A U.S. Lead Exposure Hotspots Analysis.

To identify U.S. lead exposure risk hotspots, we expanded upon geospatial statistical methods from a published Michigan case study. The evaluation of identified hotspots using five lead indices, based on housing age and sociodemographic data, showed moderate-to-substantial agreement with state-identified higher-risk locations from nine public health department reports (45-78%) and with hotspots of children's blood lead data from Michigan and Ohio (e.g., Cohen's kappa scores of 0.49-0.63). Applying geospatial cluster analysis and 80th-100th percentile methods to the lead indices, the number of U.S. census tracts ranged from ∼8% (intersection of indices) to ∼41% (combination of indices). Analyses of the number of children <6 years old living in those census tracts revealed the states (e.g., Illinois, Michigan, New Jersey, New York, Ohio, Pennsylvania, Massachusetts, California, Texas) and counties with highest potential lead exposure risk. Results support use of available lead indices as surrogates to identify locations in the absence of consistent, complete blood lead level (BLL) data across the United States. Ground-truthing with local knowledge, additional BLL data, and environmental data is needed to improve identification and analysis of lead exposure and BLL hotspots for interventions. While the science evolves, these screening results can inform "deeper dive" analyses for targeting lead actions.

A Systematic Review and Meta-analysis of Chemical Exposures and Attention-Deficit/Hyperactivity Disorder in Children.

Exposure to certain chemicals prenatally and in childhood can impact development and may increase risk for attention-deficit/hyperactivity disorder (ADHD). Leveraging a larger set of literature searches conducted to synthesize results from longitudinal studies of potentially modifiable risk factors for childhood ADHD, we present meta-analytic results from 66 studies that examined the associations between early chemical exposures and later ADHD diagnosis or symptoms. Studies were eligible for inclusion if the chemical exposure occurred at least 6 months prior to measurement of ADHD diagnosis or symptomatology. Included papers were published between 1975 and 2019 on exposure to anesthetics (n = 5), cadmium (n = 3), hexachlorobenzene (n = 4), lead (n = 22), mercury (n = 12), organophosphates (n = 7), and polychlorinated biphenyls (n = 13). Analyses are presented for each chemical exposure by type of ADHD outcome reported (categorical vs. continuous), type of ADHD measurement (overall measures of ADHD, ADHD symptoms only, ADHD diagnosis only, inattention only, hyperactivity/impulsivity only), and timing of exposure (prenatal vs. childhood vs. cumulative), whenever at least 3 relevant effect sizes were available. Childhood lead exposure was positively associated with ADHD diagnosis and symptoms in all analyses except for the prenatal analyses (odds ratios (ORs) ranging from 1.60 to 2.62, correlation coefficients (CCs) ranging from 0.14 to 0.16). Other statistically significant associations were limited to organophosphates (CC = 0.11, 95% confidence interval (CI): 0.03-0.19 for continuous measures of ADHD outcomes overall), polychlorinated biphenyls (CC = 0.08, 95% CI: 0.02-0.14 for continuous measures of inattention as the outcome), and both prenatal and childhood mercury exposure (CC = 0.02, 95% CI: 0.00-0.04 for continuous measures of ADHD outcomes overall for either exposure window). Our findings provide further support for negative impacts of prenatal and/or childhood exposure to certain chemicals and raise the possibility that primary prevention and targeted screening could prevent or mitigate ADHD symptomatology. Furthermore, these findings support the need for regular review of regulations as our scientific understanding of the risks posed by these chemicals evolves.

Update of the Blood Lead Reference Value - United States, 2021.

