| Discussion Lead Acetate Is Hazardous Products containing lead have been regulated by the federal government because the amount of lead they contain is recognized as hazardous. For example, it is illegal to sell a container of paint with more than 600 mcg of lead per gram for household use in the United States.(1) Gasoline containing lead is banned in the United States, which has resulted in a major reduction of lead exposure to the population.(12-14) Therefore, it is surprising that a hair coloring cosmetic with a lead content ranging from 2,300 to 6,000 mcg per gram--up to 10 times the limit of paint--is available on the shelves of local pharmacies. Not only do these products contain a large quantity of lead, but they also have a chemical form that makes lead extremely bioavailable when ingested. Unlike many forms of lead, lead acetate is water soluble. In animal research, lead acetate is used in feeding studies as the most bioavailable form of lead, and it is the standard against which other forms of lead are compared.(15) Method of Use Increases Exposure The directions accompanying these cosmetics instruct the user to place the product in the palm of the hand and rub it on the hair. One brochure declares that gloves are not needed because the product does not stain the hands. It is possible that skin absorption of lead acetate is 3% to 5%,(6) but that is not the major problem. The major problem is that users are instructed to coat their hands with a product containing 2,300 to 6,000 mcg of lead per gram. This places a large quantity of lead directly into the hand-to-mouth pathway of exposure. As shown in Table 2, the amount of lead on the hands increases from less than 3 mcg to between 150 and 700 mcg per hand after hair application. As discussed above, the TTDI for lead is 6 mcg for children and 30 mcg for adults. After applying the product and then thoroughly washing hands with soap and water, the hands still retained from 26 mcg to nearly 80 mcg of lead per hand. Several hair coloring products are formulated as oil-based creams. This formulation seems to be particularly difficult to wash off after initial application. Washed hands have enough lead on them to exceed the TTDI for children and nearly match or exceed the TTDI for adults. Once hands are coated with hair dye, users have a highly potent source of lead on their hands that can be easily transferred to other surfaces where it is available for further transfer. Table 2 shows that the quantities of lead transferred to surfaces exceed these limits. The current U.S. Department of Housing and Urban Development guideline for interior lead loading of the floor is 100 mcg of lead per square foot.(16) Note that the product was unintentionally transferred to the hair dryer handle and the telephone receiver at the equivalent of more than 135 mcg of lead per square foot. The instructions for use result in further difficulties. To impart color, lead acetate must remain on the hair for an indefinite time (as long as the user wishes to retain a particular color). Specifically, the user is instructed to use the product daily until the desired coloring is obtained and then twice a week thereafter. This ongoing, frequent use then contributes to continuous lead contamination of the home environment. The user is further instructed to avoid shampooing for several days after application. This requirement adds to the potential for spreading lead acetate around the environment and to other members of the household. We found that once the product is in the hair and the hair is thoroughly dried, lead acetate can be readily rubbed from the hair. Dry hands brushed through dry hair picked up between 70 and 286 mcg of lead per hand, or about two to three times more lead than wet hands brushed through dry hair. The product also spread to the forehead, even though care was taken to apply it only to the hair. Given the requirement to continually reapply these hair coloring agents, the user becomes a living purveyor of lead contamination. |
