Lead affects the developing nervous system of children, and no safe blood lead level (BLL) in children has been identified. Elevated BLLs in childhood are associated with hyperactivity, attention problems, conduct problems, and impairment in cognition. Young children are at higher risk for environmental lead exposure from putting their hands or contaminated objects in their mouth.
The National Toxicology Program found sufficient evidence that BLLs under 5 µg/dL in children are associated with attention-related behavioral problems and decreased cognitive performance (indicated by lower academic achievement, lower intelligence quotient, and decreases in certain cognitive measures). There is sufficient evidence that BLLs under 10 µg/dL are associated with delayed puberty and decreased postnatal growth, and limited evidence that BLLs under 10 µg/dL are associated with increased serum immunoglobulin E and allergy diagnosed by skin prick testing.
The NIOSH Adult Blood Lead Epidemiology and Surveillance System uses a surveillance case definition for an elevated BLL in adults as at least 10 µg/dL. The National Toxicology Program found sufficient evidence that BLLs under 5 µg/dL in adults are associated with decreased glomerular filtration rate and reduced fetal growth in pregnant women. There is sufficient evidence that BLLs under 10 µg/dL in adults are associated with increased incidence of essential tremor, increased blood pressure, increased risk for hypertension, and increased risk for spontaneous abortion and preterm birth. There is limited evidence that BLLs under 10 µg/dL in adults are associated with psychiatric effects, decreased hearing, decreased cognitive function, increased incidence of amyotrophic lateral sclerosis, increased cardiovascular mortality, and electrocardiography abnormalities. However, current occupational exposure levels are not protective of workers.
Although deteriorating lead paint in pre-1979 housing is the most common source of lead exposure in children, data indicate that at least 30% of children with elevated BLLs were exposed through a source other than paint. Take-home contamination occurs when lead dust is transferred from the workplace on employees' skin, clothing, shoes, and other personal items to their car and home. Recycling of used electronics (e-scrap) is a relatively recent source of exposure to developmental neurotoxicants, including lead.
Pediatricians should ask about parents' occupations and hobbies that might involve lead in routine lead screening questionnaires and in evaluating children with signs or symptoms of lead exposure. When evaluating children with elevated BLLs, public health professionals and clinicians should inquire about parental occupations because of the implications of take-home exposure. E-scrap recycling is an emerging area of concern as a source of occupational exposures among workers and a source of take-home exposures.
For example, in 2010, the Cincinnati Health Department and Cincinnati Children's Hospital Pediatric Environmental Health Specialty Unit (PEHSU) investigated two cases of childhood lead poisoning in a single family. In 2012, the CDC's National Institute for Occupational Safety and Health (NIOSH) learned about the lead poisonings during an evaluation of the e-scrap recycling facility where the father of the two children with lead poisoning worked.
In June 2010, a one-year-old boy and two-year-old girl were identified by routine screening to have elevated BLLs of 18 µg/dL and 14 µg/dL, respectively. The children's primary care physician referred them to the Cincinnati Children's Hospital PEHSU, and the Cincinnati Health Department's Childhood Lead Poisoning Prevention Program completed a lead risk assessment at the family's home. The father worked at an e-scrap recycler company, crushing cathode ray tubes. He did not wear personal protective equipment at work, and he reported playing with his children when he came home. The family reported there was frequently visible dust in his hair, and the children often touched his hair. The father's BLL was 25 µg/dL. The CDC considers a BLL of 5 µg/dL as the upper level of the reference range in children at which public health actions should be initiated.
The lead risk assessment revealed detectable lead dust on the floor of the home, but no lead-containing paint was detected in the home. The children attended daycare in a building that was built in 1992. The father was advised to notify the Occupational Safety and Health Administration of his BLL; it is not known if he did. The father left his job soon after the elevated BLLs were recognized, and the children's BLLs decreased to 8.7 µg/dL and 7.9 µg/dL, respectively, over the next 3 months.
