Document L378RzneR0bqrQ4ErJ66n3Nb

duce minimal lesions, 1000 ppm to produce injury requir ing hospitalization/31 Supplementary animal toxicity data relative to deveiop.ig a TLV showed that the highest concentrations that still produced no damage to the guinea pig eye, the most sensi tive target site, were 135 ppm for 15 min., 90 ppm for one hr., 20 ppm for eight periods of one hr. each and 20 ppm for five days of eight periods of one hr. each. Brief expo sures to high concentrations were productive of greater injury than lower concentrations for longer periods. The LCso values for guinea pigs for exposures of 1, 4 and 8 hours were respectively 300, 95 and 26 ppm. Lung function tests were always normal if corneal damage was absent. The la tent period of ophthalmologic changes was 16 hours for serious involvement, up to three days for mild involve ment. All corneal damage was reversible.(3) Based on a re-evaluation of the above data, a reduction in the TLV to 1 ppm, with a 5TEL of 5 ppm, is recom mended. References: 1. Smyth, H.F. |r^ Carpenter, C-P., Weil, CS.: Arch. Ind. Hyg. & Occup. Med. 4-.119 (1951). 2. Smyth, H.F. Jru Communication to TLV Committee member (February 1967). 3. Frant, (L, Groot Wesaddyk, A. Th,, Vemhuuren, H.Gu Med. Dept. Philips, Eindhove, & State Institute for Pub. Health, Utrecht, unpublished report. a-METHYL STYRENE C*HsC(CH3)-CH2 TLV, 50 ppm ( s 240 mg/m3) STEL, 100 ppm ( 485 mg/m3) a-Methyl styrene is a polymerizable liquid with a molecular weight of 778 and a specific gravity of 0.9062. It has a boiling point of 765.4* C, a vapor pressure of 1.9 mm Hg at 209 C and a closed cup flash point of 1299 F. It is insoluble in water. It is used as a polymerization monomer. During storage it is frequently stabilized with tert-butyl catechol as inhibi tor. The 100 ppm value was based on the following report of the Dow Chemical Company:*1-2* "Croups of rats, guinea pigs, rabbits, mice and mon keys were given repeated exposures seven hours dai ly, five days per week at a concenfrar/on of 200 ppm of a-methyistyrene vapor for periods of about six months. As judged by growth, mortality, gross ap pearance and behavior, organ weight studies and gross and microscopic examination of the tissues, this vapor concentration had no adverse effect upon any of the species studied. On the other hand, four human subjects exposed to a concentration of 200 ppm of a-methyistyrene reported definite unpleasant odor and slight eye irritation after about two min utes. These experiments with human subjects indi cated that concentrations of about 200 ppm are dis tinctly disagreeable. We suggest, therefore, an Industrial Hygiene Standard of 200 ppm based on toxicity. For engineering purposes, we suggest that the vapor concentration be controlled to 100 ppm a-methylstyrene in order to minimize complaints of exposed persons." A complete review of the toxicity and mode of action of methyl styrene is presented by Gerarde/31 A TLV of 50 ppm and a 5TEL of 100 ppm, comparable to that of styrene seems logical, on the basis of the limited data presently available. Other recommendations: West Germany, 100 ppm; USSR, 1 ppm. References: 1. Dow Chemical Company: Communication to TLV Committee member (1955). 2. Wolf, MA, Rowe. V.IC McCoilister. D.D., Hollingsworth, RJ,, Oyen, Fu Arch. Ind. Health 74:387 (1956). 3. Gerarde, H.W.; Toxicology & Biochemistry of Aromatic Hydro carbons, p. 129, Elsevier Pub. Co., NY (I960). MICA K^Ait(Al2SisOM)(OH)* -- Muscovite TLV, 20 mppcf Mica is a colorless, odorless, nonflammable, nonr'ibrous silicate occurring in plate form, containing less than 1% quartz, and includes nine different species. Muscovite and phlogopite are the major micas of commerce. The former is a hydrated aluminum potassium silicate, often called white mica, which as a molecular weight of 797 and a vapor pres sure of 0 mm Hg at 209 C Phlogopite, an aluminum potas sium magnesium s/Y/care, is sometimes called amber mica. Other forms include biotite, lepidolite, zimmwaidite and roscoeiite. Mica is insoluble in water. At one time mica was considered to be in the nuisance dust category, on the basis of its inert reaction when in jected intraperitoneaily in guinea pigs.*11 Dreessen and coworkers/21 however, found evidence of pneumoconiosis in 8 of 57 workers exposed to dust associated with mica-scrap grinding. Of five workers exposed at less than 10 mppcf, none had pneumoconiosis: cases were found in three men exposed at 18 mppcf for 18,. 20 and 26 years, respectively; three cases resulted from exposure at 40 mppcf for 10, 17 and 23 years; and two cases were found in workers ex posed at 50 ppm for 24 and 46 years. Only one of six work ers exposed more than 10 years at concentrations in excess of 25 mppcf failed to show evidence of pneumoconiosis. Although the signs and symptoms in these cases resem bled those of silicosis, the x-ray pattern of the lung field markings differed somewhat, and tuberculosis was not a complication in any of the mica cases. No cases were found among workers exposed to mica dust in concentra tions averaging 3 mppcf. CCR 000000135 287