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

2021; National Institute of Environmental Health Sciences; Volume: 129; Issue: 3 Linguagem: Inglês

10.1289/ehp7932

1552-9924

Kathryn B. Egan, Cheryl R. Cornwell, Joseph G. Courtney, Adrienne S. Ettinger,

Heavy metals in environment

Vol. 129, No. 3 ResearchOpen AccessBlood Lead Levels in U.S. Children Ages 1–11 Years, 1976–2016 Kathryn B. Egan, Cheryl R. Cornwell, Joseph G. Courtney, and Adrienne S. Ettinger Kathryn B. Egan National Center for Environmental Health, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, USA , Cheryl R. Cornwell National Center for Environmental Health, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, USA , Joseph G. Courtney National Center for Environmental Health, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, USA , and Adrienne S. Ettinger Address correspondence to Adrienne S. Ettinger, Rutgers Biomedical and Health Sciences, 89 French St., Suite 4100, New Brunswick, NJ 08901 USA. Email: E-mail Address: [email protected] National Center for Environmental Health, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, USA Rutgers Biomedical and Health Sciences, Rutgers University, New Brunswick, New Jersey USA Published:17 March 2021CID: 037003https://doi.org/10.1289/EHP7932AboutSectionsPDF Supplemental Materials ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail AbstractBackground: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/EHP7932IntroductionLead can adversely affect child health across a wide range of biological markers of exposure and no safe level of lead in children has been identified (ACCLPP 2012). Adverse neurobehavioral effects of lead exposure in young children, as measured by blood lead levels (BLLs), are well-known (ACCLPP 2012; Bellinger and Needleman 2003; Lanphear et al. 2005). Studies have consistently documented negative effects of lead on cognitive function and attention-related and behavioral problems (NTP 2012). Low-level exposure, including BLLs of <5 and <10μg/dL, have been associated with decreases in academic performance in school-age children (McLaine et al. 2013; Min et al. 2009; Miranda et al. 2009). Recent studies suggest that effects of childhood lead exposure on cognitive function and socioeconomic status (SES) may persist into adulthood (Reuben et al. 2017).Since 1976, the National Health and Nutrition Examination Survey (NHANES) has estimated lead exposure for the U.S. population through BLLs measured in adults and children. Previous analyses of NHANES data indicate that BLLs in U.S. children have generally declined over time (Caldwell et al. 2017; Jones et al. 2009; Pirkle et al. 1994; Raymond et al. 2014). These declines have largely been achieved through federal regulations, including the removal of lead in gasoline and the banning of both lead-based paint and lead plumbing solder for residential uses, as well as applied public health efforts (Dignam et al. 2019). Despite these overall population declines in exposure to lead, recent high-profile events, such as the Flint Water Crisis, have highlighted ongoing sources of lead exposure in children (Hanna-Attisha et al. 2016; Ruckart et al. 2019). Persistent lead hazards in the environment include deteriorating lead-based paint and dust in housing built before 1978; lead-contaminated soil from paint and petroleum products; lead pipes, fixtures, and solder in household plumbing; aviation fuel; and existing hazardous waste sites (President's Task Force on Environmental Health