Elevated Blood Lead Levels Among Employed Adults — United States, 1994–2013

Preface

CDC’s 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 BLLs among employed adults (defined as persons aged ≥16 years) in the United States for 1994–2013. This report is a part of the Summary of Notifiable Noninfectious Conditions and Disease Outbreaks — United States, which encompasses various surveillance years but is being published in 2016 (1). The Summary of Notifiable Noninfectious Conditions and Disease Outbreaks appears in the same volume of the Morbidity Mortality Weekly Report (MMWR) as the annual Summary of Notifiable Infectious Diseases (2).

Background

Since 1987, NIOSH and state health departments have maintained the Adult Blood Lead Epidemiology and Surveillance (ABLES) Program, a state-based surveillance program of laboratory-reported adult BLLs (3). The BLL is an often-used estimate of recent external exposure to lead (4,5). This report summarizes data on elevated BLLs among employed adults during January 1, 1994–December 31, 2013.

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 occurring among persons who reside in another state) and “state-residents” only, by exposure source, for BLLs ≥10 μg/dL (definition of elevated BLL from 2009 until 2014) (3,6–8), and for BLLs ≥25 μg/dL (previous definition of elevated BLL) (9). The current case definition (BLL ≥5 μg/dL) was adopted in 2015 and became effective in 2016, on the basis of mounting evidence for adverse health outcomes among adults with BLLs between 5 μg/dL and 25 μg/dL (4,5). State prevalence rates of elevated BLLs (≥10 μg/dL) for 2013 are categorized into two groups (above or below the national prevalence rate) (Figure 1). Trends of national prevalence rates of BLLs ≥10 μg/dL and BLLs ≥25 μg/dL from 1994 to 2013 are provided (Figure 2).

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 (10). To accomplish this objective, OSHA used national ABLES data to identify industries whose employees exhibit high BLLs. OSHA has agreements with state ABLES programs to use their lead exposure data to target workplace inspections.

Although federal funding for state ABLES programs was discontinued in September 2013, a total of 30 states continue to collaborate with NIOSH (down from a peak of 41 states) to provide data. In August 2015, funding to support adult BLL surveillance was resumed at a reduced level. To sustain lead exposure surveillance and prevention activities, state ABLES programs share resources with two other CDC programs: the Childhood Lead Poisoning Prevention Program and the Environmental Public Health Tracking Program. 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 ABLES findings.

The BLL is a direct index of a worker’s 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 approximately 40 days in males (11), 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 <3 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 protection from occupational lead exposure has improved. As a result, there is an overall decreasing trend in the mean BLL and in the prevalence of elevated BLLs among adults. During 2011–2012, the mean BLL in adults in the United States was 1.09 μg/dL (12). Nonetheless, lead exposures among adults continue to occur at unacceptable levels (3).

Data Sources

The ABLES program is a state-based surveillance system of adult BLLs. The number of cases (numerator) is currently provided by ABLES programs in 30 states (29 states provided data on BLLs ≥10 μg/dL). 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 (http://www.bls.gov/dataexternal icon). A direct link to annual averages of states’ employment status of the civilian noninstitutionalized population is available (http://www.bls.gov/lau/staadata.txttxt iconexternal icon). NIOSH consolidates data from reporting state ABLES programs, conducts data quality control, analyzes the data, and disseminates the findings among stakeholders. 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 per person, 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.

Interpreting Data

The primary measure of adult lead exposure in the United States is the national prevalence rate of elevated BLLs among employed adults. 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.

Efforts to reduce lead exposures have resulted in considerable progress in reducing the prevalence of elevated BLLs. However, many adults in the United States continue to have BLLs 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 increased risk of hypertension and essential tremor at BLLs <10 μg/dL (13).

Prevalence rates of adults with BLLs ≥25 μg/dL are available since 1994. Beginning in 2002, state ABLES programs reported individual BLL laboratory test results and state of residence. Formerly, state resident and nonresident data could not be separated. When an adult has multiple blood lead tests in a given year, only the highest BLL for that adult in that year is counted. Prevalence rates of BLLs ≥10 μg/dL are available for 2010 forward. Prevalence rates of BLLs ≥25 μg/dL are a subset of prevalence rates of BLLs ≥10 μg/dL. In the United States, most lead exposures among adults are occupational (9). A total of 29 states submitted work-relatedness information in 2013. Prevalence rate differences across states could reflect improved compliance with required OSHA monitoring in some states.

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

• not all states participate in the ABLES program;

• 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, the state ABLES program investigator should be contacted directly. Contact information is available at http://www.cdc.gov/niosh/topics/ABLES/state.html.

Methods for Identifying Elevated BLLs Among Employed Adults

Beginning in 2016, a nationally reportable case of an employed adult with an elevated BLL is defined as a case in an employed person aged ≥16 years at the time of blood collection with a venous blood lead level ≥5 μg/dL of whole blood. The standardized diagnostic test is the BLL 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 reporting only BLLs ≥40 μg/dL (3). The ABLES program ultimately aims to establish a national database for all BLL tests among adults and encourages all states to share information with NIOSH.

