Benzene Exposures from Petroleum- Derived Solvents Containing Trace Levels of Benzene in Occupational Settings

Transcription

1 Benzene Exposures from Petroleum- Derived Solvents Containing Trace Levels of Benzene in Occupational Settings P. Williams, J. Panko, K. Unice, J. Brown, and D. Paustenbach Presented by: Julie Panko, CIH ChemRisk Risk,, Inc. AIHCE Philadelphia, PA June 7, 2007

2 Background Several thousand lawsuits have been filed alleging a relationship between use of a petroleum based product and various illnesses due to benzene exposure. The theory is that use of products that contain less than 0.1% benzene can result in exposures greater than the TLV or PEL. The possibility for such an occurrence has been reported in the literature recently. Fedoruk et al Kopstein 2006 Nicas et al. 2006

3 Objective Discuss the benzene content and flammability hazard of petroleum-derived products, which are important for understanding the typical and safe uses of these products Characterize the likely airborne concentrations of benzene associated with the handling or use of products containing low levels of benzene Generate a robust data set for evaluating historical occupational exposures to benzene

4 Key Information Sources Peer-reviewed reviewed literature Regulatory agencies and scientific bodies NIOSH health hazard evaluations (HHEs( HHEs) Manufacturer MSDSs Data submitted to OSHA during benzene rulemaking Solvent suppliers Trade associations Independent research contractors

5 Historical Benzene Content of Petroleum-Derived Products The benzene content of various commercial products in the U.S. has decreased significantly over last 30 years Changes in refining practices Regulatory requirements (product labeling and workplace monitoring) However, benzene may still be present as an impurity or residual component of mixed petroleum products These concentrations of benzene are typically considered to be trace (i.e., <0.1%) and are not thought to pose a risk to public health

6 Reported Benzene Content of Products During the 1950s and 1960s Product Time Period % Benzene (v/v( v/v) naphtha n-hexane cyclohexane NR NR NR NR A n-heptane Stoddard solvent 1963 NR NR 3.1 <1.0 <1 NR = Not Reported A Reported as w/w

7 Reported Benzene Content of Products Product After the Mid-1970s Time Period % Benzene (v/v( v/v) n-hexane cyclohexane B <0.01 n-heptane VM&P naphtha Stoddard solvent Mineral spirits Cutting oil Printing solvent A Reported as w/w B Shell discontinued its sale of hexane that contained 3.5% benzene by < < A < <

8 Review of Published Benzene Air Monitoring Data Identified 23 studies that evaluated workers exposures to benzene from potential low-level level benzene-containing products in the U.S. These studies were conducted primarily during the 1980s and 1990s, and collectively included ~1,000 IH measurements for benzene Most studies represented data collected in actual occupational settings during normal workplace activities (several were based on simulation studies)

9 Types of Products Evaluated Paints and paint solvents Printing solvents and inks Drywall adhesives Honing and cutting oils Mineral spirits and degreasers Jet fuel

10 Paints and Paint Solvents Five studies of painters conducted during the 1980s and 1990s 2 NIOSH HHEs 2 peer-reviewed reviewed papers 1 DOE report Workplaces included bus maintenance shop, iron foundry casting cleaning facility, construction sites, automotive assembly plants, and military bases Mean airborne concentrations of benzene ranged from to 0.1 ppm for four studies Average concentration of 0.34 ppm reported for one study where LOD of 0.1 ppm assigned to non-detect samples from the 1980 s.

11 Printing Solvents and Inks Eight studies of print shops 6 NIOSH HHEs ( ) 1988) 2 peer reviewed papers ( ) 2002) Facilities included sheet-fed, silk screening, and rotogravure printing Mean airborne concentrations of benzene typically ranged from to 0.5 ppm Higher concentrations (1-2 2 ppm) were reported when the benzene content of the solvent may have exceeded >1%

12 Drywall Adhesives One NIOSH HHE conducted in the late 1990s Study was intended to evaluate solvent vapor from adhesive during the hanging of drywall sheets Airborne concentrations of benzene ranged from <0.003 to 0.02 ppm

13 Honing and Cutting Oils One NIOSH HHE conducted in the early 1980s Study was conducted at a hydraulics manufacturing facility that made hydraulic cylinders and used honing oils and solvents Airborne concentrations of benzene ranged from <0.013 to ppm

