Can the airborne lead exposure of maintenance workers be estimated by knowing the concentration of lead in paint and the type of activity being performed?
    Our department undertook a facility mapping program to evaluate the lead content of painted surfaces throughout a research and development complex. We did this to determine the potential for employee exposure to airborne lead while performing routine maintenance tasks such as hole drilling, paint scraping and sanding. Surfaces evaluated included painted exterior door and window frames, piping, walls and other miscellaneous structures that could be impacted by maintenance and construction activities. The range of lead concentrations found in over 200 paint chip samples was between none detected (0.0001 percent) and 15 percent by weight.
    In order to determine appropriate engineering controls, administrative practices or personal protective equipment, it is necessary to anticipate potential airborne concentrations of contaminants resulting from routine work activities such as power sanding and drilling. We wanted to obtain data during various construction and maintenance activities for use in predicting the controls required to achieve exposures below the applicable action level. Airborne levels of lead were measured during various simulated construction activities on surfaces covered with lead-based paint.

Health Hazards-
    Lead-based paint poses a health threat when it is ingested or when lead dust is inhaled. Lead can harm the hematopoietic, neurologic, gastrointestinal and reproductive systems.[1-3] Lead dust may be generated during maintenance or renovation activities (sanding or scraping), or from the friction or abrasion of normal activities such as opening and closing windows or doors. Also, some paints, primarily those intended for exterior use, are designed to chalk, that is, they continuously lose some of the outer layer in order to expose a fresh surface. Lead from paint can also pose an environmental concern when it contaminates soil or water surrounding the building. Condition and accessibility must be considered, in addition to lead content, in determining the risks associated with the presence of lead-based paint. Paint that is chipping, scaling or shows excessive chalking is more likely to create a potential lead exposure than "tight paint" in good condition. Also, paint on exterior structures or in inaccessible or rarely used areas presents less of an exposure potential.
    Most companies recognize that lead-based paint remediation can generate significant levels of airborne lead. However, maintenance and repair activities such as drilling, scraping and sanding that disrupt lead-based paint can also produce excessive lead exposures.[2]

Methods and Materials-
    In order to collect data which would aid in the prediction of the approximate concentrations of lead during various construction and repair activities, we established a test environment. A pre-fabricated metal partition panel, commonly used as walls in many buildings, was erected in an area free from any other source of lead. The 1.25 meter by 3 meter (4 feet by 10 feet) panel consisted of a 5 centimeter-thick (2 inch) layer of mineral wool insulation sandwiched between two painted galvanized steel sheets. A 3 meter high, 1.25 meter wide and 2 meter (6 feet) deep containment enclosure was built around the panel. This barrier, which was constructed of two layers of 6 mil-thick polyethylene on wooden battens, was partially open on one side for access.
    The panel was divided into six sections. One section was coated with the original paint which laboratory analysis by flame atomic absorption spectrometry indicated contained 0.4 percent lead by weight. Another section was coated with a commercial paint which created a surface coating containing 0.9 percent lead by weight. Finally, aliquots of a commercial interior vinyl latex nonlead-based paint were spiked with four different concentrations of basic lead carbonate [(PbC[O₃])₂] *Pb[(OH)₂], a paint pigment. [4] Two coats of the paint were applied by medium nap roller to the panel. Forty-eight hours of drying time elapsed between coats and 72 hours passed before testing. Refer to table on previous page for lead in paint concentrations.
    Two different construction activities, power sanding and drilling, were conducted on each of the painted panel sections. A random orbital power sander was fitted with 80-grit open face abrasive paper. Each 625 [cm.sup.2] (100 square inches) test area on the panel was abraded for 22 minutes. Power drilling was performed by creating 28 holes in 10 minutes with a three-eighths inch twist drill bit. The worker in the test was protected with a full-face air purifying respirator with HEPA cartridges, safety glasses and disposable full coveralls. During each activity, personal air samples were collected from the breathing zone of the worker and area samples were collected approximately 10 feet from the partition surface. The surface was vacuumed and wet wiped between sample periods to minimize carry-over of contaminants from previous activities.