Risks and Safety Risks to Children 2018). Additionally, children may come into contact with other preventable sources of lead exposure through family members by occupational take-home lead, use of traditional or folk medicines, and hobbies such as making fishing sinkers, bullets, stained glass, and ceramic glazes (Alarcon 2016). Lead has also been found in consumer products such as vitamins, cosmetics, spices, and certain foods (Pfadenhauer et al. 2016).Previous NHANES analyses of BLL data have compared trends in children over select time periods, age groups, and sociodemographic characteristics (Jones et al. 2009; Pirkle et al. 1994, 1998; Tsoi et al. 2016). For example, in the 2007–2010 NHANES survey cycles, at least half a million children ages 1–5 y were estimated to have BLLs above the Centers for Disease Control and Prevention (CDC) blood lead reference value of 5μg/dL, with higher prevalence among non-Hispanic Black or poor children (Wheeler and Brown 2013). However, these estimates did not include older children (i.e., ages 6–11 y or older). In addition, lead in drinking water is a potential source of elevated BLLs in school-age children; recent studies have documented lead in drinking water in public water systems, including in some U.S. school districts (Renner 2009; Triantafyllidou et al. 2014). Additionally, there are at least 500,000 U.S. women of childbearing age exposed to lead at levels that may pass to developing fetuses and breastfeeding infants (Ettinger et al. 2020).To date, there has been no comparable analyses of BLLs in children over the entire 40-y period. We used NHANES data to describe the distribution of BLLs in U.S. children ages 1–5 and 6–11 y from 1976 to 2016 by selected sociodemographic and housing characteristics.MethodsNHANES Sample DesignNHANES is a nationally representative, cross-sectional survey of the resident civilian noninstitutionalized U.S. population designed to monitor the nation's health and nutritional status. Prior to 1999, NHANES was conducted on a periodic basis. The NHANES II (1976–1980) and NHANES III (Phase I: 1998–1991 and Phase II: 1991–1994) survey designs and blood lead measurements have been described previously (Brody et al. 1994; CDC 1985; Pirkle et al. 1994, 1998). Since 1999, NHANES has been a continuous survey conducted on an ongoing basis among a representative sample of all ages, as previously described (CDC 2019). Approximately 5,000 NHANES participants per year are selected through a complex, stratified, multistage probability sampling design for a personal interview and a standardized physical examination. The survey collects information on chronic disease prevalence and risk factors, diet and nutritional status, immunization status, infectious disease prevalence, health insurance, and measures of environmental exposures. The household interview includes questions about sociodemographic characteristics, health history, health-related behaviors, and access to health care.The NHANES protocol was developed and reviewed to be in compliance with the HHS Policy for Protection of Human Research Subjects (45 CFR part 46, available from http://www.hhs.gov/ohrp/humansubjects/guidance/45cfr46.html). In accordance with federal regulations (45 CFR 46.111), the NCHS Research Ethics Review Board reviewed and approved NHANES protocols, including ongoing changes to the protocol through the amendment process. Informed consent was obtained from sample persons who had reached the age of maturity in their state (usually age 18 y