Document MMEBrOgZ39ekkm1MNRLv91OQa

Vista Chemical Company 900 Threadneedle Houston, Texas 77079-2990 (713) 588-3000 P.O. Box 19029 Houston, Texas 77224-9029 Fax (713) 588-3236 fA April 26, 1991 Dr. Roy Gottesman The Vinyl Institute Wayne Interchange Plaza II 155 Route 46 West Wayne, NJ 07470 Dear Roy: Dr. Peter Voytek has proposed doing a cancer risk assessment on vinyl chloride that may be of interest to Vl-member companies. I am enclosing Dr. Voytek's proposal for your review and referral to the appropriate VI committee for evaluation. It appears that Dr. Voytek will use existing dose/response data and different approach than that used by EPA to derive a unit risk factor for vinyl chloride. Presumably, this approach will show the cancer risk from vinyl chloride to be less than EPA's current Vista used Dr. Voytek to assist in meetings with the State of Mississippi on the appropriate vinyl chloride unit risk factor for their state air toxics program. Through this activity, we became aware of just how arbitrary and conservative the vinyl chloride unit risk factor Is. In our case, EPA initially told the State that the unit risk factor for vinyl chloride was 4.1 x 10'6 cases/ug/m3. EPA then changed their opinion and said that it was 4.2 x 10'*. As it turns out, both numbers were incorrectly calculated. The important point is that to attain a given fenceline risk, the vinyl chloride fenceline concentration needs to be ten times lower if the latter risk factor is used. That means process emissions must be ten times lower which can translate into significant capital expenditures at manufacturing plants. The VI is currently developing comments through Keller and Heckman on the Louisiana air toxics fenceline vinyl chloride standard. The proposed vinyl chloride allowable level is based on a highly conservative unit risk factor. This issue is likely to come up in other states and eventually at the Federal level when the residual risk provisions of the new Clean Air Act are implemented. VAB.0001166614 % I think the unit risk factor issue is important and deserves attention. I recommend that Dr. Voytek's proposal be reviewed by an appropriate committee of toxicologists to determine if his approach has merit and if so, to proceed with this work. Give me a call if you would like to discuss. Sincerely, t-doseph C. Ledvina Director of Environmental Activities HRF, RRS, PC, HDG, THH VAB.0001166615