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August 2001 |
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Contents
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| Main Page | |
| Manufacture of Asphalt Roofing Products | |
 Occupational Exposure to Asphalt Fumes |
|
| Guidelines for Protecting Workers | |
| References | |
| Abbreviations | |
| Glossary | |
| Appendix | |
Currently, no Occupational Safety and Health Administration (OSHA) standard exists for asphalt fumes. In a 1988 proposed rule on air contaminants, OSHA proposed a permissible exposure limit (PEL) of 5 mg/m3 as an 8-hr time-weighted average (TWA) for asphalt fume exposures in general industry. This proposal was based on a preliminary finding that asphalt fumes should be considered a potential carcinogen [53 Fed. Reg.* 21193]. In 1989, OSHA announced that it would delay a final decision on the 1988 proposal because of complex and conflicting issues submitted to the record [54 Fed. Reg. 2679]. In 1992, OSHA published another proposed rule for asphalt fumes that included a PEL of 5 mg/m3 (total particulates) for general industry, construction, maritime, and agriculture [57 Fed. Reg. 26182]. Although OSHA invited comment on all of the alternatives, its proposed standard for asphalt fumes would establish a PEL of 5 mg/m3 (total particulates) based on avoidance of adverse respiratory effects. The OSHA docket is closed, and OSHA has not scheduled any further action.
In the 1977 criteria document, NIOSH established a recommended exposure limit (REL) of 5 mg/m3 as a 15-min ceiling limit for asphalt fumes measured as total particulates. The NIOSH REL was intended to protect workers against acute effects of exposure to asphalt fumes, including irritation of the serous membranes of the conjunctivae and the mucous membranes of the respiratory tract. In 1988 testimony to the Department of Labor, NIOSH recommended that asphalt fumes be considered a potential occupational carcinogen [NIOSH 1988]. In 2000, NIOSH conducted a review of the health effects data available since publication of the 1977 criteria document. This review is available at the NIOSH Web site (www.cdc.gov/niosh).
The current American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) for asphalt fumes is 0.5 mg/m3 (benzene-soluble aerosol) as an 8-hr TWA concentration with an A4 designation, indicating that it is not classifiable as a human carcinogen [ACGIH 2001].
Dermal contact with hot asphalt can cause burns, and asphalt fumes or vapors can be absorbed through the skin. Information is limited on the occurrence of exposure to asphalt fumes during the manufacture of asphalt roofing products. Five NIOSH health hazard evaluations (HHEs) conducted during the 1970s listed personal breathing zone (PBZ) concentrations ranging from 0.3 to 32 mg/m3 for total particulates and 0.21 to 6.8 mg/m3 for the cyclohexane solubles [Apol and Okawa 1977, 1978; Okawa and Apol 1977, 1978a,b] (see Table 4–1). In a cross-sectional exposure assessment study conducted for the AI [AI 1991; Hicks 1995], data indicate that PBZ measurements ranged from 0.068 to 13 mg/m3 for total particulates; PBZ measurements ranged from 0.013 to 3.7 mg/m3 for benzene solubles [AI 1991; Hicks 1995] (see Table 4–1).
An analysis of the 34 full-shift PBZ samples (most sampling ranged from 7 to 9 hr) indicates that the geometric mean (GM) for total particulates was 1.4 mg/m3 and the GM for benzene solubles was 0.27 mg/m3 [Hicks 1995] (see Table 4–2). In another study [Exxon 1997], analysis of 77 PBZ samples indicates that the GM for total particulates was 0.6 mg/ m3 and the GM for the benzene-soluble fraction of the samples was 0.08 mg /m3.
In the Hicks [1995] study, PBZ and dermal wipe samples were also collected and analyzed for specific PAHs (see Tables 4–7 and 4–9 in NIOSH [2000]). Several types of polycyclic aromatic hydrocarbons (PAHs) were detected in these samples (see Table 4–7 in NIOSH [2000]). The method used in the Hicks study was high performance liquid chromatography (HPLC) with an ultraviolet/ fluorescence detector (NIOSH Method 5506) [NIOSH 1994, 1998]. This method lacks the resolution to reliably identify and quantify discrete PAHs in asphalt fumes (see NIOSH [2000], Section 3.5.3).