and over); a parent or guardian gave permission for minors to participate, and an adult proxy provided household survey data on behalf of children ages 1–15 y. In addition, children ages 7–17 y provided documented assent prior to participating. An emancipated minor did not need parental permission. Detailed information about NHANES is available at https://www.cdc.gov/nchs/nhanes/index.htm.We accessed NHANES data following submission of an approved research protocol through the National Center for Health Statistics (NCHS) Research Data Center (RDC) in Atlanta, Georgia, because our analyses involved restricted-use data (geographic variables). Restricted data includes information that could compromise the confidentiality of survey respondents, study subjects, or institutions, or information that is sensitive in nature. Our study involved secondary data analysis that did not constitute "human subjects research" and was thus exempt from additional CDC Institutional Review Board approval.Blood Lead MeasurementsWhole blood specimens were collected by venipuncture from eligible participants ages 1 y and older during the physical examination (Paschal et al. 1995). For NHANES II only, half of all children ages 7 y and older were selected for a blood lead measurement, whereas all children ages 1–6 y were eligible. Blood specimens are analyzed for lead concentration by the Division of Laboratory Sciences at the National Center for Environmental Health of the Centers for Disease Control and Prevention (CDC). Laboratory methods for NHANES II (CDC 1985), NHANES III (Gunter et al. 1996), and NHANES 1999–2016 (Jones et al. 2009) have been described previously. The limit of detection (LOD) for blood lead decreased from 2.0μg/dL in NHANES II (1976–1980) to 0.07μg/dL in NHANES 2013–2014 (current LOD) as technology improved (Caldwell et al. 2017). NHANES imputes results below the lower detection limit and replaces them with a value equal to the detection limit divided by the square root of 2 (CDC 2009).Sociodemographic CharacteristicsAll analyses were stratified by age group: 1–5 and 6–11 y. Additionally, age was categorized as: 1–2, 3–5, 6–8, and 9–11 y for subgroup analyses due to differences in lead exposure risk behaviors by age. Race/ethnicity was self-identified and self-reported according to mutually exclusive categories based on relevant U.S. Census race/ethnicity questions at the time of survey. Racial and ethnic groups were characterized based on responses to questions about race and Hispanic origin. Race/ethnicity was categorized as non-Hispanic White, non-Hispanic Black, Mexican American, other Hispanic, and "other race" (which includes individuals reporting more than one race). The category "other Hispanic" was not available as a survey response for NHANES II and III, and "other race" was not available as a survey response in NHANES II. Birthplace was categorized as United States, Mexico, or other for all survey cycles.SES was categorized using the family income-to-poverty ratio (FIPR) (equal to the ratio of total family income to the federal poverty threshold for the year of the interview) stratified as <1.3 and ≥1.3 (corresponding to income eligibility guidelines of 130% poverty level for supplemental nutrition programs) (CBPP 2019; Pirkle et al. 1998). We included health insurance coverage, Medicaid status, and participation in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), as available. These variables were not available for NHANES II. For NHANES III, health insurance