RISK ASSESSMENT OF METALS AND METALLOIDS IN COSMETIC IN NIGERIA 441 (hyperkeratosis), skin cancers, developmental effects, neurotoxicity, diabetes, pulmonary and cardiovascular diseases, and arsenic-induced myocardial infarction are some chronic effects of As toxicity (25). Cadmium concentration in the present study did not violate the 3 mg/kg standard set by Health Canada (19). Several studies have reported a signifi cantly higher concentration of cadmium in cosmetic samples in Nigeria. Nduka et al. (8), Iwegbue et al. (2), Sani et al. (22), and Omenka and Adeyi (21) reported 0.01–1.32 mg/kg, 3.1–8.4 mg/kg, 0.14–1.32 mg/kg, and ND-36.3 mg/kg concentrations of cadmium. Notably, similar concentrations have been obtained in studies outside Nigeria. Ullah et al. (15), Rusmadi et al. (24), and Sabah et al. (28) reported 0.41–0.942 mg/kg, 0.002–0.114 mg/kg, and 0.1559–0.6179 mg/kg concentrations of cadmium in cosmetics from Pakistan, Malaysia, and Sudan, re- spectively. Exposure to cadmium can lead to a variety of adverse health effects including cancer. Acute inhalation exposure (high levels over a short period of time) to cadmium can result in fl u-like symptoms (chills, fever, and muscle pain) and can damage the lungs. Chronic exposure (low level over an extended period of time) can result in kidney, bone, and lung disease (30). There are three possible ways of cadmium resorption in the human body, namely, gastrointestinal, pulmonary, and dermal (31). Binding of a free cadmium ion to sulfhydryl radicals of cysteine in epidermal keratins, or an induction and complex- ing with metallothioneins are two mechanisms that facilitate cadmium absorption through the skin (32). There is no international guidelines or limits for nickel in cosmetic products. However, several studies have shown the presence of irritants following repeated exposure to nickel greater than 10 μg/g (33–35). Concentrations of Ni (18–288 mg/kg, 0.05–17.34 mg/kg, 3.68–11.03 mg/kg, and ND-107 mg/kg) reported by Iwegbue et al. (2), Nduka et al. (8), Sani et al. (20). and Omenka and Adeyi (21) were all higher than the concentration in the present study. The most common harmful health effect of nickel in humans is an allergic reaction. Approximately 10–20% of the population is sensitive to nickel. The most seri- ous harmful health effects from exposure to nickel are chronic bronchitis, reduced lung function, and cancer of the lung and nasal sinus (36). There was no violation of the 1.00 mg/kg standard set by Health Canada for mercury. Nduka et al. (8) and Nasirudem and Amaechi (27) reported mercury at the range of 0.003–0.007 mg/kg and 30.00–90.32 mg/kg, respectively, in cosmetic samples in Nige- ria. Mercury is considered by the WHO as one of the top 10 chemicals or groups of chemicals of major public health concern. Elemental mercury and methylmercury are toxic to the central and peripheral nervous systems. The inorganic salts of mercury are corrosive to the skin, eyes, and gastrointestinal tract, and may induce kidney toxicity if ingested (37). The concentration of mercury in this study ranged from 0.001 to 0.0014 mg/kg this value was less than 3 μg/g set by Canada authority (18). Mercury concentra- tion in this study was comparable to the values reported by other workers (8,38). Not- withstanding the low levels of mercury in these cosmetics, chronic exposure may pose a public health risk. It has been observed that mercury is absorbed through the skin and used in skin whiteners because the metal is able to block the production of melanin, which gives hair and skin pigmentations (39). Mercury is ranked a top three priority pol- lutant that has become a serious health concern because of its high capacity for bioaccu- mulation and the variety of its effects on biological systems (40,41). As refl ected by the results of the study, the THQ and HI values for both adults and chil- dren were all less than 1.0 for all metals analyzed. In a study by Rusmadi et al. (22), the

JOURNAL OF COSMETIC SCIENCE 442 THQ of nickel and cadmium in skin-lightening creams in Malaysia was 1, whereas THQ for Pb in the same study was 1. HQ in the study of cosmetic brands in Nigeria by Nduka et al. (8) were all 1 for mercury and arsenic. This is an indication of a relatively low noncarcinogenic risk from heavy metals in the cosmetics analyzed. THQ is the ratio of the potential exposure to the substance and the level at which no adverse effects are expected. HQ less than or equal to one indicates that adverse non-cancer effects are not likely to occur, and thus can be considered to have negligible hazard. HQs greater than one are not statistical probabilities of harm occurring. Instead, they are a simple state- ment of whether (and by how much) an exposure concentration exceeds the reference concentration (RfC) (42). HI is the sum of HQs for substances that affect the same target organ or organ system. Because different pollutants (air toxics) can cause similar adverse health effects, combining HQs associated with different substances is often appropriate. The HI is only an approximation of the aggregate effect on the target organ (e.g., the lungs) because some of the substances might cause irritation by different (i.e., nonaddi- tive) mechanisms. An HI equal to or greater than 1.0, however, does not necessarily sug- gest a likelihood of adverse effects. Because of the inherent conservatism of the RfC methodology, the acceptability of exceedances must be evaluated on a case-by-case basis, considering such factors as the confi dence level of the assessment, the size of the uncer- tainty factors used, the slope of the dose-response curve, the magnitude of the exceedance, and the number or types of people exposed at various levels greater than the RfC (42,43). The carcinogenic risk for children and adults was all lower than the acceptable and prior- ity risk of 1-E-04 and 1-E-06. The result of cancer risk for arsenic in the study of cosmetic brands in Nigeria by Nduka et al. (8) was 1.781E-13 and 1.95E-12. The risk associated with the potential to develop cancer after exposure to chemicals is often expressed as a probability or a fraction in a range from zero to one (0.0–1.0). Usually the numbers are very small and shown in fractions of 1 million or fractions of 100,000. 1.0E-1 means one in 10, 1.0E-2 means one in 100, 1.0E-3 means one in 1,000, 1.0E-4 means one in 10,000, 1.0E-5 means one in 100,000, 1.0E-6 means one in a million, and 1.0E-9 means one in a billion, respectively (44). Cosmetics have often been considered by many dermatologists to be more harmful than good (15). These contain more than 10,000 ingredients which are linked to many dis- eases, such as cancer, birth defects, and developmental and reproductive harm. Dermal exposure is expected to be the most signifi cant route because most of the cosmetic prod- ucts are directly applied to the skin. Oral exposure can occur from wearing of cosmetics products containing heavy metal impurities around the mouth and also from hand-to- mouth contact (5). Many factors can affect the numerical value that is used to represent the degree of dermal absorption, such as exposure time, product formulation, dose, and the fate of the chemical in the skin. Information on the exposure to metal toxins through dermal contact is very scanty, and few data exist on the personal care products (45). The SED of arsenic from the use of these cosmetic products ranged from 5E-08 to 0.075 ug/kgbw/d for both 50% and 100% bioaccessibility scenario. This value was less than the provisional tolerable daily intake (PTDI) of arsenic set as 0.002 mg/kg by JECFA (46). The SED of lead ranged from 1E-05 to 13.164 μg/kgbw/d for both 50% and 100% bioac- cessibility. The PTDI for lead was withdrawn by the FAO/WHO joint committee be- cause it could no longer be considered health protective, but nevertheless, a PTDI value of 3.6 ug/kgbw/d was used as an indicator to compare with the results of the estimated