**1. Introduction**

The personal care product (PCP) industry is a significant contributor to the global economy, accounting for 3.9 million direct and indirect jobs in 2018, representing 1.9% of total US employment and USD 267.3 billion in the United States' gross domestic product [1]. Many of the compounds used in PCPs are referred to as "endocrine-disrupting compounds" (EDCs) because they can mimic or alter hormones, leading to complications in growth, development, and reproduction [2]. Given that many PCPs are applied topically, compounds classified as EDCs have been found in human tissues [3]. Triclosan, an antibacterial agent used in PCPs, has been monitored and detected in blood, breast milk, urine, adipose tissue, and liver [4]. Other EDCs used in cosmetics, including bisphenol A (BPA), phthalates, and parabens, have been studied in human urine samples to better understand potential toxicological effects [2,4]. As more EDCs are identified in consumer products, there is concern over the ability of some EDCs to lower spermatozoid production and potentially increase the risk of breast cancer and other anomalies in human bodies [5].

**Citation:** Taylor, R.; Hayden, K.; Gluberman, M.; Garcia, L.; Gorucu, S.; Swistock, B.; Preisendanz, H. Development and Demonstration of an Endocrine-Disrupting Compound Footprint Calculator. *Water* **2022**, *14*, 1587. https://doi.org/10.3390/ w14101587

Academic Editors: Nigel W. T. Quinn, Ariel Dinar, Iddo Kan and Vamsi Krishna Sridharan

Received: 26 February 2022 Accepted: 12 May 2022 Published: 16 May 2022

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Globally, EDCs are increasingly considered major contributors to a wide array of ecotoxicological impacts on non-target aquatic organisms. In the United States, EDCs have been found in surface water, particularly downstream of wastewater treatment plants [6], and have the potential to impact the endocrine systems of aquatic species at environmentally relevant concentrations [2]. In Pennsylvania, the smallmouth bass (*Micropterus dolomieu*) decline in the Susquehanna and Juniata Rivers triggered a significant amount of research and heightened awareness around the issues of EDCs in these river networks [7]. For example, the United States Geological Survey (USGS) reported that 60–100% of large- and smallmouth bass populations sampled near wildlife refuges in the Northeast exhibit intersex characteristics [8]. A causal analysis conducted by the Pennsylvania Department of Environmental Protection (PA DEP) indicated the presence of EDCs, such as pesticides, pharmaceuticals, and ingredients in PCPs as likely contributors to the decline [7]. Although a virus was ultimately determined to be the greatest contributor to the decline, the presence of intersex characteristics in the fish populations could not be explained by the virus, and therefore, a better understanding of the presence and impacts of EDCs is still needed [9]. In the Susquehanna River Basin, an increased presence of steroidal hormones was observed with the increased feminization of the local smallmouth bass population, where male fish were developing female sexual characteristics [7].

Beyond the well-documented impacts on fish populations from EDCs in surface water bodies, EDCs in wetlands and vernal pools pose potential threats to amphibians, which are also known to be declining globally at alarming rates [10–12]. The amphibian decline, which has been referred to as the sixth mass extinction [13], is attributed to a wide range of factors, including diseases, invasive species, climate change, and habitat loss. Water quality contaminants, including EDCs, are also suspected to be contributing to the amphibian decline [14,15]. In studies monitoring human wastewater contaminants from septic tanks and wastewater irrigation activities in critical amphibian habitats (vernal pools), EDCs were present at levels high enough to elicit intersex characteristics in native frog species [16–18]. Aside from causing intersex characteristics, EDCs such as triclosan have been shown to affect tadpole hindlimb development at concentrations as low as 0.15 μg/L [19]. Understanding the effects of EDCs on amphibians and other sensitive aquatic organisms is critically important for prioritizing conservation efforts.

