Document pBj3kB4GJQZwny1baz3J6548d

INDUSTRIAL HYGIENE SURVEY O' THIS DOCUMENT W ORD OF PITTSBURGH-CORNING, TYLER, WDUSTRIES, INC. DID NOT COME FROM FILES. AND CANNOT BE AUTHENTICATED BY PPG INDUSTRIES, INC. At the request of Lee B. Grant,'M.D., a dust survey was made of the Tyler plant on November 29, and 30, 1966. The purpose of this survey was to re-evaluate the plant in terms of any significant changes in levels of airborne - dust since the last survey of August, 1963, by the Industrial Hygiene Foundation. In evaluating a dust exposure, the threshold limit values as promulgated by the American Conference of Governmental Industrial Hygienists are used as guidelines. They represent levels of dustiness which should not be exceeded on a timeweighted average basis for an eight hour day for a man's useful working life. The threshold limit value for asbestos dust is 5 million particles per cubic foot of air (mppcf). Before discussing the results it would be well to explain some of the changes that have taken place in recent years with regard to dust counting techniques. Most of the threshold limit values for dust (particularly silica dust) were developed in the 1930's in the granite sheds of Vermont. In those studies, the counting technique called for light-field illumination at 100X magnification. Since that time, however, better optics, giving better resolution at higher magnification have become more common. Therefore, the desire to use the more sophisticated optical systems of today must be balanced against the excellent correlation with medical findings that the Vermont granite studies produced. This is perhaps, an over-simplification of the situation, but the point being made is that one of the better optical systems was used for evaluation of the samples from the current study. It is believed that this is the reason for tne dust counts reported herein being approximately ten times greater than previous studies of the same plant. In addition to total dust counts, however, tnis study also presents fibrous dust counts. It can be seen that these fib rous dust counts are of the same order of magnitude as previous studies. The reason being that a fiber, which is defined as a particle with a length at least three times greater than its width, is large enough to be seen at the eld 100X magnification as well as the more sophisticated systems. The results of the study are shown in Table 1. A comparison of the fibrous dust counts with the threshold limit value of 5 mppcf indicates that seven of the sixteen values exceed this limit. It is felt that the values reported herein are representative of conditions in the plant at the time of the visit, and the following recommendations are being made from the test results as well cs personal observations: 1. Better ventilation, or a better materials handling .system, or a combination of both, is needed on the feeders. , 2. Constant inspection and immediate correction of any air leaks in the equipment is needed as is indicated by a dust count of 20 mppcf in the general area of No. 2 mill. 3. Better ventilation is needed in the sawing area. An evalua. tion of the present system by means of suitable air velocity measuring equipment would be a logical first step* 4. The use of sand on the floor as a lubricant for the movement of cardboard boxes should be discontinued. Th addition of a silica hazard to an asbestos problem is'unwarranted. u 0 - * 2 The air cleaners should not be located inside the building, positive pressure bag collectors of this sort may be inexpen sive, but undetected leaks can put a significant amount of dust back into the air. Furthermore, re-circulation of exhausted air is poor practice, in addition to being illegal in some states, because it assumes a collection efficiency approaching 100% which is rarely true, especially in older installations. The proper type of dust collector would eliminate the excessive dust concentrations from shaking the dust bags. JTD/jcw 9/11/67 J. T* Destefano' Safety & Industrial Hygiene Engineer | BB 0008306*1