Lead is toxic in humans and has no useful purpose in the body. Employees are exposed to lead in the workplace by inhaling lead-containing dusts and fumes as well as by inadvertently ingesting lead particles transferred from hand to mouth.
Lead is of particular concern in the electronic scrap industry, where it is found in cathode ray tubes (CRTs), batteries, printed circuit boards and other electronic items. The CRT funnel glass may contain 22 percent to 25 percent lead; the panel glass, 2 percent to 3 percent; and the frit (the edge where the panel and the funnel meet), 70 percent to 85 percent.
Scientists in the Health Hazard Evaluation (HHE) Program of the National Institute for Occupational Safety and Health (NIOSH), which is part of the Centers for Disease Control and Prevention (CDC), have evaluated lead exposure at several electronic scrap facilities. The evaluations were done at the request of the employers, who desired to improve workplace safety and health. (More information on the HHE Program can be found at www.cdc.gov/niosh/hhe.)
This article discusses workplace exposure limits for lead, health effects of lead and relevant findings of a NIOSH evaluation of an electronic scrap facility.
Blood lead levels
ACOEM . ACOEM provides input to OSHA on key issues facing agency in 2010. Letter to David Michaels. Elk Grove Village, IL: American College of Occupational and Environmental Medicine [http://www.acoem.org/Page2Column.aspx?PageID=7392&id=6676]. Date accessed: October 2013.
ATSDR . Toxicological profile for lead. Atlanta, GA: U.S. Department of Health and Human Services, Agency for Toxic Substances and Disease Registry.
Billingsley KJ . Letter of September 30, 2013, from K. J. Billingsley, California Department of Public Health, to Juliann Sum, Division of Occupational Safety and Health (Cal/OSHA), California Department of Industrial Relations.
Brown-Williams H, Lichterman J, Kosnett M . Indecent exposure: lead puts workers and families at risk. Health Research in Action, University of California, Berkeley. Perspectives 4(1):1–9.
CDC (Centers for Disease Control and Prevention) . Childhood lead poisoning associated with lead dust contamination of family vehicles and child safety seats—Maine, 2008. MMWR 58(32):890–893.
CDC (Centers for Disease Control and Prevention) . Take-home lead exposure among children with relatives employed at a battery recycling facility—Puerto Rico, 2011. MMWR 61(47):967–970.
CDC (Centers for Disease Control and Prevention) . Fourth national report on human exposure to environmental chemicals, updated tables, March, 2013 [http://www.cdc.gov/exposurereport/pdf/FourthReport_UpdatedTables_
CDPH . Medical guidelines for the lead-exposed worker. Sacramento, CA: California Department of Public Health, Occupational Lead Poisoning Prevention Program [http://www.cdph.ca.gov/programs/olppp/Documents/medgdln.pdf]. Date accessed: October 2013.
CFR. Code of Federal Regulations. Washington, DC: U.S. Government Printing Office, Office of the Federal Register.
CSTE . Public health reporting and national notification for elevated blood lead levels. CSTE position statement 09-OH-02. Atlanta, GA: Council of State and Territorial Epidemiologists [http://c.ymcdn.com/sites/www.cste.org/resource/resmgr/PS/09-OH-02.pdf]. Date accessed: October 2013.
Institute of Medicine . Potential health risks from recurrent lead exposure of DOD firing range personnel. Washington, DC: National Academies Press.
Kosnett MJ, Wedeen RP, Rothenberg SJ, Hipkins KL, Materna BL, Schwartz BS, Hu H, Woolf A . Recommendations for medical management of adult blood lead exposure. Environ Health Perspect 115(3):463–471.
Moline JM, Landrigan PJ . Lead. In: Rosenstock L, Cullen MR, Brodkin CA, Redlich CA, eds. Textbook of clinical occupational and environmental medicine. 2nd ed. Philadelphia, PA: Elsevier Saunders, pp. 967–979.
NIOSH . Report to Congress on the workers’ home contamination study conducted under the Workers’ Family Protection Act 29 U.S.C. 671a. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 95-123 [http://www.cdc.gov/niosh/docs/95-123/]. Date accessed: October 2013.
