In December 1991, a venous blood lead level (BLL) of 50 ug/dL was detected in a 46-year-old Ohio man during a routine pre-employment examination. He was referred to a university-based pharmacology and toxicology clinic for further evaluation; clinic physicians investigated the case. Although a repeat BLL obtained 1 month later was 51 ug/dL, he reported no exposure to known sources of lead during the interim. However, he reported numbness of his fingers and palms, tinnitus, and a possible decrease in his ability to perform basic arithmetical calculations.

A comprehensive occupational and environmental history obtained at the time of the second BLL test revealed no apparent source of his lead exposure. Although he had been employed for approximately 20 years as a microwave technician during military service and while employed at a television station, he reported no history of exposure to lead from soldering or welding. He had no activities or hobbies associated with exposure to lead or lead products, no previous bullet or birdshot wounds, and he denied drinking illicitly distilled alcohol or using lead additives in his car.

His residence was built in 1974 (after lead was banned from use in residential paint) *, and household water was obtained from a well. In January 1992, blood lead testing of family members revealed levels of 5 ug/dL for his wife and less than 5 ug/dL for his 17-year-old child. His only medication was ranitidine **, which he had used for the previous 1-1/2 years for "indigestion." He reported occasional cigarette smoking.

Although results of a neurologic examination were normal, neuropsychiatric testing on March 13 demonstrated mild memory deficits, as evidenced by abnormalities on verbal and figural memory tests. Because of these abnormalities, beginning March 13, he was treated for 19 days with dimercaptosuccinic acid (DMSA), an oral chelating agent, and on April 4, his BLL had decreased to 13 ug/dL. However, BLLs on May 15 and July 23 were 49 ug/dL and 56 ug/dL, respectively.

During a July 1992 follow-up clinic visit, he mentioned that for approximately 20 years he had habitually chewed on the plastic insulation that he stripped off the ends of electrical wires. Samples of the copper wire with white, blue, and yellow plastic insulation were obtained and analyzed for lead content. The clear plastic outer coating (present on all colors of wire) and the copper wire contained no lead; however, the colored coatings contained 10,000-39,000 ug of lead per gram of coating. *** On receipt of these results, he was instructed immediately to discontinue chewing the wire coating.

In January 1993, when his BLL was 24 ug/dL, he reported subjective improvement in his symptoms; follow-up neuropsychiatric testing is pending.

Reported by: M Kelley, MD, P Walson, MD, D Thorton, PhD, Ohio State Univ and Children's Hospital, TJ Halpin, MD, State Epidemiologist, Ohio Dept of Health. Div of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, CDC.

Editorial Note

Editorial Note: This report likely represents the first documented case of lead poisoning following ingestion of lead as a consequence of chewing on plastic wire coatings. Plastic coatings previously have been associated with lead exposure in the burning of lead-containing plastics during repair of a storage tank (1), the production of plastics (2,3), and the manufacture and use of stabilizers and pigments in the plastics industry (4). Although lead exposure also can occur among workers who burn the plastic coating off copper wire to recycle the copper, lead intoxication by this route has not been reported (5).

Lead compounds may be employed in the production of colored plastics (in which lead chromates are used as pigment) and in the manufacture of polyvinyl chloride (PVC) plastics (in which 2%-5% lead salts {including lead oxides, phthalate, sulfate, or carbonate, depending on the desired quality of the final product} are used as stabilizers). Although environmental regulation has reduced considerably the amount of lead used in the United States in the manufacture of PVC plastics, manufacturers of electrical wire and cable continue to produce PVC stabilized and/or pigmented with lead compounds (6).

More than 573,400 U.S. workers are employed in occupations involving electrical work. Among these workers, potential for excessive exposure to lead may result from inhalation of fumes generated during lead soldering (7). Because the plastic coating from wires is usually removed by mechanical stripping, ingestion of lead from these plastic coatings is probably uncommon. Nonetheless, the findings in this report remind occupational and other health-care providers of the need to be aware of this potential source of lead exposure. In addition, workers should be warned of the potential hazard of chewing plastic coatings or other plastic products that may contain lead.

References

1. Skillern CP. Experience with burned lead-in-plastic material. Am Ind Hyg Assoc J 1969;30:648-9.

2. CDC. Lead chromate exposures and elevated blood lead levels in workers in the plastics pigmenting industry -- Texas, 1990. MMWR 1992;41:304-6.

3. Ong CH, Ong HY, Khoo NY. Lead exposure in PVC stabilizer production. Appl Ind Hyg 1989;4:39-44.

4. CDC. Surveillance of elevated blood lead levels among adults -- United States, 1992. MMWR 1992;41:285-8.

5. Liss GM, Halperin WE, Landrigan PJ. Occupational asthma in a home pieceworker. J Occup Med 1986;41:359-62.

6. The Vinyl Institute. Characterization of lead in plastics products in municipal solid waste, 1970 to 2000. Prairie Village, Kansas: Franklin Associates, Ltd, 1990.

7. NIOSH. Health hazard evaluation report no. HETA 90-075-2298. Cincinnati: US Department of Health and Human Services, Public Health Service, CDC, 1993.

* 16 CFR section 1303.2. Ban of lead-containing paint and certain consumer products bearing lead-containing paint. 

** Ranitidine alters gastric acidity, which theoretically can influence gastrointestinal absorption of lead. 

*** Samples were analyzed using graphite furnace atomic absorption spectroscopy, following dissolution of the plastic coating in tetrahydrofuran.

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