Lead is an incredibly dangerous heavy metal with no known beneficial use in the body. It mimics calcium, affecting all calcium-dependent biological processes, and is known to disturb the cardiovascular, renal, endocrine, and nervous systems. In children, the brain is the most sensitive target, as the blood brain barrier is less effective in children than in adults, potentially causing developmental delays even at low levels of exposure [1].
Where Does the Lead in Dust Come From?
Dust lead concentrations are significantly elevated in areas where there was heavy motor vehicle traffic during the time when leaded gasoline was still in use, and around buildings coated with lead-based paint before it was banned.
How Does Lead Dust Affect Children?
Children are more susceptible than adults to lead exposure due to increased contact with dust and dirt contaminated with lead, increased hand-to-mouth contact, and higher absorption of lead in the gastrointestinal tract. Lead from past sources of contamination is still present in some areas, and this is generally more of a problem for lower income families and minorities that live in older housing without lead remediation. It is estimated that interventions to reduce lead exposure since the 1970s have raised the mean IQ by as much as 4.5 points in the United States [2]. This is great news, but recent research has shown that even low levels of lead exposure can be damaging, especially for children. In 2012, the CDC (Centers for Disease Control and Prevention) stated that there is no safe level of lead exposure in children [3]. A recent study completed in Rhode Island found that in 71,000 children born between 1997 and 2005 a 1 µg/dL increase in blood lead levels was associated with a 3.1% reduction in 3rd grade reading scores [4]. A 2009 study found that a return of $17-221 could be achieved for every $1 invested in lead paint hazard control, due to the costs of childhood lead exposure relating to public safety, productivity and health care [5].
Has Anything Been Done Recently to Protect Children from Lead Contamination in Dust?
The EPA itself acknowledged that "lead poisoning is the number one environmental health threat in the US for children ages 6 and younger." |
Not really. The EPA (Environmental Protection Agency) set standards in 2001 for lead contamination in soil and dust. In 2011 it was widely agreed that there needed to be stricter standards, but no timelines were set. Fast forward 6 years to 2017, and the EPA requested another 6 years to implement new regulations. On December 27, 2017, the US Circuit Court of Appeals for the Ninth Circuit in San Francisco ruled 2-1 that the EPA had 90 days to propose a new rule and implement it within a year, and at this point it is unclear if the EPA will appeal the ruling or update regulations. The EPA itself acknowledged that "lead poisoning is the number one environmental health threat in the US for children ages 6 and younger."
Sensitive Lead Testing to Monitor Exposure is Necessary
The most commonly accepted way to measure exposure to lead is by testing venous or capillary whole blood. Many laboratories and doctors’ offices have outdated testing methods that once catered to the high blood lead levels of the past (≥10 µg/dL). The CDC showed that 40% of laboratories participating in the LAMP (Lead and Multi-Element Proficiency) quality assurance program couldn’t detect a target blood level of 1.48 µg/dL, and through 2015 only 22% of laboratories reported a limit of detection <1 µg/dL [6]. This is a problem, as 94.9% of over 5 million children tested between 2009 and 2015 had lead results <3 µg/dL [7]. One of the most popular lead testing devices, the Lead Care II analyzer, has a lower range limit of 3.3 µg/dL, which is not sensitive enough to differentiate levels of blood lead that are now considered dangerous. ZRT Laboratory uses gold standard ICP-DRC-MS (inductively coupled dynamic reaction cell mass spectrometry) to test capillary blood spot lead levels, with a 0.2 µg/dL limit of detection, capable of measuring lead levels across multiple orders of magnitude.
Time for Change
It is time that the EPA takes action to prevent unnecessary exposure to lead. Past lead reduction programs have been very successful in reducing blood lead levels and helping prevent biological damage. It is also crucial that parents help to protect children by participating in blood, water, and dust lead screening programs, many which are available free of cost. It is now widely accepted that there is no safe level of exposure, and that delaying regulatory changes will undoubtedly result in unnecessary harm for both children and adults.
Note:
Original of this article was published (on ZRT Laboratory Blog.
References
[1] Lidsky TI, Schneider JS. Lead neurotoxicity in children: basic mechanisms and clinical correlates. Brain. 2003;126(Pt 1):5-19.
[2] Kaufman AS, Zhou X, Reynolds MR, Kaufman NL, Green GP, Weiss LG. The possible societal impact of the decrease in U.S. blood lead levels on adult IQ. Environ Res. 2014;132:413-20.
[3] CDC (2012), Low Level Lead Exposure Harms Children: A Renewed Call for Primary Prevention: Report to the CDCP by the Advisory Committee on Childhood Lead Poisoning Prevention of the U.S. Centers for Disease Control: Atlanta, GA, USA, The Centers for Disease Control (US).
[4] Aizer A, Currie J, Simon P, Vivier P. Do Low Levels of Blood Lead Reduce Children's Future Test Scores? American Economic Journal: Applied Economics. 2018; 10:307-345.
[5] Gould E1. Childhood lead poisoning: conservative estimates of the social and economic benefits of lead hazard control. Environ Health Perspect. 2009;117:1162-7..
[6] Caldwell KL, Cheng PY, Jarrett JM, Makhmudov A, Vance K, Ward CD, Jones RL, Mortensen ME. Measurement Challenges at Low Blood Lead Levels. Pediatrics. 2017;140(2).
[7] McClure LF, Niles JK, Kaufman HW. Blood Lead Levels in Young Children: US, 2009-2015. J Pediatr. 2016;175:173-81..