Elevated Blood Lead Levels Among Employed Adults — United States, 1994–2012

Walter A. Alarcon, MD1,

State Adult Blood Lead Epidemiology and Surveillance (ABLES) Program investigators

1National Institute for Occupational Safety and Health, CDC

Corresponding author: Walter A. Alarcon, MD, National Institute for Occupational Safety and Health, CDC. Telephone: 513-841-4451 e-mail: wda7@cdc.gov.

Preface

The National Institute for Occupational Safety and Health (NIOSH) and state health departments collect data on laboratory-reported adult blood lead levels (BLLs). This report presents data on elevated blood lead levels among employed adults in the United States for 1994–2012. This report is a part of the first-ever Summary of Notifiable Noninfectious Conditions and Disease Outbreaks, which encompasses various surveillance years but is being published in 2015 (1). The Summary of Notifiable Noninfectious Conditions and Disease Outbreaks appears in the same volume of MMWR as the annual Summary of Notifiable Infectious Diseases (2).

Background

Since 1987, the National Institute for Occupational Safety and Health (NIOSH) and state health departments have maintained a state–based surveillance program of laboratory-reported adult blood lead levels (BLLs) known as the Adult Blood Lead Epidemiology and Surveillance (ABLES) Program (3). The BLL is an often-used estimate of recent external exposure to lead (4,5). This report summarizes data on elevated blood lead levels among employed adults, defined as persons aged ≥16 years, during January 1, 1994–December 31, 2012.

Reported cases of elevated BLLs in 2012 are provided in tabular form (Tables 1–4). Information is provided by geographic division and reporting state, for "all cases" reported by a state (these include cases among adult residents in the reporting state plus cases identified by the reporting state but who reside in another state) and "state-residents" only, by exposure source, age, and sex groups, for BLLs ≥10 µg/dL (current definition of elevated BLL) (3,6), and for BLLs ≥25 µg/dL (former definition of elevated BLL)(7). The current case definition was adopted in 2009 on the basis of mounting evidence for adverse health outcomes among adults with BLLs between 10 µg/dL and 25 µg/dL (4,6). State prevalence rates of elevated BLLs (≥10 µg/dL) for 2012 are categorized into two groups (above or below the national rate) (Figure 1). Trends of national prevalence rates of BLLs ≥10 µg/dL and BLLs ≥25 µg/dL from 1994 to 2012 are provided (Figure 2). Prevalence rates are provided for "all cases" (these include cases among adult residents in the reporting state plus cases identified by the reporting state but who reside in another state) and "state-residents" when available. National and state numbers of cases, employed populations, and prevalence rates of elevated BLLs are provided in tabular form (Tables 5–10). Available data include BLLs ≥10 µg/dL from 2010 to 2012 and BLLs ≥25 µg/dL from 1994 to 2012. Prevalence rates and numerators are provided for "all cases" and "state residents" when available. The number of employed adults (state residents) used as denominators for calculating rates are provided in tabular form (Tables 11 and 12).

ABLES is the only program conducting nationwide adult lead exposure surveillance. It has provided the occupational safety and health community with essential information for setting research and intervention priorities. ABLES' impact is achieved through its longstanding strategic partnerships with State ABLES programs, federal agencies, and worker-affiliated organizations. For example, in 2008, the Occupational Safety and Health Administration (OSHA) updated its National Lead Emphasis Program to reduce occupational lead exposure by targeting unsafe conditions and high-hazard industries (8). To accomplish this objective, OSHA utilized ABLES data to identify industries with elevated BLL problems and has agreements with State ABLES programs to obtain their lead exposure data to target workplace inspections.

Although federal funding for State ABLES programs was discontinued in September 2013, a total of 34 states continue to collaborate with NIOSH (down from a peak of 41). These states self-fund their ABLES programs to sustain lead exposure surveillance and prevention activities. To assist with accomplishing these objectives, State ABLES programs share resources with two other CDC programs: the Healthy Homes and Childhood Lead Poisoning Prevention Program and Environmental Public Health Tracking. Since September 2013, NIOSH has continued to provide technical assistance to states with adult blood lead surveillance programs and maintains the ABLES website for reporting ongoing analyses of ABLES data.

The BLL is a direct index of a worker's recent exposure to lead as well as an indication of the potential for adverse effects from that exposure (4,5). The half-life of lead in blood is about 40 days in men (9), so the BLL is an estimate primarily of recent exposure to lead. Because lead accumulates in bone and BLL is in equilibrium with bone lead, the BLL might be elevated in some persons who have not had recent exposure to lead. Because this equilibrium can lead to persistent BLL elevations, the public health burden of elevated BLLs in adults is measured as prevalence. In contrast, the public health burden of elevated BLLs in children aged <5 years is measured as incidence because these young children have little lead storage in their bones at birth and thus their early childhood blood lead tests reflect recent exposures.

Over the past several decades in the United States, a marked reduction has occurred in environmental sources of lead and improved protection from occupational lead exposure. As a result, there is an overall decreasing trend in the prevalence of elevated BLLs among adults. Nonetheless, lead exposures continue to occur at unacceptable levels (3). In 2012, the prevalence rate of BLLs ≥10 µg/dL was 22.5 adults per 100,000 employed population. During 2011–2012, the mean BLL in adults in the United States was 1.09 µg/dL (10).

