Protecting Workers Exposed to Lead-based Paint Hazards
A Report to Congress
DHHS (NIOSH) PUBLICATION NO. 98-112
JANUARY 1997
Chapter 4 (continued)
METHODS, DEVICES, AND WORK PRACTICES TO CONTROL OCCUPATIONAL LEAD EXPOSURES DURING LEAD-BASED PAINT ACTIVITIES
CONTROLS FOR RESIDENTIAL LEAD ABATEMENT AND RENOVATION ACTIVITIES
Lead-based paint (LBP) is widespread in U.S. housing. HUD has estimated that 74 percent of privately-owned homes built before 1980 (57 million units) have LBP, as defined by HUD (greater than or equal to 1 milligram per square cubic meter [mg/cm2] lead). Nearly 4 million of those units house young children and have peeling paint or excessive lead-containing dust.29 A recent national survey estimated that 4.4 percent of U.S. children aged 1–5 years, or about 930,000 children, have elevated BLLs 10 µg/dL, the CDC action level for childhood lead exposure.30
In 1993, OSHA estimated that each year more than 45,000 abatement workers are exposed to lead during lead abatement and in-place management projects in public and private housing.31 As national efforts to reduce residential lead hazards progress, the number of workers exposed to lead during abatements and other lead hazard reduction activities may increase. OSHA also estimated that approximately 180,000 workers annually are exposed to lead during residential remodeling and renovation.31
Occupational Exposure Assessment
NIOSH studies have found that similar work tasks and health risks occur in residential lead abatement and renovation work.32,33 The extensive literature review conducted by OSHA in support of the Interim Final Rule for Lead in Construction (29 CFR 1926.62) also found similar worker lead exposures for residential lead abatement, renovation, and remodeling activities.34
Lead exposures vary significantly during residential lead abatement and renovation work. A NIOSH study of the 1990 HUD lead abatement demonstration project found that exposures were highly variable for individual abatement methods, contractors, and housing units.32 Another NIOSH study of LBP abatement workers found that lead exposures even varied significantly among work crews and individual workers performing the same tasks who were employed by a single contractor.35 NIOSH has found that worker lead exposures are generally low during both lead abatement and renovation work, but some tasks produce hazardous LBP exposures.
Because frequent exposure assessment with air monitoring is a burden to small contractors, many have expressed a desire for an action level for occupational exposure based on paint lead concentrations. OSHA has concluded that the relationship between paint lead concentrations and worker health risk (airborne lead exposures) is not reliable for construction work. NIOSH research is consistent with this conclusion. NIOSH studies of residential LBP abatement workers found a poor correlation between paint lead concentrations and worker exposures.32,35 NIOSH analyzed 2635 airborne lead measurements and 5774 paint lead measurements made in houses undergoing abatement during the HUD lead abatement demonstration project.[These paint lead measurements were made using atomic absorption spectrometry (AAS) to confirm portable x-ray fluoresence (XRF) readings in the range of 0.2 to 1.8 mg/cm2. Portable XRF data, which were less accurate, were excluded for this analysis.] NIOSH found only a very weak correlation (Pearson r = 0.22) between paint lead and airborne lead for 140 houses (see Figure 4.1). Three of the eight houses with an average airborne lead concentration greater than the OSHA action level (30 µg/m3) had a paint lead concentration below the HUD action level (1 mg/cm2).
The following is a method-by-method discussion of engineering, work practice, and administrative controls used during residential LBP activities. Lead exposure data available for this work from NIOSH studies and other sources are presented in Table 4.2.
Figure 4.1 Paint Lead vs Airborne Lead in 140 Houses during Abatement
| Control type(s) | Description of site and control | Method | No. samples | Lead exposure during task, µg/m3 Geometric mean (Range)¶ | Comments |
|---|---|---|---|---|---|
| Administrative Engineering | LBP removal with vacuum power tools, including needleguns and sanders. | Abrasive removal | 28 | 8.8 (< 0.4 - 399) | All workers received hazard training about lead hazards and safe work practices. |
| Substitution / Engineering | Surface preparation with (A) wet scraping, HEPA vacuuming, and mopping; (B) the same method with dilution ventilation; and (C) wet scraping. | Wet method A | 6 | 24 (7.1 - 49) | All workers received hazard training about lead hazards and safe work practices. |
| Wet method B | 6 | 73 (6.8 - 235) | |||
| Wet method C | 7 | 8.1 (0.7 - 63) | |||
| Administrative Engineering | LBP abatement in single-family homes with and without dilution ventilation provided (DV). | Heat gun | 17 | 22 (0.9 - 105) | Values reported are means by house. Dilution ventilation was provided with HEPA-filtered exhaust fans. All workers received hazard training about lead hazards and safe work practices. |
| Heat gun-DV† | 14 | 12 (1.9 - 48) | |||
| Replacement | 18 | 8.1 (0.7 - 67) | |||
| Replacement-DV‡ | 15 | 5.0 (1.3 - 23) | |||
| Administrative Engineering | LBP abatement in single-family homes with prohibition of high-risk methods. | Enclosure | 50 | 1.7 (< 0.4 - 72) | All workers received hazard training about lead hazards and safe work practices. |