The negative impact of lead exposure on young children and those who become pregnant is well documented but is not well known by those at highest risk from this hazard. Scientific evidence suggests that there is no known safe blood lead level (BLL), because even small amounts of lead can be harmful to a child's developing brain (1). In 2012, CDC introduced the population-based blood lead reference value (BLRV) to identify children exposed to more lead than most other children in the United States. The BLRV should be used as a guide to 1) help determine whether medical or environmental follow-up actions should be initiated for an individual child and 2) prioritize communities with the most need for primary prevention of exposure and evaluate the effectiveness of prevention efforts. The BLRV is based on the 97.5th percentile of the blood lead distribution in U.S. children aged 1-5 years from National Health and Nutrition Examination Survey (NHANES) data. NHANES is a complex, multistage survey designed to provide a nationally representative assessment of health and nutritional status of the noninstitutionalized civilian adult and child populations in the United States (2). The initial BLRV of 5 µg/dL, established in 2012, was based on data from the 2007-2008 and 2009-2010 NHANES cycles. Consistent with recommendations from a former advisory committee, this report updates CDC's BLRV in children to 3.5 µg/dL using NHANES data derived from the 2015-2016 and 2017-2018 cycles and provides helpful information to support adoption by state and local health departments, health care providers (HCPs), clinical laboratories, and others and serves as an opportunity to advance health equity and environmental justice related to preventable lead exposure. CDC recommends that public health and clinical professionals focus screening efforts on populations at high risk based on age of housing and sociodemographic risk factors. Public health and clinical professionals should collaborate to develop screening plans responsive to local conditions using local data. In the absence of such plans, universal BLL testing is recommended. In addition, jurisdictions should follow the Centers for Medicare & Medicaid Services requirement that all Medicaid-enrolled children be tested at ages 12 and 24 months or at age 24-72 months if they have not previously been screened (3).

Blood Lead Levels in U.S. Children Ages 1-11 Years, 1976-2016.

BACKGROUND: Lead can adversely affect child health across a wide range of exposure levels. We describe the distribution of blood lead levels (BLLs) in U.S. children ages 1-11 y by selected sociodemographic and housing characteristics over a 40-y period. METHODS: Data from the National Health and Nutrition Examination Survey (NHANES) II (1976-1980), NHANES III (Phase 1: 1988-1991 and Phase II: 1991-1994), and Continuous NHANES (1999-2016) were used to describe the distribution of BLLs (in micrograms per deciliter; 1µg/dL=0.0483µmol/L) in U.S. children ages 1-11 y from 1976 to 2016. For all children with valid BLLs (n=27,122), geometric mean (GM) BLLs [95% confidence intervals (CI)] and estimated prevalence ≥5µg/dL (95% CI) were calculated overall and by selected characteristics, stratified by age group (1-5 y and 6-11 y). RESULTS: The GM BLL in U.S. children ages 1-5 y declined from 15.2µg/dL (95% CI: 14.3, 16.1) in 1976-1980 to 0.83µg/dL (95% CI: 0.78, 0.88) in 2011-2016, representing a 94.5% decrease over time. For children ages 6-11 y, GM BLL declined from 12.7µg/dL (95% CI: 11.9, 13.4) in 1976-1980 to 0.60µg/dL (95% CI: 0.58, 0.63) in 2011-2016, representing a 95.3% decrease over time. Even so, for the most recent period (2011-2016), estimates indicate that approximately 385,775 children ages 1-11 y had BLLs greater than or equal to the CDC blood lead reference value of 5µg/dL. Higher GM BLLs were associated with non-Hispanic Black race/ethnicity, lower family income-to-poverty-ratio, and older housing age. DISCUSSION: Overall, BLLs in U.S. children ages 1-11 y have decreased substantially over the past 40 y. Despite these notable declines in population exposures to lead over time, higher GM BLLs are consistently associated with risk factors such as race/ethnicity, poverty, and housing age that can be used to target blood lead screening efforts. https://doi.org/10.1289/EHP7932.

Decreases in Young Children Who Received Blood Lead Level Testing During COVID-19 - 34 Jurisdictions, January-May 2020.

Exposure to lead, a toxic metal, can result in severe effects in children, including decreased ability to learn, permanent neurologic damage, organ failure, and death. CDC and other health care organizations recommend routine blood lead level (BLL) testing among children as part of well-child examinations to facilitate prompt identification of elevated BLL, eliminate source exposure, and provide medical and other services (1). To describe BLL testing trends among young children during the coronavirus disease 2019 (COVID-19) pandemic, CDC analyzed data reported from 34 state and local health departments about BLL testing among children aged <6 years conducted during January-May 2019 and January-May 2020. Compared with testing in 2019, testing during January-May 2020 decreased by 34%, with 480,172 fewer children tested. An estimated 9,603 children with elevated BLL were missed because of decreased BLL testing. Despite geographic variability, all health departments reported fewer children tested for BLL after the national COVID-19 emergency declaration (March-May 2020). In addition, health departments reported difficulty conducting medical follow-up and environmental investigations for children with elevated BLLs because of staffing shortages and constraints on home visits associated with the pandemic. Providers and public health agencies need to take action to ensure that children who missed their scheduled blood lead screening test, or who required follow-up on an earlier high BLL, be tested as soon as possible and receive appropriate care.