14 Mineral Spirits and Degreasers Three recent studies involving mineral spirits as a cleaning solvent or degreaser 2 peer-reviewed reviewed papers (simulation studies) 1 presentation (actual workplace) Workplace activities included the spray cleaning of a locomotive generator and traction motor and mechanical or manual parts washing Airborne concentrations of benzene ranged from <0.006 to 0.13 ppm for two studies Maximum concentrations of 0.44 to 0.55 ppm in one study involving spiked mineral spirits under worst case conditions

15 Jet Fuel Six studies of jet fuel exposures in 1981 and from late 1990s to 2000s 1 NIOSH HHE 5 peer-reviewed reviewed papers Operations included aircraft maintenance, jet engine repair, fuel handling, and flightline tasks Included commercial Jet Fuel A and military fuels JP-4, JP-5, and JP-8 Mean airborne concentrations of benzene ranged from to 0.08 ppm Maximum concentration of 3 ppm was reported inside the fuel tanks

16 Summary of Published Benzene Air Monitoring Data Average airborne concentrations of benzene were found to typically range from <0.01 to 0.3 ppm for various products based on personal and area short-term term and longer-term samples These findings suggest that occupational exposures to benzene during the handling or use of such products were well below historical and current OELs ACGIH TLV = 0.5 ppm OSHA PEL = 1 ppm Higher air concentrations (1-3 3 ppm) were occasionally reported, particularly when the benzene content of the product may have exceeded 1%

17 OEL Exceedance Fraction Calculations 18 of 23 studies 95% confidence that exposures were below the TLV 95% of the time 19 of 23 studies 95% confidence that exposures were below the PEL 95% of the time In each case, except one, where the 95 th UCL of the EF exceeded the OEL more than 5% of the time, the benzene concentration in the liquid solvent was not reported. based on the study investigators recommendations the benzene contents likely exceeded 0.1%.

18 Indoor Exposure Modeling Estimated 8-hr 8 TWA benzene concentrations for three hypothetical parts-cleaning scenarios using mineral spirits Mechanical parts washing Manual parts washing Spray application Modeled estimates were intended to represent typical exposures over an 8 hour workday, rather than potential short-term term peak exposures Monte Carlo analysis was performed to o account for potential variability or uncertainty in model input parameters

19 Two-Zone Model Benzene air concentrations were estimated in the breathing zone (near field) and general workplace air (far field) Assumed that mineral spirits was used for 8 hours in a warehouse with no mechanical or local exhaust ventilation Input data for building parameters and benzene content were based on Nicas et al. (2006) and Fedoruk et al. (2003) Far Field Volume Air flow into warehouse Near Field Volume Near Field Airflow Air flow out of warehouse

20 Modeled Airborne Concentrations of Benzene Over 8 Hour Workday Near-field 8-hour 8 TWA benzene concentrations were 0.2 ppm (50 th percentile) and 0.4 ppm (95 th percentile) for mechanical parts- washing (Solid Black line) For manual parts-washing, modeled near-field concentrations were 1/20 to 1/1000 those of mechanical parts-washing (Middle dashed line) Application of a time-activity pattern would more accurately reflect historical exposures to benzene during typical degreasing operations Percentile (A) Near Field (breathing zone) 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Benzene Air Concentration (ppm)

21 Incorporating Time-Activity Pattern During Mechanical Parts Washing Solvents in parts washers are typically replaced with fresh solvent on a two or 4 week cycle. Benzene concentration in liquid solvent will be depleted over time. Modeled near field 8-hr 8 TWA concentrations assuming daily operation duration of 2 hours/day Replacement Cycle 2-week 4-week 8-hr TWA Benzene Concentration (ppm) 8-hr TWA (ppm) 50 th Percentile hr TWA (ppm) 95 th Percentile

22 Conclusions Petroleum-derived products containing <0.1% benzene are not expected to produce 8-hour 8 TWA airborne concentrations that exceed current regulatory standards under typical product use scenarios OSHA reached the same conclusion in the late 1980s, which is why product MSDSs are only required to list benzene if it is present at >0.1% unless 8-hour 8 TWA exposures are expected to exceed occupational health standards under specific conditions