| Encapsulation | 83 | 1.4 (< 0.4 - 26) | |||
| Replacement | 110 | 2.5 (< 0.4 - 121) | |||
| Cleaning | 138 | 1.9 (< 0.4 - 588) | |||
| Final cleaning | 56 | 2.1 (0.9 - 36) | |||
| Heat gun | 360 | 6.4 (< 0.4 - 916) | |||
| Chemical removal | 291 | 3.3 (0.4 - 476) | |||
| ALL METHODS | 1402 | 3.1 (< 0.4 - 916) | |||
| None | Surface preparation for home painting requiring removal of only loose and peeling LBP. | Exterior dry scraping | 15 | 28 (0.2 - 120) | |
| None | LBP removal with dry scraping and conventional power sanding. | Dry scraping Power sanding | 4 | 5800 (2,300-11,800) | Mostly painted surfaces with greater than or equal to 10 mg/cm2 lead. |
| OSHA PEL | 50 | ||||
|
* Sources: Selected NIOSH Health Hazard Evaluation reports, HUD Lead Abatement Demonstration Projects, Massachusetts DOH data. ¶ Ranges are for individual task-based samples unless noted. † Significant difference between mean air lead exposures with and without DV (p< 0.05). ‡ No significant difference between mean air lead exposures with and without DV (p> 0.05). | |||||
Selecting alternate, safer methods is one of the most effective ways to minimize worker exposures during residential lead abatement and renovation activities. Torch burning and power tools (sanders) with no LEV are common LBP removal techniques during home renovation, even though they have been found to produce worker lead exposures more than 200 times the OSHA PEL.36 In the HUD national LBP abatement demonstration project, these methods were expressly prohibited, and the maximum lead exposures were reduced by more than 90 percent.32 HUD subsequently prohibited these and other high-risk methods for LBP abatement in federally supported projects.
Of the LBP abatement methods demonstrated by HUD, paint removal with heat guns and abrasive power tools was associated with the highest worker exposures. Maximum worker lead exposures during the heat gun and abrasive methods were 18 and 8 times the OSHA PEL for lead, respectively, although administrative (heat gun nozzle air temperature restricted to 700o F) and engineering controls (power sanders and needleguns with LEV) were used.
NIOSH determined that worker lead exposures were generally low during enclosure, encapsulation, and replacement.37 Over 95 percent of the worker exposures were less than the OSHA PEL during these methods of LBP abatement, and no exposure exceeded 2.5 times the PEL. HUD also found these methods to be the most promising abatement methods in terms of overall costs and efficacy.38
NIOSH recommends safer abatement methods, such as enclosure, encapsulation, and replacement, should be used where possible instead of LBP removal by torch burning, heat gun, or abrasive methods.
Hazardous worker lead exposures often occur in residential abatement and renovation projects during manual scraping of LBP. Abatement workers, painters, and home renovators often use dry scraping with metal scrapers to remove old paint or prepare weathered painted surfaces for repainting. Dry scraping of LBP has been found to result in worker exposures up to 70 times the OSHA PEL.39
During renovation or abatement work, painted surfaces may be wetted with a fine mist of water or water mixed with a surfactant before scraping to reduce generation of airborne paint dust. A NIOSH study of LBP cleaning activities in buildings with highly deteriorated LBP found that worker lead exposures were significantly reduced by using wet methods.35 The wet methods (wet scraping and wet HEPA vacuuming) did not, however, totally eliminate hazardous LBP exposures. Workers had average short-term lead exposures ranging from 7.1 to 235 µg/m3. In a study of single-family home repair and weatherization, NIOSH measured lead exposures during exterior manual scraping of loose and peeling paint. Worker lead exposures for dry scraping (range: 0.2 to 120 µg/m3) were higher than those for wet scraping (range: 0.7 to 63 µg/m3), but both techniques were potentially hazardous.34
While NIOSH and HUD recommend the use of wet methods to control dust during paint scraping, these techniques increase the potential for electrical hazards. Wet methods should only be used with adequate safety controls including ground fault circuit interrupters, grounded and double-insulated tools, three-wire extension cords, nonconductive work shoes and gloves, and other appropriate electrical safety measures.
Chemical removal involves applying an organic solvent or caustic material and then scraping the dissolved LBP. Wet caustic pastes are typically used for chemical removal during HUD projects.[HUD recommends against the use of paint strippers containing methylene chloride, which is a potential human carcinogen.] It is important that scraping be done while the materials are still wet. The paste may be re-wetted with water mist just before manual scraping. A NIOSH study of chemical removal during HUD projects found that while the median worker lead exposure for this method was very low (3 µg/m3), the maximum exposure was nine times the OSHA PEL (476 µg/m3).32 It is probable that the high exposures occurred because workers and contractors failed to keep the surfaces wet.
When it is necessary to scrape LBP, wet scraping is preferable to dry scraping to reduce hazardous LBP exposures. However, wet methods will not eliminate hazardous occupational lead exposures and they should only be used with adequate electrical safety controls.
