Introduction

Trace metals and their toxicity in make-ups

Mercury (Hg), arsenic (As), lead (Pb), cobalt (Co), antimony (Sb), cadmium (Cd), nickel (Ni), and chromium (Cr) are prohibited in cosmetics because of their exceptional toxicity (SCOOPWHOOP, 2017). Yet, Indian herbal cosmetics have predominance of Hg and Pb that exceeds the permissible limit set by the World Health Organization (WHO). Similarly, Nigerian local facial make-ups have high levels of trace metals (Sani et al., 2016). Unacceptable levels of As in lipsticks, eye shadows, and eyebrow pencils have been reported in Germany (Saadatzadeh et al., 2019). Talcum powder contains Pb and Cr (Gondal et al., 2012). In Canada, all cosmetics have Ni. Pb and beryllium (Be) as well as at least 4 of the 8 metals of environmental health concern (As, Cd, Pb, Hg, Be, Ni, selenium and thallium) are contained in over 90% of cosmetics (Orisakwe & Otaraku, 2013). Sunscreens contain titanium, Ti (regulated), in addition to other heavy metals (not regulated) (Aldayel et al., 2018; Capelli et al., 2014).

The use of make-ups in pregnancy is responsible for prenatal Pb exposure which is associated with a greater risk of premature delivery, reduced postnatal growth, lower child mental growth, schizophrenia, and dementia in adulthood (Wang et al., 2016). Intrauterine growth retardation occurs as a result of heavy metal exposure in pregnancy (Bruzzoniti et al., 2017). Even at a low level, Cd exposure may avert neurodevelopment (Henn et al., 2016). Prenatal exposure to As is linked to low fetal growth, low birth weight, poor head and chest development in infants, atherosclerotic disease, and inflammation in adults (Li et al., 2019).

Common colorants in eye shadows, blushes, and concealers are iron oxides (Brown, 2013). Lip glosses, lipsticks, and nail polishes contain aluminum (Al) compounds as colorants (Klotz et al., 2017). Al is contained in antiperspirants, sun creams, and toothpaste. Al exposure is linked to chronic disorders, including Alzheimer’s disease and breast cancer (Becker et al., 2016). Skin bleaching agents contain a significant level of As and Hg in the Caribbean region (Mohiuddin, 2019a; Sneyers et al., 2009), leading to skin problems, lung cancer, circulatory and peripheral neuropathy, and increased risk of gastrointestinal and urinary tract malignancies (Chan et al., 2019; Lavilla et al., 2009), and nephrotic syndrome (Qin et al., 2019; Mohiuddin, 2019b; Doshi et al., 2018; Orr & Bridges, 2017; Zhang et al., 2014). The toxic legacy of Hg dental amalgam continues for decades after use, because of pervasive bioaccumulation of Hg in the environment (Tibau & Grube, 2019). Cumulative exposure to mixtures of heavy metals is associated with obesity and chronic hypertension and type 2 diabetes (T2DM) (Wani et al., 2015). Zinc oxide (ZnO) is an ingredient in sunscreens (Martin et al., 2004), yet zinc (Zn) exposure causes the same symptoms as Pb poisoning (Piao et al., 2003).

Twelve heavy metals most often associated with environmental toxicity are Cd, Cr, Co, Cu, Fe, Pb, Hg, Ni, As, Be, selenium (Se), and thallium (Tl). There is an increasing concern about the toxic effects of trace elements contained in make-ups used on daily basis mostly by young women. As, Cd, Pb, Hg, Be, Ni, Se, and Tl have been identified as the notorious daredevils (Mohiuddin, 2019c). Hence, this study investigated their toxic effects on the regular users of make-ups containing them. Obviously, the empirical study will benefit users of make-ups who are possible victims of their toxic effects and health policy-makers as well as enrich the literature.

Kidney function as a measure of toxicity of trace metals contained in make-ups

Kidney is a filter of blood that removes toxins and regulates fluid, molecules, and by-products of metabolic processes. A gradual loss of this function has been linked to trace elements circulating in the human body. Exposure to toxic elements has nephrotoxic effects. Heavy metal exposure colludes with other environmental hazards to cause kidney and liver dysfunction. The cumulative effect of toxic elements for 3 months or longer is linked to chronic kidney disease (CKD) and potentiates complications (Fevrier-Paul et al., 2018; Hall & Hall, 2011). 

