Adult Blood Lead Epidemiology and Surveillance --- United States, 2008--2009

Adult Blood Lead Epidemiology and Surveillance --- United States, 2008--2009
Weekly
July 1, 2011 / 60(25);841-845

Lead exposure can result in acute or chronic adverse effects in multiple organ systems, ranging from subclinical changes in function to symptomatic, life-threatening toxicity. Despite improvements in public health policies and substantial reductions in blood lead levels (BLLs) in adults, lead exposure remains an important health problem worldwide. Approximately 95% of all elevated BLLs reported among adults in the United States are work-related (1), and recent research has raised concerns regarding the toxicity of BLLs as low as 5 µg/dL (2,3). CDC's state-based Adult Blood Lead Epidemiology and Surveillance (ABLES) program tracks laboratory-reported elevated BLLs. To update rate trends and identify industry subsectors and nonoccupational activities with high lead exposures, CDC collected and analyzed 2008--2009 data from 40 state ABLES programs. The results of that analysis indicated that a decline in the prevalence of elevated BLLs (≥25 µg/dL) was extended, from 14.0 per 100,000 employed adults in 1994 to 6.3 in 2009. Industry subsectors with the highest numbers of lead-exposed workers were battery manufacturing, secondary smelting and refining of nonferrous metals, and painting and paper hanging. The most common nonoccupational exposures to lead were shooting firearms; remodeling, renovating, or painting; retained bullets (gunshot wounds); and lead casting. The findings underscore the need for government agencies, employers, public health professionals, health-care providers, and worker-affiliated organizations to increase interventions to prevent workplace lead exposure, and the importance of conducting lead exposure surveillance to assess the effectiveness of these interventions.

State ABLES programs 1) collect data on adult BLLs from laboratories and physicians through mandatory reporting requirements; 2) assign unique identifiers to each adult to account for multiple BLL records; 3) follow-up on adults with BLLs ≥25 µg/dL with laboratories, health-care providers, employers, or workers to ensure completeness of information (e.g., the industry where the adult is employed and whether the exposure source is occupational, nonoccupational, or both); and 4) code the industry where the adult worked using the 1987 Standard Industrial Classification (SIC) or the 2002 North American Industry Classification System (NAICS). The requirement for laboratories and health-care providers to notify state authorities about BLLs varies among ABLES states, ranging from the reporting of all BLLs to only BLLs ≥40 µg/dL.* Most ABLES states submit data on all BLLs to CDC's National Institute for Occupational Safety and Health (NIOSH), including records from adults whose BLLs fall below the state reporting requirement.

Adults were defined as persons aged ≥16 years. For adults with more than one BLL record in a given year, only the highest BLL was included. Elevated BLLs were defined as blood lead concentrations ≥25µg/dL. Prevalence numerators were either "state residents" (adults residing in the reporting state) or "state residents and nonresidents" (all adults reported by a state) with elevated BLLs (a distinction in the data since 2002); both employed and unemployed persons were included in the numerators. Denominators were the annual employed population aged ≥16 years for the period 2008--2009, as obtained from the U.S. Bureau of Labor Statistics (4). To calculate annual state prevalences, the numbers of adults with elevated BLLs from each of the 40 states reporting† were divided by the state's annual employed population and expressed as a rate per 100,000 employed adults. The combined state numerators and denominators for each year were then used to calculate national (40-state) prevalence rates for 2008--2009. The percentage of adults with BLL ≥40 µg/dL among adults with BLL ≥25µg/dL in each industry subsector was used to identify industry subsectors with the highest lead exposures. Additional information regarding interpretation of specific state ABLES data, definitions, and rate calculations is available at the ABLES program website (5).

A total of 40 states submitted data in both 2008 and 2009. Overall, the prevalence of elevated BLLs (≥25 µg/dL) among state residents and nonresidents declined from 14.0 adults per 100,000 employed adults in 1994 (4) to 7.4 in 2008 and 6.3 in 2009. Rates were slightly lower (7.1 and 6.1 respectively) when only state resident adults were included (Figure 1). The number of states with high prevalence of elevated BLLs (i.e., ≥20 adults per 100,000 employed adults) decreased from six of 17 states in 1994 to three of 40 states in 2009 (Figure 2). ABLES states reported 9,325 and 7,674 state resident adults with elevated BLLs in 2008 and 2009, respectively. State resident prevalence of elevated BLLs for 2008 ranged from 0.5 per 100,000 employed adults (Hawaii) to 37.6 (Pennsylvania); and for 2009, from 0.3 (Hawaii) to 32.0 (Pennsylvania). Prevalence of state resident and nonresident adults with BLLs ≥40 µg/dL declined from 3.5 in 1994 to 1.2 in 2008 and 0.9 in 2009. In 2008, these rates ranged from 0.2 (Arizona) to 6.5 (Pennsylvania) and in 2009, from zero (Alaska and Wyoming) to 4.2 (Pennsylvania).