coverage, Medicaid status, and participation in WIC were defined as being covered or receiving benefits in the past month, whereas for NHANES 1999–2016 coverage/participation was defined as coverage during the past 12 months. Health insurance coverage was queried as "Are you covered by health insurance or some other kind of health care plan? This includes private health insurance obtained through employment or purchased directly, as well as government programs, such as Medicare, Medicaid, SCHIP, military health care, Indian Health Service, State health plan, etc. that provide medical care or help pay medical bills." Participation in WIC (children ages 1–5 y) was only available in NHANES between 1999 and 2016.Housing Age"Year housing was built" used different categories for NHANES III and NHANES 1999–2010. Housing age was categorized in NHANES III as pre-1946, 1946–1972, 1973 to present, and unknown. From 1999 to 2010, NHANES categorized housing age as pre-1950, 1950–1977, 1978 to present, and unknown. Observations for which housing age was unavailable were recorded as unknown. Housing age was not collected in NHANES II or in the 2011–2016 surveys.Geographic VariablesAll geography below the national level is restricted for continuous NHANES due to disclosure risk; prior to 1999 all geography below the regional level is restricted; thus this information was accessed at the RDC.Urbanization was defined based on county of residence using the NCHS six-level urban-rural classification scheme for U.S. counties and county-equivalent entities ( https://www.cdc.gov/nchs/data_access/urban_rural.htm). In NHANES II, urbanization was classified as urbanized area ≥1 million, urbanized area <1 million, urban place outside of urbanized area, rural areas, central cities, and noncentral cities; we collapsed this variable to categories similar to NHANES III in which urbanization was dichotomized as counties of metropolitan areas ≥1 million or all other areas (<1 million). In NHANES 1999–2016, urbanization was defined as large metropolitan (population ≥1 million), medium and small metropolitan (population <1 million), or nonmetropolitan. Urbanization classification for years 1999–2016 was based on the NCHS urban, rural classification schemes (1990 classification scheme for years 1999–2002, 2006 classification scheme for years 2003–2010, and 2013 classification scheme for 2011–2016) as assigned by the RDC (NCHS 2017). The NCHS metropolitan categories were collapsed for this analysis to increase sample size for subgroups and produce stable estimates based on the NCHS data presentation standards for proportions: metropolitan statistical areas (MSAs) with a population of 1 million or more; MSAs with a population of less than 1 million; and, for more recent survey cycles, areas outside of MSAs.Geographic region was classified as Northeast, Midwest, South and West for all years. For NHANES 1999–2016, geographic region was categorized based on the 2010 Census Bureau's regions and is restricted data. Geographic region in NHANES II and III differs from the 2010 Census Bureau definition. Therefore, regional estimates cannot be directly compared across NHANES II, NHANES III, and NHANES 1999–2016.Statistical AnalysesAll statistical analyses were completed using SAS (version 9.3; SAS Institute, Inc.) and SAS-callable SUDAAN (version 11.0.1; RTI International) software packages. Weighted estimates were produced using the examination sampling weight to account for unequal probabilities of selection, oversampling, and