Study aim and objectives

The study sought the relationship between serum concentrations of Cd, Pb, Hg, Ni, Se, and Tl and urine level of As and Be in make-ups and the kidney functions (estimated glomerular rate, eGFR) of users with a view to ascertaining the potential for poisoning that could lead to cancer by exposure to Be or CKD and its complications by exposure to As, Cd, Pb, Hg, Ni, Se, and Tl. Preliminary observations had shown that university female students form a significant group of make-ups patrons and could justifiably be targeted for a study on toxic effects of trace elements contained in make-ups. Make-up is used in this study to represent cosmetics applied on the skin mostly by females. They include lipstick, eye shadow/lash pencil, talcum powder, antiperspirant, sun cream, and lightening cream, among others.

Delimitations of the study

Age, sex, and race influence eGFR values. Average eGFR value of 116 mL/min./1.7 3 m is associated with age bracket of 20–29. Average eGFR value of 107 mL/min/1.73 m is associated with 30–39 age bracket. Average eGFR value of 99 mL/min./1.73 m is associated with 40–49 age range. But, in Nigerian climes, asking a woman to divulge her age almost always prompted her to lie, especially to strangers, such as the researchers. All respondents were women of black race. Therefore, age, sex, and race were left out of the study.

Materials and methods

Design

University female students were subjects for the study. Students of any first generation federal university are representative of the targets because the university is not tribal, faith-based, and is for the rich and the poor. Withholding the name of the university is deliberate for anonymity as a necessary part of the condition for informed consent of the subjects.

The cross-sectional study used convenience sampling method to select 100 female university students based on suitability and relevance (of user of make-ups) and availability for and willingness to participate in the study. Besides, the subject consented to allowing the research findings to be published with anonymity (of subject and institution) as academic resource. The subjects, thus, met the inclusion criteria and fell out of the exclusion criteria (vide ultra).

Inclusion and exclusion criteria

Inclusion criteria were habitual use of make-ups for a minimum of three consecutive years; willingness to participate in, and availability for, the study; and willingness to allow study results to be published with anonymity for academic purposes.

Exclusion criteria were non-habitual use or non-use of make-ups for a minimum of three consecutive years; unwillingness to participate in, and unavailability for, the study; and unwillingness to allow study results to be published with anonymity for academic purposes.

Sample collection

The study procedure was explained to the prospective subjects, from who informed consent for participation in the study and allowing academic publication/s of the results of the study with anonymity were sought and obtained. Fresh and sterile needles, syringes, and blood sample bottles were obtained from a teaching hospital (tertiary health institution) that had imported pharmaceuticals and medical equipment from recognized pharmaceutical manufacturing companies in Europe, USA, and South Africa. They were, therefore, trace elements-free. A phlebotomist working with the teaching hospital used the fresh (sterile) needle/syringe and blood sample bottles to collect the blood samples, with swab cotton wool and methylated spirit. A sterilized sample bottle was given to each subject to supply early morning urine, with instruction to store the sample in the fridge between collection and delivery to the laboratory. The samples were analyzed by a Medical Laboratory Scientist working in the Medical Diagnostic Laboratory Unit of the Teaching Hospital for serum levels of Cd, Pb, Hg, Ni, Se, and Tl and urine levels of As and Be (independent variables) and the kidney functions (dependent variables) of the make-ups users. The two sets of data were subjected to regression to determine the relationship between the variables. Analysis was performed using Statistical Package for Social Sciences (SPSS) Version 23.0.

Ethical committee approval

Since the study involved human samples, an appropriate Health Research and Ethical Review Committee gave the ethical approval. All the methods were performed in accordance with the relevant guidelines and regulations.

