A Historical Perspective on the CDC Childhood Lead Poisoning Prevention Program

Just over 50 years ago, the Lead-Based Paint Poisoning Prevention Act of 1971 led to the establishment of the Childhood Lead Poisoning Prevention Program (CLPPP) at the Centers for Disease Control and Prevention (CDC). Since then, a broad, multifaceted environmental public health effort involving a wide array of government agencies and key stakeholders has led to marked declines in exposure levels and blood lead levels (BLLs) in the United States. Nevertheless, the effect of lead on young children and the resultant public health challenge remains. The scientific advances that have led to a better understanding of the deleterious effects of current lead exposures compel the ongoing public health efforts, with new shifts in emphasis and focus, to eliminate childhood lead poisoning. Although widely distributed in the environment, it is significantly related to poverty and inequity, particularly affecting Black and other minority children. Prevention has been a challenge only partially met, and lead poisoning still endures and remains to be fully eliminated.

HISTORICAL CONTEXT

In 1971, it was common to see children receiving chelation therapy for severe lead poisoning with BLLs greater than 70 micrograms per deciliter (µg/dL). The New York City Bureau of Lead Poisoning Control screening data for 1971 showed that the average geometric mean blood lead level in Black children aged 3 years was greater than 30 µg/dL and was in the mid-to-low 20s in Hispanic and White children.¹

New York City was not alone. In Chicago, Illinois, more than 68 000 children from high-risk areas were screened during 1967 and 1968. At the peak in June 1967, almost 15% had BLLs greater than 50 µg/dL, almost 4000 were referred to a special lead clinic for follow-up, and 1154 received chelation therapy.² In a 1972 review article, Lin-Fu summarized similar findings for other major Midwest and Northeast cities.³ At this point in time, lead paint was considered the prime source, and the significant role of leaded gasoline was not adequately understood before the National Health and Nutrition Examination Survey (NHANES), which is discussed in the next section. The role of other sources of lead (e.g., air, food, water, soil, cosmetics, folk remedies) also became more clearly delineated over the ensuing several decades.

From our current vantage point, the blood lead screening data from the late 1960s is nothing short of shocking. The tide turned in 1971. The US Surgeon General issued a Policy Statement on the Medical Aspects of Childhood Lead Poisoning (https://bit.ly/3bi5EMD) recommending screening all children aged 1 to 6 years living in old, poorly maintained housing, and screening children wherever local conditions demonstrated a lead hazard, with medical follow-up as needed. Today, this critical policy statement seems limited without corresponding emphases on primary prevention and a broader array of public health and environmental approaches; it is sobering to reflect on the pace of policy development over this 50-year period.

Eventually, the Lead-Based Paint Poisoning Prevention Act was passed in 1971 (https://bit.ly/3vploEs). Title I of the Act authorized the Secretary of the US Department of Health, Education, and Welfare, the predecessor of the US Department of Health and Human Services (DHHS), to provide funding to local government for detection and treatment of lead poisoning. Title II authorized the Secretary to make comparable funding for detection and elimination of lead-based paint from hazardous homes. This led to the creation of the first CDC lead program, the forerunner of today’s CLPPP. However, the realization of widespread testing and funding support of state-based programs has been a decades-long process, punctuated by intense public dialogue and periodic challenges to the program and its funding.

The then new CDC program took on the responsibility of providing updated lead guidance statements. The first appeared in 1975 (https://bit.ly/3OHwDij) and 1978 (https://bit.ly/3Q4wfeR), with subsequent updates approximately every six to seven years. Virtually all literature about the CDC program notes the steady reduction of lead screening levels in the guidance documents, from 60 µg/dL in the 1960s to 40, 30, 25, 10, 5, and now 3.5 µg/dL. BLLs fell rapidly in the ensuing decades, and knowledge of low-level effects kept increasing, with no evidence of a threshold level. As the focus shifted from secondary to primary prevention, the various terms delineating gradations of lead poisoning were dropped, replaced first by level of concern and most recently by a blood lead reference value (BLRV; discussed later).

NATIONAL HEALTH AND NUTRITION EXAMINATION SURVEY

Mahaffey et al.⁴ published the first report of the NHANES II data in September 1982 highlighting key demographic and socioeconomic factors associated with elevated BLLs. These were the first population estimates for the United States as a whole. They showed the widespread distribution of lead levels (e.g., the mean BLL for children aged 0.5 to 5 years was approximately 16 µg/dL). They also revealed critical differences by race and socioeconomic factors (e.g., overall, 12.2% of Black children compared with 2.0% of White children had BLLs greater than 30 µg/dL, and Black children living in urban areas of 1 million or more inhabitants averaged 22.9 µg/dL). As noted by Lin-Fu in an editorial accompanying the Mahaffey article: “How could a nation with such remarkable achievements in preventive medicine allow this preventable condition to afflict 4 percent of its preschool children—or worse, 18.6 percent of poor black children?”^5(p615)