The mechanisms through which domestic wastewater introduces EDCs into the environment are generally well-understood, with human sources of EDCs most commonly associated with the usage of PCPs and pharmaceuticals. Despite nearly two decades of research since the seminal Kolpin et al. [6] study promoted an exponential growth of research on the impacts of EDCs on drinking water quality and aquatic ecosystem health, little clear evidence remains of the reduced presence or quantity of these contaminants in the environment. These chemicals are introduced into the environment during various stages of the life cycle of PCPs, including manufacturing, use, and disposal. In each of these stages, EDCs may be present in the influent water to wastewater treatment plants (WWTPs) [20–24]. WWTPs were not designed to remove these chemicals, and therefore, the chemicals and their metabolites, which can retain potency, often persist in the wastewater effluent. This wastewater effluent is typically discharged to surface water bodies but may also be land-applied or used to recharge groundwater aquifers. Although wastewater must be treated to meet permit requirements, EDCs are currently not regulated, and therefore, the extent to which treatment plants remove EDCs prior to discharging their effluent varies widely across treatment technologies and types of EDCs [23].

Given that these chemicals do not currently have water quality regulations, one way to reduce their presence in the environment is by reducing their sources. However, it is difficult for consumers to make informed decisions about the PCPs they purchase because labels are often insufficient for determining whether or not a product may contain

EDCs, or which type of EDCs may be present. In the United States, the Food and Drug Administration (FDA) regulates some PCPs such as toothpaste, deodorant, sunscreen, and antibacterial hand soap. However, the FDA only requires that active ingredients be listed on the product's label, and not all of the EDCs found in these products are considered to be "active ingredients". The FDA requires that cosmetic labels list all ingredients from highest to lowest concentration in the product [25,26], but given that some ingredients may be more potent or exhibit higher endocrine-disrupting potential than others, this method of labeling may not provide information in an easily accessible manner for making informed decisions about product choices.

A large study was conducted by the Silent Spring Institute to quantify the presence of EDCs in commonly used PCPs [27]. The authors selected 66 target compounds that included EDCs and compounds suspected to trigger asthma that were expected to be present in PCPs, and they analyzed 85 samples for these compounds. The samples were composites of up to seven products in each product category and represented more than 200 products. They classified the results of their EDC analysis into four main categories: not detected, 1–100 μg/g, 100–1000 μg/g, and >1000 μg/g. The highest levels of EDCs detected varied by product type, with the highest UV filters in sunscreen; highest cyclosiloxanes in sunscreen and car interior cleaners; highest glycol ethers in floor and carpet cleaners, polish/wax, and sunscreen; highest fragrances in surface cleaners, car fresheners, dryer sheets, air fresheners, and perfume/cologne; highest alkylphenols in shower curtains and car interior cleaners; highest ethanolamines in glass cleaners and laundry detergent; highest antimicrobials in hand and bar soaps; highest BPA in detergent, soap, shampoo, conditioner, detergent, shaving cream, face lotion, toilet bowl cleaners, body wash, and nail polish; highest phthalates in foundation, car fresheners, and perfume/cologne; and highest parabens in face lotion, mascara, hair spray, and sunscreen. In addition to conventional products, composites of alternative products that were advertised as "greener" were also analyzed in the study. The results of the analysis demonstrated the widespread presence of EDCs in commonly used household products and the co-occurrence of multiple compounds in the same products, raising concerns regarding their biological activity and potential toxicological and ecotoxicological implications of the use of these products. Further, the study revealed multiple compounds in the products that were not listed on the product labels, highlighting concerns regarding the ability of consumers to make informed choices should they wish to select products without specific EDCs.

The goal of this research was to develop a tool that the general public could use to estimate their "footprint" (i.e., the mass) of EDCs in products that they currently or typically own and use in their personal hygiene, household cleaning, and laundry routines. Although the footprint does not provide temporal context, it serves as a "snapshot" of the EDC footprint for the products used by members of a household at the time the calculator is taken. The footprint tool was inspired by online water and carbon footprint calculators, which prompt users to answer questions about their daily activities. These types of tools are useful in increasing awareness of complex environmental issues, such as water pollution and climate change. Here, we present an example output of the EDC calculator to demonstrate the utility of its graphical outputs in helping individual users make decisions about ways they could lower their household EDC footprint through their consumer choices. Further, we analyzed EDC footprint results for 39 citizen scientists in the northeastern United States to better understand the dominant product categories and individual products each contributing to total EDC footprints. Overall, we hope that users of the EDC footprint calculator become more aware of the issue of emerging contaminants in the water cycle and feel empowered to reduce their contribution to this global environmental concern.