survey nonresponse as recommended by NHANES analytic guidelines (Johnson et al. 2013; McDowell et al. 1981; NCHS 1996). The cluster design was accounted for in estimating variances.We used data on NHANES participants ages 1–11 y with valid blood lead measurements and grouped them according to age (1–5 y and 6–11 y) and survey period: NHANES II (1976–1980), NHANES III Phase 1 (1988–1991), NHANES III Phase 2 (1991–1994), and continuous NHANES 1999–2002, 2003–2006, 2007–2010, and 2011–2016. We grouped continuous NHANES data into 4-y and 6-y periods for analysis to increase the number of children in each group to yield more stable estimates. Table 1 shows the number and proportion of children with valid blood lead measurements available from among the total number of participants by age group and study cycle.Table 1 Population estimate (N), total participants (n), and participants [n (%)] with valid BLL from among U.S. children (n) ages 1–11 y, and weighted estimates for prevalence (%) and 95% CI of BLL ≥5μg/dL and number of children with BLL ≥5μg/dL, by survey cycle (years) and age group (1–5 y and 6–11 y) in the NATIONAL HEALTH AND NUTRITION EXAMINATION SURVEY (NHANES), 1976–2016.Table 1 has three main columns, namely, Survey Cycle, Ages 1 to 5 years, and Ages 6 to 11 years. The Ages 1 to 5 years and Ages 6 to 11 years columns are sub divided into five columns each, namely, Population Estimate (Number), Total Participants (number), Participants with valid blood lead levels (Number, percent), weighted estimates for prevalence (percent) and 95% confidence interval (CI) for blood lead levels greater than or equal to 5 micrograms per deciliter, and estimated number of children with blood lead levels greater than or equal to 5 micrograms per deciliter.Survey cycleAges 1–5 yAges 6–11 yPopulation estimateTotal participantsParticipants with valid BLLBLL ≥5μg/dLBLL ≥5μg/dLPopulation estimateTotal participantsParticipants with valid BLLBLL ≥5μg/dLBLL ≥5μg/dLYearsNnn (%)% (95% CI)anNNn (%)% (95% CI)an1976–198015,263,000b3,7622,360 (62.7)99.8 (99.4, 99.9)15,232,47420,880,000b1,725830 (48.1)99.7 (98.6, 99.9)20,817,3601988–199119,657,453c19,657,453c3,2782,232 (68.1)31.4 (26.0, 37.3)6,172,44022,527,176c22,527,176c1,9431,584 (81.5)15.0 (11.3, 19.7)3,379,0761991–19942,8762,392 (83.2)21.0 (16.0, 27.0)4,128,0651,5241,345 (88.3)9.5 (7.3, 12.2)2,140,0821999–200219,323,164d2,4151,621 (67.1)8.7 (6.5, 11.5)1,681,11524,889,987d2,3551,949 (82.8)3.0 (1.9, 4.6)746,7002003–200620,257,887e2,6771,879 (70.2)4.1 (2.9, 5.8)830,57323,921,965e2,1791,790 (82.1)1.3 (0.7, 2.6)h310,9862007–201020,870,073f2,5261,653 (65.4)2.6 (1.7, 4.2)542,62224,055,655f2,5192,020 (80.2)0.4 (0.2, 0.8)96,2232011–201620,171,918g3,6092,321 (64.3)1.3 (0.7, 2.4)h262,23524,707,984g4,0313,146 (78.0)0.5 (0.1, 0.5)h123,540Note: BLL, blood lead levels; CI, confidence interval.aWeighted estimates derived from the observed data for the study population using NHANES-specified sampling weights.bNHANES II: U.S. Noninstitutionalized population as of 1 March 1978 (approximate midpoint of the survey) from the U.S. Census Current Population Survey.cNHANES III: U.S. population from combined 6-y sample, NHANES III data file, 1988–1994, from the U.S. Census Bureau Current Population Survey.dContinuous NHANES 1999–2002: distribution of the civilian noninstitutionalized U.S. population for the midpoint of 1999–2002, from the U.S. Census Bureau Current Population Survey.eContinuous NHANES 2003–2006: distribution of the civilian noninstitutionalized