Quantitative determination of the trace elements

Arsenic, lead, and cadmium

Arsenic, lead, and cadmium were determined by Environmental Protection Agency (EPA) of the USA method-200_13-trace element determination via atomic absorption graphite furnace spectrometer using Buck scientific atomic absorption spectrophotometer (GFAAS, made in USA). Pd-Mg mixture was served as the matrix modifier for As, while Ni was used as matrix modifier for Pb and Cd (Bakırdere et al., 2013).

Mercury (Hg)

Total mercury was determined by absorption spectrometry (dithizone colorimetry), neutron activation analysis or cold vapor atomic absorption spectrometry of the EPA of the USA method-200_13-trace element determination via atomic absorption graphite furnace spectrometer using Buck Scientific atomic absorption spectrophotometer (GFAAS, made in USA) (Bakırdere et al., 2013).

Beryllium (Be)

Beryllium was determined by EPA of the USA method-200_13-trace element determination via atomic absorption graphite furnace spectrometer using Buck Scientific Atomic Absorption Spectrophotometer (GFAAS, made in USA) (Bakırdere et al., 2013).

Nickel (Ni)

Nickel was determined by using 2-[(2-mercaptophenylimino)methyl]phenol (MPMP) to form a brown 1:2 MPMP-nickel(II) complex at pH > 10, which was extracted into chloroform. The complex had a maximum absorption at 421 nm. The relative standard deviation at 0.018 µg mL−1 is 1.1% (n = 8) (Shabani et al., 2008).

Selenium (Se)

Selenium was determined by digesting the sample by wet-ashing procedure and finally analyzing it using inductively coupled plasma-mass spectrometry (ICP-MS). The mean Se value was obtained (Moatkhef et al. 2020).

Thallium (Tl)

Urine samples were subjected to quantitative 24-h-urinary-thallium-level (QT) analysis. Independent-samples t test and Spearman’s coefficient were applied for analytical purposes. SPSS software 16 was used to conduct statistical analyses with P values less than 0.05 regarded as significant (Ghaderi et al., 2017).

Procedure for eGFR

Based on the sample blood creatinine level and/or blood cystatin C level, the estimated glomerular filtration rate (eGFR) was a calculated estimate of the actual glomerular filtration rate of the blood sample drawn from a vein.

Results and discussion

Table 1 shows the serum/urine levels of selected trace elements and kidney functions, while Table 2 shows the means and standard deviations for serum/urine levels of the selected trace elements and for kidney functions (eGFR ml/min in 1.73 m3). From Table 2, the mean kidney function (eGFR ml/min in 1.73 m3) was 56.9800 ± 3.22860. This fell within the range, eGFR < 60 ml/min in 1.73 m3, which indicates kidney function affected by trace elements (Fevrier-Paul et al., 2018). The mean urine As level of 106.0108 ± 23.83840 fell outside the normal range of ≤ 50 μg/L and high normal range of > 50 to < 200 μg/L (ATSDR, 2000). The mean serum Cd level of 3.7864 ± 1.76790 ng/mL was within the normal range of < 5.0 ng/mL (Agency for Toxic Substances and Disease Registry, ATSDR, 2000).

Table 1 Serum/urine levels of selected trace elements and kidney functions
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Table 2 Means and standard deviations for serum/urine levels of trace elements and for kidney functions (eGFR ml/min in 1.73 m3)
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The mean serum Pb level of 17.2548 ± 4.63788 exceeded the normal serum Pb levels in adults of up to 10 µg/dL. It fell within the range, 10 and 25 µg/dL, for regular exposure to Pb. A consistent and regular use of make-ups by subjects confirmed the literature claim of regular exposure to Pb (Agency for Toxic Substances and Disease Registry, ATSDR, 2000). The mean serum Hg was 25.9482 ± 4.14231. This value exceeded the normal level, < 10–20 μg/L, and 35 μg/L level caused by long-term exposure to Hg vapor. Hg is a highly toxic element, and there is no known safe blood level of Hg (Agency for Toxic Substances and Disease Registry, ATSDR, 2000). The mean urine Be level of 0.5574 ± 0.22715 μg/L exceeded the minimum acceptable level of 0.28 μg/L but was within the normal range of 0.28–1 μg/L. Levels in excess of this range can cause cancer (Agency for Toxic Substances and Disease Registry, ATSDR, 2002).