Sampling and Analysis-
    Two paint chip samples were taken from each section of the test partition and were analyzed by flame atomic absorption spectrometry (AAS) to determine the average lead content (percent lead by weight) of the dried paint film. X-ray fluorescence (XRF) analysis of test panel sections was performed by taking six readings on each section with a Princeton Gamma-Tech XK-3, Lead in Paint, Analyzer. The arithmetic mean of six measurements per section minus the average of six substrate correction measurements per section was recorded as the lead content of the paint (milligrams/[cm²].[5] Personal and area air samples were collected by drawing air through Millipore AA 37 millimeter diameter, 0.8 micron pore size, mixed cellulose ester filters with SKC 224-PCXR3 personal sampling pumps set at flow rates between 2.5 and 4.2 liters per minute.[6] Pumps were placed in the breathing zone of the worker with the cassette face down. Area samples were collected at a horizontal distance of 3 meters (10 feet) from the test panel at a height of 1.5 meters (5 feet). Air samples were submitted for analysis within 24 hours of collection and were subsequently analyzed in accordance with NIOSH Method 7105 (1990).   During the power sanding, a single set of samples was collected for each concentration of lead-based paint. During the drilling, two personal samples and one area sample were collected for each concentration of lead-based paint.

Results-
    As expected, the more aggressive activities such as power sanding resulted in higher airborne lead levels than less disruptive activities such as drilling. In addition, a significant correlation existed between the lead concentration in painted test panel sections and the measured airborne lead concentrations obtained at breathing zone and area sample points. The Pearson correlation coefficient for personal and area airborne lead concentrations (atomic absorption measurement of lead in paint) while power sanding were [r²] = 0.97 and [r²] = 0.84 respectively, and [r²] = 0.95 and [r²] = 0.90 for power sanding personal and area samples (X-ray fluorescence measurement of lead in paint). Since there were no detectable levels of airborne lead during the drilling, correlations were not identified between airborne lead levels and lead concentrations in paint. While correlations between airborne lead levels and lead concentrations in paint as measured by XRF and AAS were similar, XRF measurements were apparently not as sensitive as AAS measurements for the two lowest lead concentrations, 0.4 and 0.7 percent. XRF instrument readings showed no detectable levels of lead in the paint after substrate correction for both concentrations.
 
Conclusions-
    Within the limited range of the conditions evaluated, the correlation between the lead content in paint on flat surfaces and the airborne concentrations during power sanding operations is sufficient to estimate potential exposures during power sanding activities. The correlation appears to be independent of the analytical methods (AAS or XRF) for determining the lead concentration on the painted surface. A correlation was not established between drilling activities on lead-based paint test panels and personal or area airborne lead concentrations because no air samples had detectable levels of lead. The lack of lead detection may be due to large particles created by drilling not remaining airborne long enough to be efficiently collected on the sampling medium, and a relatively small sample volume (the rapid pace of drilling 28 holes resulted in an approximately 6 minute sampling time) which resulted in a higher limits of quantification of airborne lead concentrations. It is also possible that drilling holes in lead-based paint does not generate significant quantities of airborne lead.
    Based on the area samples, workers not directly involved in the sanding operation would potentially be exposed to lower concentrations of airborne lead than workers who are actually sanding lead-based paint. Depending upon the lead content in the paint and the exposure time, there is a potential for exceeding the OSHA action level of 30 ug/[m³]. For those workers directly involved in sanding, a lead exposure may be predicted. For example, if the lead content of the paint on a surface is approximately 0.4 percent or higher, the worker sanding that surface for more than 4 hours in a work shift could exceed the action level for airborne lead exposure. Similarly, if the surface were coated with paint containing approximately 10 percent lead, a worker could exceed the action level in 10 minutes. The results of this study and potentially other similar studies may be a useful aid for anticipating airborne lead exposures for maintenance and construction workers and prescribing appropriate PPE, work practices and engineering controls if the type of activity and lead content of the paint are known.