U.S. population for the average of 2003–2004 and 2005–2006 cycles, from the U.S. Census Bureau American Community Survey.fContinuous NHANES 2007–2010: Distribution of the civilian noninstitutionalized U.S. population for the average of 2007–08 and 2009–10 cycles, from the U.S. Census Bureau American Community Survey.gContinuous NHANES 2011–2016: distribution of the civilian noninstitutionalized U.S. population for the average of 2011–2012, 2013–2014, and 2015–2016 cycles, from the U.S. Census Bureau American Community Survey.hRelative Standard Error (RSE) greater than or equal to 30% indicates estimate is statistically unreliable.All analyses were stratified by age group: 1–5 and 6–11 y. Weighted estimates derived from the observed data for the study population using NHANES-specified sampling weights for the various survey cycles were used to estimate the number of children with BLLs greater than or equal to the CDC blood lead reference value (5μg/dL) based on the U.S. population of children 1–11 y (NCHS: Response Rates and Population Totals, available at https://wwwn.cdc.gov/nchs/nhanes/ResponseRates.aspx). Geometric means (GM) and 95% confidence interval (CI) for BLLs and the estimated prevalence (%) of BLLs ≥5μg/dL and 95% CI were calculated by age group (1–5 y and 6–11 y) overall and by selected characteristics. Formal statistical testing for differences in BLLs for each variable of interest was not completed. We also calculated the overall estimated prevalence (%) of BLLs ≥10μg/dL and 95% CI for children ages 1–11 y in aggregate (shown in Figure 1) by survey cycle (years) due to the small cell sizes at higher BLLs, particularly in the later years. Although no safe BLL in children has been identified, the use of a dichotomous threshold for BLLs is advantageous because it is used for case surveillance and case management definitions and, as such, is more easily interpretable than statistically derived cut points. Prevalence estimates that had a relative standard error (RSE) of the estimate ≥30% were regarded as statistically unreliable (CDC 2018). All results of cell count sample sizes <5 or percentages calculated from numerators <5 are suppressed by the RDC due to disclosure concerns per the NCHS policy.Figure 1. Estimated prevalence (%) of blood lead levels ≥10μg/dL (gray bars) ≥5μg/dL (hatched bars) among U.S. children ages 1–11 y plotted on the log-10 scale; geometric mean blood lead levels (μg/dL) for children ages 1–5 y (squares, solid line) and ages 6–11 y (circles, dashed line) in the National Health and Nutrition Examination Survey (NHANES), 1976–2016, by survey cycle (years); data shown in Table S1.ResultsThe percentage of NHANES participants ages 1–5 and 6–11 y with valid blood lead measurements varied over time and ranged from 62.7 to 83.2% and 48.1 to 88.3%, respectively, over the 40-y period (Table 1). The estimated prevalence of children ages 1–5 y with a BLL ≥5μg/dL sharply decreased from 99.8% in NHANES II (1976–1980) to 1.3% during 2011–2016. Similarly, for children ages 6–11 years, the estimated prevalence of BLL ≥5μg/dL declined from 99.7% in NHANES II to 0.5% in 2011–2016. Figure 1 illustrates the downward trends in the estimated percentage of U.S. children ages 1–11 y with BLLs ≥5 and ≥10μg/dL over time (Table S1). Nonetheless, in 2011–2016, an estimated 262,235 and 123,540 children ages 1–5 and 6–11 y, respectively, or 385,775 in total, had BLLs greater than or equal to the CDC blood lead reference value of 5μg/dL (Table 1).The GM BLL in U.S. children