New research highlights the dangerous effects of exposure to lead and other toxic metals early in life, suggesting that it may increase a child’s risk of autism.
In a study published this month in the medical journal Nature Communications, researchers with the Icahn School of Medicine at Mount Sinai in New York tested levels of lead and other metals in infants’ teeth, to see if there was any connection between elevated levels and the later diagnosis of autistic spectrum disorders (ASD).
The research involved an analysis of the levels of metal from the teeth of 154 pairs of twins, looking for lead, zinc and manganese through the use of lasers.
According to the findings, higher levels of lead were generally associated with an increased risk of autism. However, researchers also found that having lower than expected levels of manganese and zinc also appeared to be related to increased risk.
Researchers found that in twins where one was autistic and the other was not, lead levels were consistently higher in the twin diagnosed with autism from 20 weeks before birth to 30 weeks after. At 15 weeks postnatally, lead levels were 1.5 times higher in autistic children than in those who had not been diagnosed with autism.
The study authors note that while about half of autism cases are likely genetic, exposure to lead and other environmental factors could play a role very early in life.
“Early signs of ASD first manifest 6-12 months after birth, suggesting a narrow window for environmental factors to contribute to ASD risk,” the researchers determined. However, they said that the study does not definitively prove that lead exposure, or a lack of zinc or manganese actually can cause autism.
Lead exposure is known to place children at risk for side effects of lead poisoning, which can cause serious nervous system injury, brain damage, seizures, growth or mental disability, as well as other severe health problems throughout the rest of their childhood and life.
One of the more common causes of of lead poisoning is lead-based paint, which was banned in the United States in 1978 due to the risk of severe and permanent brain damage and developmental problems, particularly in children. However, a number of older homes still contain the toxic paint on the walls, and if it flakes or peals off, young children could ingest the paint chips or breathe dust that comes from the paint, resulting in lead poisoning.
In recent years, there has also been an increased focus on lead in drinking water, stemming from the recent and ongoing Flint water crisis, during which a change to the water system in the Michigan city resulted in high levels of lead in residents’ drinking water, causing thousands of children to suffer lead exposure and, potentially, lead poisoning.
The CDC estimates that 535,000 children ages 1-5, or about 2.6% of such children in the U.S., have levels of lead in their blood that place them at risk for adverse health effects. To come up with that number, the CDC analyzed data from the National Health and Nutrition Examination Survey from the years 1999 to 2002, and 2007 through 2010.
The CDC is currently considering dropping its level of concern for lead levels even lower, which could significantly increase that number.
The majority of those children are poor and live in older urban areas, mainly in the inner city. Most are minorities, meaning such exposures add to numerous problems already plaguing inner city black and Latino youths, such as poverty, high crime and poor schools.