RELATED ARTICLE:
    Regulations and Standards Lead compounds, mainly salts and oxides, have been widely used as paint pigments and additives. Due to concerns about the health hazards associated with lead, its use in paint has been restricted and controlled on both interior and exterior coatings. In 1976, the Consumer Product Safety Commission (CPSC) established a maximum allowable lead content in paint of 0.5 percent by weight in a dry film of newly applied interior paint. In 1978, the CPSC lowered the allowable lead level in paint to 0.06 percent. Other agencies, including housing authorities and local governments, considered any lead amount greater than 0.05 percent as indication of lead-based paint. The U.S. Department of Housing and Urban Development (HUD) has established 0.5 percent lead by weight or 1.0 mg/[cm²] as criteria for classification of lead-based paint. In specialty paints, those used for outdoor structures, pavement painting and industrial coatings, the lead content is unregulated.
    In 1978, OSHA reduced the allowable airborne lead exposures of workers in general industry from 200 micrograms per cubic meter (ug/[m.sup.3] to 50 ug/[m³].[8] In addition, the standard required that the exposure limit be achieved, to the extent possible, by engineering and work practice controls rather than reliance on personal protective equipment. The standard also mandated a written exposure control plan, medical surveillance and removal provisions, respiratory protection and air monitoring.
    The construction industry, which includes painting and renovation of structures, was excluded from this new standard. OSHA explained that it had exempted the industry because of insufficient information in the record to resolve issues raised about the applicability of the standard to conditions in the construction industry.[9] OSHA stated it would request the Construction Advisory Committee to review the record and make recommendations for a lead standard for the construction industry. Subsequently, OSHA's exemption of the construction industry was challenged through litigation as was OSHA's attempt at a broad-based revision of permissible exposure limits that would, among other changes, include construction under the lead standard for general industry. OSHA, in the fall of 1990, announced it would begin to develop a proposal for a comprehensive standard regulating occupational lead exposure in construction. Because of OSHA's lack of progress in promulgating a lead in construction standard, Congress included in the Housing and Community Development Act of 1992 Sections 1031 and 1032 of Title X.[9] These sections essentially required OSHA to complete a lead standard for the construction industry in 180 days. The final rule was published in May 1993, and became effective in June 1993. The Lead in Construction standard[10] reduces the allowable exposure limit for construction workers to 50 ug/[m³] and imposes many of the same requirements as the general industry lead standard.

References
1) Department of Health and Human Services, Agency for Toxic Substance and Disease Registry, Toxicological Profile for Lead, 1990.

2) American Conference of Governmental Industrial Hygienists, Documentation of the Threshold Limit Values and Biological Exposure Indices, Sixth Edition, 1993. p.847.

3) Landrigan, P.J. "Current Issues in the Epidemiology and Toxicology of Occupational Exposure to Lead." Environmental Health Perspectives 89:61-66 (1990).

4) Sax, Irving, R. Lewis ed. Hawley's Condensed Chemical Dictionary Eleventh Ed. New York, New York: Van Nostrand Reinhold Co. Inc. 1987 p. 688.

5) Princeton Gamma-Tech Inc.: User's Manual XK - 3 Lead-in-Paint Analyzer, Princeton, N.J.: Princeton Gamma-Tech Inc., 1989.

6) U.S. Department of Health and Human Services, CDC, NIOSH, Manual of Analytical Methods Third Edition, Method 7105, 1990.

7) "Lead," Code of Federal Regulations Title 29, Part 1910.1025, 1992, p. 156-157851.

8) "Occupational Exposure to Lead" Final Standard, Federal Register 43:220 (Nov. 14,1978) p. 52986.

9) The Housing and Community Development Act: Title X PL 102-550, 1992.

10) "Occupational Exposure to Lead in Construction" Federal Register 58 (4 May 1993), p. 26627.
 
 

Edward J. Guszkowski, CSP, is a senior industrial hygiene and safety engineer for Bell Laboratories, a division of Lucent Technologies.  Prior to working at Lucent, he was employed by AT&T and the Amerada Hess Corp. Richard J. D'Orazio, CIH, CSP, is an industrial hygienist with Bell Laboratories.  He is a former industrial hygiene supervisor with OSHA. COPYRIGHT 1996 Penton Publishing Inc. Assessing the risks of lead-based paint. (estimation of exposure to air-borne lead)(includes related article on regulations and standards).
Copyright © 1998 Infonautics Corporation. All rights reserved. - Terms and Conditions