Mayor de Blasio has decided it’s time to get the lead out. Earlier this year, he launched LeadFreeNYC. Its stated mission: to eliminate childhood lead exposure by 2029. The initiative claims to be “the most aggressive and holistic approach to protecting kids from lead of any city or state in the nation.” In support, the City Council passed a flurry of legislation late last month.
The vision zero mission is admirable: lead poisoning is a serious problem. Research has demonstrated no safe level of lead, and any pollutants actively harming a child must be tracked down and eliminated.
But the strategy outlined to accomplish this mission dangerously underestimates how difficult this task really is. It relies on mandatory blood tests to screen kids and trigger investigations, based on the assumption that New York’s most vulnerable children are easily identified when every kid is tested.
This is incorrect. As counterintuitive as it may seem, routine screening obscures which children are most at-risk. A misunderstanding of laboratory tests is now poised to initiate a major distraction — at best unnecessarily burdening families, homeowners and day-cares — at worst diverting resources away from New York’s neediest children.
The problem with routine screening is that laboratory tests measure the amount of lead in a child’s blood with error, falsely identifying some healthy kids as sick and some sick kids as healthy. The majority of positive tests are wrong for children without symptoms or risk factors. Studies have found more than 70% of positive tests to be error. Ignoring this — as policymakers typically do — harms children in two ways.
First, falsely identified children are put at increased risk for lead exposure when remediation, such as scrubbing lead paint, releases toxic dust that posed no hazard if left undisturbed. Not to mention closing an apartment or day-care leaves parents scrambling for costly, alternative arrangements.
These errors are mitigated by administering additional tests, but the disadvantages are consequential enough that the U.S. Preventive Services Task Force — the independent panel of experts tasked with developing recommendations for clinical preventive services — explicitly advises against the “routine screening for elevated blood lead levels in asymptomatic children aged 1 to 5 years who are at average risk.” It grades the policy a D, its lowest possible rating, concluding the benefit does not justify the harm.
Second, New York’s neediest children are underrepresented when the number of positive tests citywide are combined to form a measure of community well-being. This is because not all kids are equally likely to test positive in error. A wealthier neighborhood with many positive tests likely has fewer risk factors and therefore fewer children that are actually positive.
For example, in 2017 both East New York and Southeast Queens had 1.3% of tests come back positive, but East New York households have half the average income and 200 times the number of violations for lead paint as recorded by the Department of Housing Preservation and Development. Other differences, such as who takes which kind of test — and the frequency and conditions under which the tests are taken — further influence the measure, likely to the detriment of disadvantaged neighborhoods.
The extent to which resources will be diverted away from needy children is difficult to determine. Any comprehensive, transparent evaluation is complicated by the laws that protect the details of children’s medical records. But history suggests the number of positive tests will continue to dominate public discussion, placing tremendous pressure on agencies to prioritize the areas with the highest number of positive tests — not necessarily the areas with the greatest risk of lead exposure.
To be clear: There is nothing wrong with a law that requires every child to take a lead test. But diagnosis is best left to medical professionals who can evaluate each kid on a case-by-case basis. Indeed, the Centers for Disease Control and Prevention, which sets the standard for the lead test, urges “recommending environmental assessments PRIOR to blood lead screening of children at risk for lead exposure” (their emphasis). Without this additional evidence, the mere existence of positive tests is inconclusive, unexceptional, and unworthy of public outrage.
Policies that override the judgement of experts have fallen out of fashion. Over the past decade, researchers in medicine, education, public safety and academia have worked hard to eliminate uninformative tests from decisionmaking. Each time, the story is the same. At first the test appears fair, transparent and economical, but unintended consequences ultimately undermine its value.
LeadFreeNYC disregards these lessons — and the explicit recommendations of the U.S. Preventive Services Task Force — leaving one to wonder whether de Blasio is interested in cleaning up New York or just his image after NYCHA’s lead paint scandal.
Auerbach is a PhD candidate in Columbia University’s Department of Statistics.