aged 1–5 y declined from 15.2μg/dL (95% CI: 14.3, 16.1) in 1976–1980 to 0.8μg/dL (95% CI: 0.8, 0.9) in 2011–2016 representing a 94.5% decrease over time (Table 2). For children ages 6–11 y, the GM BLL declined from 12.7μg/dL (95% CI: 11.9, 13.4) in 1976–1980 to 0.6μg/dL (95% CI: 0.6, 0.6) in 2011–2016, representing a 95.3% decrease over time (Table 3). A large proportion of these declines occurred before 1992, as the GM BLLs for ages 1–5 and 6–11 y, respectively, had decreased to 3.6μg/dL (95% CI: 3.2, 4.0) and 2.4μg/dL (95% CI: 2.1, 2.7) by 1988–1991 (Tables 2 and 3).Table 2 Weighted geometric mean and 95% CI for BLLs in μg/dL among U.S. children ages 1–5 y,a overall and by selected characteristics in the NATIONAL HEALTH AND NUTRITION EXAMINATION SURVEY (NHANES), 1976–2016.Table 2 has two main columns, namely, Ages 1 to 5 years and geometric mean (95 percent confidence intervals) of blood lead levels in micrograms per deciliter begin superscript lowercase a end superscript. Geometric mean (95 percent confidence intervals) of blood lead levels in micrograms per deciliter begin superscript lowercase a end superscript column is sub divided into fourteen columns, namely, lowercase n, 1976 to 1980, lowercase n, 1988 to 1991, lowercase n, 1991 to 1194, lowercase n, 1999 to 2002, lowercase n, 2003 to 2006, lowercase n, 2007 to 2010, lowercase n, and 2011 to 2016.Ages 1–5 yGeometric mean (95% CI) BLLs in μg/dLan1976–1980n1988–1991n1991–1994n1999–2002n2003–2006n2007–2010n2011–2016Overall2,36015.2 (14.3, 16.1)2,2323.6 (3.2, 4.0)2,3922.7 (2.5, 3.0)1,6211.9 (1.8, 2.1)1,8791.6 (1.5, 1.7)1,6531.3 (1.3, 1.4)2,3210.8 (0.8, 0.9)Age group 1–2 y72115.7 (14.5, 16.9)9244.0 (3.6, 4.5)9873.1 (2.8, 3.5)7792.2 (2.0, 2.4)9191.8 (1.7, 1.9)7931.5 (1.4, 1.6)1,0240.9 (0.9, 1.0) 3–5 y1,63914.9 (14.1, 15.8)1,3083.3 (2.9, 3.7)1,4052.5 (2.3, 2.7)8421.8 (1.6, 2.0)9601.5 (1.4, 1.6)8601.2 (1.2, 1.3)1,2970.8 (0.7, 0.8)Sex Female1,11815.0 (14.1, 15.8)1,1443.5 (3.1, 3.9)1,1812.7 (2.4, 2.9)7701.9 (1.8, 2.1)9281.6 (1.5, 1.7)7811.3 (1.2, 1.4)1,1080.8 (0.7, 0.9) Male1,24215.4 (14.4, 16.4)1,0883.6 (3.2, 4.0)1,2112.8 (2.5, 3.1)8511.9 (1.8, 2.1)9511.6 (1.5, 1.7)8721.3 (1.3, 1.4)1,2130.9 (0.8, 0.9)Birthplace United States2,27015.1 (14.2, 16.1)2,1443.6 (3.2, 3.9)2,2762.7 (2.5, 3.0)1,5631.9 (1.8, 2.1)1,8301.6 (1.5, 1.7)1,6181.3 (1.3, 1.4)2,2520.8 (0.8, 0.9) Mexico—b—b556.3 (4.4, 8.2)813.6 (2.8, 4.3)343.1 (1.8, 4.4)322.2 (1.8, 2.6)101.8 (NA, NA)c—b—b Other6216.8 (15.5, 18.1)243.5 (1.8, 5.3)342.8 (1.5, 4.1)241.8 (1.1, 2.6)171.9 (0.9, 3.0)241.3 (0.7, 1.8)690.8 (0.7, 1.0)Race/ethnicity Non-Hispanic White1,58413.9 (11.5, 19.4)6583.1 (2.8, 3.4)6312.3 (2.1, 2.6)4541.8 (1.6, 2.0)5351.4 (1.4, 1.5)5361.3 (1.1, 1.4)5630.8 (0.7, 0.9) Non-Hispanic Black42420.3 (19.0, 21.7)6795.2 (4.6, 5.8)7834.3 (3.6, 5.0)4392.8 (2.5, 3.1)5302.4 (2.1, 2.8)3381.8 (1.6, 1.9)6081.1 (1.0, 1.2) Mexican American10115.5 (11.5, 19.4)8033.9 (2.9, 4.9)8273.1 (2.7, 3.5)5411.9 (1.8, 2.0)6111.6 (1.5, 1.7)4901.3 (1.2, 1.4)5260.8 (0.7, 0.8) Other—b—b924.2 (2.0, 6.3)1512.8 (2.2, 3.4)—b—b—b—b—b—b—b—b Other Hispanic—b—b—b—b—b—b1081.8 (1.3, 2.2)991.8 (1.5, 2.2)1871.3 (1.2, 1.5)2870.8 (0.7, 0.9) Other race—b—b—b—b— b—b791.8 (1.4, 2.3)1041.6 (1.3, 1.9)1021.2 (1.0, 1.4)3370.8 (0.8, 0.9)Family income-to-poverty ratio <1.382817.7 (16.5, 19.0)1,0194.7 (4.0, 5.4)1,2493.8 (3.3, 4.2)8082.5 (2.2, 2.7)9362.0 (1.9, 2.2)8641.6 (1.5, 1.7)1,1491.0 (0.9, 1.1) ≥1.31,47014.1 (13.3, 15.0)1,0043.1 (2.8, 3.4)1,0012.2 (2.0, 2.3)6861.6 (1.4, 1.7)8571.4 (1.3, 1.5)6761.2 (1.1, 1.3)9970.7 (0.7, 