Archived Newsletters
Feature Regulatory Update - Cal/OSHA FAC to Consider Low PEL for Trichloroethylene
Barbara Kanegsberg
The FAC, Feasibility Advisory Committee will meet on October 6 to discuss the feasibility and costs of setting worker exposure limits. While several compounds will be discussed, from the standpoint of critical cleaning, the most significant chemical to be considered is trichloroethylene (TCE, CAS# 790106). The FAC is considering a PEL of 0.4 ppm, 8 hour TWA based on findings of cancer in test animals. Such a worker exposure limit, if ultimately adopted by the Cal/OSHA Standards Board, would be more than an order of magnitude lower than the ACGIH level of 10 ppm TWA, 25 ppm STEL (2010). NESHAP-compliance vapor degreasers would not be adequate to achieve 0.4 ppm.
HSIA Opposition, Comments about n-propyl bromide and n-hexane
As might be expected, in a letter to Cal/OSHA, the Halogenated Solvents Industry Alliance (HSIA), a trade organization, opposes the proposed level for TCE. Although HSIA describes halogenated solvents in a broad sense to include any halogen, it focuses on certain chlorinated solvents, specifically methylene chloride, trichloroethylene, and perchloroethylene. Citing a U.S. EPA study, the HSIA letter notes that in 2006 there were 589 vapor-degreasing operations in California out of 1094 in the U.S
HSIA indicates that 0.4 ppm is not feasible and that manufacturers would switch to hexane and n-propyl bromide (NPB) (ref. Faye Graul, HSIA, letter to Bob Barish, Cal/OSHA, September 15, 2010). It is interesting that some of the undesirable impact of hexane was associated with its use in blends. Unexpected synergistic (more that additive) effects have to be considered. Many proposed TCE substitutes are blends. Recall that the Cal/OSHA Standards Board set a PEL of 5 ppm for NPB.
Consequences
If there is a very low PEL, manufacturing with TCE will be challenging, to say the least. Choices include investing in a new degreaser, issuing respirators to employees, and solvent substitution. Any of these options have associated problems. Cal/OSHA sets worker exposure limits that are legally-enforceable throughout California; the levels might be expected to influence industry and other agencies beyond the borders of California.
Cleaning equipment changes
To meet the proposed level, companies needing to use TCE would have to conduct manufacturing operations in airless degreasing systems, or they would have to issue respirators. Some airless systems are available; however, the range of choices is limited. Some of the systems are not designed for chlorinated solvent. They may not have in-house support staff. The initial capital investment is high (usually $200,000 plus), even for a system with a very small cleaning chamber. They have a large 3-dimensional footprint. In general, the throughput time is slower than with standard, NESHAP-compliant open-tops. Substantial employee training/education is required. In part because of the number of pumps involved, system upkeep is more complicated than for a standard, open-top vapor degreaser. We have seen airless systems adopted successfully; and we have provided case studies where manufacturing runs even more smoothly with airless systems. There are also air-tight systems, which are basically enclosed degreasers. Like airless systems, they have a large footprint; and studies quantifying solvent loss and employee exposure may not be available.
Respirators
Based on Cal/OSHA staff reports associated with NPB, Cal/OSHA might suggest the use of respirators as an option. Employees have to be very carefully trained and monitored in use of respirators. Improper use can pose hazards to employees. Respirators are not a cure-all.
Solvent substitution
One other problem is that most TCE substitutes are blends. Some of the blends are higher-boiling than TCE; so there can be potential residue problems. In addition, blends have the potential for variability; and we simply don’t know all about potential non-additive, synergistic toxicity effects. Many of the non-aqueous blends and aqueous blends would require new cleaning equipment. Further, not all parts are effectively cleaned with high-boiling solvents or with water-based cleaning agents.
Also under consideration
Other chemicals/materials under consideration include Benzyl chloride (PEL of 0.03 ppm 8-hour TWA); 1,1,2,2-tetrabromoethane (PEL of 0.03 ppm (0.42 mg/M3) 8-hour TWA ); Western red cedar (PEL 0.5 mg/M3 “total” airborne particulate); Wood dust (PEL 1 mg/M3 “total” airborne particulate as an 8-hour TWA, with retention of the existing 15-minute STEL of 10 mg/M3)
The FAC meeting is Wednesday October 6, 2010. Oakland, California. Cal/OSHA meetings are public.
http://www.dir.ca.gov/dosh/DoshReg/5155Meetings_2009.htm