The mean serum Ni of 0.6237 ± 0.23037 was within the healthy range, 0.14–0.65 µg/L, but above 0.2 µg/L, which is the most reliable value in adults (Agency for Toxic Substances and Disease Registry, ATSDR, 2000). The mean serum Se level of 103.8950 ± 88.80677 μg/L was within the average range of 100.6 ± 12.9 μg/L for adults (over 16 years), 93.9 ± 13.6 μg/L for adult women, and 102.1 ± 12.3 μg/L for adult men (Safaralizadeh et al., 2005). The mean serum Tl level of 201.4900 + 20.63316 μg/L was much higher than the normal level of < 2 µg/L and within the toxic range of > 200 µg/L (National Institute for Occupational Safety and Health, NIOSH, Center for Disease Control, CDC, 2003).

Table 3 shows the model summary of the serum levels of selected trace elements and kidney functions. The R square value of 0.100 means that 10% of the variation in the dependent variable is explained by the variation in the independent variables. Table 4 shows the ANOVA of the serum levels of the selected trace elements and kidney functions. The R square value of 0.100 (see model summary table) was not significant (0.271) at 1%, 5% and 10% (see ANOVA table). 

Table 3 Model summarya of the serum/urine levels of selected trace elements and kidney functions
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Table 4 ANOVAa of the serum/urine levels of selected trace elements and kidney functions
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Table 5 shows the regression coefficients of the serum/urine levels of selected trace elements and kidney functions. At − 0.009, the coefficient for As showed that for every 1% rise in urine As level, kidney function decreased by 0.9%. This was, however, not significant (0.518) at 1%, 5%, and 10%. The coefficient of − 0.155 for Cd showed that for every 1% rise in serum Cd level, kidney function decreased by 15.5%. This was, however not significant (0.423) at the three levels of 1%, 5%, and 10%.

Table 5 Coefficientsa (regression) of the serum levels of selected trace elements and kidney functions
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At − 0.039, the coefficient for Pb showed that for every 1% rise in serum Pb level, kidney function decreased by 3.9%. This was, however, not significant (0.595) at 1%, 5%, and 10%. The coefficient of 0.061 for Hg showed that for every 1% rise in serum Hg level, kidney function increased by 6.1%. This was, however, not significant (0.462) at 1%, 5%, and 10%.

The coefficient of Be, − 1.585, showed that for every 1% rise in urine Be level, kidney function decreased by 158.5%. This was, however, not significant (0.292) at 1%, 5%, and 10%. At 1.384, the coefficient for Ni showed that for every 1% rise in serum Ni level, kidney function increased by 138.4%. This was, however, not significant (0.354) at 1%, 5%, and 10%.

The coefficient, − 0.002, for Se showed that for every 1% rise in serum Se level, kidney function decreased by 0.2%. This was, however, not significant (0.635) at 1%, 5%, and 10%. At 0.039, the coefficient for Tl showed that for every 1% rise in serum Tl level, kidney function increased by 3.9%. This was significant (0.015) at 5%. This finding internally validated the finding on the mean serum Tl level of 201.4900 + 20.63316 which was much higher than the normal level of < 2 µg/L and within the toxic range of > 200 µg/L.

Conclusions

Against the backdrop of increasing concern for the toxicity of trace elements in make-ups, 8 such elements (As, Cd, Pb, Hg, Be, Ni, Se, and Tl), described as notorious daredevils, have been investigated. The study was aimed at ascertaining the potential for poisoning from make-ups use that could lead to cancer by exposure to Be or CKD and its complications by exposure to As, Cd, Pb, Hg, Ni, Se, and Tl. Female university students who consistently used make-ups for upwards of 3 years were the subjects. The serum/urine levels of these trace elements were regressed against the kidney functions of the subjects. Only the level of Tl in the body was significant (0.015) at 5%. This finding internally validated the finding on the mean serum Tl level of 201.4900 + 20.63316, which was much higher than the normal level of < 2 µg/L and within the toxic range of > 200 µg/L. This finding warrants concerns for the toxicity of Tl contained in make-ups used in Nigeria.