Lead Chromate Exposures and Elevated Blood Lead Levels in Workers in the Plastics Pigmenting Industry -- Texas, 1990

In June 1990, the Dallas (Texas) County Health Department received a physician's report of an elevated blood lead level (BLL) (52 ug/dL) for an employee of a company that formulates color concentrates for the plastics industry. The physician had been evaluating the employee for severe headaches of uncertain etiology; however, he requested a BLL analysis when the employee's occupational history suggested possible lead exposure.

The physician also reported the exposure to the Occupational Safety and Health Administration (OSHA) and contacted the medical toxicologist at the North Texas Poison Control Center to obtain treatment and management recommendations. Because the company lacked an ongoing medical-monitoring program for employees, as mandated by OSHA, * the physician consulted with the company officials, then performed blood-lead analyses for 22 additional employees. For seven of these employees, BLLs exceeded 40 ug/dL (range: 43-107 ug/dL; mean: 62 ug/dL). Two employees, with BLLs of 78 ug/dL and 107 ug/dL, were hospitalized for chelation therapy (the first with calcium ethylenediaminetetraacetic acid (EDTA) and penicillamine; the second with EDTA, penicillamine, and dimercaprol). Two others (with BLLs of 60 ug/dL and 59 ug/dL) received chelation therapy with penicillamine as outpatients.

During August 1990, to determine the sources of exposure to lead and other chemicals, the Environmental Epidemiology Program, Epidemiology Division, Texas Department of Health (TDH), conducted an industrial hygiene inspection of the facility. In the plant, powdered metal-based pigments are mixed in a formulation laboratory and blended with plastic pellets in 500- to 2000-gallon mixers located in the production area. The pigment-pellet mixes are then heated and extruded, forming colored pellets; these completed pellets are sold and then used to produce colored plastic products.

The TDH determined that ventilation and other engineering measures in the plant inadequately controlled dusts generated by the process. Employees were equipped with half-mask, air-purifying respirators fitted with organic vapor cartridges and particulate filters; however, in several environmental samples, airborne lead exposures exceeded the protective capacity of the respirators. Based on environmental monitoring, the highest exposures occurred during the following operations: hand weighing the pigments, blending, emptying the blenders into open bins, cleaning the blenders with compressed air, and manually agitating the mixes when blenders and extruders clogged.

Personal-breathing-zone exposure samples documented that employees had substantial airborne exposure to lead, chromium (as lead chromate), and cadmium--components of the various pigments used in the process. Exposure to airborne lead in the extruding area was 648 ug/m3 (as a 10-hour, time-weighted average) and 226 ug/m3 in the blending area. ** Chromium exposure (as chromates) in the extruding area was 132 ug/m3, above the OSHA permissible exposure limit (PEL) of 100 ug/m3 (as a ceiling concentration) ***. The highest airborne cadmium exposure was 48 ug/m3 (the current PEL is 200 ug/m3 ****). In addition, contamination with lead and chromium was detected in wipe samples obtained from a desk next to the pigment table, the top of the coffee maker in the formulation laboratory, and different sites in the lunchroom. The highest lead (0.24 ug/cm2) and chromium (0.04 ug/cm2) levels were detected on the handle, door, and controls of the lunchroom microwave oven.

The TDH made specific recommendations to correct the observed violations of OSHA standards, including substantial improvements in work practices, implementation of a respirator program, and medical treatment of the affected workers. As of April 1991, the mean BLL for the eight workers with elevated BLLs had decreased to 36 ug/dL (range: 23-46 ug/dL). Nonetheless, repeat environmental monitoring indicated that airborne lead exposures remained high in many areas of the facility and required further efforts to reduce exposures.

The TDH is investigating to determine whether the exposures in this plant are characteristic of this industry elsewhere in Texas.

Reported by: C Kelly, Dallas County Health Dept; J Pichette, MS, L Schulze, DM Perrotta, PhD, JP Henry, MS, Epidemiology Div, Texas Dept of Health. Div of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, CDC.

Editorial Note

Editorial Note: Although the U.S. Consumer Products Safety Commission banned lead in residential paints in 1977, ***** pigments containing lead continue to be used in many industrial and commercial applications and pose a substantial risk to workers and their families. During 1983, 24 industries used lead chromate (National Occupational Exposure Survey of CDC's National Institute for Occupational Safety and Health (NIOSH), unpublished data, 1991); during May 1991, 30,600 U.S. workers in these industries potentially were exposed to lead chromate -- 12,500 of whom worked in the miscellaneous plastics products industry (Table 1).

This investigation documents the first identified cases of elevated BLLs among workers in the plastics industry in Texas. In addition to the risk for lead exposure for workers involved in this process, the subsequent use of the pigment-infused pellets by manufacturers of colored plastic products presents a potential for lead exposure through the heating, remolding, and cutting of processed plastic parts. During 1988, states that conducted surveillance of elevated BLLs received 17 reports of elevated BLLs in the plastics materials and resins industry (Standard Industrial Code (SIC) 282 (2)) and 11 reports in the miscellaneous plastics products industry (SIC 307) (NIOSH, unpublished data, 1988).

In Texas, state law requires physicians and laboratories to report elevated BLLs (i.e., BLLs of greater than or equal to 40 ug/dL for adults); from May 27, 1985, through December 31, 1990, the TDH received 5952 such reports for 1054 adults. In cooperation with NIOSH, the TDH participates in the Sentinel Event Notification System for Occupational Risks (SENSOR) (3) -- a state-based system for surveillance of occupational illness and injury; surveillance for elevated BLLs is conducted in conjunction with SENSOR. The identification and follow-up investigation of cases of elevated BLLs in the plastics pigmenting industry reported here demonstrates the utility of lead surveillance systems for identifying new or unrecognized sources of occupational exposures.

References

1. Office of the Federal Register. Code of federal regulations: occupational safety and health standards. Subpart Z: Toxic and hazardous substances--lead. Washington, DC: Office of the Federal Register, National Archives and Records Administration, 1985. (29 CFR section 1910.1025).

2. Office of Management and Budget. Standard industrial classification manual. New York: Prentice Hall Information Services, 1987.

3. Baker EL. Sentinel Event Notification System for Occupational Risks (SENSOR): the concept. Am J Pub Health 1989;79(suppl):18-20.

• The OSHA lead standard requires that employers monitor for airborne lead exposures in workplaces where lead is used; when airborne lead levels exceed 30 ug/m3 (as an 8-hour, time-weighted average (TWA)), employers must provide an industrial hygiene program and a medical-monitoring program that includes monitoring of BLLs (1). ** The OSHA permissible exposure limit (PEL) for lead is 50 ug/m3, as an 8-hour TWA. If an employee is exposed to lead for more than 8 hours in a work day, the PEL is adjusted according to this formula: maximum permissible limit=400 ug/m3 divided by hours worked in a day. Because employees at this facility worked 10-hour shifts, the applicable PEL was 40 ug/m3 (1). *** CDC's National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit for chromates is 1 ug/m3. NIOSH considers chromates as potential occupational carcinogens. **** NIOSH considers cadmium to be a potential occupational carcinogen and recommends that exposure be reduced to the lowest feasible level. ***** 16 Code of Federal Regulations, part 1303. Ban of lead-containing paint and certain consumer products bearing lead-containing paint.

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