(Health Secrets) New information shows the U.S. Centers for Disease Control and Prevention (CDC) has been incorrect in its assessment of how much lead exposure is safe for children. Researchers from the University of Maryland (UM) in Baltimore recently found that children with blood lead levels ranging between 5 and 9 mcg/dL (micrograms per deciliter) scored a staggering 4.5 points lower on reading readiness measures than children exposed to 5 mcg/dL of lead or less. For the past 25 years, the CDC has told the public that lead exposure below 10 mcg/dL is safe.
The first assessment of its kind to look at lead exposure in association with reading readiness, the new study, led by UM Assistant Professor Pat McLaine, D.P.H., and her colleagues, looked specifically at urban kindergarteners with varying blood levels of lead to see if the toxic heavy metal affects reading and learning aptitude, particularly at low levels. Records containing this critical information were obtained from the Rhode Island Department of Health and the Providence Public School System.
Using a reading readiness assessment tool known as Phonological Awareness Literacy Screening – Kindergarten (PALS-K), which measures cognitive capacity with regard to reading ability, the team discovered that lead exposure, even at relatively minute levels below 10 mcg/dL, is still harmful. Based on their assessment, children who fall below the CDC’s longstanding “level of concern” threshold for lead exposure, which was recently dropped to 5 mcg/dL, are still prone to suffering cognitive impairment.
“Learning to read is critical to the entire process of formal education,” stated McLaine and her colleagues about the findings. And this, they say, requires “proficiency in phonologic processing skills (using the sounds of one’s language to process written and oral language) and in the ability to decode new words.”
PALS-K testing is normally administered to kindergarteners in the fall, and students are expected to score an 81 or higher on it by the time spring rolls around — children who fail the test initially are later given a second chance. Students who score lower than 28 on the test, which is scaled out of a total of 102, are typically given special attention throughout the year to help them catch up to the other students.
Most urban school children have excessive lead levels
With this in mind, it becomes clear why lead exposure can make it or break it for some students. According to data gathered as part of the new study, the median blood level of lead amongst all the 3,406 children evaluated was 4.2 mcg/dL. An astounding 20 percent of this group had blood lead levels exceeding 10 mcg/dL, and more than 66 percent tested with at least one reading of 5 mcg/dL or higher.
“These results are markedly higher than [National Health and Nutrition Examination Survey] estimates from the same time and suggest that national population estimates may seriously underestimate the lead problem in urban schools,” added the researchers.
“Our results suggest the need to evaluate current screening approaches for early reading intervention and to determine whether adding a history of elevated [blood lead levels] could improve targeting of children who are at risk of school failure and are not presently being captured in that system.”
As for the CDC, the agency now admits that there is really no safe level of lead exposure, despite years of suggesting that blood lead levels below 10 mcg/dL are safe. The CDC established new guidelines last year to progressively lower the “level of concern” threshold for lead every four years until it eventually reaches zero.
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