Document Q5DOdr2vaMZezddpRy61pvk6

THOMAS B. BONNET PITTSBOBQH OFFICE MR. P. F. WOODWARD VANCOUVER OPERATIONS July 6, 1972 / RE: MARINUE DUST CONTROL In your May report of Air and Water Pollution Control, I noted the results of efficiency tests of Rotoelone-N scrubbers In controlling Marini te dusts. If your Rotoolanee discharge into the working area, it la important that the asbestos fiber content of the discharge air be below the present standard of five fibers per cc. By 1976, the concentration will hare to be something less than 2 fibers per cc. The above are the usual limitations of contan! nants not being returned to the room in concentrations considered as harmful. The Threshold Limit Value is the concentration used by hygienists in determining if a concen tration is "harmful." You should be aware that sane Jurisdictions do not allow recirculation unless specifically approved. If you don't already know, it would be wise to determine if the state of Washington has sosh restrictions. I must admit to having some misgivings about returning this air to the working area. This is based on the toxicity of asbestos dust, the horrible publicity It h** gotten nnd the usual lack of attention given to Rotoelone maintenance. To minimize concern and to assure compliance, frequent monitoring of exhaust returned to the room will be necessary. If you already exhaust the Rotoclones to the outside, or are forced to do so in the future, SPA may require that asbestos-contaminated air be captured by specific methods prior to exhausting it to the atmosphere. The proposed emission standard for asbestos is quite specific on this. Although it doesn't appear wise to take any action on changing air cleaning devices at this time, you should keep in mind that this is a distinct possibility and keep an eye out for the final standard which should be published soon in the Federal Register. T31US B. BONNET TBB:lel ARCH 19060