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The US Centers for Disease Control and Prevention has updated its blood lead reference value-children aged 1-5 are considered to have high levels of lead exposure. Since 2012, the threshold has been set at 5 micrograms of lead per deciliter of blood; children at or above this level account for the top 2.5% of the highest blood lead levels in the country.
Now, in response to the most recent federal health survey, the CDC has updated this figure to 3.5 micrograms per deciliter. Environmental scientist Gabriel Filippelli has studied urban lead poisoning in children, and he explained what this change means for public health.
The Centers for Disease Control regularly reviews national data on blood lead levels in children. This new lower value is the average blood lead level exceeded by 2.5% of the children tested.
Many clinics have on-site screening equipment that uses electrochemical testing to quickly detect small amounts of blood pierced by the fingertips. If the child tests positive, the doctor will recommend that they take a larger blood sample from a vein and analyze it in a diagnostic laboratory. Clinical trials are fast, inexpensive, and relatively painless, but intravenous blood sampling is the gold standard for diagnosing lead poisoning.
Read more: The U.S. has introduced stricter standards for lead poisoning in children
On-site clinical equipment can usually detect lead as low as 3.2 micrograms per deciliter, so the new CDC guidelines mean that almost all children who show a positive result at the screening level will be referred for follow-up testing. From a public health point of view, this is more protective.
However, this will roughly double the number of children classified as the highest risk of lead poisoning. Previously, children must have at least 5 micrograms per deciliter of lead in their blood to be included in this group; now it will include thousands of children with slightly lower blood lead levels.
More children means that many states will find it difficult to afford testing and follow-up care-which may involve dietary changes and medications, as well as the elimination of lead exposure sources-unless Congress increases federal support for the prevention and treatment of lead poisoning programs.
The most common source, especially in cities, is soil and soil dust. Due to years of emissions from degraded leaded paint, leaded gasoline, and industrial sources, lead concentrations in typical urban soils range from benign to toxic. When children touch or play with contaminated dirt or breathe in dust, they will be exposed.
The U.S. Environmental Protection Agency has a limit of 400 parts per million of lead in the soil of public play areas. This is significantly higher than the typical background level, which is about 20 to 50 parts per million.
Some states in the United States, such as California, have much lower limits. According to my experience, the lead content in urban soil is much higher, especially near the outer walls of buildings. Lead may accumulate due to paint degradation or dust accumulation, which is not uncommon.
Communities with the most lead pollution in cities tend to be the poorest and homes with the highest proportion of non-white children. This is the legacy of racist housing practices that concentrate people of color in less-than-ideal neighborhoods. Residents in these areas have a significantly higher rate of elevated blood lead levels than those in wealthy communities.
Lead paint is also a major exposure risk, especially in poorly maintained buildings. Lead paint tastes sweet, so children sometimes chew on paint chips or painted wood.
Read more: How quarantine and neglect can plunge Benton Harbor, Michigan into toxic water
Lead water pipes are the third source, although not as common as paint or soil. Many cities and towns in the United States have leading service routes to supply water to households. If their water is treated properly, a protective plaque will form inside the pipe and seal the lead content in the water.
But some cities, including Washington, DC, Newark, New Jersey, and Flint, Michigan, have changed their water sources or treatment processes to remove protective plaque and bring lead to household taps. These water crises have disproportionately affected communities of color.
Historically, public health interventions have focused on acutely poisoned children who exhibit obvious neurocognitive problems, such as attention deficit, memory loss, agitation and even tremors. With the gradual removal of lead from most household uses in the mid-20th century, and the decline in blood lead levels in the American population, the clinical manifestations of these obvious lead poisonings have declined.
What we are seeing now are more subtle neurocognitive deficits, which are measured by scientists and medical experts through neurological and behavioral tests. Children diagnosed with high blood lead levels today may perform poorly on standardized tests, perform poorly in class or at home, or have difficulty remembering information. Flint's follow-up research shows that many infants and young children who were exposed to lead in water there in 2015 are now struggling in school.
These types of tests show that even lower blood lead levels than the new standard still affect performance. This research is the basis for a statement by scholars and the Centers for Disease Control and Prevention that there is no safety statement for children's blood lead levels.
Since the elimination of most major environmental lead sources in the 1970s, such as leaded gasoline, lead paint, and industrial emissions, lead levels have been declining. Recent analysis shows that the median blood lead level of all American children between the ages of 1 and 5 today is approximately 0.7 micrograms per deciliter, compared with 15 micrograms per deciliter in the late 1970s.
But the average blood lead level of black and poor children is 13% higher than the national average, which means that many of them are at risk.
For example, in a 2019 study, I worked with colleagues from the University of Notre Dame to analyze the blood lead levels of more than 18,000 children in St. Joseph County, Indiana, including the town of South Bend. In some communities, more than 30% of children have blood lead levels above 5 micrograms per deciliter, and more than 65% of census tracts have average blood lead levels above this safe limit.
We also found that there is no systematic and risk-prompt testing method. In areas with the highest potential risk based on poverty levels, fewer than 6% of eligible children reported lead test results to the county health department—the same rate as in other wealthier census areas. Without more screening and more work to eliminate lead exposure in the most dangerous communities, this problem will not be resolved in a long time.
This article is republished from The Conversation under a Creative Commons license. Read the original text.
Left: On March 6, 2016, in Flint, Michigan, a child was tested for lead poisoning in his blood at a clinic when the drinking water in the city was contaminated with dangerously high levels of lead. Jim Young/Reuters
Michael Felice, Associated Press
Author: Mike Stobbe, Associated Press
Gabriel Filipeli, dialogue with Gabriel Filipeli, dialogue
Gabriel Filippelli is Professor of Earth Sciences and Director of the Center for Urban Health at Indiana University-Purdue University Indianapolis.
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