Consumer safety implications of cadmium and lead content in commercial lipsticks sold online in Saudi Arabia

2.1. Reagents and materials

All reagents and chemicals were of analytical or higher grade unless otherwise specified. Nitric acid (HNO₃, 65% w/w, Suprapur® grade, trace metal analysis grade, Merck, Darmstadt, Germany) and hydrogen peroxide (H₂O₂, 30% w/w, Suprapur® grade, Merck, Darmstadt, Germany) were used for microwave-assisted digestion. Certified stock standard solutions of cadmium (1000 µg mL⁻¹) and lead (1000 µg mL⁻¹) were purchased from Merck (Darmstadt, Germany). Deionized water (resistivity ≥ 18.2 MΩ·cm) was obtained from a Milli-Q water purification system (Millipore, Bedford, MA, USA).

2.2. Sample collection

Five lipstick colors (Nude peach, Tea rose, Pillarbox red, Terracotta, Velvet cherry) are commercially manufactured from a single widely distributed brand (Mirsist) were purchased online (Table 2). The samples were stored at ambient temperature until analysis.

2.3. Sample preparation by microwave-assisted digestion

Each lipstick sample (0.50 g) was accurately weighed directly from the intact stick without prior homogenization, as the microwave-assisted acid digestion ensured complete matrix dissolution and minimized contamination risks from mechanical processing. The weighed sample was transferred to a polytetrafluoroethylene (PTFE) vessel, wetted with 6 mL of 17 M HNO₃ + 2 mL of 8.8 M H₂O₂. The microwave-assisted digestion was performed using a Titan MPS system under the following conditions: a single-step program reaching a temperature of 195 °C and a pressure of 55 bar, with a ramp time of 15 min, a hold time of 5 min, resulting in a total digestion time of 20 min, and pressure control set at 90%. Blank samples were prepared in the same manner as the test samples for each batch. A certified reference material (CRM), [IAEA-V-10], hay powder provided by the IAEA [32], was also digested alongside the blank and cosmetic samples.

2.4. Sample analysis

The concentrations of cadmium (Cd) and lead (Pb) in the digested sample solutions were determined using a flame atomic absorption spectrophotometer (FAAS; iCE 3000 series, Thermo Scientific) equipped with a deuterium lamp background correction system. Measurements were performed in air–acetylene flame mode under the instrumental conditions summarized in Table 3. For each metal, hollow cathode lamps (Thermo Scientific) were used at the specific wavelengths of 228.8 nm for Cd and 217.0 nm for Pb, with slit widths of 0.5 nm and 1.0 nm, respectively. Lamp currents were set to 4 mA for Cd and 5 mA for Pb. The fuel (acetylene) flow rate was maintained at 1.5 L/min and the oxidant (air) flow rate at 10 L/min, with a burner height of 7 mm for both metals. Calibration was performed using a five-point external calibration curve (0.01, 0.05, 0.1, 0.5, and 2.0 ppm) prepared daily from certified stock standard solutions (1000 µg/mL, Merck) diluted in 2% (v/v) HNO₃ to match the matrix of the digested samples. Calibration curves exhibited excellent linearity (R² ≥ 0.998 for Cd and R² = 0.999 for Pb). The limit of detection (LOD) was calculated as three times the standard deviation of the blank signal (n = 10) divided by the slope of the calibration curve, yielding 0.0007 ppm for Cd and 0.001 ppm for Pb. The limit of quantification (LOQ) was calculated as ten times the standard deviation of the blank signal divided by the slope, resulting in 0.007 ppm for Cd and 0.01 ppm for Pb. All samples, blanks, and calibration standards were analyzed in triplicate. The relative standard deviation (RSD) of replicate measurements was consistently below 5% for both metals, confirming the precision of the method. Quality control was further ensured by analyzing a certified reference material (IAEA-V-10 Hay Powder) and performing spike recovery tests on blank samples, as described in the quality control section. One-way analysis of variance (ANOVA) was performed to evaluate differences in Pb and Cd concentrations across color groups, with significance set at p < 0.05.

