Document gm5dKVpwND0p9ZnvjbwODrVe

August id , iy/*t SUBJECT: An E stim ate of a Safe D etection L evel of A sbestos F ib e r in Baby Powder T alc. TO: M r. 0 . Sandland, Chairm an Subcom m ittee on A sbestos in T alc Sum m ary C om parative calculations have illustrated that liberal dusting of an infant with a hypothetical cosm etic talc containing one percen t asbestos fiber by weight would re s u lt in an infant cumulative exposure of asbestos only 1/48, 000th as much as the T hreshold Lim it Value - Tim e Weighted Average, which is considered safe for the repeated exposure of industrial w orkers. On the basis of these data any analytical procedure capable of detecting one p e r cent by weight of asbestos fib ers in talc would be adequate to insure that the a s bestos content of talc is acceptably low. D iscussion * To date, a safe upper lim it for the percentage of asbestos fibers in baby powder ta lc has not been established. On the b asis of existing inform ation, however, it is possible to determ ine the maximum concentration of asbestos fibers which could be p resen t in talc without subjecting an infant to asbestos exposure in excess of the TLV . We can also d e te rm in e if and what additional safety fa c to rs ex ist when talc is lib e rally applied to infants. Since the TLV is the only available standard for a "sa fe " concentration of asbestos fibers in a ir, -its use in providing a point of refe ren c e is justified in this instance. A ccording to the F e d e ra l Regis t e r Vol. 37 No. 110, Wednesday, June 7, 1972, the p e rm issib le exposure (TLV) to airb o rn e concentrations of asbestos fibers is as follows: "The 8-hour tim e-w eighted average airborne concentrations of asbestos to which any employee may be exposed shall not exceed five fibers, longer than 5 m ic ro m e te rs, per cc of a ir - -- " This lim it of 5 fibers will be reduced to 2 fib e rs p e r cc on July 1, 1976. E xcu rsio n s up to 10 fib ers p er cubic c en tim eter (ceiling concentration) will be perm itted provided that the Time Weighted Average (TWA) does not exceed 2 fib ers per cc. The 2 fiber standard and the ceiling lim it will be employed as the basis for calculations in this m em orandum . F o r any person exposed to asbestos fibers the allowable weekly exposure under the TLV is 2 fib ers per cc of a ir for a total of 2400 m inutes p er week (40 h rs. x 60 m in u tes p er hr* ). if this p erson w ere exposed to the ceiling concentration of 10 fib e rs p e r cc, the m axim um p e rm itte d exposure tim e according to the TWA would be 480 m inutes per week (2 x 2400/10). in an e a rlie r r e p o r t ^ the total weekly exposure tim e for an infant to talcum powder when the latter was applied liberally onto the diaper area was estim ated at 43. 8 m inutes. Daring the actual talc application (13.6 percent of the total ex posure tim e) the talc concentration was 8.58 particles per cc of air, and during the tim e the talc dust settled (86. 4 percent of the total exposure tim e) the average c o n cen tratio n was 4. 38 p a rtic le s p er cc of a ir (See Note 1). Page 2 Even if the 8.58 particles p e r cc w ere asbestos fibers, the exposure of an infant would be le s s than the ceiling lim it of 10 a sb esto s fib ers p er cc. The total weekly exposure tim e of 43.8 m inutes would be considerably less than the 480 m inutes p e rm itted under the TWA for any exposed p erso n , and in v ersely the safety factor for the infant would be considerably g re a te r. The safety factor under this type of exposure and for a hypothetical cosm etic talc containing only one percent asb esto s can be estim ated as follows: 1, Compute the number of asb esto s fib ers which any person exposed to the TLV could inhale in a week, based on an inhalation ra te of 12.72 lite rs per minute (See Note 2). . . 2 fiber s /cc x 12.72x1000 cc of a ir/m in x 2400 m ins. =61,100,000 fibers/w eek* 2. Compute the num ber of fib ers an infant might inhale if we assum e all talc partid e s w ere asbestos fib ers during the application of powder and during the dust ' settling period based on an inhalation ra te for an infant of 0. 584 lite rs per m inuteW . ( 8 .58x,, 136 + 4 . 38x. 864) fib e rs per cc x 584 cc per m in. x 43. 8 m ins. . . = 126, 600 fibers per week* 3. Compute safety factor if all particles w ere asbestos fibers. 61,100,000/126,600 = 483 4. Compute safety factor for a hypothetical cosm etic talc containing only one p e r cent asbestos fibers by weight 483 x 100 = 48, 300 ' With a safety factor of this m agnitude it appears that an upper lim it of one percent of asbestos fib ers in talcum used on infants would insure that the exposure of in fants to asbestos fib ers would be far less than the TLV for adults. Thus, ah ana lytical method capable of detecting one percent asbestos in talc would be m ore than adequate to confirm an acceptably low level of asbestos in a talcum powder used on infants. ^Normal lung clearance m echanism was not considered in either case; therefore, the num ber of fib ers shown do not rep re se n t fibers retained in the lung. (b) (5) N. Sivertson M anager, Statistical and ' Computer. Operations JL O g C \J Notes 1. In re fe re n c e (1) it was shown that the tim e spent in applying talc lib e ra lly to the diaper site was 0.17 m inutes per application and that there was an additional tim e period of 1.08 m inutes per application during which the dust settled. Thus, the total weekly exposure is 43. 8 m inutes = (0.17 + 1.08) minutes per applica tion x 5 applications per day x 7 days per week. The exposure conditions outlined in re fe re n c e (1) were based on conservative assum ptions and rep resen t exposure levels which were greater than average. F o r example, the data w ere based on applying the talc directly tot he diaper a re a from the container, which is the mode of application that creates the g rea test concentration of talc dust, while in practice many m others use hand application. In addition, D r. Pooley(^) in his sim ulation studies produced a ^g re a te r dust concentration by applying ta lc to a hard,, dry su rface than would be produced using a soft, m o ist su rface such as an infant's skin. In re fe re n c e (1) the a irb o rn e concentration was re p o rte d a s 0. 243 m illion p a r tic le s per cubic foot (mppcf) while ''applying ta lc " and as 0.124 m ppcf during the dust settling period. T hese values w ere converted to p articles per cc of a ir by m ultiplying by the facto r 35. 3 re su ltin g in the 8.58 and 4. 38 p a rtic le s per cc of a ir, respectively, as stated in the body of this m em orandum , 2. According to the data in re fe re n c e (2) an adult m ale at r e s t has a m inute vol ume (inhalation ra te ) of 7.43 lite rs per minute and 28.6 lite rs per m inute when perform ing light work. If we assum e conservatively that an adult exposed to asbestos dust perform s light work one-fourth of the tim e and is at r e s t threefourths of the tim e, his expected inhalation ra te is: . 25(28. 6) + . 75(7.43) = 12.72 lite rs per m inute ** R eferen ces (1) C om parison of T alc Dust E xposure for Infants and T alc M iners, J. N. Sivertson, Johnson & Johnson Statistical and Computer Operations, Feb. 19, 1974. (2) Biology DataBook, F ederation of A m erican Societies for E xperim ental Biology, 1964, p. 220. (3) See R eference (1), Section II. > *3