The Flint, Michigan water crisis has brought concern about lead toxicity in drinking water back into the headlines. But the public health issue goes well beyond Flint: According to recent estimates, more than half the population of the US was exposed to high levels of lead as children. This information has presented scientists with a new question: How does damage from lead exposure manifest as people age?
Children who are exposed to lead-contaminated drinking water may end up with a worse baseline of cognitive function in old age, according to new research.
The analysis of data from the US-based longitudinal Health and Retirement Study (HRS), published Wednesday in the peer-reviewed journal Science Advances, notes that lead exposure in childhood does not speed the rate of cognitive decline. Rather, juvenile exposure to lead can permanently harm the central nervous system, impairing cognition defined by metrics such as IQ and academic performance.
“The conditional association between childhood lead exposure and baseline cognitive functioning… was equivalent to the effect of eight additional years of age," researcher Haena Lee said.
Life-long consequences of exposure to lead
It has long been known that lead exposure is a danger in childhood, but this study is one of the first to examine its impact later in life.
“The conditional association between childhood lead exposure and baseline cognitive functioning… was equivalent to the effect of eight additional years of age."
Haena Lee
To do so, the team analyzed data from three HRS cognitive tests repeatedly taken by participants from 1998 to 2016. They looked at 1940 census records to pinpoint where those participants lived as children.
This gave researchers a sample of 1,089 older adults with varying degrees of past lead exposure who were living in 398 different cities in 1940.
The researchers theory was that among this sample, cognitive function would be worse, and the rate of cognitive decline would be steeper for those who spent their early years in places with lead-contaminated water. However, their results surprised them, showing no indication of their second prediction being correct. Although cognitive ability was worse in adults with a history of lead exposure, the rate of cognitive decline was surprisingly similar across both groups.
The authors argue that this unexpected finding demonstrates that little is known about the impact of childhood lead exposure later in life – and that repairing this knowledge gap is vital because adults who grew up in the leaded gasoline era are growing older.
“More research is clearly and urgently needed to better understand the lifelong implications of childhood lead exposure for brain aging and to identify effective interventions to mitigate lead’s long-term consequences,” the authors write.
“Our findings are also germane to public health concerns about American children born during the 1960s, 1970s, and 1980s who were exposed to historically unprecedented levels of lead via leaded gasoline and other sources."