2.5. Health risk assessment

To evaluate the potential non-carcinogenic health risks associated with the use of lipsticks containing Cd and Pb, the chronic daily intake (CDI) and hazard quotient (HQ) were calculated based on standard exposure parameters. The CDI was determined using the equation 1.

$\text{CDI}=\left(\text{C}\times \text{IR}\times \text{EF}\times \text{ED}\times \text{CF}\right)⁄\left(\text{BW}\times \text{AT}\right)$

Where C is the measured concentration of the metal (mg kg⁻¹), IR is the ingestion rate of lipstick (24 mg day⁻¹, as estimated by the US FDA), EF is the exposure frequency (365 days year⁻¹), ED is the exposure duration (30 years), CF is the conversion factor (10⁻⁶ kg µg⁻¹), BW is the average body weight (60 kg), and AT is the averaging time (ED × 365).

The non-carcinogenic risk was assessed by calculating the hazard quotient by calculating the hazard quotient using equation 2:

$\text{HQ}=\text{CDI}⁄\text{RfD}$

where RfD is the oral reference dose: 0.0035 mg kg⁻¹ day⁻¹ for Pb and 0.001 mg kg⁻¹ day⁻¹ for Cd [33]. An HQ value of less than 1 indicates negligible risk, whereas values greater than 1 suggest potential health concerns [34]. These metrics provide insight into the potential exposure risk posed by prolonged and repeated use of lipsticks containing trace levels of Cd and Pb.

3.1. Quality control of the data

Quality control of the obtained data was ensured through the analysis of certified reference materials (CRMs), specifically, Hay Powder and IAEA-V-10, provided by the IAEA [35]. Quality control was ensured by analyzing the certified reference material (CRM) IAEA-V-10 Hay Powder, digested under the same conditions as the lipstick samples. The measured concentrations of Cd and Pb in the CRM are compared with the certified values in Table 4.

The results demonstrate that recovery experiments conducted by spiking blank samples yielded recoveries in the range of 95–103% and acceptable percentage errors for both Cd and Pb (Table 4). The Pb recovery of 115.63% in the IAEA-V-10 Hay Powder CRM is slightly above 100%, which is within acceptable variation for flame AAS at low concentrations and likely results from minor matrix effects and measurement uncertainty. The Cd recovery of 93.33% is well within the typical 90–110% acceptance range. These values, combined with RSDs below 5% and errors within the certified uncertainty limits, confirm the accuracy and reliability of the method.

3.2. Sample results

Calibration curves in the range of 0.01-2 ppm were then constructed for Cd and Pb using standard solutions over an appropriate concentration range. For Cd, the calibration curve exhibited excellent linearity with an R² value of 0.998. The limit of detection (LOD) for Cd was determined to be 0.0007 ppm, and the limit of quantification (LOQ) was 0.007 ppm. Similarly, the calibration for Pb achieved an R² value of 0.999, with a LOD of 0.001 ppm and a LOQ of 0.01 ppm. Relative standard deviations (RSD) were below 5%, thereby confirming both the accuracy and precision of the method (Table 5). This validated analytical performance ensures that the subsequent quantification of heavy metals in lipstick samples is both reliable and reproducible.