NIOSH . NIOSH pocket guide to chemical hazards. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2010-168c [http://www.cdc.gov/niosh/npg/]. Date accessed: October 2013.
NIOSH . Adult Blood Lead Epidemiology and Surveillance (ABLES) [http://www.cdc.gov/niosh/topics/ABLES/description.html]. Date accessed: July 2014.
NTP . Report on carcinogens.12th ed. Research Triangle Park, NC: U.S. Department of Health and Human Services, National Institutes of Health, National Institute of Environmental Health Sciences, National Toxicology Program [http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/Lead.pdf]. Date accessed: October 2013.
NTP . Monograph on the health effects of low-level lead. Research Triangle Park, NC: U.S. Department of Health and Human Services, National Institutes of Health, National Institute of Environmental Health Sciences, National Toxicology Program.
Schwartz BS, Hu H . Adult lead exposure: time for change. Environ Health Perspect 115(3):451–454.
Schwartz BS, Stewart WF . Lead and cognitive function in adults: a question and answers approach to a review of the evidence for cause, treatment, and prevention. Int Rev Psychiatry 19(6):671–692.
WHO . IARC monographs on the evaluation of carcinogenic risks to humans. Vol. 87. Inorganic and organic lead compounds. Summary of data reported and evaluation. Geneva, Switzerland: World Health Organization [http://monographs.iarc.fr/ENG/Monographs/vol87/volume87.pdf]. Date accessed: October 2013.
The best way to monitor a worker’s recent lead exposure is to measure it in a blood sample. This “blood lead level” (BLL) indicates a worker’s exposure in the previous 26 to 45 days. The geometric mean BLL in adults in the United States is 1.23 micrograms per deciliter of whole blood (µg/dL). NIOSH uses a surveillance case definition of greater than or equal to 10 µg/dL for an elevated BLL in adults.
Health effects of lead
Neither the NIOSH nor the Occupational Safety and Health Administration (OSHA) workplace exposure limits are adequate to protect lead-exposed workers from the effects of lead on hypertension, renal dysfunction and reproduction and cognition. People with chronic lead poisoning may not have symptoms or they may have nonspecific symptoms that are unrecognized as being associated with lead exposure. These symptoms include headache, joint and muscle aches, weakness, fatigue, irritability, depression, constipation, anorexia and abdominal discomfort.
According to the Agency for Toxic Substances and Disease Registry (ATSDR) and the National Toxicology Program (NTP), lead is reasonably anticipated to cause cancer in humans. The International Agency for Research on Cancer classifies lead as probably carcinogenic to humans.
Workplace exposure limits
In the United States, employers in general industry are required by law to follow the OSHA lead standard (29 CFR1910.1025). This standard was created in 1978 and has not yet been updated to reflect the current scientific knowledge regarding the health effects of lead exposure. The OSHA permissible exposure limit (PEL) for airborne exposure to lead is 50 micrograms per cubic meter of air (µg/m3) for an 8-hour time-weighted average (TWA). The standard requires medical monitoring for employees exposed to airborne lead at or above the action level of 30 µg/m3 (8-hour TWA). The standard also requires medical removal of employees whose average BLL is 50 µg/dL or greater. These workers cannot return to jobs involving lead exposure until their BLL is below 40 µg/dL.
The NIOSH recommended exposure limit for lead also is 50 µg/m3 averaged over an 8-hour work shift.
In 2013, the California Department of Public Health recommended Cal/OSHA lower the PEL for lead to 0.5 to 2.1 µg/m3 (8-hour TWA) to keep BLLs below the range of 5 to 10 µg/dL. This recommendation considers more recent information on health effects of low levels of lead.
Neither NIOSH nor OSHA has established surface contamination limits for lead in the workplace. OSHA requires that all surfaces be maintained as free as practicable of accumulations of lead. An employer with workplace exposures to lead must implement regular, effective cleaning of surfaces in places such as changing areas, storage facilities and lunchroom/eating areas to ensure they are as free as practicable from lead contamination.
