RISK ASSESSMENT OF METALS AND METALLOIDS IN COSMETIC IN NIGERIA 431 aqua regia (HCl:HNO3, 3:1) this was heated to dryness. Then, 20 ml deionized water was added, stirred, and the mixture fi ltered. The fi ltrate was made up in a standard volu- metric fl ask, and lead, cadmium, and nickel concentrations were assayed with atomic absorption spectrophotometry at 205 Å (8). Arsenic was measured with direct fl ow injec- tion through a hydride generation system (9), with a limit of detection (LOD) of 0.11 μg/l. Mercury was determined by the cold vapor technique after reduction with stannous chloride (SnCl2), to release the mercury in the sample solution. Precaution was taken at all times because of the toxic nature of mercury. A stock standard solution was prepared by dissolving 1.080 g of mercury (II) oxide, in a minimum volume of 1:1 HCL, and diluted to 1 l with deionized water. This solution was then analyzed by the AAS us- ing an air-acetylene, oxidizing (lean, blue) fl ame at a wavelength of 253.7 nm. Appropriate quality procedures and precautions were carried out to assure the reliability of the results. All reagents used in the study were of analytical grades. A spike-and-recovery analysis was performed to assess the accuracy of the analytical tech- niques used. Post-analyzed samples were spiked and homogenized with varying amounts of the standard solutions of different metals. The spiked samples were then processed for analysis by the dry ashing method (1). The LOD for arsenic, mercury, cadmium, and nickel was 0.001, whereas the LOD for lead was 0.01 ppm, with blank values reading as 0.00 ppm for all the metals in deionized water with an electrical conductivity value of less than 5 μS/cm. Samples were analyzed in triplicate. HEALTH RISK ASSESSMENT The human health risk models including carcinogenic and noncarcinogenic ones raised by United States Environmental Protection Agency were adopted. These models and their threshold values were used to assess the potential human health risks posed by heavy metal contamination for this study. Human beings could be exposed to heavy metal from cosmetic products via dermal contact with cosmetic particles. The chronic dermal expo- sure to lead, cadmium, mercury, arsenic, and nickel was calculated using the equation according to Environmental Protection Agency (EPA) (10) (Table I). dermal CS×SA×AF×ABS×EF×ED×CF CDE = Bw×AT Table I Parameters used for Calculation of Chronic Daily Exposure of Heavy Metals in Cosmetics (11) Parameters Unit Child Adult Body weight (BW) kg 15 70 Exposure frequency (EF) days/year 350 350 Exposure duration (ED) years 6 30 Skin surface area (SA) cm2 2,100 5,700 Adherence factor (AF) mg/cm2 0.2 0.07 Dermal absorption factor (ABS) none As (0.03) other metals (0.001) As (0.03) other metals (0.001) Conversion factor (CF) kg/mg 10-6 10-6 Average time (AT) days 365 × 70 365 × 70 For carcinogens 350 × ED 350 × ED For noncarcinogens

JOURNAL OF COSMETIC SCIENCE 432 The risk effect is made up of carcinogenic and noncarcinogenic risk assessments for all the metals through the dermal exposure pathway. Cancer risk can be evaluated from the fol- lowing formula: Cancer risk =CDE×SF, where cancer risk represents the probability of an individual lifetime health risks from carcinogens, CDE is the chronic daily exposure of carcinogens (mg/kg/d), and SF is the slope factor of hazardous substances (mg/kg/d). The noncarcinogenic risk from individual heavy metal can be expressed as the hazard quotient (HQ): HQ=CDE RfD, where the non-cancer HQ is the ratio of exposure to hazardous substances, and RfD is the chronic reference dose of the toxicant (mg/kg/d). œCDE Hazard index due to heavy metals= RfD, where the hazard index (HI) is the sum of more than one HQ for multiple substances, CDE is the chronic daily exposure of heavy metal, and RfD is the chronic reference dose for the heavy metal. The acceptable value for the HI is 1. For the present study, the fol- lowing reference doses were used: As: 3.00E-04, Pb: 5.2E-04, Hg: 3.00E-04, Ni: 5.60E- 03, and Cd: 5.70E-5 and cancer slope for As: 1.5 (12,13). SAFETY EVALUATION OF COSMETIC PRODUCTS The risk associated with the exposure to metallic impurities in cosmetic products can be evaluated using the uncertainty factor called the margin of safety (MoS), and it is calcu- lated by dividing the lowest No Observed Adverse Effect Level (NOAEL) value of the cosmetic substance under study by its estimated systemic exposure dosage (SED) Scien- tifi c Committee on Consumer Safety (SCCS) (14). NOAEL MoS= SED The systemic availability of the cosmetic substance is estimated by taking into account the daily amount of the fi nished product applied, the concentration of the substance un- der study, dermal absorption of that particular contaminant, and a human body weight value (14). The SED is given by the following expression: -1 -1 Cs×AA×SSA×F×RF×BF SED μg kg bw day = ×103 BW where Cs is the concentration of the substance in the cosmetic product (mg kg-1), AA is the amount of the cosmetic product applied, SSA is the skin surface area, RF is the reten- tion factor (1.0 for leave-on cosmetic products), BF is the bioaccessibility factor, 103 is the unit CF, BW is the body weight (kg). A default body weight of 60 kg was assumed in this study. The AA, SSA, and RF values adopted for this study were the standard values estab- lished by the SCCS (14) and the values are shown in Table II. The reference dose (RFD)