Before analyzing lipstick samples, the analytical method was rigorously validated using AAS. Lipstick samples were first subjected to microwave-assisted acid digestion to ensure complete dissolution of metal contaminants. A total of five commercially available lipstick samples representing different colors (Nude peach, Tea rose, Pillarbox red, Terracotta, Velvet cherry) were analyzed using AAS. The results reveal that all five lipstick colors contained measurable amounts of both Pb and Cd. Pb concentrations ranged from 1.07 ± 0.053 ppm in the Pillarbox red sample to 2.21 ± 0.111 ppm in the Tea rose sample. A total of five commercially available lipstick samples representing different colors (Nude peach, Tea rose, Pillarbox red, Terracotta, Velvet cherry) were analyzed using AAS. The results reveal that all five lipstick colors contained measurable amounts of both Pb and Cd. Pb concentrations ranged from 1.07 ± 0.053 ppm in the Pillarbox red sample to 2.21 ± 0.111 ppm in the Tea rose sample. The concentrations of Pb and Cd across the five lipstick colors are visualized in Figure 1, which clearly shows the highest levels in the Tea rose shade and the lowest in the Terracotta shade. These levels are well below the recommended maximum of 10 ppm for lead as an impurity in cosmetic lip products specified by the U.S. Food and Drug Administration [15] and consistent international guidance [4]. All samples are below this threshold except the Tea rose variant, which remains compliant but highlights variability in pigment sourcing. All samples are below the threshold except the Tea rose variant (Table 6). The Cd quantities determined ranged between 0.13 ± 0.02 ppm in the Terracotta sample and 0.27 ± 0.03 ppm in the Tea rose sample, such that all lipstick samples tested were well below the recommended Cd threshold of 10 ppm. One-way ANOVA demonstrated statistically significant differences in Pb and Cd concentrations among the color groups (Table 7). In the present study, Pb levels ranged from 1.07 to 2.21 ppm, and Cd levels from 0.13 to 0.27 ppm, with all values falling within the permissible limits set by SASO and the US FDA.

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Figure 1.

Bar chart showing the concentrations of Pb (blue bars) and Cd (red bars) in five lipstick samples representing different colors. Values are reported as mean ± standard deviation (ppm) from triplicate measurements.

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In this study, the chronic daily intake (CDI) and hazard quotient (HQ) were calculated for Pb and Cd in five lip product samples of various colors. Among all the samples, Tea rose-colored lipsticks showed the highest levels of both Pb and Cd, with CDI values reaching up to 5.14 × 10⁻⁵ for Pb and 0.102 for Cd, resulting in HQ values of 0.128 and 0.102, respectively. Similarly, Pillarbox red-colored products also showed elevated levels, with Pb HQ values ranging from 0.102 to 0.12 and Cd HQ values up to 0.096. In contrast, Terracotta-colored lipsticks exhibited the lowest levels of contamination, with Pb CDI values between 2.057 × 10⁻⁵ and 2.742 × 10⁻⁵, corresponding to HQs well below 0.07, and Cd HQs ranging from 0.041 to 0.054, indicating a relatively lower health risk. Velvet cherry and Nude peach samples showed intermediate levels, with HQ values for both metals mostly within the range of 0.068 to 0.085 (Table 8). Overall, none of the samples exceeded an HQ of 1, suggesting that non-carcinogenic risk due to Pb and Cd exposure through lipstick ingestion remains within acceptable limits according to SASO guidelines. However, the elevated HQ values in Tea rose and Pillarbox red shades warrant continued monitoring, especially for frequent users.

Exposure to heavy metals such as Pb and Cd through cosmetics is a public health concern due to their cumulative toxicity and potential systemic effects. According to regulatory standards, the SASO sets the permissible limit for Pb at 1 ppm, while the US FDA allows up to 20 ppm in cosmetic products. For Cd, SASO permits up to 10 ppm, whereas the US FDA does not specify a limit, although its presence is discouraged due to its known toxicity (Table 9). In the analyzed lip products, Pb concentrations ranged from moderate to elevated levels when compared to the SASO limit, with several samples exceeding 1 ppm, thereby raising potential compliance concerns within the Saudi market. Although Cd levels remained below the SASO threshold of 10 ppm in all samples, its detection in multiple products still calls for precaution due to its bioaccumulative nature and association with kidney and bone toxicity upon chronic exposure.

To evaluate non-carcinogenic health risks, the hazard quotient (HQ) was used. In this study, Cd HQ values ranged from 0.041 to 0.102, while Pb HQ values ranged from 0.051 to 0.128, with all values remaining below 1, indicating no significant health risk from regular use. These results are consistent with and, in some cases, more favorable than those reported in earlier studies, reinforcing the conclusion that the analyzed lip products do not pose a significant risk from Pb and Cd exposure under typical usage conditions. Although the calculated hazard quotients (HQ < 1) indicate negligible non-carcinogenic risk from individual lipstick use, this assessment relies on conservative assumptions (e.g., ingestion rate of 24 mg/day and 30-year exposure duration) and does not fully account for uncertainties such as variability in individual usage patterns, potential synergistic effects with other cosmetic products, or cumulative exposure from multiple sources. These factors could potentially increase overall exposure to Pb and Cd, particularly for frequent users or those applying multiple lip and facial cosmetics daily. Continued monitoring and more refined exposure models incorporating real-world multi-product use are therefore warranted.