The asphalt roofing products manufacturing industry summarized exposure data collected during 1980–1997 at 53 plants of 4 companies (A, B, C, and D). The data were from 1,920 samples for total particulates and 1,184 samples for benzene or cyclohexane solubles as TWAs [Fayerweather 1998]. Exposure data were not provided by job title because job titles were inconsistent among companies and did not always relate to a location or task on the manufacturing line. An attempt to classify the jobs into three exposure groups was unsuccessful because sampling was reported to have been conducted during nonroutine tasks and conditions. Figures 4–1 and 4–2 compare the average exposure data for total particulates and benzene/cyclohexane solubles for 1980–1989 and 1990–1997 from the four companies. (No comparison data were available for company D, since data were collected only for 1995–1997.) These figures indicate that average exposures, expressed either as total particulates or as benzene/cyclohexane solubles, declined after 1990 for companies A, B, and C.
No conclusions can be drawn as to the statistical significance of this observation, however, since statistical analyses were not conducted and raw data are not available for additional analyses.
The asphalt roofing manufacturing industry attributes this apparent reduction in average exposures after 1990 to the following: (1) the elimination of the saturator process by converting from paper roofing felts to glass fiber mats, (2) the improvement of capture efficiency of exhaust hoods, (3) the conversion to closed saturators on several operations, and (4) the reduction of fugitive emissions subject to the U.S. Environmental Protection Agency (EPA) regulations under the new source performance standards (NSPS) and other 1990 Clean Air Act Amendment requirements. By 1990, most plants had eliminated the saturator process and implemented other controls (not specified).
| Breathing-zone samples | Exposure concentration (mg/m3) | ||||
|---|---|---|---|---|---|
| Reference, source of exposure, and occupation | Type* |
Number | Range |
Geometric mean | Arithmetic mean |
| Apol and Okawa [1977], production of asphalt shingles and rolled roofing materials: | |||||
| Saturator operator | Total particulates Cyclohexane solubles |
3 2 |
2.2–7.3 0.81–2.6 |
4.9 1.4 |
5.6 1.7 |
| Coater operator | Total particulates Cyclohexane solubles |
2 2 |
14–15 0.87–6.8 |
14 2.4 |
14 3.9 |
| Coater trainee | Total particulates Cyclohexane solubles |
2 2 |
11–15 0.30–2.3 |
13 0.84 |
13 1.3 |
| Press operator | Total particulates Cyclohexane solubles |
2 2 |
6.1–32 1.4–1.5 |
14 1.4 |
19 1.42 |
| Seal-down operator | Total particulates Cyclohexane solubles |
2 2 |
0.99–1.4 0.43–1.2 |
1.2 0.71 |
1.21 0.81 |
| Foreman | Total particulates Cyclohexane solubles |
2 2 |
5.3–6.3 0.47–0.53 |
5.8 0.50 |
5.8 0.5 |
| Laminator operator | Total particulates Cyclohexane solubles |
7 5 |
0.96–2.16 0.23–0.76 |
1.6 0.46 |
1.6 0.50 |
| Okawa and Apol [1977], production of asphalt shingles: | |||||
| Laminator operator | Total particulates Cyclohexane solubles |
8 8 |
0.38–5.2 0.24–3.1 |
1.0 0.76 |
1.4 1.05 |
| Saturator/coater | Total particulates Cyclohexane solubles |
6 6 |
5.3–29 0.66–1.3 |
8.03 0.88 |
12 0.91 |
| Apol and Okawa [1978], production of asphalt shingles and rolled roofing materials: | |||||