Annest et al.⁶ followed in June 1983, with a review of the 1976–1980 NHANES II data showing a 37% decrease in national BLLs, closely correlated with the reduction of gasoline lead levels. This report probably sealed the fate of leaded gasoline, which was phased out in the United States in passenger cars over the following decade. It also showed the enormous value of NHANES for detailing national trends. Multiple publications of subsequent NHANES lead data documented the ensuing decrease of lead levels in the United States. Most recently, Egan et al.⁷ summarized the NHANES data from 1976 to 2016. The geometric mean BLLs in US children aged 1 to 5 years decreased from 15.2 µg/dL to 0.83 µg/dL between the 1976–1980 and the 2011–2016 NHANES cycles. In addition, the proportion of US children with BLLs greater than the previous BLRV of 5 µg/dL decreased from 99.8% to 1.3% during the same 40-year period for children aged 1 to 5 years, and from 99.7% to 0.5% for children aged 6 to 11 years.

CDC’S LEAD GUIDANCE STATEMENTS

The CDC Lead Guidance Statements of 1985 (https://bit.ly/3zhn9Vh), 1991 (https://bit.ly/3S84iET), and 1997 (https://bit.ly/3Brc7j6) span a transitional period, moving from secondary prevention toward primary prevention, and from a quest for universal screening (never fully accomplished) to targeted screening. This transition occurred as the blood lead screening level was reduced from 30 to 10 µg/dL, as knowledge about low-level effects of lead accumulated, and concerns about lead sources broadened. During this phase, the CLPPP prepared a report for the DHHS Secretary, which was released in 1991 as a Strategic Plan for the Elimination of Childhood Lead Poisoning (https://bit.ly/3zECaC4). It was coordinated with the release of plans from the Environmental Protection Agency (EPA) and US Department of Housing and Urban Development in a combined effort by the agencies to eliminate this disease, and the 1992 legislation, Title X of the Housing and Community Development Act, was another critical input at this time. The success of the lead poisoning prevention programs has ultimately benefitted from the ongoing collaboration among these three agencies, as well as key input from other federal agencies.

Also, within DHHS, the contribution of the National Institute of Environmental Health Sciences, National Institutes of Health in supporting the decades-long scientific effort to elucidate the effects of lead at low BLLs has been foundational. In addition, in 1997, President Clinton created the Task Force on Environmental Health Risks and Safety Risks to Children, cochaired by Donna E. Shalala, Secretary of DHHS, and Carol M. Browner, EPA Administrator. The Task Force was charged with recommending strategies for protecting children’s environmental health and safety, and it published Eliminating Childhood Lead Poisoning: A Federal Strategy Targeting Lead Paint Hazards (https://bit.ly/3zG0seQ) in 2000.

The 2005 CDC lead statement Preventing Lead Poisoning in Children (https://bit.ly/3zkbMMb) retained the level of concern at 10 µg/dL and was accompanied by a companion document, A Review of Evidence of Adverse Health Effects Associated With BLLs < 10 µg/dL in Children (https://bit.ly/3PIswnF). In 2012, with the recognition that any level of lead in the blood can be harmful, the CDC’s Advisory Committee on Childhood Lead Poisoning Prevention recommended that the agency abandon use of “BLL of concern,” and adopt the BLRV in its report titled Low Level Lead Exposure Harms Children: A Renewed Call for Primary Prevention (https://bit.ly/3OEphMp). The BLL of concern was used as a marker for determining when follow-up actions were required for elevated BLLs, but, by 2012, no level of lead in blood was considered normal (i.e., of no concern). Consequently, CDC accepted the Advisory Committee’s recommendation and established the BLRV at 5 µg/dL, based on the 97.5th percentile of BLLs for children aged 1 to 5 years from 2007 to 2010 NHANES data. The agency also agreed to update the BLRV every four years.

In 2021, a workgroup of the CDC’s Lead Exposure and Prevention Advisory Committee presented a report to the committee recommending lowering the BLRV from 5 µg/dL to 3.5 µg/dL (Recommendations for a Revised Blood Reference Value; https://bit.ly/3JdRUPs). Despite potential difficulties with implementing a BLRV of 3.5 µg/dL, including (1) the sensitivity and precision of the laboratory measurements,⁸ (2) challenges with messaging regarding action and follow-up services, and (3) a variety of resource constraints, the CDC agreed with the Lead Exposure and Prevention Advisory Committee that the benefits of lowering the BLRV outweighed these concerns. Thus, in October 2021, CDC lowered the BLRV from 5.0 µg/dL to 3.5 µg/dL to help ensure that BLLs less than 5 µg/dL will be routinely reported to parents and others who can take actions to reduce further exposure and to mobilize health and community resources to prevent additional harm to individuals, families, and communities.

