Regarding your second point you have added a new exposure limit. TLV exposure limits are a product of the American Conference of Governmental Industrial Hygienists. In 1978 NIOSH published Criteria for a Recommended Standard-Occupational Exposure to Isocyanates. The 5ppb TWA NIOSH recommended at that time is the same value as ACGIH TLV. Today NIOSH lists TDI as a carcinogen. The Pocket Guide Appendix A describes the NIOSH policy with respect to carcinogens.
Just two more fast comments and then, uncharacteristically, I'll shut up.
1. Rob asked for documentation about OSHA's opinion of their PELs. The statement is the Federal Register at 58 FR 35337-35351, June 30, 1993 when OSHA had to formally reinstate the old PELs thus revoking both the upgraded levels and addition of new PELs on substances for which there were no standards in 1968:
"OSHA continues to believe that many of the old limits which it will now be enforcing are out of date (they predate 1968) and not sufficiently protective of employee health based on current scientific information and expert recommendations. In addition, many of the substances for which OSHA has no PELs present serious health hazards to employees."
How I wish you would all add this short paragraph to your explanations of air quality standards somewhere for students to really understand the issue.
2. Please also let students understand that there is no air quality limit that is not "feasible" no matter how low it is set. Then the only consideration is money.
For example, if we have to use a two component urethane system in an open shop, I require the employer put our union workers in air-supplied respiratory protection to keep below the 0.005 ppm TLV for the isocyanates. Once the employer has spent 4-5 large for the compressors and lines WHICH THEY SHOULD HAVE IN THE SHOP ANYWAY, it only cost about $100 more per employee than air-purifying systems.
Done well, this system can keep the exposure to essentially zero. And better yet, the employer can install local exhaust ventilation such as a walk-in sized spray booth.
The only balancing act, then is between money and workers health. As the old union song goes: Whose Side Are You On?
Previous post | Top of Page | Next post