| Saturator operator | Total particulates Cyclohexane solubles |
1 1 |
† † |
2.4 0.76 |
2.4 0.76 |
| Coater | Total particulates Cyclohexane solubles |
2 2 |
12–16 0.21–1.1 |
14 0.47 |
14 0.64 |
| Wrapping machine operator | Total particulates Cyclohexane solubles |
1 1 |
† † |
1.4 0.77 |
1.40 0.77 |
| Apol and Okawa [1978], continued: | |||||
| Lead man | Total particulates Cyclohexane solubles |
1 1 |
† † |
5.3 0.76 |
5.29 0.76 |
| Presser | Total particulates Cyclohexane solubles |
2 2 |
8.3–22 0.30–0.54 |
13 0.402 |
15 0.42 |
| Okawa and Apol [1978a], production of asphalt shingles and rolled roofing materials: | |||||
| Coater | Total particulates Cyclohexane solubles |
2 2 |
4.2–5.1 3.3–3.9 |
4.6 3.6 |
4.7 3.6 |
| Cooling section operator | Total particulates Cyclohexane solubles |
2 2 |
0.3–1.0 0.7–1.6 |
0.55 1.06 |
0.65 1.2 |
| Machine tender | Total particulates Cyclohexane solubles |
2 2 |
0.4–2.8 0.6–1.8 |
1.06 1.04 |
1.6 1.2 |
| Okawa and Apol [1978b], production of asphalt shingles and rolled roofing materials: | |||||
| Saturator operator | Total particulates Cyclohexane solubles | 1 1 |
† † |
1.0 2.1 |
1.0 2.1 |
| Coaterman | Total particulates Cyclohexane solubles |
1 1 |
† † |
2.1 0.22 |
2.1 0.22 |
| Slateman | Total particulates Cyclohexane solubles |
1 1 |
† † |
3.4 0.21 |
3.4 0.22 |
| Pozzoli et al. [1985], asphalted paper production: | |||||
| Paper production workers (smokers) | Total PAHs | 4 | 0.0048–0.036 | 0.009 | 0.014 |
| Paper production workers (nonsmokers) | Total PAHs | 2 | 0.0034–0.311 | 0.010 | 0.017 |
| AI [1991]; Hicks [1995], Roofing manufacturing (temperature of product at fume source from 300 to 468 °F [149 to 244 °C]): |
|||||
| Loader/asphalt handler | Total particulates Benzene solubles | 6 6 |
0.0068–0.94 0.041-0.71 |
0.51 0.31 |
0.66 0.41 |
| Slate blend operator | Total particulates Benzene solubles | 4 4 |
1.1–13 0.013-0.94 |
3.9 0.077 |
5.6 0.27 |
| Coater operator | Total particulates Benzene solubles | 8 8 |
0.42-2.5 0.049-1.6 |
1.0 0.2 |
1.3 0.37 |
| Machine operator | Total particulates Benzene solubles | 8 8 |
0.84–4.4 0.071-3.6 |
1.6 0.55 |
1.9 1.5 |
| Press operator/cooling operator | Total particulates Benzene solubles | 7 7 |
0.55–11 0.085-3.7 |
2.6 0.32 |
4.8 1.0 |
| Supervisor | Total particulates Benzene solubles | 1 1 |
† † |
1.4 0.32 |
1.4 0.32 |
| Concentration (mg/m3) | ||||
|---|---|---|---|---|
| Sample type | Range | Geometric mean (GSD)* | Arithmetic mean (SD) | Median |
| Total particulates | 0.068–13 | 1.4 (3) | 2.6 (3.1) | 1 |
| Benzene-soluble fraction | 0.071–3.7 | 0.27 (4.4) | 0.76 (1.1) | 0.24 |
Figure 4-1. Total particulates pre- and post-1990, by company. (Source: Fayerweather[1998].)
Figure 4-2. Benzene/cyclcohexane solubles pre- and post-1990, by company. (Source: Fayerweather[1998].)
The basic manufacturing process for all asphalt roofing products is essentially the same, with slight modifications, depending on which product is being produced. Figure 3–1 presents the diagram of a typical asphalt roofing manufacturing line.
The operations that pose a potential for worker exposure to asphalt fumes involve hot liquid asphalt. These operations include the following:
* Federal Register. See Fed. Reg. in references.
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