Chiral Personal Care Products: Occurrence, Fate, and Toxicity
Synthetic chemicals in products are released into the environment during the life cycle of the product. They may cause adverse effects to humans and the environment. There has been a significant increase in knowledge pertaining to the deleterious effects of chemical pollutants in the past 60 years. However, chemical pollution is one of the leading causes of premature deaths and noncom- municable diseases worldwide (Brooks et al., 2020). In 2015 and 2017, exposure to contaminated air, water, soil, and food contributed to the death of around 9 million and 8.3 million people globally, respectively (Landrigan et al., 2018). The adverse effects of chemical pollution are higher in developing countries. Poor sanitation, industrial contamination of drinking water and air. indoor air pollution from the burning of fossil fuels, and a lack of adequate waste management infrastructure are prevalent in developing countries (Briggs, 2003). These factors increase the risk of chemical pollution. In addition, in low- and middle-income countries, pollution-related diseases cause a 2% reduction in gross domestic product per year due to loss of productivity (Das and Horton, 2018). However, the actual disease and death toll due to chemical pollution might be higher because current estimates do not include data from poorly understood health effects of known pollutants and emerging pollutants (Figure 5.1). There are currently more than 350,000 registered chemicals and mixtures worldwide (Wang et al., 2020), of which 5,000 high-production volume chemicals are
FIGURE 5.1 The death toll of chemical pollutants is estimated from known pollutants with known health effects (Zone 1) and not known (Zone 2) or emerging pollutants (Zone 3) with unknown or unclear health effects. GBD stands for the Global Burden of Disease study. (From Landrigan et ah, 2018. Used with permission from Elsevier Ltd.)
ubiquitous in the environment (Landrigan et al., 2018). Less than half of these high-production volume chemicals underwent toxicity testing. Chemical pollution can cause ecological changes that can indirectly affect human health, however (Das and Horton, 2018). For example, chemical pollution can cause loss of biodiversity, which may cause loss of important food sources for humans. Uncharacterized chemicals and ecological changes might be responsible for much of the diseases, deaths, and ecological changes associated with chemical pollution (Landrigan et al., 2018). Unfortunately, the discharge of chemicals into the environment and their corresponding health effects are going to increase since the global production of chemicals is expected to double by 2030 (Brooks et al., 2020).
5.1.1 Usage of Personal Care Products
A wide range of chemical pollutants present at trace levels in the environment emerged in the past two decades due to advances in sample preparation, separation, and detection. Pharmaceuticals and personal care products are an example of one such group. An active pharmaceutical ingredient is a chemical substance that imparts pharmacological activity to a pharmaceutical product or aids in the cure, treatment, diagnosis, mitigation, or prevention of disease through shifting the physiological functions of a person (Sanganyado et al., 2017). Personal care products (PCPs) are a diverse group of bioactive chemicals that are directly used on the human skin and body to improve the quality of life by altering or enhancing human sensory such as taste, smell, or touch (Ying, 2012). They are widely used in health, beauty, and cleaning household products such as disinfectants, fragrances, food additives, insect repellents, hair products, preservatives, organic UV filters, shampoos, and detergents (Hopkins and Blaney, 2016; Montes-Grajales et ah, 2017). Most PCPs contain bioactive active ingredients such as alcohols, aromatic hydrocarbons, and surfactants.
It is estimated that an average household spends more than $750 on PCPs per year, and the annual revenue from PCPs exceeds $189 billion in the United States (Hopkins and Blaney, 2016). Previous studies have shown that an average person uses 6-12 PCPs per day (Alani et ah, 2013). As standards of living continue to improve globally, the number and quantity of PCPs an individual uses per day are expected to increase significantly. Each year, hundreds of new PCPs are developed to meet the demands of the increasingly sophisticated global market (Zhou et ah, 2017). Nevertheless, the effects of most of these new chemicals on human and environmental health are poorly understood. The increase in usage of PCPs will result in increased discharge of PCPs into the environment.
5.1.2 Scope of Chapter
Personal care products are regarded as contaminants of emerging concern because they are bioactive and high production volume compounds. However, some PCPs such as synthetic musks, phthal- ates, azole fungicides, and organic UV filters are chiral compounds. Chiral compounds exist at least as two enantiomers that have disparate behaviors in chiral systems (Sanganyado et ah, 2020). Hence, enantiomers of chiral PCPs may have a different distribution, fate, and toxicity in humans and the environment. This chapter focuses on synthetic musks, organic UV filters, and azole fungicides since more studies have investigated their enantioselective behaviors. Furthermore, this chapter explores the impact of the physicochemical properties on their distribution and fate in the environment. The routes of entry and potential effects of PCPs in the environment are also examined. The chapter concludes by offering recommendations for future studies.