CDC CHILDHOOD LEAD POISONING PREVENTION FUNDING PROGRAM

Since the early 1990s, CDC has provided funds to state and local health departments to support childhood lead poisoning prevention.⁹ Some key elements of the CLPPP were initiated in the 1990s, including the development of software and standardized data elements for the state-based surveillance programs and building linkages between health, housing, and environmental agencies. Funded programs helped to improve blood lead screening rates, surveilling high-risk populations, and linking lead-exposed children to effective follow-up services. Through its lead guidance documents and the active surveillance of BLLs in children, CDC has been a catalyst to and a partner of multiple agencies whose policies and regulatory actions have been critical to reducing lead levels in US children.

Despite progress, childhood lead poisoning remains a major preventable environmental health problem disproportionately affecting disadvantaged groups, including non-Hispanic Black children and those from low-income backgrounds. In 2021, CDC established cooperative agreements with 62 state and local health departments, including a new agreement with the Puerto Rico Department of Health. Almost $25 million was used to support these important partnerships, which is highly significant given that in 2012 the CDC’s appropriations were reduced to only $2 million resulting in the loss of funding for state and local programs.

CDC AND STATE AND LOCAL PARTNERS’ LEAD SURVEILLANCE SYSTEMS

In 1995, children’s BLLs became the first nationally notifiable noninfectious condition in the United States. Since then, CDC has relied on its state and local partners to provide data for the national surveillance system.

Childhood Blood Lead Surveillance

The Childhood Blood Lead Surveillance allows CDC to monitor progress toward childhood lead poisoning elimination, target prevention measures on a community scale, and identify individuals who are lead exposed so that appropriate medical management and environmental follow-up can take place. Cooperative agreements allow state and local childhood lead poisoning prevention programs to collect and report data on BLLs via the Healthy Homes and Lead Poisoning Surveillance System. The system is a Web-accessible centralized data warehouse for BLLs, environmental lead sampling, and follow-up information for case management.

Health Equity Considerations

The CLPPP embraces the principles of health equity and environmental justice, which are major strategic priorities of the agency. Health is a fundamental human right, and yet, health inequities abound globally and in the United States. Health equity is achieved when all people have the opportunity to reach the highest level of health they are capable of achieving. Health equity requires valuing everyone equally, with focused and ongoing efforts to address avoidable inequalities and historical and contemporary injustices. Health equity means reducing and ultimately eliminating disparities in health and its determinants that adversely affect groups that have been excluded or marginalized.

The connection between health and socioeconomic factors such as housing, education, and race is clear.¹⁰ This argument is amply supported by the epidemiology of childhood lead poisoning in the United States, which, over the last 40 years, has consistently shown that the consequences of this scourge are disproportionately borne by people from racial and ethnic minority groups and those living in poverty.^7,11

In full recognition of these factors, CDC stipulated in its 2021 Notice of Funding Opportunity that public health action is needed to improve health equity by supporting strategies and activities to eliminate disparities in BLLs by social, demographic, and geographic factors and, ultimately, to eliminate childhood lead poisoning as a public health problem.

The Flint Registry

Out of the unfortunate circumstances of the Flint, Michigan, water crisis, there came greatly increased national interest in lead poisoning as a public health problem.¹² Congress provided special funding for novel approaches to lead poisoning prevention and mitigation on a community scale in Flint, including establishment of a registry. The Flint Registry was designed, built, and implemented with funds provided to Michigan State University by CDC. The major goals of the Flint Registry are to achieve the lead poisoning prevention objectives of reduced lead exposures at work, home, and play and increased use of preventive services.¹³ As of July 2021, more than 16 000 persons were enrolled and more than 22 000 referrals made for follow-up services. Children are most frequently referred to neurodevelopmental services (44%) and the Lead Safe Home Program (35%). Two thirds of all enrollees receive at least 1 referral, with an average of two referrals per participant according to the registry’s inaugural report (https://bit.ly/3SyJdU6). More recent reports indicate that as of May 2022, 18 000 persons were enrolled and 26 500 referrals made.

CDC’s Lead-Free Communities Initiative

CDC is developing a Lead-Free Communities Initiative, which will aid in organizing and prioritizing screening for children at most risk for lead exposure. The initiative will work with states to support capacity building in disadvantaged communities that, because of a history of being underserved and underresourced, face greater risks of being exposed to lead hazards and other environmental injustices.

CONCLUSIONS

The CLPPP has been sustained by the CDC for more than 50 years. It has been a key component of a broad national effort to greatly diminish BLLs among US children. However, an ever-growing body of scientific evidence shows effects of lead on children at lower and lower levels, with no apparent threshold. As a result, public health programs have evolved to meet the challenge of eliminating lead exposures at lower levels. Furthermore, the development of public policy in this area has often been challenged by key vested interests (e.g., housing, mining, industrial) and others, leading to conflicting perspectives and challenges to program support. In addition, throughout this entire period, lead exposure risk is disproportionately concentrated among the most vulnerable children in our society. The CLPPP continues its efforts, with others, to eliminate childhood lead poisoning.