Thirty-seven states in 2008 and 38 states in 2009 submitted data on industry and exposure source (8,450 and 7,112 state resident adults with elevated BLLs, respectively).§ Among all reported cases of elevated BLLs, exposures at work accounted for 6,081 (71.9%) in 2008 and 4,998 (70.1%) in 2009 (Table). Among only those cases with known exposure type (i.e., occupational or nonoccupational), occupational exposures accounted for 94.8% of cases in 2008 and 93.8% in 2009. The greatest proportions of adults with elevated BLLs were employed in three main industry sectors: manufacturing (72.1% in 2008 and 72.3% in 2009), construction (13.2% in 2008 and 14.4% in 2009), and mining (6.6% in 2008 and 5.1% in 2009). Industry subsectors with the highest numbers of workers with elevated BLLs were manufacturing of storage batteries, secondary smelting and refining of nonferrous metals, and painting and paper hanging (Table). Industry subsectors with the greatest proportions of adults with BLLs ≥40 µg/dL among adults with BLLs ≥25 µg/dL were painting and paper hanging; bridge, tunnel, and elevated highway construction; copper foundries; special trade contractors; and heavy construction industries (Table). Nonoccupational exposures accounted for 337 (4.0%) and 328 (4.6%) of all adult cases in 2008 and 2009, respectively. The most common nonoccupational exposures were from shooting firearms; remodeling, renovating, or painting; retained bullets; and lead casting (Table).

Reported by
Walter A. Alarcon, MD, Janet R. Graydon, Geoffrey M. Calvert, MD, Div of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, CDC. Corresponding contributor: Walter A. Alarcon, CDC, walarcon@cdc.gov, 513-841-4451.

Editorial Note

Job activities known to involve the use or disturbance of lead include the following: handling of lead-containing powders, liquids, or pastes; production of dust or fumes by melting, burning, cutting, drilling, machining, sanding, scraping, grinding, polishing, etching, blasting, torching, or welding lead-containing solids; and dry sweeping of lead-containing dust and debris (3). Since 1994, ABLES surveillance results indicate an overall decreasing trend in the prevalence of elevated BLLs in U.S. adults and a decrease in the number of states with the highest rates (i.e., ≥20 adults per 100,000). This decrease, in part, might be attributable to a decline in the number of manufacturing jobs with potential for lead exposure over time and prevention measures that have been enacted since the early 1990s, including 1) improved interventions by state ABLES programs,¶ worker-affiliated organizations, and federal programs such as the Occupational Safety and Health Administration (OSHA) National Emphasis Program to reduce lead exposure** and 2) measures implemented by industry (e.g., engineering and work practice controls,†† and respiratory protection). However, the decrease in rates also might reflect low employer compliance with testing and reporting requirements (6).

ABLES data also underscore that elevated BLLs among adults are almost exclusively an occupational health problem in the United States. Those states with higher rates of elevated BLLs might represent 1) states where higher proportions of workers are employed in high-risk industries (e.g., lead-related manufacturing, construction activities involving lead paint exposure, and lead mining), 2) states where workers in high-risk areas are less likely to be protected by engineering and workplace controls, or 3) states where greater compliance with testing requirements by employers and reporting requirements by laboratories result in larger numbers of reported cases of elevated BLLs. Similar to findings in previous years, the 2008--2009 data indicate that five industry subsectors accounted for approximately 65% and 14 subsectors accounted for approximately 80% of adults with elevated BLLs who were exposed at work. Higher lead exposures likely are present in those industries with the greatest proportions of elevated BLLs ≥40 µg/dL.

ABLES data are used to track Healthy People 2020 objective OSH-7, to reduce the prevalence of persons who have elevated BLLs from work exposures (7). The Healthy People 2020 target incorporates the new ≥10 µg/dL operational definition for elevated BLLs established by ABLES consistent with guidance from the Association of Occupational and Environmental Clinics and the Council of State and Territorial Epidemiologists (8).

The findings in this report are subject to at least four limitations. First, the number of adults with elevated BLLs reported to ABLES likely is underreported because some employers might not provide BLL testing to all lead-exposed workers as required by OSHA regulations and because some laboratories might not report all tests as required by state regulations (9). Second, because denominators are the numbers of employed persons, aged ≥16 years, unemployed adults who might be at risk for lead exposure, although included in the numerator, are not included in the denominator. Third, although state ABLES programs ascertain the work-relatedness of a lead exposure by following up with laboratories, physicians, employers, or workers, the possibility of misclassification of occupational versus nonoccupational cases cannot be excluded. Finally, analyzing lead exposures using a threshold of 25 µg/dL likely underestimates harmful occupational lead exposure because lead-related toxicity can occur at levels as low as 5 µg/dL and the Healthy People 2020 target is set at 10 µg/dL

Progress toward meeting the Healthy People 2020 target for reducing the prevalence of adults with BLLS ≥10 µg/dL from workplace lead exposures can be aided by improving 1) worker protection programs developed and maintained by employers§§; 2) government activities such as ABLES programs, which can effectively intervene to prevent lead exposures and the OSHA National Emphasis Program to reduce lead exposure; 3) research and interventions by stakeholder organizations; and 4) education of the public regarding preventing nonoccupational exposures. Emphasis should be placed on those industries identified in this report with the highest numbers of workers with elevated BLLs: manufacturing of storage batteries, secondary smelting and refining of nonferrous metals, painting and paper hanging, and bridge, tunnel, and elevated highway construction.

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Adult Blood Lead Epidemiology and Surveillance --- United States, 2008--2009