Evaluating The Levels Of Some Selected Trace Metals, Renal Function Parameters And Liver Function Parameters Of Heavy Cosmetics Users Among Female Undergraduates And Compare Levels With Non-cosmetic Users

2.3 Basic Toxicants in Nail and Hair Care Products
Upon due consideration of the various nail and hair care products, the following are basic toxicants worthy of note; viz;
1.    Parabens
2.    Formaldehydes
3.    Toluene
4.    Phthalates
5.    Coal tar
6.    Acetone
2.3.1 Parabens
Parabens are preservatives used in wide range of cosmetics, pharmaceuticals, and food products. They are esters of para-hydroxybenzoic acid and commonly include methylparaben,ethylparaben,butylparaben and propylparaben (CIREP, 2008). The recent health concern about parabens stems from a study published in 2004 that detected parabens in breast tissue from patients with breast cancer (Darbre et al., 2004). Their use in cosmetic consumer product is more is prevalent than their use elsewhere. Products found to contain parabens include;hand soap,body lotion, shampoo, conditioner, face lotion, facial cleansers, foundations, lipsticks, mascara, hair spray/gel/mousse and sunscreens (Witorsch and Thomas, 2010; Yazar et al., 2011). Methylparabens and propyl parabens are the most commonly used parabens in pharmaceutical products at concentrations up to 20% (CIREP, 2008).
Toxicity Of Parabens
Human and animal studies have failed to show acute toxicity of parabens by various means of administration and as such focus has been on long term effect of chronic exposure (Kirchhof and de Gannes, 2013). The estrogenic activity of parabens was first identified in 1998 and has been validated both invitro and invivo (Routledge et al., 1998; Harvey and Darbre, 2004) promoting breast caner development. They bind human estrogen receptor although with affinities of 10,000 to 1,000,000 times less than estradiol (Routledge et al., 1998; Blair et al., 2000) with butyl and propylparabens having greater affinities than methyl and ethyl parabens.
Also, invitro study have shown loss of viability of sperm when exposed to parabens at concentration of 1mg/mL (Song and Peng, 1989). However invivo study in mice did not replicate this result, with no spermatotoxic effect at concentration of 1% (Oishi, 2002)  suggesting conflicting findings.
There are also reports of immediate immunoglobin E mediated allergic reactions to parabens resulting in Urticaria and in one case bronchospasm (Kajimoto et al., 1995; Gizanka et al., 2010).
2.3.2 Formaldehydes
Formaldehyde is a naturally occuring organic compound with the formula CH2O. It is a colourless, flammable gas at room temperature. It is the simplest aldehyde and is known by its systemic name methanal.
Formaldehyde exist in polymeric form as paraformaldehyde; and when  dissolved in water is called formol or formalin which is used for preserving biological specimens as well as embalming human remains. Cosmetologically, it is commonly used in nail hardners and nail varnish. Formaldehyde or formaldehyde releasing preservatives are frequently used in cosmetic preparations such as shampoos and skin-care products for the prevention of microbial and fungal growth (Joshua and Hillebrand, 2010). In view of widespread use, toxicity of formaldehyde is a significant consideration for human health (IARC, 2006).
Toxicity of Formaldehyde
In 2011, the US national toxicology program described formaldehyde as a human carcinogen (Gardiner, 2011). The critical health effects of formaldehyde for risk characterisation are sensory irritation, skin sensitisation and carcinogenicity (ACCC, 2010).
2.3.3 Acetone
Acetone (CH3)2CO also called propanone in the IUPAC nomenclature, is a colourless, volatile and flammable liquid with a pungent irritating odour. It is the simplest ketone. About 6.7 tonnes were produced worldwide in 2010 mainly for use as a solvent and in the production of methyl methacrylate and bisphenol A (Sifniades and Levy, 2005). It forms active ingredients in nail polish remover and as paint thinner.
Biologically, it is produced and disposed of in the human body through the normal metabolic processes usually by decarboxylation of acetoacetic acid. It is produced in larger amounts in people with diabetes. Pregnant women, nursing mothers and children have higher levels of acetone (ACC, 2003).