Publication Criteria

Cases meet the publication criteria if the employed adult (aged ≥ 16 years) had a venous BLL ≥25 μg/dL during 1994–2013 or a venous BLL ≥10 μg/dL during 2010–2013. When an adult had multiple blood lead tests in a given year, only the highest BLL for that adult in that year was counted. Prevalence rates of BLLs ≥25 μg/dL are a subset of prevalence rates of BLLs ≥10 μg/dL and are included for historic comparison.

Highlights

In 2013, the prevalence rate of BLLs ≥10 μg/dL was 20.4 adults per 100,000 employed population, calculated from 29 reporting states. In 2013, a total of 30 states submitted data on 5,504 adults with BLLs ≥25 μg/dL, and 29 states submitted data on 20,880 adults with BLLs ≥10μg/dL (Table 1). A total of 23 states submitted individual level data, and seven states submitted count data only. Overall, the national prevalence rate of BLLs ≥10 μg/dL declined from 26.6 adults per 100,000 employed in 2010 (among 37 states) to 20.4 in 2013 (among 29 reporting states). In 2013, of the 29 reporting states, 12 had prevalence rates of BLLs ≥10μg/dL equal to or above the national prevalence rate (20.4/100,000) (Figure 1). The national prevalence rate of BLLs ≥25 μg/dL among state residents and nonresidents declined from 14.0 adults per 100,000 employed in 1994 (among 17 states) to 5.2 in 2013 (among 30 states).

Historically, in the United States, most lead exposures among adults have been occupational. In 2013, a total of 29 states submitted data on 5,491 adults with BLLs ≥25 μg/dL of which 944 (17.2%) had no known exposure history (Table 2). Among the 4,547 adults with known exposure, 93.7% had occupational exposure, ranging from 42.9% to 100% among reporting states. Individual level data on 2,313 occupational cases with BLLs ≥25 μg/dL were available from 22 states. The majority of these adults were employed in four main industry sectors: manufacturing (n = 1,227 [53.1%]), construction (n = 468 [20.2%]), services (n = 194 [8.4%]), and mining (n = 182 [7.9%]). Within manufacturing, the majority of cases (n = 878; 71.6%) were among workers employed in storage battery manufacturing (North American Industry Classification System [NAICS] 33591), alumina and aluminum production and processing (NAICS 33131), and nonferrous metal (except copper and aluminum) rolling, drawing, extruding, and alloying (NAICS 33149) industries. Within construction, the majority of cases (n = 329 [70.3%]) were among workers employed in painting and wall covering contractors (NAICS 23832); highway, street, and bridge construction (NAICS 23731); and residential building construction (NAICS 23611) industries. Within the services sector, the majority of cases (n = 128 [66%]) were among workers employed in remediation services (NAICS 56291); all other amusement and recreation industries (NAICS 71399); automotive, mechanical, and electrical repair and maintenance (NAICS 81111); and fitness and recreational sports centers (NAICS 71394). Copper, nickel, lead, and zinc mining (NAICS 21223) accounted for 98.9% of the mining cases.

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

Sherri Davidson, MPH, Alabama Department of Public Health; Brigitte Dufour; Matthew Roach, MPH; Kaleb Tsang, MS, Arizona Department of Health Services; Susan F. Payne, MA, California Department of Public Health; Amanda M. DeLoreto, MPH; Thomas St. Louis, MSPH, Connecticut Department of Public Health; Sudha Rajagopalan, MPH; Sharon Watkins, PhD; Juanita Chalmers, MPH, Florida Department of Health; Tiefu Shen, Illinois Department of Public Health; Jeffery M. Turner, Indiana State Department of Health; Kathy Leinenkugel, MPA, Iowa Department of Public Health; MaAdwoa Asamoah, MPH, Kentucky Department for Public Health; Jocelyn Lewis, PhD, Louisiana Department of Health and Hospitals; Ezattolah Keyvan, MD, Maryland Department of the Environment; Kenneth Roseman, MD; Joanna Kica, MPA, Michigan State University; Stephanie Yendell, DVM, Minnesota Department of Health; Carol R. Braun, Missouri Department of Health and Senior Services; Derry Stover, MPH, Nebraska Department of Health and Human Services; Marija Borjan, PhD; Margaret E. Lumia, PhD; Devendra Singh, New Jersey Department of Health; Edward O. Irobi, PhD; Heidi Krapfl, New Mexico Department of Health; Alicia M. Fletcher, MPH, New York State Department of Health; Sheila Higgins, MPH, North Carolina Division of Public Health; Susan J. Quigley; Christin T. Benner, MPH, Oklahoma State Health Department; David Dreher; Oregon Health Authority; Tanecia Richardson, Pennsylvania Department of Health; Mike Sullivan, MBA, Vermont Department of Health; Carrie Tomasallo, PhD, Wisconsin Department of Health Services; Steve Melia, MSPH, Wyoming Department of Health, ABLES Programs coordinators in Alaska Department of Health and Social Services, Colorado Department of Public Health and Environment, Georgia Department of Public Health, Massachusetts Department of Labor Standards, Washington Department of Labor and Industries.