0.8)Health insurance Yes—b—b1,7423.5 (3.1, 3.9)1,9782.7 (2.5, 2.9)1,3461.9 (1.7, 2.0)1,6401.6 (1.5, 1.7)1,4911.3 (1.2, 1.4)2,1740.8 (0.8, 0.9) No—b—b1293.7 (3.0, 4.4)4093.1 (2.6, 3.6)2522.4 (2.0, 2.7)2291.7 (1.4, 1.9)1611.5 (1.3, 1.6)1441.0 (0.8, 1.2)WIC Yes—b—b5404.7 (3.8, 5.7)7614.1 (3.6, 4.7)7122.5 (2.3, 2.7)8902.0 (1.8, 2.1)9521.5 (1.4, 1.6)—b—b No—b—b1,6873.4 (3.0, 3.7)1,6272.4 (2.3, 2.6)7391.7 (1.5, 1.8)9871.5 (1.4, 1.5)7001.2 (1.1, 1.3)—b—bMedicaid Yes—b—b6265.3 (4.2, 6.4)9843.9 (3.5, 4.4)5922.6 (2.4, 2.8)7592.0 (1.8, 2.1)6741.6 (1.5, 1.7)1,1520.9 (0.9, 1.0) No—b—b4083.4 (3.1, 3.8)1,4032.3 (2.1, 2.5)9981.7 (1.6, 1.9)1,1081.5 (1.4, 1.6)9781.2 (1.2, 1.3)1,1660.8 (0.7, 0.8)Housing age Pre-1946/Pre-1950—b—b3785.2 (4.4, 6.0)3683.8 (3.0, 4.6)2082.7 (2.4, 3.1)2422.1 (1.8, 2.3)2641.6 (1.3, 1.9)—b—b 1946–1972/1950–1977—b—b9313.6 (3.2, 4.0)8892.8 (2.6, 3.1)3411.8 (1.7, 2.0)4131.5 (1.4, 1.7)3431.3 (1.2, 1.5)—b—b 1973–present/1978–present—b—b6022.9 (2.5, 3.3)7442.0 (1.9, 2.2)4701.5 (1.3, 1.6)5281.3 (1.2, 1.4)5031.1 (1.0, 1.2)—b—b Unknown— b—b1704.9 (3.7, 6.0)3513.6 (3.0, 4.2)5762.5 (2.2, 2.7)6822.0 (1.8, 2.2)5291.6 (1.5, 1.7)—b—bUrbanization MSA ≥1 million53316.9 (15.7, 18.0)1,1063.7 (3.1, 4.2)1,3232.8 (2.3, 3.3)7761.81 (1.63, 1.99)1,1931.69 (1.53, 1.84)9171.27 (1.09, 1.45)1,3080.77 (0.70, 0.85) MSA <1 million1,82714.7 (13.5, 15.8)1,1263.5 (2.9, 4.1)1,0692.7 (2.2, 3.1)6312.00 (1.68, 2.32)4381.46 (1.16, 1.77)4761.36 (0.97, 1.75)6050.83 (0.69, 0.96) Non-MSA2142.11 (1.71, 2.51)2471.58 (0.76, 2.39)2601.45 (1.01, 1.88)4080.98 (0.49, 1.48)Geographic region Northeast39715.9 (14.5, 17.3)2095.4 (2.4, 8.3)2683.3 (2.0, 4.6)2232.34 (1.98, 2.70)2622.17 (1.43, 2.91)2331.64 (0.97, 2.30)3111.08 (0.84, 1.32) Midwest64415.5 (14.1, 16.8)4253.6 (3.2, 4.1)4053.3 (2.7, 3.8)2262.49 (1.94, 3.05)4481.69 (1.26, 2.12)3831.30 (1.23, 1.38)5030.94 (0.69, 1.18) South67014.3 (12.0, 16.7)8213.4 (2.9, 3.9)1,1782.7 (2.3, 3.0)7161.95 (1.79, 2.10)6911.57 (1.47, 1.67)6541.38 (1.22, 1.53)8930.79 (0.72, 0.85) West64915.4 (13.4, 17.3)7772.9 (2.3, 3.5)5412.1 (1.6, 2.7)4561.42 (1.29, 1.54)4771.29 (1.15, 1.43)3831.10 (0.92, 1.27)6140.70 (0.63, 0.77)Note: BLL, blood lead level; CI, confidence interval, MSA, metropolitan statistical area; WIC, the Special Supplemental Nutrition Program for Women, Infants, and Children.aWeighted estimates derived from the observed data for the study population using NHANES-specified sampling weights.bVariable not assessed in this survey cycle.cNA, not applicable, indicates that the upper/lower limits of a confidence interval could not be derived due to small sample sizes.Table 3 Weighted geometric mean and 95% CI for blood lead levels in micrograms per deciliter among U.S. children ages 6–11 y,a overall and by selected characteristics in the National Health and Nutrition Examination Survey (NHANES), 1976–2016.Table 3 has two main columns, namely, Ages 6 to 11 years and geometric mean (95 percent confidence intervals) of blood lead levels in micrograms per deciliter begin superscript lowercase a end superscript. Geometric mean (95 percent confidence intervals) of blood lead levels in micrograms per deciliter begin superscript lowercase a end superscript column is sub divided into fourteen columns, namely, lowercase n, 1976 to 1980, lowercase n, 1988 to 1991, lowercase n, 1991 to 1194, lowercase n, 1999 to 2002, lowercase n, 2003 to 2006, lowercase n, 2007 to 2010, uppercase n, and 2011 to 2016.Ages 6–11 yGeometric mean (95% CI) BLLs in μg/dLan1976–1980n1988–1991n1991–1994n1999–2002n2003–2006