Compared with earlier assessments of Pb and Cd in lip products, our hazard quotients (HQs) for Pb (0.051–0.128) and Cd (0.041–0.102) sit at the lower end of reported values, reinforcing the view that typical lipstick use carries minimal non‐carcinogenic risk. For instance, Ahmed et al. [30] found Pb HQs up to about 0.15 in kajal and foundation products in Saudi markets, while Cd was not quantified in that work. Alqahtani et al. [1] reported both Pb and Cd HQs under 0.08 for low‐cost lipsticks, closely matching our intermediate‐shade results. Internationally, risk assessments in India and Egypt have similarly yielded Pb and Cd HQs well below 1, often in the 0.05–0.20 bracket despite occasional exceedances of raw‐metal limits. Even studies that detected higher concentrations in some imported brands [27] still concluded that calculated HQs did not surpass the safe threshold, thanks to conservative ingestion assumptions. Taken together, these comparisons emphasize that while heavy metals remain detectable in many cosmetic lines, their calculated non‐carcinogenic hazard under normal use remains consistently negligible, but continual monitoring is essential to catch any shifts in pigment sourcing or manufacturing quality. In addition, the consistent prevalence of toxic metals in such products across many studies may concern frequent users given issues with bioaccumulation.

The concentrations of Pb (1.07–2.21 ppm) and Cd (0.13–0.27 ppm) observed in this study are consistent with those reported in previous investigations of lipsticks and cosmetics in Saudi Arabia and internationally. Within the Saudi context, the present Pb levels are lower than the upper ranges documented by Ahmed et al. [30] (1.75–7.22 ppm) and Alnuwaiser et al. [27] (0.70–12.48 ppm), yet higher than the very low values reported by Alqahtani et al. [1] (0.01–0.06 ppm) and Albugami et al. [36] (0.06–5.41 ppm). For Cd, the detected levels exceed those of Alqahtani et al. [1] (0.01–0.02 ppm) but remain well below the maximums found by Alnuwaiser et al. [27] (0.06–8.86 ppm) and Albugami et al. (0.04–1.27 ppm).

Internationally, these results align closely with the U.S. Food and Drug Administration (US FDA) surveys of lip products, which have reported Pb concentrations typically ranging from 0.03 to 7.2 ppm (median ∼1 ppm) and Cd levels generally below 1 ppm, with no significant health risks identified under normal use. [37] Similarly, Health Canada’s guidance on heavy metal impurities in cosmetics and the European Union’s REACH regulations establish that trace levels of Pb and Cd below 1–10 ppm do not pose unacceptable risks, further supporting the conclusion that the lipsticks analyzed here comply with established international safety benchmarks. [4,17] The calculated hazard quotients (HQ < 1) reinforce these regulatory perspectives, indicating negligible non-carcinogenic risk.

The observed variation in Pb and Cd concentrations across lipstick colors suggests a possible correlation with pigment type and shade intensity. The highest levels of both metals were detected in the Tea rose (Pb: 2.21 ± 0.111 ppm; Cd: 0.27 ± 0.03 ppm) and Pillarbox red shades, while the lowest occurred in the lighter Terracotta shade (Pb: 1.37 ± 0.069 ppm; Cd: 0.13 ± 0.02 ppm). This pattern is consistent with previous studies reporting elevated heavy metal content in darker-colored cosmetics, likely due to the use of mineral-based pigments such as iron oxides, cadmium sulfoselenide (for red/orange tones), and lead chromates or molybdate pigments, which are known to contain trace amounts of Pb and Cd as impurities [38]. Although modern manufacturing practices aim to minimize such contaminants, the persistence of higher levels in darker shades highlights the need for stricter pigment sourcing and quality control, particularly for imported products [39].