In 2007 a panel of experts published guidelines for management of adult lead exposure to prevent acute and chronic health effects. The guidelines are available at www.cdph.ca.gov/programs/olppp/Documents/medmanagement.pdf. The panel recommended BLL testing for all lead-exposed employees, regardless of the airborne lead concentration. The panel’s recommendations, outlined in Table 1 on this page, do not apply to pregnant women, who should avoid BLLs greater than 5 µg/dL.
Removal from lead exposure should be considered if control measures over an extended time do not decrease BLLs to less than 10 µg/dL or if an employee has a medical condition that would increase the risk of health effects from lead exposure. The Council of State and Territorial Epidemiologists (CSTE) and the American College of Occupational and Environmental Medicine (ACOEM) endorse these standards.
Occupational exposures to lead can result in exposures to household members, including children. This take-home contamination occurs when lead dust is transferred from the workplace on employees’ skin, clothing, shoes and other personal items to their vehicles and homes.
Workplace measures effective in preventing take-home exposures are: (1) reducing exposure in the workplace, (2) changing clothes before going home and leaving soiled clothing at work for laundering, (3) storing street clothes in areas separate from work clothes, (4) showering before leaving work and (5) prohibiting removal of toxic substances or contaminated items from the workplace.
NIOSH evaluated a company that had about 80 employees and processed a variety of electronic scrap, including CRTs. CRT processing (demanufacturing and glass breaking) was done in one warehouse, and the area of this activity was open to the rest of the warehouse. The CRT glass was broken in an automated crushing machine that was ventilated, but the exhausted air was recirculated back into the workspace through a particulate filter that was not high efficiency. Electronic sorting, demanufacturing, shredding and baling operations for all other electronics were done in another warehouse that was connected to the warehouse where CRTs were processed. The facility had no showers and only a few sinks for employees to wash their hands, arms and faces in before lunch, breaks or going home.
We at NIOSH observed open beverage containers in the CRT glass breaking area.
The facility provided a change-out room with lockers for the CRT crushing machine operators, but the room was not near the CRT area and was not separate from the production area. The design of the change-out room did not allow employees to store their potentially contaminated work clothing and personal protective equipment separately from their nonwork clothing or personal items.
The company had performed BLL testing on CRT breaking and maintenance employees. In 2011, the BLLs of five employees who broke CRT glass, along with one maintenance employee, ranged from 8.5 µg/dL to 21 µg/dL; five were above 10 µg/dL. When we tested 13 employees (including glass breakers, CRT demanufacturers, maintenance personnel and shredders) during our 2012 evaluation, the employees’ BLLs ranged from below the limit of detection to 13.7 µg/dL; two were above 10 µg/dL.
We looked at the potential for take-home contamination by collecting wipe samples from the hands and uniforms of employees and on surfaces throughout the facility. Eight of 12 pairs of hands tested positive for lead. Twelve of 13 uniforms tested positive for lead. We found lead on all wipe samples collected on 31 work surfaces in production and nonproduction areas, including an air supply diffuser in the office area, even though this ventilation system was independent of the production area.
We were contacted by the local children’s hospital; two children of an employee at this facility had BLLs of 18.4 µg/dL and 13.9 µg/dL. The health department evaluated their home to determine the source of lead exposure, and, though they found lead in the house dust, no other home sources (such as lead-based paint or lead-glazed ceramics) were found. This implies that the workplace was the source of the children’s lead exposure.
We made recommendations to the employer to reduce lead exposure to employees and their families. The full report containing these recommendations is available online at www.cdc.gov/niosh/hhe/reports/pdfs/2012-0100-3217.pdf.
Employees who recycle electronic scrap are at risk for substantial exposure to lead if adequate controls are not in place. This exposure is not limited to employees who break CRT glass but also includes employees in other areas. Workers also are at risk of taking lead dust home and exposing family members.
A comprehensive health and safety program that considers the latest scientific information can help prevent overexposures to lead.
The author is a medical team leader with the Health Hazard Evaluation Program of the National Institute for Occupational Safety and Health, which is part of the Centers for Disease Control and Prevention. She can be contacted at firstname.lastname@example.org.