Personal Care Products

Humans use various chemicals such as cosmetics, disinfectants, preservatives, food additives, fragrances, and toothpaste to improve quality of life (Brausch and Rand, 2011). These personal care products contain a diverse group of bioactive ingredients that can potentially cause adverse effects to the environmental balance and human health (Hopkins and Blaney, 2016; Langdon et al., 2010; Nohynek et al., 2010). The main route of exposure for personal care products to humans is through dermal absorption (Tseng and Tsai, 2019). Thus, dermal exposure to personal care products may often result in acute effects such as dermatitis (Nohynek et al., 2010). Moreover, several studies have shown that personal care products can have carcinogenic, mutagenic, and estrogenic effects in humans (Jimenez-Dfaz et al., 2014). Personal care products often enter the environment as parent products since they are often used externally, but their absorption also results in its metabolism and excretion as parent and/or metabolites (Kim and Choi, 2014; Schlumpf et al., 2010). Like pharmaceuticals, personal care products primarily enter the environment via wastewater effluent. Several studies have detected high concentrations of personal care products such as parabens, organic UV filters, synthetic musks, and disinfectants in wastewater effluent, rivers, and lakes (Brausch and Rand, 2011; Jimenez-Diaz et al., 2014; Li et al., 2018). Most personal care products are considered pseudo-persistent because they are continuously discharged into the environment, which is not overcome by their transformation. Several studies have shown that personal care products can cause adverse health effects on aquatic biota (Li et al., 2020). For that reason, personal care products are considered contaminants of emerging concern. Hence, understanding the sources, physicochemical properties, and environmental behavior of personal care products is important for improving the accuracy of environmental risk assessments.

Some personal care products such as synthetic musks and organic UV filters are chiral compounds. Chiral synthetic musks are extensively used as fragrances in several consumer products such as perfumes, shampoo, soaps, and cosmetics. Synthetic musks can be classified as macrocyclic, nitro, or polycyclic musks. Polycyclic musks are the most widely used synthetic musks. Examples of chiral polycyclic musks include galaxolide, tonalide, phantolide, traseolide and cashmeran. Galaxolide and traseolide have two chiral centers while tonalide, phantolide, and cashmeran have one unique stereogenic center (Table 1.1) (Lee et al.. 2016). It is interesting to note that only two of the galaxolide stereoisomers can be sensed by the human nose. This suggests that the other stereoisomers are unnecessary contaminants that might need to be removed to reduce waste. However, the use of enantiomers can lead to more toxic effects as was observed in the failed chiral switching of fluoxetine (Agranat et al., 2002; Calcaterra and D'Acquarica, 2018). Chiral polycyclic musks have high lipophilicity (log Kow = 4.5-6.3). hence they readily bioaccumulate in tissue as well as readily suffer partition into sediment and organic particles (Brausch and Rand, 2011). Previous studies have shown that chiral polycyclic musks can undergo enantioselective transformation in sewage sludge (Gao et al., 2019), surface water (Lee et al., 2016), sediments (Song et al., 2015), recycling water (Wang and Khan, 2014), and WWTPs (Lee et al., 2016). In biota, galaxolide, tonalide, phantolide, and traseolide were shown to undergo enantioselective metabolism in different fish species (Gatermann et al.. 2002). A few studies have investigated the toxicity of chiral musks; for example, (R)-muscone was shown to cause higher toxicity to zebrafish embryo than (S)-muscone (Li et al., 2020). The enantiomeric composition of polycyclic musks in environmental matrices is widely determined using enantioselective capillary electrophoresis and gas chromatography coupled to mass spectrometry or tandem mass spectrometry (Martlnez-Giron et al., 2010; Wang et al., 2013).

TABLE 1.1

A List of Five Polycyclic Musks and Their Molecular Structures

Chemical name

T rade Structure name

4,6,6,7,8,8-Hexamethyl-13,4,6,7,8- hexahydrocyclopenta[g]isocromene, HHCB

Galaxolide,

Abbalide

7-Acetyl-l,l,3,4,4,6-hexamethyl- tetraline, AHTN

Tonalide,

Fixolide

5-Acetyl-1,1,23,3,6- hexamethylindane, AHD1

Phantolide

5-Acctyl-l ,1,2,6-tctramcthy 1-3- isopropyl indane, ATI I

О

Г2

■q

У

2

H

1,1,233-Pentamcthyl-l 2 3,5,6,7- hexahydro-4H-inden-4-one, DPMI

Cashmeran

Source: Chemical structures of the polycyclic musks are from Wang et al. (2013). Used with permission from Elsevier Ltd.

Organic UV filters are commonly used in sunscreens, lotions, hair products, and cosmetics for protecting the skin against UV radiation. UVA. UVB. and UVC light can cause radiation damage on the skin (Hopkins and Blaney, 2016). Organic UV filters are pseudo-persistent contaminants since they are continuously discharged into the environment due to their extensive usage. Several studies have detected organic UV filters in various environmental systems such as surface water, freshwater and marine sediments, and soil (Montes-Grajales et al„ 2017). Organic UV filters can potentially bioaccumulate in tissue as they have been detected in mussels and fish (Yang et ah, 2020). They can readily partition to organic matter in sediments or soil due to their high lipophilicity (log Kosv = 3.8-6.9) (Hopkins and Blaney, 2016; Rainieri et ah, 2017). The exposure to organic UV filters has been shown to cause adverse effects in the reproduction, mobility, and development of fish. Daphnia magna, and coral larvae (Campos et ah, 2017; Gilbert et ah, 2013; Lozano et ah, 2020; Park et ah, 2017; Quintaneiro et ah, 2019; Tsui et ah, 2017). Organic UV filters have also been shown to cause anti-estrogenic, androgenic, and anti-androgenic activity in humans. Hence, organic UV filters are considered an important class of contaminants of emerging concern. However, some organic UV filters such as 4-methylbenzylidene camphor are chiral compounds that have stereoisomers which exhibit different fate and toxicity profiles in the environment (Buser et ah, 2005). For example, the transformation of 2-ethylhexyl 4-dimethylaminobenzoate in rabbit liver and kidneys was shown to favor the (+)-enantiomer (Liang et ah, 2017). Table 1.2 shows examples of chiral organic UV filters approved for use as sunscreens by the European Union. Therefore, the chiral nature of organic UV filters should not be overlooked when assessing their human health and environmental risks.

TABLE 1.2

Physicochemical Characteristics of Four Chiral Organic UV Filters Approved for Use by the European Union

Name

CAS no

Structure

Log Kow

Solubility (g L'1)

Xmax(Om)

2-Ethylhcxyl 4- (dimcthylamino)benzoate

21245-02-3

6.15

2.1 x 1СГ3

310

Homosalate

118-56-9

6.16

0.02

Ethylexyl mcthoxycinnamatc

5466-77-3

5.8

0.15

306

4-methylbcn/ylidcnc camphor

36861-47-9

4.95

5.1 x 10-3

300

Source: The log Kow solubility, and Xm„ data for the selected chiral organic UV filters is from Di'az-Cruz et al. (2008). Used with permission from Elsevier Ltd.

 
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