In 2012, unrelated to the lead poisoning incident described above, NIOSH conducted a health hazard evaluation at the facility, as part of an initiative to learn more about exposures in e-scrap recycling. NIOSH was unaware of the childhood lead poisonings, as was the employer. The PEHSU investigator became aware of the NIOSH evaluation through a notification to a local affiliated occupational medicine training program and contacted the NIOSH investigators to notify them.
NIOSH investigators performed air and surface sampling for lead throughout the facility, which employed approximately 80 people. Three wipe samples taken from work surfaces in the cathode ray tubes area indicated high levels of lead. Cathode ray tubes are made from leaded glass, with lead concentrations in the funnel glass up to 25% and in the frit (where the panel glass joins the funnel glass) up to 85%. Lower surface lead concentrations were found outside the production area, including in the conference room supply air duct, multiple places in the break room (e.g., floor, tables, and refrigerator handle), and the water fountain near the restrooms.
Wipe samples were taken from the hands of 12 employees from the cathode ray tubes processing area and other areas before they left work, using wipes from the SKC Full Disclosure colorimetric test kit. This test kit identifies lead on surface wipe samples through a color change process and has a visual identification limit of 18 µg of lead. The hands of eight of 12 employees tested positive for lead, even though they had washed their hands with soap and water before testing. NIOSH also took a wipe sample from uniforms of employees' front shoulder area. Twelve of 13 uniforms tested positive for lead.
NIOSH investigators noted that the local exhaust ventilation system at the cathode ray tubes crushing operation recirculated potentially contaminated air back into the production area. There were no showers in the facility, and employees used brooms to sweep the work area, creating airborne dust. Because the changing area for employees who broke cathode ray tubes was not adjacent to the cathode ray tubes work area, employees could track lead-containing dust through the facility. Personal items, food, and work clothing and equipment were stored together in the changing area. All findings from the NIOSH health hazard evaluation were communicated to the employer and employees, along with recommendations to reduce exposure.
The U.S. Congress passed the Workers' Family Protection Act in 1992. The Act requires NIOSH to study take-home exposure of hazardous chemicals and substances, including lead. NIOSH found evidence that take-home exposure is a widespread problem. Workplace measures found to be effective in preventing take-home exposures included (1) reducing exposure in the workplace using the hierarchy of controls; (2) changing clothes and shoes before going home and leaving soiled clothing at work for laundering; (3) storing street clothes in separate areas of the workplace to prevent contamination; (4) showering before leaving work; and (5) prohibiting removal of toxic substances or contaminated items from the workplace.
NIOSH noted that preventing take-home exposure is key because decontaminating homes and vehicles is not always effective in the long term. Normal house cleaning and laundry methods are inadequate, and decontamination can potentially lead to hazardous exposures among those workers performing the cleaning activities.
The investigation of lead poisoning includes examining common sources of lead exposure, such as deteriorating lead paint, as well as other sources when investigation of the home does not suggest a source. With the increasing use of electronic devices and subsequent disposal and recycling of those devices, exposure to substances such as lead contained within the devices is an emerging occupational health concern in the e-scrap industry. The patchwork of state regulations overseeing e-scrap recycling in the United States addresses possible damage to the environment, but health-based regulations are lacking.
Approximately 130 million metric tons of e-scrap were recycled in the United States in 2010, and this scrap stream contains many types of toxicants (cadmium, polybrominated diphenyl ethers, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons) that are not routinely screened for in adult workers or children. The cases described above were uncovered through routine lead screening, but other undetected chemicals might also be coming home from e-scrap worksites. Pediatric health care providers should query parents about their occupations and assess the risk for exposure to various substances found in occupational settings.
See the CDC Report
See also Medical Law Perspectives, August 2015 Report (to be published August 4, 2015): Pediatrician Liability Involving Diseases and Conditions of Childhood
See the Medical Law Perspectives September 23, 2014, Blog: Heat Stress Kills Workers