Research continues to find that low BLLs are associated with harmful effects in adults (11). In 2009, NIOSH and State ABLES programs led the occupational safety and health community to establish a new case definition for an elevated BLL (i.e., BLLs ≥10 µg/dL) (3). The Council of State and Territorial Epidemiologists also recommended that CDC use this case definition (12). In 2010, for the first time, CDC included elevated BLLs, defined as those ≥10 µg/dL, in the List of Nationally Notifiable Noninfectious Conditions (6). The U.S. Department of Health and Human Services' Healthy People 2020 initiative also uses the 10 µg/dL level for its Occupational Safety and Health Objective No. 7 (OSH-7), which is to reduce the proportion of persons who have elevated blood lead concentrations from work exposures (13). Before 2009, the case definition for an elevated BLL was ≥25 µg/dL.

Data Sources

The ABLES program is an occupational health state-based surveillance system. The number of cases (numerator) is provided by 41 State ABLES programs. The number of employed adults (denominator) is obtained from the Local Area Unemployment Statistics (LAUS), Bureau of Labor Statistics, in the U.S. Department of Labor (available at http://www.bls.gov/data). A direct link to annual averages of states employment status of the civilian noninstitutionalized population is available at http://www.bls.gov/lau/staadata.txt).

State ABLES programs 1) collect data on adult BLLs from laboratories and physicians through mandatory reporting; 2) assign unique identifiers to each adult to account for multiple BLL records to protect individual privacy and permit longitudinal analyses; 3) follow-up on adults with BLLs ≥10 or ≥25 µg/dL with laboratories, health-care providers, employers, or workers to ensure completeness of information (e.g., the industry in which the adult is employed and whether the exposure source is occupational, nonoccupational, or both); 4) provide guidance and information to workers and employers to prevent lead exposures; and 5) submit data annually to NIOSH. Most ABLES states submit data on all BLLs (both occupational and nonoccupational) to NIOSH, including records from adults whose BLLs fall below the state mandatory reporting requirement. NIOSH conducts data quality control, analyzes the data, and disseminates the findings among stakeholders.

Interpreting Data

The primary measure of adult lead exposure in the United States is the National Prevalence Rate of Elevated BLLs. This measure is provided by the ABLES program and can be used to estimate the magnitude and monitor trends of lead exposures and to target areas requiring further investigation or interventions. The results indicate that efforts to reduce the prevalence of elevated BLLs have resulted in considerable progress towards reducing lead exposures. However, the ABLES data from 2012 establish that lead exposure remains a national health problem and that continued efforts to reduce lead exposures both within and outside the workplace are needed.

Many adults in the United States continue to have BLLs above levels known to be associated with acute and chronic adverse effects in multiple organ systems ranging from subclinical changes in function to symptomatic intoxication. These include neurologic, cardiovascular, reproductive, hematologic, and kidney adverse effects. The risks for adverse chronic health effects are even higher if the exposure is maintained for many years (4,5). Current research has found decreased renal function associated with BLLs at 5 µg/dL and lower, and increased risk of hypertension and essential tremor at BLLs below 10 µg/dL (11).

Prevalence rates of adults with BLLs ≥25 µg/dL are available since 1994. Beginning in 2002, State ABLES programs reported individual BLL laboratory test and state of residence. Formerly, state-resident and non-resident data could not be separated. When an adult has multiple blood lead tests in a given year, only the highest blood lead level for that adult in that year was counted. Prevalence rates of BLLs ≥10 µg/dL are provided since 2010. Prevalence rates of BLLs ≥25 µg/dL are a subset of rates of BLLs ≥10 µg/dL. In the U.S. most lead exposures are occupational. Among all participating states in 2012, when an exposure source was known, the proportion of BLLs ≥25 µg/dL from occupational exposures was 93.3%. The greatest proportions of adults with elevated BLLs were employed in four main industry sectors: manufacturing, construction, services, and mining.

These counts and rates of elevated BLLs must be considered minimum estimates of the actual magnitude of the problem of lead exposures in the U.S. This is for multiple reasons:

• not all states are included in the system;
• not all employers provide BLL testing to lead-exposed workers as required by OSHA regulations;
• not all nonoccupationally exposed adults are tested; and
• some laboratories might not report all tests as required by state laws or regulations.

For specific explanations, interpretation, and possible updates on data for any individual state, we strongly recommend contacting the State ABLES program investigator. Their contact information is available from the ABLES State-based Programs webpage (http://www.cdc.gov/niosh/topics/ABLES/state.html).

Methods for Identifying Elevated BLLs Among Employed Adults

A nationally reportable case of an employed adult with an elevated BLL is defined as a case in an employed adult (≥16 years at the time of blood collection) with a venous blood lead level ≥10 µg/dL (0.48 µmol/L) of whole blood. The standardized diagnostic test is the blood lead level test using a venous blood sample. All participating state health departments have a requirement for laboratories and/or health-care providers to report laboratory blood lead results to the state health department. However, this requirement varies among ABLES states, ranging from the reporting of all BLLs to only BLLs ≥40 µg/dL (3). The ABLES program ultimately aims to collect a complete list of variables for all BLL tests, including BLLs <10 µg/dL, and encourages all states to supply this information to NIOSH.