Vacuum power tools, including needleguns, sanders, and other power tools used with LEV, reduce worker exposures during residential LBP removal or surface preparation. Vacuum power tools must be used with a portable vacuum cleaner to create the exhaust. To prevent environmental contamination, the vacuum must contain a HEPA filter to collect the lead dust (the used filter may be a hazardous waste).
A NIOSH study of HUD work in single-family homes found that abrasive LBP removal with vacuum belt sanders and needleguns resulted in relatively low average worker exposures (8.8 µg/m3), although the maximum exposures were hazardous, up to eight times the PEL.32 Similar results were obtained during another HUD demonstration project where needleguns with LEV were used for LBP removal in public housing units.40 In contrast, OSHA has determined that the use of conventional power tools in housing abatement projects would result in average lead exposures approximately six times the OSHA PEL.34 NIOSH documented exposure at 24 times the OSHA PEL for a worker removing paint with a conventional power grinder.41
Disadvantages of vacuum power tools include the following: (1) higher initial cost of equipment, (2) ergonomic factors (increased equipment weight and possibly vibration), and (3) dependence on proper use and maintenance by the operator. HUD reported that high lead concentrations during needlegun use in a demonstration project may have occurred because workers modified the protective shrouds on the needleguns (presumably to increase productivity).40
When it is necessary to use abrasive power tools to remove LBP, vacuum power tools should be used instead of conventional tools to reduce lead exposures and emissions of lead dust.
General Dilution Ventilation and Containment Structures
Containment of work areas is often required during residential LBP abatement or renovation projects to isolate the work areas and control emissions of airborne lead to the surroundings. Interior residential work areas are usually contained by sealing all openings to the outside (doors and windows) with heavy-gauge (6-mil) clear plastic sheeting. Exterior residential areas are contained with plastic sheeting on the ground or by temporary structures made of plastic sheeting on a frame. Containment areas may be ventilated with HEPA-filtered exhaust fans (commonly known as "negative air" machines), which filter air from the work area and move it to the outside. The purpose of this ventilation is to maintain a negative air pressure inside the containment area with respect to the outside and provide general dilution ventilation to the work area.
In some cases, general dilution ventilation reduces worker exposures during abatement, but NIOSH studies have shown that this is not always true. In a study of lead abatement workers performing cleaning activities, NIOSH investigators found portable HEPA-filtered exhaust fans providing an estimated 37 air changes per hour to work areas actually increased worker lead exposures.35 The fans generated additional lead dust in the rooms, either by air turbulence, or because they had to be moved frequently during cleaning (the rooms were relatively small). Similarly, a Massachusetts study of residential LBP removal by dry scraping found very high personal exposures, 9 to 70 times the OSHA PEL, inside a contained area that was ventilated with a HEPA-filtered exhaust fan.11 A NIOSH evaluation of HUD lead abatement work found that HEPA-filtered exhaust fans significantly reduced average lead exposures during the heat gun method (p <0.05), but had no effect on exposures during the replacement method.32
Although it may not be effective in reducing lead exposures, dilution ventilation may be needed to prevent accumulation of hazardous gases or vapors. Contractors sometimes use portable heaters during abatement projects because all of the utilities are turned off, but they should never be used without adequate ventilation with outside air. NIOSH found that use of portable gas-fired heaters inside contained work areas without ventilation, even for short periods, resulted in elevated concentrations of carbon monoxide and carbon dioxide.32
During LBP abatement projects, administrative controls are typically employed to reduce occupational lead exposures. Administrative controls include prohibition of methods which have high lead exposure potential (torch burning, dry scraping, and conventional power tools), contractual requirements for competent persons (knowledgeable about lead hazards and controls) on each job site, and preemployment hazard training for all workers and supervisors. During the HUD lead abatement demonstration, these administrative controls were employed and lead exposures were generally low—95 percent were less than the OSHA PEL. On the other hand, worker exposures were highly variable, and personal lead exposures exceeding the OSHA PEL were measured for eight of 11 NIOSH-assigned lead abatement method categories.32 The potentially hazardous methods were abrasive removal, chemical removal, heat gun removal, cleaning, enclosure, replacement, setup, and "other" methods. The highest exposures were generally for task-based samples of short (one to several hours) duration, rather than full-shift (8–hour) samples. The risk of these high-exposure tasks would depend on the frequency with which they were used.
Respiratory protection can be thought of as a type of administrative control. The effectiveness of respirators depends on proper selection, worker training, and usage. Respirators will be needed when other controls cannot protect workers. Respirator selection for each job category at a worksite should be determined by a certified industrial hygienist or other competent person.
Regardless of the magnitude of airborne lead exposures, good hygiene practices are needed during LBP abatement and renovation projects when surfaces become contaminated with paint chips or dust. Handwashing before eating, drinking, smoking, chewing tobacco, or applying cosmetics is especially important to prevent ingestion of lead. Lead contamination of workers' hands is substantially reduced by handwashing at the work site with soap, running water, and disposable paper towels.35 Take-home exposures can be prevented by proper use, laundering, and disposal of protective work clothing, including disposable shoe covers.
Continue with Chapter 4