Qualitative Assessment of Contaminants of Emerging Concern in the Environmental Media across Delhi

Endocrine disrupting compounds (EDCs) are chemicals produced by human activities that are contaminating the environment and posing a threat to human and aquatic health, ecosystems, and the cost of water treatment. EDCs interfere with normal hormonal balance and can cause adverse health impacts. Examples of natural EDCs include estrogens, androgens, and phytoestrogens, while examples of synthetic EDCs include polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs), dioxins, furans, alkylphenols (APs), pharmaceuticals, personal care products (PPCPs), and pesticides [1]. EDCs are found in a wide range of consumer products, including industrial chemicals used in manufacturing, such as paints, plastics, detergents, and textiles. EDCs are concerning due to their extensive use, environmental distribution, persistence, and potential for bioaccumulation [2]. Phthalates and bisphenol A (BPA) are chemicals found in potable water, soil, air, wildlife, and plants at concentrations ranging from nanograms to micrograms [3,4]. Environmental factors such as chemical complexity, half-lives, and pH determine the interaction and fate of these chemicals in different environmental matrices, especially soil and water. Limited studies are available on the distribution and health risks of these chemicals in India. The study aims to provide a qualitative assessment of phthalates and BPA in waste water, river water, and soil in Delhi to help create regulations for their use and reduce the risk to the environment and human health. Delhi, the capital of India, is geographically located between the 28.39 to 28.88° North latitude and 76.82 to 77.34° East longitudes at an average elevation of 216 m above the mean sea level. According to the census report 2011, Delhi has a population of 16.7 million with an average annual growth rate of 1.92% and has population density of 11,297 km-2. Moreover, the region has industrial production and outer peripheral is mixed rural-urban region. It is characterized by a surge of physical and economic growth of Delhi and progressive development on its outskirt. This has changed the region's pattern of land use and land cover, which has an impact on the environment. Sampling of water (wastewater and surface water) and soil (agricultural and non-agricultural soil samples) was done during 2022 from randomly selected locations (Figure 1) with varying levels of human activity, including traffic congestion, commercial and industrial activity, and other factors. Surface water and wastewater samples were collected in 1000 mL amber glass bottles. A minimum of 3 replicates of water and soil samples were collected from each sampling locations and then mixed at laboratory to form composite samples. For surface water sampling, five samples from three distinct locations from Yamuna River were taken. All samples were transferred within 12 hrs, catalogued, and stored at -20°C until further analysis. Standards for phthalates namely dimethyl phthalate (DMP), diethyl phthalate (DEP), benzyl-butyl phthalate (BBP), and bisphenol A (BPA) were procured from AccuStandard Inc. All solvents used in the study were of HPLC grade and supplied by Merck (Germany). The method described in EPA Method 3510 was used for extraction of water samples. The collected water samples were filtered to remove suspended particles and then 250 mL of the filtered sample was mixed with 50 mL of sodium chloride solution and 50 mL of dichloromethane. The mixture was agitated and left undisturbed to separate into two layers, and the lower layer was collected and passed through anhydrous sodium sulphate. This process was repeated two more times, and the resulting organic phase was concentrated in a rotary evaporator at 40°C. The final residue was concentrated to 2 mL and analyzed using GC/MS. Collected soil samples were air dried at room temperature to remove the moisture content. After the soils had dried completely, they were pulverised in a pestle and mortar, put through a 2 mm mesh sieve, and then placed in glass bottles for storage. For the extraction of soil samples modified QuEChERS (rapid, easy, cheap, effective, robust, and safe) method was used [5]. The procedure for qualitative analysis of phthalate and BPA using GC/MS. Standard solutions were prepared and run under a standardized protocol with specific oven temperature settings and injection mode. The peak area obtained from the runs was used to create a standard curve for each analyte in terms of concentration with respect to retention time. The mass spectra from a library database were used to confirm the results. The concentrations of selected analytes in different environmental media are shown in Figure 2 and 3. All targeted analytes were frequently detected in soil, wastewater, and surface waters from the sampling sites; out of which BPA was most abundant. Generally, the distribution of chemicals in different environment depends on a variety of factors that govern the mobility and fate of these chemicals. The concentration of EDCs in agricultural and non-agricultural soil samples are given in Fig. 2. Among the targeted EDCs, detection frequency of BPA was 100% in soil samples. The mean concentrations in the non-agricultural soil samples were in the order of BPA > DMP > DEP > BBP whereas, in agricultural soils BPA > DMP > BBP > DEP. Overall, BPA had the highest concentration ranging from 1.20 to 3.54 ng/g (avg. 2.74 ng/g). The prevalence of BPA at higher concentration in agricultural soil may be further investigated through continuous assessment. Average concentrations of DMP, DEP, BBP and BPA samples obtained from wastewater are shown in figure 3. Among phthalates, DEP (low molecular weight) had the highest concentration ranging from 5.63 to 11.25 µg/L (avg. 7.69 µg/L) followed by BBP (high molecular weight) in the range of 2.68 to 6.23 µg/L (avg. 4.50 µg/L). However, BPA had the highest concentration among all the wastewater samples obtained from selected sampling locations. The order of maximum concentration in all the wastewater samples were BPA > DEP > BBP > DMP. The detection frequency of BPA, DMP and DEP was 100% on the other hand, lowest detection frequency was observed for BBP in wastewater and was consistent with the findings of previous studies [4,6]. Detection of all the targeted EDCs were observed (figure 3), among the four highest concentration of BPA was observed for all the sampling locations ranged from 8.76 to 13.23 µg/L followed by DEP ranged from 0.76 to 1.67 µg/L. However, lowest concentration was observed for DMP ranging from ND- 0.85 µg/L. The mean concentration of all analytes in the surface water were found in the order of BPA > DEP > BBP > DMP, which was consistent with the previous findings [4]. The presence of EDCs in the Yamuna River may be contributed to the direct discharge of effluent from the WWTPs and industries. The detection of these chemicals in surface water and wastewater can be a potential source to groundwater contamination in the study area. The study found that bisphenol A (BPA) and phthalates are present in various environmental media throughout Delhi, which raises concerns due to their potential to bioaccumulate and biomagnify in the food chain, leading to harmful effects on human health. Therefore, future studies should focus on the pollution load of endocrine disrupting compounds (EDCs), their toxicity, interactions, and fate in the environment to plan effective mitigation strategies. Location map of Delhi showing sampling sites Concentration of targeted analytes in soil samples Concentration of targeted analytes in surface water (SW) and wastewater (WW)