Publication Criteria

Adult cases meet the publication criteria if between 1994 and 2012 a venous BLL was ≥25 µg/dL and since 2010 if the venous BLL was ≥10 µg/dL. BLLs ≥25 µg/dL are a subset of BLLs ≥10 µg/dL and are included for historical comparison. When an adult had multiple blood lead tests in a given year, only the highest blood lead level for that adult in that year was counted.

Highlights

In 2012, a total of 41 states submitted data on 7,529 adults with BLLs ≥25 µg/dL and 38 states submitted data on 27,218 adults with BLLs ≥10µg/dL. Overall, the prevalence of BLLs ≥10 µg/dL among state residents and nonresidents declined from 26.6 adults per 100,000 employed in 2010 to 22.5 in 2012. The prevalence of BLLs ≥25 µg/dL among state residents and nonresidents declined from 14.0 adults per 100,000 employed in 1994 to 5.7 in 2012. In 2012, state prevalence rates of BLLs ≥25 µg/dL were above the national rate (5.7/100,000) in 10 states and state prevalence rates of BLLs ≥10µg/dL were above the national rate (22.5/100,000) in 12 states.

In 2012, more than half (53.0%) of adults with BLLs ≥10 µg/dL were aged 40–64 years 33.3% were aged 25–39 years, and the great majority (91.5%) were males. Historically, in the United States, most lead exposures have been occupational. During 2002–2012, the annual proportion of BLLs ≥25 µg/dL from occupational exposures was 94.7% among participating states (minimum: 93.3% in 2012; maximum: 95.5% in 2004). In 2012, among the 37 states that reported the exposure source for adults with BLLs ≥25µg/dL, the proportion of occupational cases ranged from 38.9% to 100%.

References

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State Adult Blood Lead Epidemiology and Surveillance (ABLES) Program Investigators

(All ABLES program investigators meet the CDC and MMWR criteria for contributors)

Sherri Davidson, MPH, Martha L. Sanchez, MD, Alabama Department of Public Health; Sandrine E. Deglin, PhD, Alaska Department of Health and Social Services; Diane Eckles, Arizona Department of Health Services; Susan F. Payne, MA, California Department of Public Health; Albert L. DeLoreto, MPH, Thomas St. Louis, MSPH, Connecticut Department of Public Health; Christy Kuriatnyk, MSPH, Georgia Department of Public Health; Barbara Brooks, PhD, Hawaii Department of Health; Van Nguyen, MS, Tiefu Shen, MD, Illinois Department of Public Health; Jeffery M. Turner, Indiana State Department of Health; Kathy Leinenkugel, MPA, Iowa Department of Public Health; Alisha Langham, Kansas Department of Health and Environment; Monica L. Clouse, MPH, Kentucky Department for Public Health; Michelle Lackovic, MPH, Jocelyn Lewis, PhD, Louisiana Department of Health and Hospitals; Ezattolah Keyvan, MD, Maryland Department of the Environment; Robert J. Nicotera, DJ, Massachusetts Department of Labor Standards; Joanna Kica, MPA, Michigan State University; Stephanie Yendell, DVM, Minnesota Department of Health; Carol R. Braun, Missouri Department of Health and Senior Services; Doug Gillespie, Derry Stover, MPH, Nebraska Department of Health and Human Services; Karla R. Armenti, ScD, Paul L. Lakevicius, MBA, New Hampshire Department of Health and Human Services; Marija Borjan, PhD, Margaret E. Lumia, PhD, Devendra Singh, New Jersey Department of Health; Leilani Schwarcz, MPH, New Mexico Department of Health; Alicia M. Fletcher, MPH, New York State Department of Health; Sheila Higgins, MPH, North Carolina Department of Health and Human Services; Chris Alexander, MS, Tyler Serafini, MPH, Ohio Department of Health; Susan J. Quigley, Christin T. Benner, MPH, Oklahoma State Health Department; Daniel Cain, MA, Oregon Health Authority; Sasidevi Arunachalam, Pennsylvania Department of Health; James Bruckshaw, Rhode Island Department of Health; H. Reed Corley, MPH, South Carolina Department of Health and Environmental Control; Jennifer Karnik, MPH, Teresa Willis, Texas Department of State Health Services; Bonnie Hinds, Martha Keel, PhD, Morey Parang, Phillip Woodard, University of Tennessee; Mark E. Jones, Sam Lefevre, Utah Department of Health; Mike Sullivan, MBA, Vermont Department of Health; Todd M. Schoonover, PhD, Washington Department of Labor and Industries; Carrie Tomasallo, PhD, Wisconsin Department of Health Services; Steve Melia, MSPH, Wyoming Department of Health; ABLES Programs coordinators in Colorado Department of Public Health and Environment, Florida Department of Health, Maine Department of Health and Human Services, and Montana Department of Public Health and Human Services.