μg / dl, respectively.
Analysis of published blood lead levels in developing countries contains three important findings:
1. There is a shortage of low- and middle-income countries in terms of accurate data on lead exposure in the general population. In the 137 countries designated by the World Bank as low- and middle-income countries, only 44 countries had sufficient information on blood lead levels for adults and even less (34 countries) for children;
۲. Children’s blood lead figures may indicate that the global exposure of these countries is too low; Because they included only 34 of the 137 low- and middle-income countries;
3. While lead-based paints used in residential areas are a source of lead exposure in the United States, they do not appear to be an important source of lead exposure in low- and middle-income countries.